Invited Presentations

ICTON invited presentations

Germán Arévalo
Migration of a 40-channel WDM optical ring, from 400Gb/s-OOK to a 2Tb/s-DSP-assited-PAM4 solution: A real case study in Ecuador
G. V. Arévalo, R. Tenesaca, and M. Tipán
Telecommunications Research Group, Universidad Politécnica Salesiana, Ecuador
The evolution of data transport services demands a continuous upgrade of the bandwidth for communication systems. This upgrade must be efficient, low cost, and maximize transmission capabilities. This study analyzes the feasibility of migrating a DWDM optical fiber ring deployed by the Ecuador National Electricity Company to increase its bandwidth from 400 Gb/s to 2 Tb/s, using four-level amplitude modulation, predistortion, and digital signal processing techniques. With the implementation of analogic predistortion in the transmitter, combined with a one-pole one-zero filter for pre-emphasis, the system can increase its bandwidth keeping an optimal performance and low bit error rate. The results show an improvement in the bit error rate/received power ratio when predistortion is applied. The bit error rate further improves using digital filtering on the transmitter side.

Yossef Ben-Ezra
Superoscillating signal transmission over dispersive media
Y. Ben-Ezra and B. I. Lembrikov, Faculty of Electrical Engineering, Holon Institute of Technology, Israel
Superoscillating signals are band-limited signals that oscillate in some regions faster than their largest Fourier component [1], [2]. Superoscillatory functions have a variety of interesting applications in quantum mechanics, signal processing, subwavelength imaging, optics, etc. (see, for instance, [3] and references therein). However, the superoscillation amplitude is usually small compared to the typical values of the amplitude in non-super oscillating regions. Such small values are constructed by the near-perfect coherent destructive interference among the function’s spectral components. For large superoscillations, persisting over an extended region requires an exact relationship of phases. Such interference is sensitive to noise, especially in the form of random phases in the Fourier components [4]. Due to the chromatic dispersion in the single-mode fibers different spectral components of the signal travel at slightly different group velocities. This phenomenon is referred to as group-velocity dispersion (GVD) [5]. GVD can significantly change the phase relations of the Fourier components of the superoscillating signal and even lead to its complete deconstruction. Superoscillations have been investigated by using the wavelet transforms [6]. In this work, we studied theoretically the influence of the chromatic dispersion in a single mode fiber on the transmission of the superoscillating signals. We have carried out numerical simulations demonstrating the influence of the dispersion on variety of superoscillating signals. We have demonstrated perfect reconstruction of a superoscillating signal transmitted over dispersive media using the digital signal processing and machine learning algorithms.
Keywords: superoscillation, optical communication, digital signal processing.
[1] E. Katsav, M. Schwartz, Yield-optimized superoscillations, IEEE Transactions on Signal Processing, 61:3113-3118 (2013).
[2] P. J. S. G. Ferreira, A. Kempf, Superoscillations: Faster than the Nyquist rate, IEEE Transactions on Signal Processing, 54:3732-3740 (2006).
[3] M. Berry, N. Zheludev, Y. Aharonov, F. Colombo, I. Sabadini, D. C. Struppa, J. Tollaksen, E. T. F. Rogers, Fei Qin, Minghui Hong, Roadmap on superoscillations, Journal of Optics, vol. 21, no. 5, (2019).
[4] M. V. Berry, Suppression of superoscillations by noise, J. Phys. A: Math. Theor., 50:025003 (2017).
[5] G. P. Agrawal, Fiber-Optic Communication Systems, John Willey & Sons, Fifth edition, (2021).
[6] Y. Ben Ezra, B. I. Lembrikov, M. Schwartz, S. Zarkovsky, Applications of wavelet transforms to the analysis of superoscillations, in: Wavelet Theory and its Applications. Edited by S. Radhakrishnan, IntechOpen, London, UK, pp. 195-214 (2018).

Steinar Bjørnstad
A scalable data collection system for continuous state of polarisation monitoring
S. Bjørnstad^1,2, T. Dreibholz², and J. Ali²
¹Tampnet AS, Stavanger, Norway
²SimulaMet, Oslo, Norway
The society dependency on the telecommunication infrastructure is continuously increasing as different infrastructures, such as energy and telecommunication, now have mutual dependencies. This calls for increased monitoring of the fibre network, which is a highly critical part of the infrastructure. State of Polarisation (SoP) of light propagating through fibre transmission systems is impacted by any vibrations and mechanical impacts on the fibre. By continuously monitoring SoP, any unexpected movements of a fibre along a fibre-path may be traced. Movements may be caused by e.g. work in node rooms impacting patch-cords, trawlers or other types of sub-sea equipment touching or hooking into sub-sea fibre cables, digging close to a fibre-cable or geophysical phenomena like earthquakes. In this paper, we describe a low-cost scalable system for SoP monitoring and give examples of patterns monitored in different types of fibre infrastructures. The monitoring system consists of single-unit rack mount instruments connected to taps from live optical transmission signals. Each instrument has local storage for 1-2 years of data and is periodically automatically uploading data to a server for backup and data-access purposes. Examples of patterns observed are movements of a fibre-patch cord in a node-room, thunderstorm impact on a Fibre-To-The-Home (FTTH) cable and 50 Hz pattern on a fibre-cable spun around a high-voltage power air-cable.

Ivan Djordjevic
Entanglement assisted MIMO quantum radars
I. B. Djordjevic, University of Arizona, Tucson, USA
In this invited paper, we will describe our entanglement assisted (EA) MIMO quantum radar technique with multiple entangled transmitters and coherent detection-based receivers. This scheme exploits the phase sensitive quantum correlation on the receivers’ sides to improve the receiver sensitivity. To increase overall signal-to-noise ratio, we use the spatial MIMO concept. To reduce the system cost and complexity, the optical phase conjugation (OPC) on signal photons is performed on a transmitter side, so that commercially available classical, balanced coherent detectors can be used on receiver side instead of traditional OPC-based EA receivers.

Roberto Gaudino
Analysis of TDEC evaluation for different types of PON receivers
M. Casasco¹, G. Caruso², I. Cano², M. Valvo³, A. Pagano³, R. Mercinelli³, V. Ferrero¹, and R. Gaudino¹
¹Dipartimento di Elettronica e Telecomunicazioni, Politecnico di Torino, Italy
²Huawei Technologies, Munich, Germany
³Telecom Italia, Torino, Italy
The Transmitter and Dispersion Eye Closure (TDEC) is a metric originally introduced by IEEE 802.3 that was then recently re-adapted by ITU-T for the 50-GPON Recommendation G.9804.3 in September 2021. TDEC evaluates the performance of a transmission system as the penalty that the system under test presents when compared to an ideal transmitter. To this end, the standard defines a procedure to be followed involving filtering, equalisation and the definition of precise time instants within the eye diagram. All these operations can be performed via software and the aim is to calculate the ratio between two noise powers, one added to the eye diagram of the received signal and one calculated mathematically as the noise to be added to an ideal signal, to obtain a target BER. The purpose of this article is to review the metrology and provide some guidelines about the implementation of the TDEC algorithm in test equipment to obtain consistent results. Furthermore, it is shown how it is possible to use this technique on signals acquired with both types of oscilloscopes on the market, i.e. real-time and sampling oscilloscopes. The recommended equaliser is then tested in two different scenarios, in the presence and absence of noise, and the differences on the respective TDECs are commented on. To conclude, the link between TDEC and received power sensitivity is shown and modifications to the TDEC formula when considering different typical PON receivers (PIN, APD and SOA+PIN) are illustrated.
[1] ITU-T, G.9804.3 : 50-Gigabit-capable passive optical networks (50GPON): Physical media dependent (PMD) layer specification.
[2] IEEE Standard for Ethernet, Std 802.3-2018, pp. 1–5600 (2018).
[3] J. G. Proakis and M. Salehi, Chapter 10: Adaptive Equalization, in Digital Communications, (McGraw-Hill Education, 2008), pp. 689–705.
[4] I. N. Cano, G. Caruso, D. Nesset, and G. Talli, Relation between TDEC, extinction ratio and chromatic dispersion in 50G PON, in 2022 13th International Symposium on Communication Systems, Networks and Digital Signal Processing (CSNDSP), pp. 555–557.
[5] OIF-CEI, Implementation agreement OIF-CEI-04.0 Common Electrical: Common Electrical I/O (CEI) – Electrical and Jitter Interoperability agreements for 6G+ bps, 11G+ bps and 25G+ bps I/O, (2017).

Miguel Gonzalez-Herraez
Time-expansion in distributed optical fiber sensing
M. Gonzalez-Herraez, University of Alcalá, Madrid, Spain
In order to achieve high spatial resolutions in time-domain distributed optical fiber sensing, typically detection bandwidths in the GHz range are required, substantially increasing the system cost and complexity, and reducing the system dynamics. In this talk, we present a radically novel approach of distributed sensing that allows a customized time-expansion of the received optical traces. The technique reaches cm-scale spatial resolutions while requiring a remarkably low detection bandwidth, in the MHz range Thanks to a careful engineering of the optical signals used, the signal to noise ratio can be maximized while the processing requirements of the system are minimized. In an optimized scheme, the technique allows quantitative and dynamic strain/temperature measurements over 2 km, with 2 cm spatial resolution (100,000 measurement points) and 80 Hz acoustic sampling, with a detection bandwidth of only 100 MHz.

Norbert Hanik
The nonlinear Fourier transform and its extension to the strong coupling multi-mode case
B. Leible and N. Hanik, Technical University of Munich, Germany
Searching for ways to overcome the impending “capacity crunch” in fiber-optic data-transmission networks, the interest in communication systems utilizing the nonlinear Fourier transform (NFT) for signal generation/detection has been rekindled in recent years. The NFT provides a domain for signal modulation, in which, for a specific underlying channel, all modulated components are independent from each other during propagation. While there are still some open problems, especially concerning perturbations that are not part of the NFT’s underlying channel model and issues linked to the complexity of potential implementations, the topic has been studied in a plethora of publications, even dealing with adjacent topics like NFT-aided measurement methods for fiber parameters. Another topic, that has been studied with increased vigor in recent years, is the field of space division multiplexing (SDM), including multi-mode fiber channels. The NFT, mostly studied for the case of single-mode fiber channels, can also be utilized in the context of the strong-coupling multi-mode channel, leading to potential synergies with SDM. In this paper, we present the basics of the NFT for the strong coupling multi-mode channel, show that several properties of the single-mode case can be extended to the multi-mode channel and present some modified algorithms to implement the necessary transformations.

Rongqing Hui
Telemetry techniques for fiber-optic networks based on digital coherent optical transceivers
Rongqing Hui, Electrical Engineering and Computer Science, The University of Kansas, Lawrence, USA
We present results of our recent research on optical telemetry techniques to characterize physical layer properties of fiber-optic networks. Utilizing commercially available polarization-multiplexed coherent transceivers with DSP capabilities, various physical layer properties can be extracted from the measurements, such as fiber types, fiber dispersion and attenuation of each span, OSNR, and nonlinear phase shifts caused by the optical signal.

Carmen Mas Machuca
Cost-efficient capacity scaling using multi-wavelength transponders and adaptive modulation
C. Mas Machuca and J. Müller, Technische Universität München, Germany
Scaling the capacity of optical networks to meet increasing traffic demands while keeping costs and power usage low is crucial. Multi-wavelength transponders have potential as cost-efficient options, but they make network planning more complex. Additionally, the improved symbol and modulation rate adaptivity further increases the network throughput. We extend our previous network planning study for multi-wavelength transponders by considering an increased modulation rate adaptivity using probabilistic shaping. Additionally, we take reduced requirements for guard-bands of multi-wavelength transponders into account, thereby improving the spectral efficiency. We report results for planning studies on a continental as well as a national optical backbone network topology, showing the potential of multi-wavelength transponders for cost-efficient capacity scaling.

Francesco Prudenzano
Optical combining in medium infrared wavelength range and its applications
A. Annunziato, F. Anelli, A. M. Loconsole, M. C. Falconi, V. Portosi, V. V. Francione, and F. Prudenzano
Department of Electrical and Information Engineering, Politecnico di Bari, Italy
A review on the optical combining in medium infrared wavelength range is illustrated. Moreover, details on the design, fabrication and characterization of combiners based on multimode step-index fluoroindate optical fibers (InF₃) are given. The electromagnetic design of the combiner is carried out through modal investigation and the beam propagation method is exploited to evaluate the transmission efficiency. In the fabrication process, including the normalization procedure, the low melting temperature and the mechanical properties of fluoroindates are taken into account. The repeatability and absence of crystallization are verified. The experimental results agree with the simulation and pave the way for a number of applications in the mid-infrared spectral range.

Ben Puttnam
Wideband transmission in standard diameter single and multi-core fibers
B. Puttnam, R. Luis, G. Rademacher, Y. Awaji, and H. Furukawa, National Institute of Information and Communications Technology, Tokyo, Japan
We explore wideband transmission covering full S, C + L-band transmission in standard single-mode fiber and low-core count multi-core fibers. We first review progress in wideband transmission demonstrations and explore potential benefits of increased spectral efficiency in MCF transmission by exploiting reduced (IC-XT) at lower wavelengths. Finally, we describe some transmission experiments including >250 Tb/s transmission in SSMF and both 1 Pb/s transmission with 20 THz transmission bandwidth and 319 Tb/s transmitted over 3000 km in a 4-core MCF with standard cladding diameter.

Carla Raffaelli
Moving serverless computing from cloud to fog: Approaches and considerations in emerging communication scenarios
D. Borsatti, W. Cerroni, G. Davoli, G. F. Pittalà, and C. Raffaelli
DEI, University of Bologna, Italy
With the ever-increasing availability of computational power in user devices, Fog Computing has been gaining prominence and ability to successfully support the Cloud in providing many services, especially those that prioritize latency over intensive performance. In this context, lightweight service models such as serverless computing/Function-as-a-Service represent a viable candidate for relocation of the services to the Fog. The paper introduces specific challenges of the approach and discusses its valuable benefits.

Anastasiia Sheveleva
Experimental investigation of phase-space portraits of ideal four-wave mixing
A. Sheveleva¹, A. Ermolaev², P. Colman¹, J. M. Dudley², and C. Finot¹
¹Laboratoire Interdisciplinaire CARNOT de Bourgogne, Université de Bourgogne, Dijon, France
²Université de Franche-Comté, Institut FEMTO-ST, Besançon, France
Due to the growth of higher-order sidebands and to optical losses which restrict the potential interaction distance, it is notoriously challenging to experimentally observe the idealized four-wave mixing dynamics. In order to address this issue, we propose to iteratively change the phase and amplitude conditions of a signal made of three equally spaced spectral lines that is then injected into a short segment of optical fiber. Such segmented approach enables us to mimic an effective propagation over tens of kilometers – a distance that greatly exceeds the 500 m fiber in use. Our experimental study reveals the complete phase-space topology exhibiting several Fermi-Pasta-Ulam-Tsingou recurrence cycles, the existence of a stationary wave as well as the presence of a system separatrix, which marks the transition between two distinct spatiotemporal evolution regimes. When plotted on a phase portrait, the wave dynamics follows close orbits that are uniquely defined by initial conditions, hence do not intersect. By changing abruptly during propagation the control parameters, such as the average power, we demonstrate both theoretically and experimentally that it is possible to connect two states that are not initially located on the same closed trajectory. Finally, we also investigate the benefits of supervised machine learning techniques in two different ways. Firstly, we combine non-iterated measurements with a feed-forward neural network. Results demonstrate that the network can extract the key characteristics of the phase-space topology and can accurately forecast the nonlinear dynamics. Secondly, we have implemented the technics of sparse identification of nonlinear dynamics. Starting from a set of several trajectories that can be potentially affected by noise, we are able to retrieve quantitatively the governing terms in the differential equations systems.

Marco Tacca
Experimental demonstration and results of cross layer monitoring using open source network observability platform
N. Ellsworth¹, S. Troia², Tianliang Zhang¹, M. Tacca¹, G. Maier², and A. Fumagalli¹
¹University of Texas at Dallas, USA
²Politecnico di Milano, Italy
Continuous monitoring of key network elements plays a crucial role in ensuring the smooth operation and optimal performance of communication networks. By monitoring various network parameters in real-time, network administrators can detect and prevent potential issues before they lead to significant disruptions. In this paper, we propose and demonstrate results from the implementation of a cross-layer monitoring in optical transport networks using an open source network observability platform (open-NOP). We exploit open source tools as cost-effective and efficient solutions for network monitoring and management. The experiment involves using different network devices and collecting and analyzing data from various network layers, including physical, data link, network and transport layers. The results demonstrate that open-NOP provides comprehensive network visibility and enables effective cross-layer monitoring.

Emanuele Virgillito
Waveplate model based simulation of earthquake detection using SOP monitoring of IM-DD optical data channels
E. Virgillito¹, S. Straullu³, R. Bratovich², H. Awad¹, R. Proietti¹, F. M. Rodriguez², A. D’Amico¹, F. Aquilino³, A. Castoldi², R. Pastorelli², and V. Curri¹
¹Politecnico di Torino, Italy
²SM-Optics, Vimercate, Italy
³Links Foundation, Torino, Italy
Optical telecommunications networks have become pervasive to satisfy the continuously growing internet traffic demand. At the same time, there’s a huge interest in deploying a wide sensor network for in order to offer enhanced network services for environmental monitoring, such as early detection of earthquakes. In this context, there’s a large interest in using the large infrastructure deployed for telecommunications also for environmental sensing. In this paper we focus on mechanical stress induced by seismic waves detection by monitoring the state of polarization (SOP) of intensity modulated channels, still widely deployed in metro and access network. We propose a simulative tool based on the waveplate model aimed at testing if the SOP variation induced by seismic waves propagated along fiber network segments can be detected even in presence of further SOP noise induced by anthropic activities.

Tianhua Xu
Physics-informed neural network for fibre channel modelling in optical communication systems
J. Uduagbomen¹, S. Lakshminarayana¹, Zheng Liu², M. S. Leeson¹, and Tianhua Xu^1,2
¹School of Engineering University of Warwick, Coventry, UK
²School of Precision Instruments and Opto-Electronics Engineering, Tianjin University, China
Over 95% of the data traffic is carried over optical fibre communication links. The split-step Fourier method (SSFM) has been widely employed to model the evolution of optical signals along the fibre channels in optical communication systems. However, the split-step Fourier method requires very high computational resources, especially for ultra-long-haul and wideband communication systems. Meanwhile, deep learning techniques can be applied to investigate the evolution of optical signals along the fibre links, where the nonlinear Schrödinger equation (NLSE) can be solved directly using neural networks to avoid the huge complexity of the split-step Fourier simulations. In this work, we will discuss the application of neural networks in modelling the evolution of different types of optical pulses along fibre transmission channels.

Xuelin Yang
High-speed random number generation and secure key distribution using amplified spontaneous emission
Xinran Huang, Liuming Zhang, Zhi Chai, Zanwei Shen, and Xuelin Yang
State Key Laboratory of Advanced Optical Communication Systems and Networks, Shanghai Jiao Tong University, China
Amplified spontaneous emission (ASE) noise with inherent random nature is promising for true random number generator (TRNG) and secure key generation and distribution (SKGD). In this paper, a high-speed TRNG and a physical-layer SKGD scheme were proposed and demonstrated using the polarization dynamics of an ASE source. The TRNG is effectively enhanced using the two orthogonal polarization modes of ASE, and the SKGD scheme utilized the dynamical fluctuations of states of polarization (SOP) of ASE. A 16.8 Tb/s TRNG based on ASE is successfully demonstrated with spectrum slicing, and an error-free SKGD with a key generation rate (KGR) of 10.1 Gb/s is experimentally demonstrated over 10 km standard single-mode fiber (SSMF).

Mario Zitelli
Characterization of the modal distribution from linear and nonlinear mode coupling in multimode fibers
M. Zitelli, M. Ferraro, F. Mangini, and S. Wabnitz, Department of Information Engineering, Electronics and Telecommunications, Università degli Studi di Roma Sapienza, Italy
Beam mode power content is experimentally investigated in long spans of multimode graded-index fiber; two different power distribution laws are found in the weakly nonlinear regime affected by linear disorder, and in the strong nonlinear regime.

5GT invited presentations

Domenico Di Mola
Enabling customer self-driving networking experience via cloud delivered Metro cloud solution
D. Di Mola and G. Grammel, Juniper Networks
Network sustainability and scalability are key challenges for network operators while they are ramping up 5G services and cloud delivered applications. Automation and AIOps represent key enabler for self-driving network, helping with network TCO reductions and time to market. Cloud solutions must provide a robust architecture to security concerns.

Antonio Napoli
Point-to-multi-point coherent optics on data processing units (DPUs) for beyond-5G low-latency applications
F. Cugini, C. Castro, and A. Napoli, Infinera, Munich, Germany
Coherent pluggable transceivers supporting both point-to-point and point-to-multi-point optical transmissions are proposed to be encompassed within Data Processing Units (DPUs) for cost-effective converged infrastructures including packet, optical, and edge computing resources.

Marc Ruiz
Adaptive telemetry data aggregation and compression
A. El Sayed¹, M. Ruiz¹, H. Harb², and L. Velasco¹
¹Advanced Broadband Communications Center, Universitat Politècnica de Catalunya, Spain
²College of Engineering and Technology, American University of the Middle East, Kuwait
With the advent of the beyond 5G (B5G) era, high bandwidth-demanding use cases like digital twins require the continuous collection of an enormous and widely distributed amount of telemetry data, which can overwhelm the transport layer. Therefore, the reduction in such transported telemetry data is an essential objective of smart network operation. In this paper, we review and compare different methods for adaptive aggregation, compression, and redundancy elimination in telemetry data streams.

Yaping Zhang
Experimental study of a 10 Gbps narrow band DBR laser with an electroabsorption modulator for 5G smart applications
Mengxiao Li^1,2, Jianfei Gu^1,2, Yuchao Zhang^1,2, Haikun Zhang¹, and Yaping Zhang^2,3
¹University of Jinan, Jinan, Shandong, China
²Shandong Institute of Industrial Technology, Innovation Park, Jinan, Shandong, China
³OptoChip Optoelectronics Ltd, B120, Qilu Soft Park, Jinan 250000, China
It is desirable to establish an affordable smart network for various 5G applications, such as smart city, smart community, smart government, and smart education globally, which can be realized by implementing a Dense Wavelength Division Multiplexing (DWDM) 5G smart network based on a set of 10 Gbps narrow band DBR lasers integrated with electroabsorption modulators. This paper presents a thorough experimental investigation on various designs of narrow band Distributed Bragg Reflector (DBR) tunable lasers integrated with different designs of electroabsorption modulators (EAMs), in terms of material compositions and structure designs, with an objective to optimize the modulation efficiency and minimize the noise level in the device. This study has provided a cost effective base for the widely implementation of affordable smart 5G networks based on ITU-T G698.4 DWDM standard narrow band 10 Gbps DBR lasers.

6G invited presentations

Xavier Hesselbach
Intelligent network slicing in the multi-access edge computing for 6G networks
X. Hesselbach, Dept. Network Engineering, Universitat Politècnica de Catalunya, Barcelona, Spain
Multi-access Edge Computing (MEC) provides a service environment at the edge of the network where the latency it is expected to be extremely reduced and the overall performance is tuned to support cloud computing and new services. This type of network architecture is critical to deploy the next generation of pre-6G networks. The behavior must be optimized to exploit the capacity of the core optical fiber network. This paper proposes a network slicing aware intelligent queueing theory architecture for the MEC in order to optimize the performance metrics, in online and offline scenarios.

Access invited presentations

Marcus Brunner
The 6th generation fixed network (F6G): Vision and direction
M. Brunner, Huawei Technologies Switzerland AG, Zurich, Switzerland
For the European green and digital twin transition the fixed network are paramount as the foundational infrastructure. Optical communication is a cornerstone in that transition and therefore the 6th generation fixed network is the target for research and innovation in ICT. The vision of that roadmap towards F6G has various dimensions to be advanced. Since the digital transformation is touching all areas, the F6G networks need to be able to fulfil a broad set of application demands. The growth of photonics communication from the core networks towards the end-points including the edges of the network, fibre to the room, fibre to the machine, optics to the things is expected.

Nicola Calabretta
Transparent photonically interconnected edge computing networks with fast control plane
N. Calabretta, IPI-ECO Research Institute, Eindhoven University of Technology, The Netherlands
We propose and demonstrate a low and deterministic latency photonically connected edge computing network. The photonic nodes utilize SOA-based optical add/drop multiplexers and the fast control plane is implemented with an FPGA-based supervisory channel. Results show microsecond-time control, time-slotted operation and deterministic latency with nanosecond jitter and error-free multi-node communication.

Ivan Cano
FDMA in point to multipoint fibre access systems for non-residential applications
I. N. Cano, G. Caruso, G. Talli, C. Bluemm, J. Wei, S. Calabro, H. von Kirchbauer, U. Wuensche, P. Leyva, H. Rongfang, and Z. Kuo, Huawei Technologies Düsseldorf GmbH, Germany
Optical access networks are seeing growing applications for use cases beyond residential, for example in campuses and as Industry 4.0 intra-factory networks, which introduce different requirements in terms of bandwidth delivery and latency. We present an uplink access system with simultaneous transmission and detection of several users by means of frequency division multiplexing (FDM). We demonstrate a multiple uplink access system with DBPSK signals and coherent detection that targets a low and deterministic latency. We achieve Rx sensitivities of -43.5dBm, -40dBm, and -34dBm at BER of 10-3 at 2.5GBaud, 5GBaud, and 8GBaud respectively after 20km of fibre. Furthermore, we show the possibility of employing time-division multiplexing (TDM) within the frequency bands. We also present real-time services showing that the system can allow latency-sensitive and best-effort applications to share the network.

Roberto Gaudino
Experimental demonstration and scalability study of a 400 Gb/s full coherent transmission in a deployed metro-access scenario
M. Casasco¹, G. Rizzelli², A. Pagano³, R. Mercinelli³, M. Valvo³, V. Ferrero¹, and R. Gaudino¹
¹Dipartimento di Elettronica e Telecomunicazioni, Politecnico di Torino, Italy
²Links Foundation, Torino, Italy
³Telecom Italia, Torino, Italy
The challenge of next generation optical access network is to increase the capacity to 200 – 400 Gbps per wavelength even in the metro and access segments. This target may be feasible by using coherent systems based on multilevel modulation formats. The full coherent system performances, in term of receiver sensitivity, are significantly better than standard OOK receiver, obtaining power budgets that can be as high as 40 dB. In this scenario of large target power budget, optical network architecture based on the Metro and Access convergence may be attractive since the nodes at the boundary between the two segments may be simplified by using 1R regeneration (optical amplification) instead of classical 3R one. In this framework, is fundamental to study the interconnection between the power budget of the metro network and the one of the access network in order to optimize the overall optical performance, particularly if Passive Optical Network (PON) architectures are used in the access segment, due to their very stringent loss budget requirements. In this paper, we show our latest experimental results obtained on a 33-km installed metropolitan fibre link with a PM-16 QAM full coherent transmission at 50 Gbaud (400 Gbps), presented in terms of BER curves as a function of received optical power for a metro+PON optically transparent approach. In order to emulate an optical node using 1R regeneration, a wavelength selection switch (WSS) is introduced in the middle of the link to emulate a metro-access transparent connection. In the WSS, the received signal is filtered and amplified and then sent into an access network based on PON architecture. Our experimental results are focus on BER curves as a function of received optical power for different OSNR values, to derive the relation between the achievable optical path losses of the metro network and of the access network for a given target BER (1e-2).
[1] G. Rizzelli Martella, A. Nespola, S. Straullu, F. Forghieri, R. Gaudino, Scaling laws for unamplified coherent transmission in next-generation short-reach and access networks, Journal of Lightwave Technology, vol. 39, no. 18 (2021).
[2] S. J. Savory, Digital coherent optical receivers: Algorithms and subsystems, IEEE Journal of Selected Topics in Quantum Electronics, vol. 16, no. 5 (2010).
[3] K. Kikuchi, Fundamentals of coherent optical fiber communications, Journal of Lightwave Technology, vol. 34, no. 1 (2016).

Maria Medeiros
ML-based optimization of geometric constellation shaping for unamplified coherent optical systems
B. M. Oliveira¹, M. S. Neves¹, F. P. Guiomar¹, M. C. R. Medeiros², and P. P. Monteiro¹
¹Instituto de Telecomunicações and University of Aveiro, Portugal
²Department of Electrical and Computer Engineering, Univ Coimbra, Portugal
With increasingly higher data rate requirements imposed on short-reach links, coherent optical systems are expanding to shorter distances. To achieve a cost-efficient and low-complexity solution, optical amplifiers can be removed, enabling the deployment of the already standardized use of unamplified coherent links. However, the system performance is now governed by a peak power constraint, and therefore the conventional constellations become sub-optimal. We will present how an end-to-end machine learning algorithm can optimize the constellation geometry. We also show the importance of a well-suited model for the channel, by experimentally comparing the performance achieved with geometries optimized for both amplified and unamplified links.
Keywords: coherent optical communications, machine learning, unamplified links.

Antonio Napoli
Digital subcarrier based point-to-multipoint coherent transceivers for bidirectional transmission
A. Napoli, Infinera, Munich, Germany
Coherent P2MP technology can enable high-capacity bidirectional transmission for x-Haul networks. In this contribution, we review the technology, requirements, and potentiality to support next generation mobile transport networks.

Francisco Rodrigues
PIC based transceiver for access networks: package and functionalities verification towards a commercial solution
F. Rodrigues, PICadvanced SA, Ílhavo, Portugal
InP monolithic PIC design packaged towards a standard form factor transceiver level is presented, showcasing the packaging options taken and presenting the overall transceiver performance against key specifications for access networks demonstrating the commercial feasibility of PIC based transceivers for these applications.

Josep Segarra
Band evaluation of coherent udWDM-PON with paired lasers
J. Segarra, V. Sales, and J. Prat, Universitat Politècnica de Catalunya, Barcelona Spain
The development of coherent high density WDM-PONs with hundreds of channels is a promising technology to increase the spectral efficiency and to reduce the consumption per user. Nevertheless the employment of low cost lasers with limited tunability can reduce the ability to assign the channels. In this work we consider the use of non-preselected transmitter and receiver paired lasers, with a fixed distance between their wavelengths, which facilitates the bidirectional channel assignment and alignment. However, a discontinuous bandwidth configuration in neighbor up/down segments is mandatory, decreasing the laser tunability capability when it is compared to two different separated up/down bandwidths. We evaluate the channel assignment in a dynamic wavelength allocation (DWA) procedure for this case of paired lasers with bandwidth organization in up/down segmented bandwidth.

Behnam Shariati
F5G OpenLab: Enabling twin transition through ubiquitous fiber connectivity
B. Shariati, M. Balanici, P. Safari, J. Fischer, and R. Freund, Fraunhofer Heinrich Hertz Institute, Berlin, Germany
The paper introduces a new open laboratory, the F5G OpenLab, which aims at fostering the advancement of fiber-based solutions for everything. F5G OpenLab intends to aid in creating a sustainable and eco-friendly ICT industry and accelerate the digital transformation through autonomous networking solutions that are secure and trustworthy. In particular, the purpose of the F5G OpenLab is to establish an ecosystem for the validation of optical networking solutions that facilitate twin transition, provide a vendor-neutral platform for the assessment of vertical use cases, and enable the development of fiber-based solutions. It provides a platform to verify and unify next-gen networking solutions, access to early hardware and software releases, and unique testing and measurement facilities. Finally, the F5G OpenLab supports the development of blueprints for a green and digital transformation, capitalizing on the benefits of fiber technology for all industry sectors. We present its architecture as well as key features and capabilities. Moreover, we report several proof-of-concept demonstrations focused on industry 4.0 vertical use-cases.

Chris Vagionas
Multi-RAT fiber-wireless technologies towards 6G networks
C. Vagionas, Aristotle University of Thessaloniki, Greece
At the dawning of the beyond 5G era, broadband last mile connectivity is stimulating rapid developments in optical and wireless technologies that will efficiently handle the traffic generated by mobile users and demanding network applications. To this end, multiple Radio Access (multi-RAT) technologies operating at various millimeter wave (mmWave) frequencies, e.g. V-/E-/D-band are being actively pursued, in parallel with the investigation of efficient fiber wireless fronthaul schemes, e.g. Analog Radio over Fiber (ARoF) or Intermediate Frequency over Fiber (IFoF), to deliver low-complexity, broadband, last-mile connectivity. However, integrating such novel technologies in an actual mobile network infrastructure remains a challenge, as it needs to support compatibility with the network operators’ equipment. The current talk aims to present a holistic Fiber Wireless (FiWi) connectivity, demonstrating the co-existence of Analog and Digital RoF traffic along with flexible, reconfigurable point-to-multipoint connectivity to multi-RAT antenna units. Experimental results on high capacity FiWi fronthaul links operating in the V- (60 GHz) and D- (145 GHz) will be presented. Moreover, end-to-end, integrated real-time traffic and network operation will also be discussed and experimentally presented, indicating a possible technology roadmap towards multi-RAT 6G networks.

Carmen Vázquez Garcia
Performance evaluation of high data rate transmission and optically powered IoT ecosystem over SI-POF for smart home applications
F. M. A. Al-Zubaidi , D. S. Montero , P. J. Pinzón, and C. Vázquez , The Carlos III University, Madrid, Spain
In this work, we present a real time multi-Gbit/s data transmission based on SI-POF for in-home and short-range networks. Power over Fiber (PoF) solutions are also integrated with the SI-POF communication link to feed Internet of Things (IoT) nodes for smart home applications. The work presents different powering architecture, examples of low power consumption IoT nodes, power budget analysis, scalability analysis of PoF systems and its impact on data signal quality.

B5GNeO invited presentations

Morteza Ahmadian
ML-aided SOP compensation to increase key exchange rate in QKD systems
M. Ahmadian, M. Ruiz, J. Comellas, and L. Velasco, Universitat Politècnica de Catalunya, Barcelona, Spain
Secure communications have become a requirement for virtually all kind of applications. Currently, two distant parties can generate shared random secret keys by using public key cryptography. However, quantum computing represents one of the greatest threats for the finite complexity of the mathematics behind public key cryptography. In contrast, Quantum Key Distribution (QKD) relies on properties of quantum mechanics, which enables eavesdropping detection and guarantees the security of the key. Among QKD systems, polarization encoded QKD has been successfully tested in laboratory experiments and recently demonstrated in closed environments. In this paper, we propose a Machine Learning (ML) -based polarization tracking and compensation that is able to keep shared secret key exchange to high rates even under large fiber stressing events. Exhaustive results using both synthetic and experimental data show remarkable performance, which can simplify the design of both quantum transmitter and receiver, as well as enable the use of aerial optical cables, thus reducing total QKD system cost.

Sima Barzegar
Reinforcement learning for autonomous traffic flow capacity management
S. Barzegar, Universitat Politècnica de Catalunya, Barcelona, Spain
As the dynamicity of the traffic increases, the need for self-network operation becomes more evident. One of the solutions that might bring cost savings to network operators, is that of the dynamic capacity management of large packet flows, especially in the context of packet over optical networks. Machine Learning, and particularly Reinforcement Learning (RL), seem to be an enabler for autonomicity, as a result of its inherent capacity to learn from experience. In this tutorial, we introduce RL and review its application for autonomous capacity management of traffic flows.

Davide Careglio
Disaggregated delay modeling in multidomain networks
D. Careglio, M. Ruiz, and L. Velasco, CCABA, Universitat Politècnica de Catalunya, Barcelona, Spain
Accurate delay estimation is one of the enablers of future network connectivity services. If such connectivity services require isolation (slicing), such delay estimation should not be limited to a maximum value defined in the Service Level Agreement, but to a finer-grained description of the expected delay in the form of, e.g., a continuous function of the load. Obtaining accurate end-to-end (e2e) delay modeling is even more challenging in a multi-operator (Multi-AS) scenario, where the provisioning of e2e connectivity services is provided across heterogeneous multi-operator (Multi-AS or just domains) networks. In this work, we propose a collaborative environment, where each domain models intra-domain delay components of inter-domain paths and share those models with a broker system providing the e2e connectivity services. The broker, in turn, models the delay of inter-domain links based on e2e monitoring and the received intra-domain models.

Alberto Castro
Predicting loss in optical transport segments: A GNN-GRU approach for a nationwide optical network
F. Donnangelo, I. Bianchi, and A. Castro, School of Engineering, Universidad de la República, Uruguay
Optical networks play a crucial role in providing high-speed Internet and communication services. The performance and reliability of these networks are critical to ensuring the quality of the services provided to customers. Hence, predicting and preventing potential downtime in optical networks is of utmost importance. In this paper, we present a novel approach for predicting loss in optical networks. Our strategy combines Graph Neural Networks (GNNs) and Gated Recurrent Units (GRUs) to capture both spatial and temporal features of the optical network. By utilizing the GNN to capture spatial data and the GRU to detect temporal relationships, this methodology can predict the location of future problematic links and simulate the effects of traffic redistribution. We gathered and analyzed real data from a nationwide Internet Service Provider optical network to train and test the proposed algorithm. By exploiting the satisfactory results obtained from our methodology, network operators can proactively take measures to improve the network’s performance and avoid potential downtime.

Daniel Chaves
Multipath protection with RSA ordering selection optimization in elastic optical networks
H. A. Dinarte¹,², G. W. Teixeira², K. D. R. Assis³, R. C. Almeida Jr¹, and D. A. R. Chaves²
¹Federal University of Pernambuco, Recife, Brazil
²University of Pernambuco, Recife, Brazil
³Federal University of Bahia, Salvador, Brazil
To ensure protection in elastic optical networks, survivability strategies are usually implemented during routing and spectrum assignment (RSA). The order in which the RSA is performed may affect the network performance. Therefore, finding an efficient RSA policy can provide a considerable increase in network resilience by providing protection, as well as increasing the number of served connections. RSA problem is usually solved by dividing it into two sub problems, routing (R) and spectrum assignment (SA). RSA can prioritize either shortest routes over contiguous slots groups of lower indexes by solving R first and then solving SA (R-SA order), or the opposite (SA-R order). Another form to improve the network performance is by utilizing the multipath strategy during the RSA. The multipath strategy allows traffic from a single user to be split into several independent flows and then be routed across the network via different paths. In this paper, we propose a new protection RSA scheme by applying a genetic algorithm, which defines the most suitable policy between R-SA and SA-R for each source-destination node pair, and that uses multipath protection in order to provide resource optimization.
Keywords: elastic optical networks, RSA ordering, genetic algorithm, multipath protection, bandwidth squeezing.

Jaume Comellas
PILOT: A methodology for modeling the performance of packet connections
J. Comellas, M. Ruiz, and J. Velasco, Optical Communications Group, Universitat Politècnica de Catalunya, Barcelona, Spain
Network Services automation requires predictable Quality of Service (QoS) performance, measured in terms of throughput, delay and jitter, to allow making proactive decisions. QoS is typically guaranteed by overprovisioning capacity dedicated to the packet connection, which increases costs for customers and network operators, especially when the traffic generated by the users and/or the virtual functions highly varies over the time. This paper presents the PILOT methodology for modeling the performance of packet connections during commissioning testing in terms of throughput, delay and jitter. PILOT runs in a sandbox domain and constructs a scenario where an efficient traffic flow simulation environment, based on the CURSA-SQ model, is used to generate large amounts of data for Machine Learning (ML) model training and validation. The simulation scenario is tuned using real measurements of the connection obtained from a set of active probes.
Keywords: sandbox domain, performance modeling and prediction.

Mariano Devigili
Dual time and frequency domain optical layer digital twin
M. Devigili¹, M. Ruiz¹, N. Costa¹, A. Napoli², J. Pedro¹, and L. Velasco¹
¹Universitat Politècnica de Catalunya, Barcelona, Spain
²Infinera, Munich, Germany
We demonstrate a digital twin for failure detection in optical networks. Artificial neural networks-based models for optical constellation analysis enable predicting the transmitted signal in the time domain whereas analytical models are usually used to estimate their spectral evolution.

Pol González
GODAI: A distributed telemetry architecture for optical networks
P. González, L. Velasco, and M. Ruiz, Optical Communications Group, Universitat Politècnica de Catalunya, Barcelona, Spain
A distributed telemetry system is proposed with agents receiving and analyzing data before sending it to a centralized manager. Intelligent data aggregation on optical constellations telemetry largely reduces data rate without introducing significant error.

Masab Iqbal
Implementing Reliable Quantum Communication
M. Iqbal, L. Velasco, and M. Ruiz, Optical Communications Group , Universitat Politècnica de Catalunya, Barcelona, Spain
The quantum Internet is expected to provide information-theoretic security for data transmission by combining quantum and classical communication. Classical networks have well-established protocols for reliable end-to-end transmission that implicitly duplicate classical bits. However, due to the no-cloning theorem, quantum bits (qubits) cannot be copied. In this paper, we summarize our previous work on the use of a Universal Quantum Copying Machine (UQCM) to create imperfect clones. In this way, the Quantum Automatic Repeat Request (QARQ) protocol, inspired by its classical counterpart, can be developed. To investigate the viability of QARQ, a simulation platform is created that implements QARQ for quantum communication. The results explore whether its application is suitable, while maintaining enough quality of the qubit state.
Keywords: reliable quantum communication, qubit retransmission, universal quantum cloning machine.

Prasunika Khare
Evaluation of stimulated Raman scattering power profile method in multichannel optical communication
P. Khare, L. Velasco, M. Iqbal, N. Costa, J. Pedro, A. Napoli, J. Comellas, F. Arpanaei, and M. Ruiz
Universitat Politècnica de Catalunya, Barcelona, Spain
A multi-channel optical communication suffers from linear and non-linear effects. A computer model is presented to provide solution for non-dispersive Stimulated Raman scattering in WDM optical fiber system. The model can calculate the output power in optical fiber at all given wavelength range. This method also provide a Raman Crosstalk expression to evaluate the SRS effect. We found that the model is potentially reliable tool for multi -channel coherent optical communication systems.

Marc Ruiz
CURSA-SQ models for time-sensitive networking
M. Ruiz, D. Careglio, and L. Velasco, Universitat Politècnica de Catalunya, Barcelona, Spain
Considerable research and standardization efforts are being made to support time-sensitive traffic, e.g., generated by applications like Industry 4.0 and 5G fronthaul, on packet networks. This paper focuses on analyzing the impact of conveying time-sensitive traffic in operators’ networks when such traffic is mixed with best-effort traffic. In particular, extensions to a continuous G/G/1/k queue model are proposed to evaluate two different Ethernet technologies, synchronous and asynchronous, supporting time-sensitive flows in terms of their influence on the performance of best-effort traffic.

Luis Velasco
Secure optical communications based on fast cryptography
L. Velasco, M. Iqbal, and M. Ruiz, Optical Communications Group, Universitat Politècnica de Catalunya, Barcelona, Spain
Although security solutions, like Advanced Encryption Standard (AES) and ChaCha, are common at the packet layer, secure transmission at the optical layer is still not implemented. The reason is that such cryptographic methods are not fast enough to support high-speed optical transmission and might introduce significant delay. Moreover, methods for key exchange, key generation and key expansion need to be implemented on standard coherent transponders. In this paper, we summarize a secure cryptographic solution for optical connections named Light Path SECurity (LPsec), which involves fast data encryption using stream ciphers and key exchange using Diffie-Hellman (DH) protocol through the optical channel. To support encryption of high-speed data streams, a fast, general purpose Pseudo-Random Number Generator (PRNG) is used. Moreover, to make the scheme more secure against exhaustive search attacks, an additional substitution cipher is proposed. In contrast to the limited encryption speeds that standard stream ciphers can support, LPsec can support high-speed rates.

Luis Velasco
Using a SNR digital twin for failure management
L. Velasco, S. Barzegar, and M. Ruiz, Optical Communications Group, Universitat Politècnica de Catalunya, Barcelona, Spain
The development of Digital Twins to represent the optical transport network might enable multiple applications for network operation, including automation and fault management. In this work, we use GNPy as a Signal to Noise Ratio (SNR) digital twin of the optical network for failure management applications. The methodology proposed for failure management consists in comparing the QoT measured in the transponders with the one estimated using the digital twin and try to explain detected deviations as changes in the value of input parameters of the Quality of Transmission (QoT) model representing the optical devices, like noise figure (NF) in optical amplifiers (OA) and reduced Optical SNR in the Wavelength Selective Switches (WSS). By applying reverse engineering, the value of those modeling parameters can be estimated as a function of the observed QoT of the lightpaths. Experiments reveal high accuracy estimation of modeling parameters, and results obtained by simulation show large anticipation of soft-failure detection and localization, as well as accurate identification of degradations before they have a major impact on the network.

Shaoxuan Wang
The impact of 6G RAN on autonomous fixed network operation
Shaoxuan Wang, M. Ruiz, and L. Velasco, Optical Communications Group, Universitat Politècnica de Catalunya, Barcelona, Spain
The advent of 6G will revolutionize the way Radio Access Networks (RAN) will be operated. Expected massive small cell deployments and features, such as flexible and adaptive functional splitting, are expected to change not only the volume, but also the requirements of the traffic to be supported by the fixed transport network. This paper presents an insight into 6G RAN operation, focusing on how such operation will impact the autonomous operation of the fixed network.

CTS invited presentations

Jordi Casademont
Awareness information dissemination using aggregation into collective perception messages for connected vehicles
J. Marias Parella, J. Casademont, E. Llagostera, A. Pons, and E. Lopez-Aguilera, i2CAT Foundation, Barcelona, Spain, and Universitat Politècnica de Catalunya, Barcelona, Spain
The ecosystem of Cooperative Connected and Automated Mobility (CCAM) is built on the foundation of vehicles connected to everything (V2X) and enables the emergence of new and innovative cooperative traffic safety and traffic efficiency applications. These applications are based on the real-time exchange of status updates between vehicles, which are typically broadcasted periodically. The European Telecommunications Standards Institute (ETSI) has standardized various types of messages for use in Intelligent Transport Systems (ITS) applications. The Cooperative Awareness Message (CAM) contains basic information such as vehicle position, direction, and speed. The Decentralized Environmental Notification Message (DENM) is used to alert road users of detected events, such as traffic jams, slippery roads, or stationary vehicles, etc. Additionally, ETSI has released a Technical Report outlining the Collective Perception Service (CPS), which allows for the communication of detected objects, such as pedestrians and obstacles, via on-board sensors. This information is conveyed through the use of Collective Perception Messages (CPM). On the other hand, the communication protocol architecture for ITS applications includes an Access Technologies layer at the base, which is responsible for the Radio Access Technologies (RAT) used to transmit messages between vehicles (V2V) and between vehicles and infrastructure (V2I). One of the main challenges in this field is that various stakeholders are supporting different RATs, which results in scenarios where multiple radio systems must be used and integrated to enable interoperation between vehicles using different communication systems. The current situation in the field of ITS is that car manufacturers are slow to integrate V2X communication devices. Instead, they are more prone to integrate cellular communication capabilities to enable features such as emergency calls, real-time traffic updates, and infotainment for their users. To facilitate the implementation of ITS services, it would be greatly beneficial to have the ability to transmit V2X messages over cellular networks. However, in order to allow the interchange of V2X messages between vehicles using different RATs, including cellular networks, we need the support of the infrastructure side. The most feasible solution is to use Multi-access Edge Computing (MEC) connected to Road Side Units (RSUs) of different radio technologies, and to the Internet to access vehicles connected using cellular networks. This infrastructure can be used to facilitate interoperation between vehicles with different RATs and to extend the reach of relevant data by forwarding information acquired in one area to other regions. One potential solution for propagating information obtained through CAMs is to simply forward them directly, without modification. However, this approach may put a strain on network resources, particularly the cellular network which, currently, uses unicast addressing. A more efficient solution is to aggregate CAM information into CPMs, so, a single CPM can transport information from multiple CAM messages. However, this approach presents challenges such as deciding which information should be selected to be included in a CPM and how frequently new CPMs should be generated to include the latest information. Careful consideration must be given to these factors in order to avoid overloading the communication channel and diminishing the packet delivery ratio, ultimately compromising the efficiency of cooperative perception. This paper introduces an algorithm for creating and customizing CPMs using information from various CAMs. The final goal is to minimize latency and network congestion while maximizing the distribution of information to multiple regions and between different RATs via MEC servers.

Matthias Koepp
An automotive communication bus using OFDMA
M. Koepp, K. Habel, and V. Jungnickel, Fraunhofer Heinrich Hertz Institute, Berlin, Germany
Today’s automotive communication systems use baseband pulse modulation and time division or carrier sense multiple access (TDMA/CSMA). In future in-vehicle networks (IVNs), more devices need to be connected in a multipoint-to-multipoint topology. We have developed a new automotive bus system based on orthogonal frequency division multiple access (OFDMA) enabling better channel adaptation and fine-granular multi-user access. We highlight the advantages of OFDMA in automotive and industrial applications, introduce our system concept and demonstrate its feasibility by means of an FPGA-based prototype. Finally, we discuss the use of electrical and optical media.

DACINT invited presentations

Oskars Ozolins
High-baudrate silicon photonics ring resonator and Mach-Zehnder modulators for short-reach applications
O. Ozolins^1,6,7‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬, A. Ostrovskis^1,2, M. Koenigsmann³, T. Salgals^1,2, B. Krüger³, F. Pittalà³,‪ R. P. Scott⁴, H. Haisch³, H. Louchet³, A. Marinins¹, S. Spolitis^1,2, J. Porins¹, Lu Zhang⁵, R.Schatz⁶, Xianbin Yu⁵, V. Bobrovs¹, M. Gruen³, Xiaodan Pang^{1‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬,6,7}
¹Institute of Telecommunications, Riga Technical University, Latvia
²Communication Technologies Research Center, Riga Technical University, Latvia
³Keysight Technologies Deutschland GmbH, Böblingen, Germany
⁴Keysight Technologies, Inc., Santa Clara, USA
⁵College of Information Science and Electronic Engineering, Zhejiang University, and Zhejiang Lab, Hangzhou, China
⁶Department of Applied Physics, KTH Royal Institute of Technology, Stockholm, Sweden
⁷RISE Research Institutes of Sweden, Kista, Sweden
Silicon photonics (SiP) is a key enabling technology for high-baudrate communication. It is a key technology for future 800 Gbps and 1.6 Tbps solutions to meet the ever-increasing demands. The 800G pluggable multi-source agreement (MSA) suggests that intensity-modulated direct-detection (IM/DD) is the most sustainable way forward [1]. The high operational bandwidth of each transceiver component is essential. An ultra-compact SiP slow light modulator with record-high bandwidth of 110 GHz shows the potential [2]. Therefore, both multilevel pulse amplitude modulation (PAM) and on-off keying (OOK) should be considered. SiP offers excellent production yield and has a substantial role in optical interconnects. SiP ring resonator modulators (RRM) have unique advantages like a small footprint, simple driver configuration, low power consumption, and suitability for multichannel applications. On the other hand, the SiP Mach-Zehnder modulator (MZM) offers differential drive benefits. In this paper, we demonstrate SiP MZM/RRM-based transmitters to achieve highest-baudrate OOK and PAM4 signals below 6.7% overhead (OH) hard-decision forward error correction (HD-FEC) threshold of 4.5×10-3. These are characterized with [3]. We also managed to achieve high baudrate OOK, PAM4, and PAM6 signal transmission with SiP MZM and RRM over 100 meters single mode fiber (SMF).
[1] M. Spyropoulou, et al., The future of multi-terabit datacenter interconnects based on tight co-integration of photonics and electronics technologies, OFC’23, p. Tu3I.3.
[2] C. Han, et al., Ultra-compact silicon modulator with 110 GHz bandwidth, OFC’22, p. Th4C.5.
[3] Keysight Integrated Photonics Test Setup, https://www.keysight.com/us/en/products/software/pathwave-test-software/integrated-photonics-test-products.html‬‬‬

DCN invited presentations

Liam Barry
Enabling high capacity WDM transmission systems for data centre and access networking applications
M. Troncoso Costas, L. N. Venkatasubramani, A. G. Reza, M. McCarthy, C. Browning, and L. Barry
The Rince Institute, Dublin City University, Ireland
With the ever-increasing popularity of online services, such as streaming platforms, online storage and gaming, the bandwidth requirements in optical transmission systems continue to grow. This increase in transmission capacity requirements is driving the need for low-power, cost-effective and more spectrally efficient solutions in data centre (DC) interconnects and passive optical network (PON) based optical access systems. With coherent technology not expected to be introduced in DC and PONs in the short to medium term, the transition to more advanced intensity modulation with direct detection (IM/DD) modulation formats such as PAM can enable capacity increases without requiring an increase in bandwidth/sampling rate from the electronic components. However, the power budget in both DC and PON systems becomes more challenging as the baud rate and modulation format cardinality increase. To overcome power budget issues the use of integrated semiconductor optical amplifiers (SOA) in the transmission systems can provide required gain at low cost, low power consumption and small footprint. The use of an SOA to increase the power budget however introduces additional penalties coming from excess noise and nonlinear distortions including amplified spontaneous emission (ASE) and power saturation in single channel systems, in addition to four-wave mixing (FWM) and cross-gain modulation (XGM) in WDM systems. This work outlines key technologies that can enable optically amplified high capacity WDM Transmission Systems for Data Centre and Access Networking Applications, including the use of optical frequency combs, advanced DSP and probabilistic shaping.

Alberto Castro
Optical datacenter network performance prediction
F. Donnangelo and A. Castro, School of Engineering, Universidad de la República, Uruguay
With the exponential growth of data and the increasing demand for data storage and processing, optimizing the performance of datacenter networks has become a critical challenge. In this paper, we present a novel approach to tackle this challenge by focusing on predicting ToR-to-ToR communication latency in an optical datacenter network using XGBoost, a powerful and efficient machine learning algorithm. By leveraging XGBoost and utilizing tabular data describing the datacenter network configuration, our methodology offers a cutting-edge solution for improving network reconfiguration in data centers, enabling proactive network optimization and performance improvement. In our experiments, XGBoost was trained and tested on a dataset comprising network configurations and corresponding latency measurements. The results of our experiments are encouraging, showing that XGBoost can accurately predict network latency. By forecasting network latency, datacenter network operators can make informed decisions about network reconfiguration, significantly improving network performance.

Yun Chung
High-speed IM/DD system based on OTDM technique for next-generation datacenter network
Y. C. Chung, Korea Advanced Institute of Science and Technology, School of Electrical Engineering, Daejeon, Korea
We report on the novel optical-time-division-multiplexing (OTDM) technique which can double the per-wavelength data rate of the intensity-modulation/direct-detection (IM/DD) system. By using this technique, we demonstrate the transmission of a 300-Gb/s PAM8 signal with LiNbO₃ Mach-Zehnder modulators having a 3-dB bandwidth of only 17.2 GHz. We also fabricate the proposed OTDM transmitter in a silicon-photonics chip and utilize it in the same transmission experiment.

Jaume Comellas
Optical interconnection for datacenters: To switch or not to switch
J. Comellas and G. Junyent, Optical Communications Group, Universitat Politècnica de Catalunya, Barcelona, Spain
Optical interconnection is seen as a promising solution to alleviate the congestion problems inside datacenters. Previously reported studies focus solely on optical circuit switching to establish connections. In this work we compare performance of these previous schemes with a model where static optical channels are deployed. A switch architecture using only demultiplexers and couplers, is proposed for datacenter optical interconnection, and its performance is compared with that of a WSS based switch. Results obtained by simulation show that the performance of the proposed simpler interconnect approaches that of the WSS-based one when datacenter traffic profile follow normal random distributions.
Keywords: optical routing, datacenter architecture, optical interconnection.

Andrej Kos
IoT honeypot data analysis for detection of new cyber threats and insights
M. Kren, A. Kos, U. Sedlar, Faculty of Electrical Engineering, University of Ljubljana, Slovenia
Honeypots are one of the important mechanisms in cybersecurity; they represent resources that appear interesting to attackers – either computing resources or data – but are deployed with the sole purpose of studying the techniques and tools of the attackers themselves. In this paper we present a framework to collect cyber attacker data based on IoT honeypot technology that is necessary to build cyber profiles of technologies and propose a real time detection of possible new threats and important insights.

Stephan Pachnicke
Comparison of passive photonic reservoir computing architectures for signal equalization of future generation intra-DCN and mobile fronthaul systems
S. Kühl, L. E. Kruse, and S. Pachnicke, Christian-Albrechts-University of Kiel, Germany
Fiber-optic transmission systems must be evolving continuously to meet the increasing demand for bandwidth. This directly leads to more complex modulation formats and higher symbol rates being used in the future. The latter, in particular, poses a challenge for Digital Signal Processing (DSP) algorithms necessary for equalization and non-linearity mitigation of the transmitted signals, since implementations based on electric components will inevitably reach their fundamental physical limits with exponentially increasing baud rates. As an alternative, the concept of Neuromorphic Signal Processing (NSP) is being investigated. It is inspired by the information processing methods that have naturally developed in biological systems, which often operate highly parallel and energy efficient. Derived from Artificial Recurrent Neural Networks (RNNs), Reservoir Computing (RC) implements the NSP paradigm by passing the signal through a non-linear reservoir, transforming it into a higher dimensional computational space. It has been shown, that it is sufficient to classify the behavior of the reservoir with linear algorithms to recover the information carried by the signal. By implementing the reservoir itself with passive photonic components, most of the computational complexity can be shifted into the optical domain. This reduces the complexity of the required electronic DSP considerably, enabling higher data rates and lower power consumption. The architecture of the reservoir itself remains an open research topic with a variety of factors at play such as their equalization performance, physical size, power consumption, and fabrication cost. In this paper we provide a comprehensive comparison of the equalization performance of various passive photonic RC architectures operating under the same conditions for realistic optical transmission system architectures to be used in future short reach intra-Data Center Network (DCN) or mobile fronthaul systems.

Weiqiang Sun
Challenges and opportunities of a vastly distributed cloud computing infrastructure – In the context of the Dong Shu Xi Suan (DSXS) Project of China
Ruiyun Liu, Shengnan Yue, Junyi Shao, Shuai Zhang Jiawen Zhu, Baojun Chen, Weiqiang Sun, and Weisheng Hu, Shanghai Jiao Tong University, China
It has been widely recognized that placing cloud data centers near clean energy sources or in cooler environments may reduce the operational cost and carbon footprint. But when the scale of the system, in terms of the overall computing power and territorial coverage, is large, such benefits may be offset by the additional cost of moving data around and the complexity of efficiently utilizing the network and computational resources. In this short paper, we discuss the benefits and challenges of a vastly distributed cloud computing infrastructure, in the particular context of the east-west synergized cloud computing project in China, i.e., the Dong Shu Xi Suan Project (DSXS). We discuss the state of art research that are relevant to this topic, and explore the potential technological advances such a project may bring.

ESPC invited presentations

Romuald Houdré
Design and optimization of doubly resonant second harmonic generation in photonic crystal cavities based on a bound state in the continuum
Jun Wang¹, M. Clementi², J.-F. Carlin¹, A. Barone², M. Galli², D. Gerace², N. Grandjean¹, and R. Houdré¹
¹Institut de Physique, Faculté des Sciences de Base, EPFL, Lausanne, Switzerland
²Dipartimento di Fisica, Università degli Studi di Pavia, Italy
We will report on the design and optimization of the generation, in gallium nitride photonic crystal cavities, of second harmonic in the visible range achieved with a doubly resonant structure between a heterostructure cavity mode and a bound state in the continuum. We will discuss on the possibility of the reversed frequency down-conversion process.

Anna Tasolamprou
Surface states in topologically trivial and non-trivial photonic crystals
A. C. Tasolamprou, M. Kafesaki, C. M. Soukoulis, E. N. Economou, and T. Koschny
Institute of Electronic Structure and Laser, FORTH, Heraklion, Crete, Greece
Topological insulators exhibit topologically non-trivial electronic band structure, which features an electronic band gap that causes insulating behavior in the bulk while simultaneously supporting protected, unidirectional transport of electrons along their surface without any back-scattering, mostly unperturbed by local defects and impurities. In 2005 this unique electronic feature was transferred to the realm of photonics with the discovery of the quantum Hall effect analogue in photonic crystals. Topological photonics attracts such great scientific attention mainly due to the fundamental feature coming from the topological protection the unidirectional, back-scattering-free propagation of electromagnetic energy, immune to any perturbations. Here we discuss and compare the cases of topologically non-trivial and trivial surface states found at the interfaces of a photonic crystal and the free space.

Fibre Lasers invited presentations

Mario Falconi
Recent advances in mid-infrared fluoroindate fiber lasers
M. C. Falconi, A. Annunziato, F. Anelli, A. M. Loconsole, V. Portosi, V. V. Francione, and F. Prudenzano
Department of Electrical and Information Engineering, Politecnico di Bari, Italy
Fluoroindate glasses have been the subject of considerable research efforts in recent years due to their interesting properties for mid-infrared laser emission at wavelengths above 3 μm. Compared to other glasses, e.g. ZBLAN glasses, they offer a lower phonon energy and a better thermal stability and they can host dopant concentrations as high as 10 mol%. The purpose of this review is to illustrate some of the latest examples of rare-earth-doped fluoroindate fiber lasers, operating in both continuous-wave and pulsed regimes. Details about the theoretical models, the pumping schemes, the experimental setups, and the performance in terms of output power and slope efficiency are extensively discussed.

Jan Mrázek
Transparent ceramic fibers for short- and mid-infrared lasers
J. Mrázek, O. Podrazký, J. Aubrecht, I. Bartoň, Y. Baravets, and J. Proboštová
Institute of Photonics and Electronics of the Czech Academy of Sciences, Prague, Czech Republic
Fiber laser power has increased significantly over the past two decades, reaching hundreds of kilowatts. However, the traditional glass materials do not longer meet the demanding requirements that must be fulfilled to prepare high-power lasers operating in short- and mid- infrared for their limited thermal stability or high phonon energy. Transparent ceramic materials represent a promising alternative to the glass. In this contribution we demonstrate laser-assisted processing of transparent ceramic bulks and fibers emitting within the spectral range 2.0 – 2.9 μm. The samples of rare earth-doped (Er3+, Eu3+, and Ho3+) yttrium titanates Y2Ti2O7 and yttrium dioxide Y2O3 transparent ceramics were prepared by selective laser sintering of nanocrystalline powders. We studied the laser-processing conditions on the structure of the transparent ceramic samples and we evaluated the optical properties with special attention to the luminescence in the spectral range 2.0 – 2.9 μm. We tested the selective samples as active laser media in Fabry-Perrot laser set-up and we evaluated the basic laser characteristics. The further tailoring of chemical composition and processing conditions can further contribute to the preparation of novel ceramic luminophores emitting in short- and mid- infrared as a high-thermally and chemically stable alternative to conventional glass fibers allowing to extend the properties of fiber lasers.

Pavel Peterka
Thulium cross sections temperature dependence and its effect on fiber laser operation
P. Peterka et al., Institute of Photonics and Electronics, The Czech Academy of Sciences, Prague, Czech Republic

Diego Pugliese
Design, synthesis and characterization of custom Pr³⁺-doped phosphate glasses for laser operation at visible wavelengths
D. Pugliese, E. Lupica, N. G. Boetti, D. Janner, G. Perrone, M. Y. S. Sarmiento, and J. Lousteau, Politecnico di Torino, Italy
For the last few years there has been a growing interest in the development of rare-earth-doped fiber lasers operating at a visible wavelength when optically pumped at 450 nm wavelength. Such laser device could prove highly beneficial across numerous fields and in particular for biomedical applications, such as the treatment of age-related ocular diseases. Thanks to its very high solubility in laser-active rare-earth ions, outstanding thermo-mechanical properties and high chemical stability, phosphate glass represents a genuine alternative to the more traditional and employed zirconium fluoride (ZBLAN) glass as visible laser host material. We will report and discuss on the design, processing and characterization of novel Pr³⁺-doped custom phosphate glasses in the system P₂O₅-Al₂O₃-BaO-K₂O doped with Pr³⁺ ions at four distinct concentration values to conclude on the prospect of laser emission from this glass material.

François Sanchez
Optical domains in fiber lasers
Yichang Meng^1,2, A. Nady^1,3, G. Semaan¹, A. Komarov^1,4, M. Kemel¹, M. Salhi¹, and F. Sanchez¹
¹Laboratoire de Photonique d’Angers, Université d’Angers, France
²Hebei University of Science and Technology, Shijiazhuang, People’s Republic of China
³Faculty of Science, Beni-Suef University, Egypt
⁴Institute of Automation and Electrometry, Russian Academy of Sciences, Novosibirsk, Russia
Optical domains are constituted by domains of different polarization or different wavelength. In this communication we present our recent experimental and theoretical results concerning polarization and / or wavelength domains. While polarization domains usually occur in quasi-isotropic cavity, wavelength domains take place in strongly dichroic cavities. We also report the formation of polarization/color domains in which a domain is characterized by its own polarization and wavelength.

Sergey Sergeyev
Harnessing vector multipulsing soliton dynamics
S. V. Sergeyev¹, H. Kbashi¹, and C. Mou²
¹Aston Institute of Photonic Technologies, College of Engineering and Physical Sciences, Aston University, Birmingham, UK
²Key Lab of Specialty Fiber Optics and Optical Access Network, Shanghai Institute for Advanced Communication and Data Science, Joint International Research Laboratory of Specialty Fiber Optics and Advanced Communication, Shanghai University, China
We demonstrate that mode-locked fiber laser polarization dynamics is characterized by switching between orthogonal states of polarization. In this way, soliton structures such as breathers and rogue waves appear. We use injecting optical signal with a slowly evolving state of polarization to control the dwelling time nearby each state of polarization and support regular rather than random switching between the quasi-equilibrium states.

Filip Todorov
Thulium-doped optical fibers and all-fiber lasers operating in the 2-µm spectral range
F. Todorov, P. Peterka, et al., UFE, Prague, Czech Republic
Institute of Photonics and Electronics, Czech Academy of Sciences, Praha, Czech Republic
There are many applications in industry, medicine, spectroscopy and signal processing where the 2-µm lasers could benefit against other laser sources. Fiber lasers, due to their all-fiber design, are in general reliable, compact and well thermally manageable coherent light sources. Thulium- and holmium-doped fiber lasers are the first choice in 2-µm fiber laser sources. In this paper, we give an overview of our recent results in the research on thulium-doped optical fibers and fiber lasers with a brief demonstration of material processing by thulium all-fiber laser emitting in the 2-µm spectral range.

Flex-ON invited presentations

Joan Gené
Practical spectral efficiency estimation for optical networking
J. M. Gené¹, J. Perelló¹, J. Cho², and S. Spadaro¹
¹Universitat Politècnica de Catalunya, Barcelona, Spain
²Infinera Corporation, Holmdel, USA
Assigning the right spectral resources is the key to flex-grid optical networking. Finding the optimal spectral allocation is a daunting task, as there are many variables at play that make accurate network models very complex. From a fiber transmission perspective, several impairments such as amplified spontaneous emission (ASE) noise from amplifiers or nonlinear interference noise (NLIN) and crosstalk (XT) generated through transmission set a limit on spectral efficiency. From a modem or router perspective, modulation format, signal intensity, and spectral allocation affect the achievable capacity. On top of that, the network conditions are dynamic, causing the channel capacity to change over time. If one is willing to sacrifice a small fraction in efficiency, some bounds can be found to guarantee a static level of service. In this work, we present a simplified strategy that provides a good tradeoff between performance and complexity.

Eiji Oki
Performance of defragmentation approach based on route partitioning in 1+1 protected elastic optical networks
E. Oki¹ and B. C. Chatterjee²
¹Kyoto University, Japan
²South Asian University, New Delhi, India
Spectrum fragmentation suppresses spectrum usage in survivable elastic optical networks (EONs). Survivable EONs with full and quasi-1+1 protected services require an effective spectrum defragmentation approach. Full-1+1 path protection ensures dependability without disrupting traffic when the backup route cannot be reallocated. If a working path fails while its backup route is being moved, the reliability of a service that provides full-1+1 protection goes down. To defragment them, network operators must carefully study EONs with full-1+1 and quasi-1+1 protected lightpaths. In 1+1 protected EONs with full and quasi-1+1 protected services, route partitioning-based defragmentation reduces spectrum fragmentation and blocking probability. Retuning interference arises when a full-1+1 protected lightpath cannot be returned to fill up a gap created by a terminated lightpath owing to interfering from another lightpath that stops it from retuning farther. The introduced defragmentation approach minimizes this interference. A simulation study demonstrates the efficacy of the presented defragmentation approach with route partitioning.

Jordi Perelló
Evaluating the impact of the guard band width on the benefits of probabilistic constellation shaping in future flex-grid over multicore fibre optical backbone networks
J. Perelló¹, J. M. Gené¹, J. Cho2, and S. Spadaro¹
¹Universitat Politècnica de Catalunya – BarcelonaTech, Spain
²Infinera Corporation, Holmdel, USA
Probabilistic constellation shaping (PCS) has emerged as an advanced modulation technique that provides a fine-grained software-defined trade-off between achievable spectral efficiency (SE) and transmission reach to deliver optimal channel capacity at any distance. This paper quantifies the network throughput benefits resulting from adopting PCS in future Flex-Grid over multicore fibre optical backbone networks, compared to using traditional uniform modulation formats. In particular, different inter-channel guard band width configurations are accounted in our study, aiming to set guidelines on the filtering requirements at network spectrum selective switches (SSS) to take full PCS advantage in future optical backbone networks.
Keywords: optical networks, flex-grid, SDM, guard bands, probabilistic constellation shaping.

GOC invited presentations

Nicola Sambo
Energy efficiency in next-generation optical networks
N. Sambo, Scuola Superiore Sant’Anna, Istituto TeCIP, Pisa, Italy
Energy consumption in optical network infrastructures is investigated identifying energy-hungry key components and network functionalities. Solutions based on smart pluggables are presented to increase energy efficiency at the edge of the metro segment.

GOWN invited presentations

Antonio Tartaglia
Perspectives for co-packaged optics in radio access networks
A. Tartaglia, F. Cavaliere, M. Lostedt, A. Palagi, U. Parkholm, A. Tavemark, S. Stracca, A. D’Errico, S. Lessard, and M. Johansson, BNEW DNEW TP OS&FH Optical Systems, Ericsson, Genova, Italy
Co-packaged optics (CPO) is an emerging technology for providing optical interconnections with a bandwidth density of the order of Terabit/s per millimeter square. All current development and standardization efforts focus on data centers, for example to connect very high-capacity switches improving energy efficiency and footprint compared to designs based on pluggable optics. We think CPO will have an important role also in 6G networks, to meet the demand for high capacity at low energy consumption. This paper illustrates use cases and requirements for CPO natively designed for radio applications and outlines standardization and industrialization paths. HIGH-LEVEL DESCRIPTION OF THE TALK: Moore’s law cannot longer sustain the demand for higher compute bandwidth without radical innovation in the integrated circuits process, packaging and architectures. With the increase of the baud rate, traditional copper interconnects are posing increasing challenges to meet targets in energy efficiency, bandwidth, link loss and transmission distance at acceptable cost points. Solving these issues requires a new approach embracing a wide assortment of expertise such as integrated circuits design, digital signal processing, optical communications, switching and packaging. CPO captures this trend proposing an advanced integration of optics and silicon on a single packaged substrate. The cloud infrastructure is today the main market driver for CPO, first introduced in multi-terabit switches and high-performance computing units in data centers. But the exponential traffic growth expected with the introduction of the 6G mobile generation will create a similar need for high interconnect bandwidth at low energy also in the radio access network (RAN); not only in the transport network connecting radio units (RU), distributed units (DU) and central units (CU) but also for chip-to-chip interconnects in hardware-dense boards, like massive Multi-Input Multi-Output (MIMO) antenna systems, especially when moving to higher frequencies, up sub-Terahertz. Today, there is no common understanding in the industry on which are the use cases and the requirements for the use of CPO in the RAN. This holds for both silicon manufacturers and suppliers of optical transceivers: all current development and standardization efforts focus on data centers. Part of that work is also applicable to radio systems, but there are significant differences mainly related to the different deployment environment (operation at high temperature, eye-safety issues with external lasers, cabling issues over long distances, stringent synchronization and timing requirements, etc.). We will illustrate the new requirements of “CPO for RAN applications” and the technical advances made in that direction. We will also highlight the work which remains to be done to secure the creation of an open, standard-based ecosystem. We believe 6G poses the opportunity for this to happen, and for all the relevant industries to gather around one same table.

Carmen Vázquez Garcia
Reconfigurable MCF-SDM designs for 5/6G RAN and PON with optical feeding capability
F. M. A. Al-Zubaidi, R. Altuna , J. D. López-Cardona, D. S. Montero, and C. Vázquez, The Carlos III University, Madrid, Spain
We explore the use of MCF to implement an SDM optical network capable of addressing future challenges of 5/6G fronthaul architecture. The work proposes different designs that can support RAN and PON in parallel with the integration Power over Fiber (PoF) technology. Different scenarios will be presented that will be analyzed theoretically with simulation and some experiments. The analysis will show the data transmission capacity, PoF feeding capability and its impact on data signal quality.

LFSRS invited presentations

Kentaro Nishida
Super-resolution imaging of plasmonic and dielectric nanostructures by using photothermal scattering nonlinearity
K. Nishida1 and Shi-Wei Chu^1,2,3
¹Department of Physics, National Taiwan University, Taipei, Taiwan
²Molecular Imaging Center, National Taiwan University, Taipei, Taiwan
³Brain Research Center, National Tsing Hua University, Hsinchu, Taiwan
Optical scattering microscopy allows us to visualize the material structure with the advantages of label-free and contactless. Conventionally, the spatial resolution of optical microscopy was restricted to about half of the light wavelength, and the application to nanomaterial observation was challenging. In our research, we developed the techniques for super-resolution scattering imaging of plasmonic and dielectric nanostructures by efficiently utilizing their photothermal scattering nonlinearity. We discovered that plasmonic scatterings from metallic nanoparticles exhibit strong saturation at the center of the illumination focal spot, where excitation intensity is specifically high, due to the thermal increase of imaginary permittivity. By reconstructing the image with the saturated scattering signal, we obtained the high spatial resolution scattering image, reaching about λ/8 of the excitation wavelength. In addition, we recently discovered the giant nonlinearity of Mie scattering from a single silicon nanoparticle based on the thermal shift of resonant spectrum, and demonstrated the application to super-resolution imaging of silicon nanostructure.

Constantin Simovski
Accurate estimation of non-resonant far-field superresolution by a glass microparticle
C. Simovski and R. Heydarian, Aalto University, Helsinki, Finland
It has been known since 2011 that metamaterial superlenses and hyperlenses are not necessary for far-field superresolution without fluorescent labels. Optical engineers built practical imaging devices based on simple glass microspheres which grant much better spatial resolution and much higher magnification than the best known hyperlenses. However, this phenomenon was explained theoretically only in some resonant cases. We theoretically revealed a non-resonant mechanism of this imaging and have shown that the diffraction limit is beaten, because the location of a virtual image (shaped by a microsphere from the radiation of a real subwavelength dipole) is determined not by the intensity maximum of this radiation but by its intensity zero. This is so because the virtual image of the point dipole is created by the dipole moment component directed to the image center. Further, via extensive numerical simulations we revealed a new scenario of nanoimaging in which the virtual source of the imaging beam arises not in front of the sphere (as in all reported experiments) but behind it — in the space between it and the objective lens. However, in these works our estimates of the ultimate spatial resolution were heuristic (not reliable enough). In this presentation we accurately obtain optimistic and pessimistic bounds for the spatial resolution achievable in a realistic nanoimaging system (an object, a glass microparticle and a microscope). Since the point-spread function method is not applicable to hollow wave beams (and our imaging beam is namely hollow) the maximal and minimal bounds for the ultimate spatial resolution were obtained combining the back-propagation method and the COMSOL Multiphysics solver. Using the same solver, we also convincingly explain the role of the substrate in obtaining the needed radial polarization of the object. As we assumed earlier, it results from the cross-polarization effect that arises for a tiny scatterer located in a crevice between the microsphere and the substrate.

MALOC invited presentations

Sima Barzegar
Intent-based networking for zero-touch optical networking
S. Barzegar, M. Ruiz, and L. Velasco, Universitat Politècnica de Catalunya, Barcelona, Spain

Andrea Bianco
Explainable AI as a tool to improve ML models for quality of transmission estimation
A. Omran¹, H. Houssieny¹, C. Rottondi², and A. Bianco²
¹SUPSI, Lugano, Switzerland
²Politecnico di Torino, Italy
We apply an explainable artificial intelligence framework to interpret quality of transmission predictions produced by a machine learning model. Through explanations, we identify model’s behavior that hinders its generality and modify input dataset accordingly.

Stefano Biasi
Microresonator-based photonic neural network
S. Biasi and L. Pavesi, Nanoscience Laboratory, Department of Physics, University of Trento, Italy
Over the past decade, artificial intelligence has improved computing capabilities by playing an important role in applications ranging from object recognition [1,2] to playing board games [3]. The implementation of machine learning technology finds fertile ground in the field of photonics [4]. Thus, many demonstrations based on optoelectronic structures have reported state-of-the-art performance in various tasks. Integrated optics, especially silicon photonics, may be the disruptive technology [5]. Indeed, it can meet the demand for scalability of neural networks in space and time by mitigating problems related to control complexity, physical size, and power consumption. Here, we show how a silicon microresonator coupled to a bus waveguide can be used as a CMOS-compatible neuron for large-scale integration. To this end, we discuss the use of a single microresonator as a reservoir computing through the virtual node approach [6]. In addition, we show the limitations of using three microresonators as active nodes within an all-on-chip feed-forward neural network [7] and finally we demonstrate an implementation of the extreme learning machine algorithm using an array of coupled microresonators.
[1] C. Zhang and Y. Lu, Study on artificial intelligence: The state of the art and future prospects, Journal of Industrial Information Integration, vol. 23, p. 100 224, (2021).
[2] O. Russakovsky et al., ImageNet large scale visual recognition challenge, Int. J. Comput. Vis 115, 211–252 (2015).
[3] D.Silver et al. Mastering the game of go with deep neural networks and tree search, Nature 529, 484–489 (2016).
[4] N. L. Kazanskiy, M. A. Butt, and S. N. Khonina, Optical computing: Status and perspectives, Nanomaterials, vol. 12, no. 13, p. 2171, (2022).
[5] P. Xu and Z. Zhou, Silicon-based optoelectronics for general-purpose matrix computation: A review, Advanced Photonics, vol. 4, no. 4, p. 044 001, (2022).
[6] M. Borghi, S. Biasi, and L. Pavesi, Reservoir computing based on a silicon microring and time multiplexing for binary and analog operations, Scientific Reports, vol. 11, no. 1, pp. 1–12, (2021).
[7] S. Biasi, R. Franchi, D. Bazzanella, and L. Pavesi, On the effect of the thermal cross-talk in a photonic feed-forward neural network based on silicon microresonators, Frontiers in Physics, vol. 10, p. 1 093 191, (2022).

Octavia Dobre
Machine learning-based approach for nonlinearity compensation in high baud rate subcarrier multiplexing (SCM) systems
W. S. Saif¹, S. K. O. Soman², O. A. Dobre¹, D. Chang³, and C. Li³
¹Memorial University, Canada
²Ulster University, UK
³Huawei Technologies, Canada
In this paper, for the first time in the literature, we investigate the potential of applying machine learning (ML) techniques for nonlinearity compensation in high-speed subcarrier multiplexing (SCM) systems. Our proposed method aims to effectively deal with the effects of both self-subcarrier and cross-subcarrier nonlinearities in a 64-quadrature amplitude modulation dual-polarization system with 120 Gbaud transmission. The performance of the proposed approach is evaluated and discussed in comparison with non-ML approaches in the literature. The results of this study demonstrate the potential of using ML techniques to improve the performance of SCM systems and to make them suitable for real-world implementation. We envisage that our results will initiate further research on applying ML techniques in SCM systems for high baud rate systems.

Georgios Ellinas
ML-aided traffic-driven service provisioning in elastic optical networks
H. Maryam, T. Panayiotou, and G. Ellinas
Department of Electrical and Computer Engineering School of Engineering, University of Cyprus, Nicosia, Cyprus
In this work, the capabilities of an encoder-decoder learning framework are leveraged to accurate predict multi-step ahead traffic over a long future horizon (i.e., for several planning intervals ahead). To effectively exploit this information, a traffic-driven service (re)provisioning algorithm is developed aiming at minimizing undesired service disruptions while maintaining service overprovisioning at desired levels.

Mariana Ramos
Machine learning-based polarization drift compensation for high speed DV-QKD homodyne receiver
M. F. Ramos, E. Gutmann, and H. Hübel, Austrian Institute of Technology, Wien, Austria
Discrete variables quantum key distribution (DV-QKD), namely the BB84 protocol, benefits from being very attractive for highly secure communications. However, current detection schemes rely on the use of InGaAs SPDAs, which limits not only its use in room temperature environment, but also high secure communication rates. A possible approach is the use of coherent homodyne detection schemes for polarization encoding based DV-QKD combined with post-selection techniques to obtain discrete outcomes. In order to enable the deployment of polarization encoding DV-QKD over standard single mode optical fiber based high speed networks, the polarization drift suffered due to birefringence over the channel must be actively compensated in order to keep the error rate due to system misalignments below the acceptable threshold. In this work, we use a machine learning (ML) polarization tracking and compensation algorithm combined with a coherent homodyne receiver, thus allowing the deployment of high-speed polarization encoding based DV-QKD in standard optical fibers. The ML-algorithm uses a training set to anticipate the required rotations considering a certain installation scenario and keep the error rate below the desired threshold during the secure key exchange. In this way, the overhead to polarization monitoring is avoided during key exchange since no control signals are required.

Abraham Sotomayor
A comparison of machine learning techniques for fiber non-linearity compensation: Dense neural network vs. learned digital backpropagation
A. Sotomayor¹, E. Pincemin¹, V. Choqueuse², and M. Morvan³
¹Orange Labs, Lannion, France
²ENIB, Brest, France
³IMT Atlantique, France
In this paper, we compare the respective benefits and drawbacks of a Dense Neural Network (DNN) and the physical-based Machine Learning model called Learned Digital Backpropagation (LDBP), which has been proposed in the literature, for fiber non-linear impairments (NLI) compensation in uncompensated coherent transmission systems. Both methods are applied numerically in identical conditions to a single-channel 200Gb/s 16QAM system along multiple spans of 100 km of standard single-mode fiber (SSMF). The results show better performance for the LDBP, even at 1 step/span, than the DNN trained with optimized hyperparameters. Moreover, because the LDBP is a straightforward method without the need for a sophisticated optimization of hyperparameters, it becomes simple to achieve a lower computational complexity than the DNN by reducing the size of linear layers into the LDBP (with a minor BER penalty).

Huy Quang Tran
Integration of ML pipeline in transport network management as code for RMSA optimization in EONs
H. Q. Tran, J. Errea, V.-Q. Pham, D. Verchere, and D. Zeghlache
NSSR Lab, Bell Labs Core Research, Paris-Saclay, France
The emerge of 5G and upcoming 6G traffic requires advanced mechanisms to control optical network infrastructure and manage spectrum resource. We applied the Optical Transport Network Management as Code (OTNMaC) approach to automate the cloud-native control functions deployment for infrastructure management. Additionally, ML-aided Routing, Modulation and Spectrum Allocation (RMSA) algorithms are important to optimize spectrum resource given the dynamicity of service requests in Elastic Optical Networks (EONs). Thus, a ML pipeline is introduced to facilitate the creation of ML-aided RMSA models. Moreover, the requested bandwidth distribution of the traffic matrix may vary at a certain time which leads to a data drift. This effect degrades the accuracy of the ML model. For that reason, we propose the integration of ML pipeline in OTNMaC to provide an adaptation mechanism to automate RMSA models deployment in network infrastructure control and resource management for EONs.

Xu Wang
Machine learning assisted underwater wireless optical communication
Xu Wang, Heriot Watt University, Edinburgh, UK
Underwater wireless optical communication (UWOC) provides high transmission data rate, high security, and low latency communication to link the nodes in underwater sensing network. The main change for an UWOC system is the large absorption and scattering losses in the water that reduces the received optical signal-to-noise ratio (OSNR), thus limits the transmission distance. Advanced signal processing technologies are hereby essential in UWOC systems to improve the transmission distance. In this work, we have applied the Deep Echo State Network (DeepESN) in high-speed UWOC system to assist signal processing for both PAM and QAM-OFDM signals. We have experimentally verified the effectiveness of DeepESN in UWOC systems and demonstrated over 40.5 meters error-free underwater transmission with 100-167 Mbps data-rate.

MOF invited presentations

Tijmen Euser
Hollow-core photonic crystal fibre microreactors for photocatalysis
T. Euser, Nanophotonics Centre, Cavendish Laboratory, University of Cambridge, UK
Our team uses optofluidic hollow-core optical fibres, connected to microfluidic coupling cells, to monitor photocatalytic reactions in systems that combine molecular catalysts with particulate light absorbers. Our recent work focuses on molecular catalysts combined with carbon-nanodots. Carbon nanodots are one of the most promising light-absorber materials due to their unique scalability, biocompatibility, water solubility, and stable optical properties. Key to improving their performance in solar catalysis are charge-transfer processes. I will show how these processes can be investigated through fibre-enhanced absorption-, fluorescence-, and Raman spectroscopy. I will also discuss how higher-order modes can be excited in HC-PCFs, with the aim to selectively probe surface- and bulk processes within microreactors.

Peter Mosley
Quantum frequency conversion in photonic crystal fibre for universal wavelength interfaces
P. J. Mosley, Centre for Photonics and Photonic Materials, Department of Physics, University of Bath, UK
In order to scale up quantum networks it is essential to ensure wavelength compatibility between photons emitted by information-processing nodes. Bragg-scattering four-wave mixing in photonic crystal fibre (PCF) provides a means to convert single photons between pairs of wavelength bands separated by a frequency shift controlled by the detuning of two pump fields. However, typically a different PCF is required for phase matched conversion of each particular pair of source and target wavelength, and the conversion efficiency drops rapidly if another source wavelength differs by only a few nanometres. In this talk, we discuss how careful design of the PCF dispersion enables frequency conversion to the telecoms C-band of photons from anywhere within an ultra-broad range of source wavelengths spanning hundreds of nanometres. We present recent experimental results demonstrating the implementation of this type of universal quantum frequency conversion interface [1]. We show that our device can convert heralded single photons at 1551 nm to any wavelength between 1226 – 1408 nm and we discuss ongoing efforts to extend this span even further by reducing noise generated during the conversion process.
[1] Bonsma-Fisher et al., Phys. Rev. Lett. 129, 203603 (2022).

Radan Slavik
Stable latency (hollow core) optical fibres
R. Slavík, Zitong Feng, F. Poletti, and D. J. Richardson, Optoelectronics Research Centre, University of Southampton, UK
Light propagating through an optical fibre changes its group delay due to ambient temperature variations. This is detrimental in applications that are time-sensitive, including modern and next-generation telecom networks and infrastructures such as data centres. We review strategies how to reduce this effect and in particular how the emerging hollow core optical fibres can address this impairment.

MOON invited presentations

Andrea Fumagalli
Accurate representation of signal spectra in the optical network emulation (ONE) engine
A. Gomathinayakam Latha¹, M. R. Rahim¹, Tianliang Zhang¹, R. Hui², and A. Fumagalli¹
¹OpNeAR Lab, The University of Texas at Dallas, Richardson, USA
²University of Kansas, Lawrence, USA
The Optical Network Emulation (ONE) engine is a software tool that offers students the opportunity to learn how to control and operate open optical (wavelength division multiplexing) networks, such as those based on the Open ROADM MSA standards. This paper describes multiple modeling techniques that are implemented in ONE to represent the signal spectra at any link/fiber section of the emulated transport network. These techniques make use of various polynomial fitting and deconvolution computation methods.

MWP invited presentations

Tibor Berceli
Optical modulation methods for transmission of OFDM wireless signals
T. Berceli, Budapest University of Technology and Economics, Hungary
The next generation mobile communication systems require new modulation methods to achieve high transmission capacity with low distortion. The signal transmission in the mobile network is strongly affected by frequency selective fading. The OFDM modulation can counterbalance that problem. However, the OFDM modulation method is sensitive to the nonlinearity of the transmission channel. In this paper several optical modulators are investigated transmitting OFDM wireless signals with high bit rate. By evaluating our investigation results optimum modulator types with optimum operation points can be determined for specific applications.

Robert Minasian
Integrated microwave photonic signal processing and sensing
R. Minasian and Xiaoke Yi, The University of Sydney, Australia
Integrated microwave photonic signal processing offers a new powerful paradigm due to its inherent advantages including wide bandwidth and immunity to electromagnetic interference. Microwave photonics, which merges the worlds of RF and photonics, shows strong potential as a key enabling technology to provide new signal processing systems and sensors that can overcome inherent electronic limitations. Currently there is a significant global drive to achieve integration of photonic signal processors on silicon platforms, especially since this leverages the CMOS fabrication technology to enable boosting the performance of future systems performing communications and sensing with the potential for implementing high bandwidth, fast and complex functionalities. Advances in silicon photonics integrated signal processing are presented. These include dense optical integration techniques for LIDAR on-a-chip systems, widely tunable microwave photonic filters, compact nanophotonic signal processors and high-resolution integrated sensors. These photonic processors herald new capabilities for achieving high-performance signal processing.

Diego Perez-Galacho
Linearization of optical modulators for microwave photonics links using side band processing
L. Torrijos-Morán¹, C. Catalá-Lahoz¹, I. Belio-Apaolaza¹, Li Xu², Wang Tianxiang², D. Pérez-López³, and D. Perez-Galacho^1,4
¹ITEAM research institute, Universitat Politècnica de València, Spain
²Central Research Institute, Huwaei Co. LTD.
³iPronics Programmable Photonics S.L.
⁴Telecommunication Research Institute (TELMA), Universidad de Málaga, Spain
Microwave Photonics (MWP) has been attracting special attention in the las few decades as the best suited technology for transport, generate, process and measure RF signals. Exploiting the advantages of the optical domain such as abundant capacity, low propagation loss and better size weight and power budget, MWP is expected to play a key role in the future RF systems. However, nonlinear distortion arises as the main limitation for the use of MWP systems. In this sense the optical modulator is a key component, as it strongly determines the distortion experienced by the transmitted radio signal. In this work, we will present our recent advances on linearization of optical modulators using the side band processing technique.

Claudio Porzi
Silicon photonics for millimeter-wave band signal generation
C. Porzi¹, A. Malacarne², P. Ghelfi², and A. Bogoni^1,2
¹TeCIP Institute, Scuola Superiore Sant’Anna, Pisa, Italy
²Photonic Networks and Technologies National Laboratory, CNIT, Pisa, Italy
By providing large bandwidth and supporting efficient frequency re-use, the millimeter (mm-) wave band enables low-latency high-capacity wireless communications in 5G and 6G radio access/backhaul networks. Optical heterodyning of two laser carriers in a high-speed photodiode is a convenient approach for generating radio waveforms up to the (sub)THz range. However, in order to increase the stability of the operation, reduce the dimensions and power consumption, and simultaneously breaking down the fabrication costs of the subsystem, photonic integration represents a promising viable solution. We report of recent advancements in our approach for realizing ultra-compact and broadband photonics-based RF processors in silicon on insulator (SOI) technology for mm-wave clock signal distribution, high data rate transceivers, opto-electronic oscillators, and microwave photonics filters. Developments of fully packaged solutions matching the requirements for field trials and practical application scenarios are also discussed.

Chris Roeloffzen
Integrated microwave photonics: A chip platform by hybrid integration of InP and SiN TriPleX
C. Roeloffzen, LioniX International, Enschede, the Netherlands
Integrated microwave photonics (IMWP) is a novel field in which the fast-paced progress in integrated optics is harnessed to provide breakthrough performances in well-established microwave photonic processing functions, which are traditionally realized using discrete optoelectronic components. A field where IMWP is expected to have a strong impact is the one of phased array antennas. Such arrays offer a number of attractive characteristics, including a conformal array profile, broadband beamforming (beam shaping and beam steering) and interference nulling. This, however, is very challenging to achieve using only electronics processing. For this reason, the last few years, an increasing amount of effort has been directed to the development of our hybrid chip platform where Si₃N₄-based-TriPleX and InP optical waveguides are combined to enable broadband and high frequency radio signal processing in the optical domain including conversion.

Zeev Zalevsky
Microwave-based remote bio-sensing behind walls
O. Meshulam¹, N. Ozana¹, D. Scheffer², S. Zach³, and Z. Zalevsky¹
¹Bar-Ilan University, Ramat-Gan, Israel
²IARD – Sensing Solutions Ltd., Kibbutz Yagur, Israel
³10 Nachum st., Kfar Saba, Israel
In this paper a novel method for microwave based remote sensing of vital signs behind walls is presented. The method is based on temporal spatial analysis of back scattered microwave signals. The use of non-optical electromagnetic radiation enables monitoring from larger distances and behind objects in contrast to similar concepts in optics. Further, such use of non-optical radiation omits the need for direct line of sight between the monitoring system and the target and enables monitoring through walls or other barriers. Micro vibrations due to breathing and heart pulsation affect the reflection of microwaves and cause the self-interference random patterns (i.e. speckle patterns) to vary in time and space. By using this approach, the temporal change of the speckle patterns due to changes in vital signs can be tracked behind walls. In this paper we present a system in WiFi frequencies band consists of radio-frequency (RF) transmitters and RF receivers to detect single or multiple breathing or non-breathing human subjects, behind different type of walls. The sensing is also obtained from distances of tens of meters away from the inspected target. The results showed that the system was able to distinguish between breathing states, to determine the vibration frequency of heartbeats, and to distinguish between subjects’ vital signs in few cases.
Keywords: speckle patterns, antennas, microwaves, waves scattering, bio-sensing, remote-sensing.

NAON invited presentations

Sylwester Latkowski
Next-generation photonic integration technologies for high-demand communication networks
S. Latkowski, K. Panina, Yuqing Jiao, J. van der Tol, and K. Williams
Institute for Photonic Integration, Eindhoven University of Technology, The Netherlands
Optical and terrestrial networks are subject to everlasting strive for reduced cost, size, weight, and power consumption along with continuous demand to increase data bandwidth. For all of these to be fulfilled high degree of parallelism at extreme line rates is necessary. Such can be achieved with the use of integrated photonics. Current advances in next-generation photonic integration developed at the Eindhoven University of Technology provide an unprecedented density of integration. This no-compromise monolithic integration technology offers a fully comprehensive set of active and passive functions including detection, amplification, and lasers that can be combined with nanophotonics on a chip level. This next-generation technology is supported with an open-access PDK, and is currently accessible via JePPIX.

Radu Malureanu
Investigation of material properties for use in UV metasurfaces
L. Beliaev, M. H. Jakobsen, A. Lavrinenko, and R. Malureanu
Technical University of Denmark, Department of Photonics Engineering, Lyngby, Denmark
The conventional use of UV light – light between the wavelengths 200 and 400nm – is limited due to difficulties in controlling its properties, but it has huge potential for applications, particularly in medicine (pharmacology, phototherapy and sanitation) and nanotechnology (high-resolution lithography). Metasurfaces (MSs) are structured surfaces with a wide range of specific functionalities, from standard ones like lenses and polarisers to more complex ones, including beam shaping, beam splitting and light modulation. They are used in a broad wavelength range, starting from visible and ending in the radio range, where they are generally known as frequency-selective surfaces. The main bottleneck in developing dielectric MSs for UV light is that there are limited materials available. The situation is similar to the one in plasmonics research several years ago when a massive effort was aimed at finding alternative plasmonic materials. Most conventional dielectrics for visible and near-infrared optics are extremely lossy in the UV range, making them unsuitable for the purpose. In this paper, we will present an initial investigation of the properties of several materials we have identified that have the potential to be used in fabricating UV MSs. We will discuss the various optical properties but also asses their feasibility from a nanofabrication point of view.

Ana Quirce
Quantum random number generation using polarization switching in gain-switched VCSELs: Experiments and theory
M. Valle-Miñón¹, A. Quirce¹, A. Valle¹, and J. Gutiérrez²
¹Instituto de Física de Cantabria, Universidad de Cantabria, Santander, Spain
²Departamento de Matemática Aplicada y Ciencias de la Computación, Universidad de Cantabria, Santander, Spain
We have experimentally and theoretically demonstrated that the random excitation of the linear orthogonal polarization modes of a gain-switched vertical-cavity surface-emitting laser (VCSEL) can be used for quantum random number generation. Our VCSEL presents polarization switching under continuous wave operation. Adjusting the modulation conditions and sampling times, both polarization modes of the VCSEL can be excited with equal probability. Random bits are obtained comparing the two orthogonal polarized signals at a sampling time. The random bits obtained fully pass the National Institute of Standards and Technology (NIST) statistical tests. Experimental and theoretical results are in good qualitative agreement.
Keywords: VCSELs, gain switching, polarization switching, quantum random number generation.

Anna Sitek
Low-energy electronic states in tubular wires
A. Sitek¹ and A. Manolescu²
¹Institute of Theoretical Physics, Wroclaw University of Science and Technology, Poland
²Department of Engineering, Reykjavik University, Iceland
We present a theoretical study of electrons confined in core-shell nanowires of different material and geometry. These radial heterostructures have attracted considerable attention due to their unique and controllable properties which render them possible building blocks of many quantum nanodevices. In this presentation we study how cross-section geometry and material parameters determine the low-energy levels and the corresponding localization of electrons confined in prismatic shells. In particular, we specify conditions allowing to obtain a well-separated group of corner states. We also show how spin-orbit interaction affects the energy levels. Core-shell nanowires are usually grown vertically and, due to the crystallographic structure, have polygonal cross sections, most commonly hexagonal, but triangular, and rectangular systems have also been obtained. Moreover, recently structures combining two polygons in one cross section, such as triangular shells grown on hexagonal cores, became technologically feasible [1]. Appropriate band alignment or core etching allows to obtain conductive shells. The polygonal cross section of such shells induces non-uniform electron localization along the wire circumference. In particular, in the corner areas effective quantum wells are formed which attract low energy electrons. This results in electron accumulation in corner areas and formation of conductive channels along the sharp edges, i.e. one structure may contain a few 1D wires. The corner states can be energetically separated from higher, corner or side states, by a gap which may considerably exceed the room-temperature energy, and thus such states provide a robust subspace [2]. The electron localization is very sensitive to imperfections which are inevitably present in realistic structures. If one facet of the shell is considerably thicker than the other ones, then the corner localization is destroyed and the ground state is localized on the thickest facet which becomes the only conductive channel in the structure [3]. Spin-orbit interaction has recently been studied in prismatic wires [4], but not much is known about its role in prismatic tubular systems. In this presentation we show how spin-orbit interaction affects the energies of electrons confined in the outer regions of core-shell wires with possible consequences on the optical absorption.
[1] D. J. O. Göransson, et al., Appl. Phys. Lett. 114, 053108 (2019).
[2] A. Sitek, et al., Phys. Rev. B 91, 235429 (2015).
[3] M. M. Sonner, A. Sitek, et al., Nano Lett. 19, 3336 (2019).
[4]P. Wójcik et al., Phys. Rev. B 97, 165401 (2018); Phys. Rev. B 103, 085434 (2021).

NetOrch invited presentations

Vincenzo Eramo
Neural graphs: An effective solution for the resource allocation in NFV sites interconnected by elastic optical networks
V. Eramo, F.G. Lavacca, F. Valente, V. Filippetti, A. Rosato, A. Verdone, and M. Panella
DIET, Sapienza University of Rome, Italy
The paper proposes and investigates neural graph-based solution for the prediction of the processing capacities needed by the Virtual Network Function Instances in a Network Function Virtualization environment. The proposed solution is centralized and performed by the Orchestrator which: i) acquires the processing capacity values measured by the Virtual Network Function Manager; ii) builds neural graphs each one relative to a measure period and where each node of a graph represents a VNFI and it is labelled with the measured processing capacity of that VNFI; iii) evaluates the prediction of the processing capacities needed by each VNFI node by means of spatial and temporal convolution operations that allow for a capture of spatial and temporal correlations of the processing capacities required by the VNFIs. Instead of applying regular convolutional and recurrent units, we formulate the problem on graphs and build the model with complete convolutional structures, which enable much faster training speed with fewer parameters.

Salvatore Spadaro
Control and orchestration solutions for end-to-end time sensitive services in future 6G networks
S. Spadaro, F. Agraz, and A. Pagès Cruz, Universitat Politècnica de Catalunya, Barcelona, Spain
The provisioning of time sensitive end-to-end services in future 6G networks imposes multiple technical challenges, spanning from the data plane to the control and orchestration planes. In particular, the automation of the provisioning and maintenance of connectivity services with deterministic constraints over multiple technology/administrative domains requires Control and Orchestration solutions able to assure the strict time service requirements. In line with that, the paper investigates the main requirements imposed to the Control and Orchestration planes and it also shows potential enabling architectures for end-to-end guarantees.
Keywords: time sensitive networks, SDN, control and orchestration.

NOA invited presentations

Helene Carrere
Supporting data traffic growth with low cost amplification solutions
C. Cruz^1,2, Q. Hochart^1,2, A. Wilk², O. Delorme², R. S. Joshya¹, A. Balocchi¹, N. Vaissière², J. Decobert², C. Calo², and H. Carrere¹
¹Laboratoire de Physique et Chmie des Nano-Objets, Université de Toulouse, France
²III-V Lab, Palaiseau, France
Global telecommunication networks based on optical fiber technology are evolving constantly. The near-exponential traffic growth of intra- and inter-data center interconnects and metropolitan networks, in particular, brings increasing challenges for the development of new low-cost and energy-efficient solutions to support bandwidth demand. Dense Wavelength Division Multiplexing solutions, capable of leveraging already existing infrastructures and potentially upscaling the existing networks by exploiting multiple optical fiber bandwidths, are being considered by network operators as an attractive way to extend the optical bandwidth of systems at a lower cost. In this work, we present the versatility of InP semiconductor optical amplifiers in the low-loss window of optical fibers. We review solutions for broadband amplification in the O, C and L bands of optical fiber transmission, and extend the study to the S band. Finally, we investigate the impact of the choices of materials and of the device geometries on their performances.

Juan Diego Ania-Castañon
Pulsed ultra-long ultrafast ring fiber oscillators
J. D. Ania-Castañón¹, I. Cáceres Pablo¹, F. Gallazzi², and P. Corredera¹
¹Instituto de Óptica “Daza de Valdés”, IO-CSIC, Madrid, Spain
²Tampere University, Finland
In this talk we will review the state of the art on the topic of ultra-long passively mode-locked femtosecond pulse fiber oscillators. This new fiber laser architecture relies on the use of polarization-insensitive InN-based semiconductor saturable absorber mirrors (SESAMs) and the careful management of nonlinearities in multi-kilometric fibre rings with Erbium Doped Fiber Amplifier (EDFA)-based amplification. These new sources are capable of supporting the stable generation of soliton-like pulses with durations below 200 fs, overcoming previously assumed limitations to pulse duration in ultra-long lasers, and reach ultra-low repetition rates as low as a few tens of kHz with the assistance of Raman amplification. The unique characteristics of this new family of ultrafast fiber oscillators make them suitable for a broad range of potential

Vladimir Gordienko
Fibre optic parametric amplifiers for communications
V. Gordienko, C. Gaur, F. Bessin, and N. J. Doran, Aston Institute of Photonic Technologies, Aston University, Birmingham, UK
We present our recent achievements with polarisation-insensitive fibre optical parametric amplifiers (PI-FOPAs) for optical communications. We have demonstrated a robust fully automated (black-box) PI-FOPA operation in the C and L bands simultaneously with gain of ~20dB and output power over 23dBm when amplifying polarisation-multiplexed WDM QAM signals and a bursty traffic. Additionally, we have demonstrated a PI-FOPA to amplify WDM signals in the S band and across a continuous bandwidth of 40nm. Finally, we have demonstrated a power budget improvement of a transient-sensitive link by up to 8 dB when employing a PI-FOPA with noise figure of ~6 dB as a drop-in replacement of an EDFA.

Boris Lembrikov
Optical phase conjugation (OPC) in a Silicon-Smectic A liquid Crystal (SALC) optical waveguide
B. I. Lembrikov, D. Ianetz, and Y. Ben-Ezra, Department of Electrical Engineering, Holon Institute of Technology, Israel
Phase conjugation is the process in which the phase of the output wave is complex conjugate to the phase of an input wave [1]. The phase conjugation may occur in such nonlinear optical processes as difference-frequency generation, parametric amplification, and four-wave mixing (FWM) [1]. Optical phase conjugation (OPC) can be used in order to correct aberrations caused by the phase distortion of the input wave and to compensate for nonlinear phase noise [1], [2]. Silicon based waveguide (WG) devices are used in ultrahigh-speed optical signal processing up to 1.28 Tb/s [3]. FWM takes place in such WG structures utilizing the materials with the third-order optical nonlinearity [3]. In particular, optical WGs based on liquid crystals (LCs) can be implemented on a Si platform [4]-[6]. LCs are characterized by large birefringence, easy susceptibility to external field perturbation, and large optical nonlinearity [4]. Nematic LCs (NLCs) with the orientational long-range order have been mainly used and investigated theoretically and experimentally [4]-[6]. Smectic A LCs (SALCs) characterized by a layered structure and a positional long-range order can be also used in nonlinear optical signal processing due to the low scattering losses [4], [7]. Nonlinear optical two-wave mixing in a Silicon-SALC optical waveguide had been investigated theoretically in detail [8], [9]. OPC caused by FWM in the bulk SALC has been studied theoretically [10], [11]. In this work, we studied theoretically OPC caused by FWM in Si-SALC optical WG. We solved simultaneously the Maxwell equations for the optical modes propagating in the Si-SALC WG and the hydrodynamic equations for smectic layer displacement. It is shown that the optical phase conjugation of the WG modes is possible when the input WG mode interacts with the smectic layer displacement dynamic grating created by two coupled pumping WG modes. We evaluated the smectic layer displacement dynamic grating caused by the interference of four coupled WG modes, the nonlinear polarization in the Si-SALC optical WG created by the WG interaction with the smectic layer displacement dynamic grating, and the slowly varying amplitude (SVA) of the phase-conjugate WG mode.
Keywords: optical phase conjugation (OPC), four-wave mixing (FWM), nonlinear optics, optical waveguide, smectic A liquid crystal (SALC), dynamic grating.
[1] Y. R Shen, The Principles of Nonlinear Optics, Wiley, Hoboken, New Jersey, USA, 2003.
[2] S. L. Jansen, D. van den Borne, B. Spinnler, S. Calabrò, H. Suche, P.M. Krummrich, W. Sohler, G-D. Khoe, and H. de Waardt, Optical phase conjugation for ultra-long-haul phase-shift-keyed transmission, Journal of Lightwave Technology, vol. 24, no. 1, Jan. 2006, pp. 54-64.
[3] A. E. Willner, O. F. Yilmaz, Jian Wang, Xiaoxia Wu, A. Bogoni, Lin Zhang, S. R. Nuccio. Optically efficient nonlinear signal processing. IEEE Journal of Selected Topics in Quantum Electronics, Vol. 17, No.2, March-April 2011, pp. 320-332.
[4] I.-C. Khoo, Liquid Crystals,. 2nd ed. Wiley, Hoboken, New Jersey, USA, 2007.
[5] D. C. Zografopoulos, R. Asquini, E.E. Kriezis, A. d’Alessandro, R. Beccherelli, Guided-wave liquid crystal photonics, Lab on a Chip, vol. 12, 3598-3610, 2012.
[6] S. Obayya, M. F. O. Hamid, N. F. F. Areed, Computational Liquid Crystal Photonics, Wiley, UK, 2016.
[7] T. G. Giallorenzi, J.A. Weiss, J.P. Sheridan. Light scattering from smectic liquid-crystal waveguides. Journal of Applied Physics, Vol. 47, No. 5, May 1976, pp. 1820-1826.
[8] B. I. Lembrikov, D. Ianetz, Y. Ben-Ezra, Nonlinear optical phenomena in Silicon-Smectic A Liquid Crystal (SALC) waveguiding structures, 20th Int’l. Conf. on Transparent Optical Networks (ICTON 2018), Bucharest, Romania, 1-5 July 2018, p. Mo.D4.1.
[9] B. I. Lembrikov, D. Ianetz, Y. Ben-Ezra, Nonlinear optical phenomena in a Silicon-Smectic A Liquid Crystal (SALC) waveguide, Materials, 12, 2086, June 2019, pp. 1-17.
[10] G. F. Kventsel and B. I. Lembrikov, The four-wave mixing and the hydrodynamic excitations in Smectic A Liquid Crystals, Molecular Crystals and Liquid Crystals, 262, pp. 591-627, 1995.
[11] B. I. Lembrikov, D. Ianetz, Y. Ben-Ezra, Nonlinear optical phenomena in Smectic A Liquid Crystals, in: Liquid Crystals – Recent Advancements in Fundamental and Device Technologies, Ed. P. K. Choudhury, IntechOpen, Croatia, 2018, pp. 131-157.

Novel Glasses invited presentations

Ioannis Konidakis
Post-melting encapsulation for the development of advanced composite glasses
I. Konidakis and E. Stratakis, IESL-FORTH, Heraklion, Greece
Inorganic oxide glasses offer an outstanding platform for the development of transparent materials, architectures, and coatings with unique optoelectronic, optical, and photonic features. A recent approach in this field towards advancing applications potential consists of the incorporation of functional materials like perovskite nanocrystals (PNCs), two-dimensional (2D) materials, and metallic nanoparticles (NPs), within various types of glass matrices [1]. However, there are several limitations on the fabrication routes regarding the feasible growth and positioning of these materials within glasses. The main one emerges from the necessity of typical high temperature melting protocols, in some cases exceeding 800 ^oC, that are required for most glasses [1]. The high temperature melting procedure is cost ineffective for large scale production, while it causes concerns for the stability of the incorporated functional materials. Moreover, typical glass melting approaches result to the random incorporation of the functional materials inside the glass, without offering a possible way to control the position of the embedded material [1]. To tackle these scientific challenges, we have developed a post-glass melting low temperature fabrication procedure that allows the controllable encapsulation of functional materials within glasses, i.e. after the initial melting of the pristine glass [1]. Based on this simplified approach the controllable incorporation of PNCs [2], 2D materials [3], metal NPs [4], and photochromic salts [5], within transparent phosphate glasses is achieved at the moderate temperature of 160 ^oC. The perspectives of our fabrication route will be presented towards the realization of stable composite glasses with superior optical and luminescence properties, that fulfil the demands of a wide range of optoelectronic and photochromic applications. In particular, the developed perovskite glasses (PV-Glasses) exhibit remarkable photoluminescence (PL) stability since the glass matrix offers great moisture protection to the sensitive PNCs, while a simple continuous wave (cw) laser processing allows the feasible formation of highly luminescent periodic micro-patterns inside the glass [2]. In case of 2D materials composite glasses (2D-Glasses), the post-glass melting encapsulation approach allows the enhancement of room temperature PL properties upon inducing B-exciton emission in few-layers of embedded MoS2 [3]. Moreover, the embedment of silver NPs allows the development of erasable waveguides within phosphate glasses [4], while the incorporation of AgCl results to photochromic glasses with extremely fast photo-switching response times [5]. Based on the above, it is believed that the recently developed post-melting encapsulation route paves a promising way beyond the current state-of-the-art, towards the development of advanced composite glasses and coatings for a wide range of next-generation applications.
[1] I. Konidakis et al., Nanoscale 14, 2966 (2022).
[2] I. Konidakis et al., Nanoscale 12, 13697 (2020).
[3] A. S. Sarkar et al., Sci. Rep. 10, 15697 (2020).
[4] K. Tsimvrakidis et al., Materials 15, 2983 (2022).
[5] M. Adamidis et al., J Materiomics, submitted (2022).

Petr Nemec
Ga-Sb-Te thin films deposited by magnetron co-sputtering
M. Kotrla, J. Gutwirth, P. Janíček, J. Přikryl, T. Halenkovič, F. Cheviré, V. Nazabal, and P. Němec, University of Pardubice, Czech Republic
More than 50 years ago, reversible electrical switching phenomenon in amorphous chalcogenides was first time reported by Ovshinsky [1]. In the end of 1980s and beginning of 1990s, phase change materials based on Ge-Sb-Te and/or Ag-In-Sb-Te systems have been discovered. The main scientific as well as technological interest of these inorganic materials is their ability to transform quickly and reversibly between amorphous and crystalline phases. Fast phase transformation can be induced reversibly through varying the electric field or temperature by heating via a laser pulse in optical recording applications. The extraordinary properties of phase change materials based on Ge-Sb-Te ternary system are connected with changes of optical reflectivity (up to 30%) and/or electrical resistivity (several orders of magnitude) taking place upon phase transition [2]. Radio-frequency (RF) sputtering is widely used for thin films fabrication due to its relative simplicity, easy control, and often stoichiometric material transfer. Specifically, rf co-sputtering technique brings advantage of adjustable electrical power ratio applied on individual cathodes which enables to obtain thin films with various compositions making this method cost-effective for compositional dependencies’ studies of materials’ properties. Magnetron sputtering is widely used for the growth of chalcogenide phase change thin films. However, co-sputtering method is less frequent and mainly used for the doping of Ge-Sb-Te materials with other elements such as C, Al, Ti, Ni, Cu, Se, Zr, Sn or Bi. Contrary, RF co-sputtering is used in this work to explore fabrication of thin Ga-Sb-Te films within broad region of chemical composition varying only the electrical power ratio applied to GaSb, GaTe or Te sputtering targets without necessity of exploiting many different compositions of the targets from Ga-Sb-Te system when simple RF sputtering is employed. The characterization of thin films in as-deposited state (amorphous phase) as well as in crystalline state (induced by thermal annealing) was performed exploiting atomic force microscopy, scanning electron microscopy with energy-dispersive X-ray analysis, classical as well as grazing incidence temperature dependent X-ray diffraction, electrical resistivity, and variable angle spectroscopic ellipsometry data. The results are discussed in relation with the chemical composition of the fabricated thin films. The financial support of the Czech Science Foundation under the project No. 22-07635S is greatly acknowledged.
[1] S. R. Ovshinsky, Phys. Rev. Lett. 21, 1450-1453 (1968).
[2] M. Bouska, S. Pechev, Q. Simon, R. Boidin, V. Nazabal, J. Gutwirth, E. Baudet, P. Nemec, Scientific Reports 6, 26552 (2016).

Caroline Vigreux
Functionalization of GeSeTe chalcogenide layers for the realization of biosensors
A. H. Aldrouby, R. Escalier, A. Mehdi, and C. Vigreux
ICGM, Univ. Montpellier, CNRS, ENSCM, Montpellier, France
Due to their transparency in the infrared range where many absorption lines of biomolecules are located, chalcogenide glasses are materials of choice for the realization of biosensors. Motivated by a project aiming at reducing the systematic use of pesticides for the prevention of fungal diseases in plants, we are currently interested in the functionalization of thin layers of the GeSeTe system. The objective is to design optical microsensors able to selectively detect the spores of phytopathogenic fungi, responsible for these diseases. Different ways of functionalization are studied. Silanization is one of the explored ways. It is realized with different precursors or mixture of precursors, in order to obtain functionalized surfaces with different functional groups. These surfaces will then be tested against the immobilization of spores from different fungi, phytopathogenic or harmless, to verify the possibility of realizing sensors that are selective.

OMT invited presentations

Georges Boudebs
Photothermal efficiency of gold nanoparticles using cw Z-scan technique in the visible range
G. Boudebs¹, J.-B. Zinoune^1,4, C. Cassagne¹, M. Loumaigne³, M. Chis⁴, and M. H. V. Werts²
¹Univ Angers, LPHIA, SFR MATRIX, Angers, France
²Univ Rennes, CNRS, SATIE – UMR8029, Rennes, France
³Univ Angers, MOLTECH-ANJOU, SFR MATRIX, Angers, France
⁴ESAIP, St-Barthélemy d’Anjou Cedex, France
The photothermal effect may be used in a variety of applications such as biological microscopy. Light scattering from plasmonic NPs can be sufficiently strong to enable single-particle observations in dark-field microscopy. The relative contributions of light scattering and light absorption are of paramount importance in the characterization of nanoparticles and their selection and optimization for a specific application. Cw single beam Z-scan technique is applied to determine the absorption and scattering efficiencies on different size of spherical gold nanoparticles. Experimental tests are carried out at three different wavelengths in the blue, the green and the red. The quantum yields are determined through Thermal Lens (TL) effect. Details of the measurement method characteristics are given for relatively high absorption Gaussian procedure using top-hat beams. The validity of our approach is confirmed by comparing the obtained scattering data with that of the theoretical values given by the Mie theory. Very good agreement is found within the experimental errors.

Juan Bueno
Second harmonic generation microscopy of the living human eye: Limitations, performance and image improvement
J. M. Bueno¹, R. M. Martínez-Ojeda¹, F. J. Ávila², and P. Artal¹
¹Laboratorio de Óptica, Universidad de Murcia, Spain
²Departamento Física Aplicada, Universidad de Zaragoza, Spain
Second Harmonic Generation (SHG) microscopy provides high resolution images of collagen-based structures, in particular ocular tissues. However, the implementation into in vivo conditions has been challenging. Here, we present a compact SHG microscope specifically developed to image the living human eye (cornea and sclera). The instrument was successfully employed to obtain non-contact and non-invasive SHG images within well-established light safety limits. Since SHG image quality is often limited by different physical factors (mainly at deeper locations), we also present some alternative methods to enhance the acquired images. These include a blind deconvolution approach and the use of incident radially polarized light. The effectiveness of a sub-10fs used as illumination source is also analyzed.

Adrian Enache
Highlighting cerebral metastases using two-photon microscopy
A. Enache^1,2,4, L. Eftimie^1,2,3, R. Hristu¹, A.-M. Graur^4,5, R. R. Glogojeanu³, M. Sajin⁴, and G. A. Stanciu¹
¹Center for Microscopy-Microanalysis and Information Processing, University Politehnica of Bucharest, Romania
²Central University Emergency Military Hospital, Pathology Department, Bucharest, Romania
³Department of Special Motricity and Medical Recovery, The National University of Physical Education and Sports, Bucharest, Romania
⁴University of Medicine and Pharmacy ‚Carol Davila’, Pathology Department, Bucharest, Romania
⁵Central University Emergency Military Hospital, Radiology Department, Bucharest, Romania
The research issue examines the establishment of a pathological diagnostic that is as detailed as practicable for cerebral metastases utilizing a new technique that is used in connection with optical microscopy to accurately detect cerebral malignancies. Two-photon microscopy is a further refinement of precision fluorescence microscopy. This approach can improve the accuracy of the cerebral metastases’ diagnosis and possibly other neoplasms. In this work, we propose an additional use for TPM imaging of fixed tissues stained for conventional histopathology. Through the identification of the nucleus, cytoplasm, and individual cells, TPM can clearly differentiate a single neuron in the brain tissue and the individual malignant cell in the human tumor specimen. We demonstrated that TPM could detect cerebral metastases, by acquiring high-quality images. Because excitation is restricted to a focal point, it also causes less photobleaching and phototoxicity, making TPM particularly useful for extended observation of cells. A key benefit of two-photon microscopy is its ability to restrict excitation to a tiny focal volume in thick samples. In fact, the application of TPM imaging in cerebral tumors has attracted increasing amounts of attention.

Sorin Hermon
Multi-sensor scanner and machine-learning data processing: A novel instrumentation and data analysis method in heritage science
R. Moreau and S. Hermon, STARC, The Cyprus Institute, Nicosia, Cyprus
Over the past two decades, scanning X-ray fluorescence or macro X-ray fluorescence (MA-XRF) has proven to be a revolution within the field of Cultural Heritage (CH) scientific investigation for painted artwork, with its ability to map elemental distribution over the scanned area and thus investigate the pigment composition. Despite the recognized added value of such scanning operations, the full scan of an area takes a certain amount of time that cannot be avoided, from few minutes to hours, depending of the size of the artefact and the data quality expected. Considering this point, the addition of other imaging methods simultaneous data acquisition while performing a MA-XRF scan become of great interest as not only its takes advantage of the time consumption of the method but it allows to build a fully integrated data-cube of different data sharing the same acquisition size and spatial resolution. The most suited imaging methods for such an implementation are Reflectance Imaging Spectroscopy (RIS) and Luminescence Imaging Spectroscopy (LIS) that are known to complement usefully MA-XRF analysis for the investigation of CH painted works materials. A scanner combining MA-XRF, RIS and LIS for analysis of CH painted artworks was developed, first as a prototype at the Centre de Recherche et de Restauration des Musées de France (C2RMF) and secondly at The Cyprus Institute (CyI). The implementation of such imaging techniques acquisition set up on a MA-XRF scanner is made possible thanks to the use of optical fiber. Optical fiber allows deporting illumination sources and collection devices away from the analytical head, considerably lowering the weight and the clutter of the latter, as well as randomizing the polarization of the output signals, which can be an issue in data processing. The data generated with these instrument, consisting on a combined MA-XRF, RIS and LIS cubes, is of great interest as each point of these data-cube has an X-ray fluorescence, Reflectance and Luminescence spectroscopic signature, allowing for extensive characterization and deep understanding of the studied CH materials. Numerous painted artworks have been studied with such devices, revealing and adding every day more information about CH artworks savoir-faire through time.

Radu Hristu
Collagen disorder in second harmonic generation images for the assessment of thyroid nodule capsular invasion
R. Hristu¹, D. Rutkauskas², S. G. Stanciu¹, L. G. Eftimie³, A. Enache³, and G. A. Stanciu¹
¹Center for Microscopy-Microanalysis and Information Processing, University Politehnica of Bucharest, Romania
²Center for Physical Sciences and Technology, Vilnius, Lithuania
³Department of Pathology, Central University Emergency Military Hospital, Bucharest, Romania
Second harmonic generation (SHG) microscopy is an imaging technique which enables the visualization of collagen architecture within tissue samples. Going beyond simple intensity, an extension of SHG microscopy involves the acquisition of polarization dependent image stacks which are further processed with theoretical collagen models to provide quantitative information for the collagen structure and architecture. We use SHG microscopy images for the visualization of the collagen distribution in thyroid nodule capsules. More precisely, we are interested in capsular invasion, a hallmark of follicular carcinoma and a method for evaluating possible lymph node metastasis in the case of papillary thyroid carcinoma. Different image processing methods are used to assess the collagen organization which is further related to possible invasion sites in the thyroid nodule capsule.

Avi Karsenty
Overcoming the limitations of silicon: How geometrical innovation can revolutionize nanophotonics and nanoelectronics?
A. Karsenty, Jerusalem College of Technology, Israel
Despite technological advancement having pushed silicon-based computing to its speed limit, new innovations are still based on this cheap, widely available material, which makes up almost 28% of the planet’s volume. Pushing silicon beyond its current boundaries will require replacing electronic communication with photonic communication. However, silicon is a priori limited by its indirect band gap, and researchers in this area are forced to look for alternative materials in addition to silicon components. Perhaps there is another path besides that of replacing silicon with other elements (Ge, GaAs, In), if their properties can be replicated by those of carefully designed silicon nanophotonics based on special structures and adapted shapes. Today, nanoelectronics and nanophotonics are at the forefront of the nano revolution. As microelectronics are based on silicon, advancements in the field of silicon photonics and photonics integrated circuits (PICs) will allow for the realization of integrated optical signaling and electronic data processing. As can be expected, development of these devices for use in the next generation of ultrafast computers is proceeding in concert with more general efforts to develop the next generation of optoelectronic communication systems. As part of these efforts, there is a need to create a full family of new silicon nanoscale electro-optical components that can be smoothly integrated into the microelectronics industry in the future. A series of such devices (light-emitting transistors, nano-amplifiers, capacitors embedded with nano-crystals, photo- and thermo-activated modulators, sensors, waveguides, Y-junctions and more), coupling both electrical and optical properties, are currently being developed by the research team at ALEO (Advanced Laboratory of Electro-Optics), under the leadership of Dr. Avi Karsenty, and in collaboration with other institutes in USA, Europe and Israel, such as Massachusetts Institute of Technology (MIT), University Politehnica Bucharest (UPB), and Bar-Ilan University (BIU). The ALEO team, comprised of both professional engineers as well as PhD, MSc and BSc students, is engaged in advanced research on multiple fronts in collaboration with world-famous institutions in the United States, Europe, and Israel. The benefits of these devices will be experienced by a wide range of application domains: Optical communication in computers, near-field and super-resolution nanoscopy, space and airborne sensors, smart autonomous vehicle (SAV) technology, quantum computing, and of course the field of nanophotonics and nanoelectronics itself. This talk will present several examples of smart nanoscale silicon-based devices (MOSQWELL, HAND, SOIPAM, EOTEC and Au-NP tips) whose special geometrical structure enables them to overcome the well-known limitations of silicon (indirect band gap limiting photon emission), and to reinforce physical phenomena (absorption and emission spectra).

Aude Lereu
Resonant multi-dielectric coverslip for enhanced total internal reflection fluorescence microscopy
Y. Toumi¹, A. Mouttou^1,2, F. Lemarchand¹, G. Demesy¹, C. Koc¹, D. Muriaux², A. Moreau¹, J. Lumeau¹, C. Favard², and A. L. Lereu¹
¹Aix Marseille Univ, CNRS, Centrale Marseille, Institut Fresnel, France
²Institut de Recherche en Infectiologie de Montpellier, CNRS, Univ of Montpellier France
Multi-dielectric coated coverslip can be designed to reach large optical field enhancement when working under proper illumination conditions and in total internal reflection. As objective-based total internal reflection fluorescence microscopy (TIRF-M) is also based on total internal reflection illumination, we propose to use the resulting large field enhancement supported in such coverslip to improve TIRF-M sensitivity by amplifying the collected fluorescence signal. We present here the optimization, realization and testing in TIRF-M of resonant coverslips designed to take into account the experimental constraints. The latter’s are due to the inverted configuration of TIRF-M together with the use of a high numerical aperture objective. The challenge is therefore to find the best coating design compromising between the angular tolerance and the field enhancement. We will report here enhanced-TIRF-M imaging over model samples but the ultimate goal here is to be able to monitor and quantify dynamics of pathogens at the membrane of living cells. The authors acknowledge the CNRS for financial supports through the 80|PRIME interdisciplinary program and the French research agency through the ANR NIS.

Adrian Podoleanu
Advances in optical coherence tomography
A. Podoleanu, Applied Optics Group, School of Physical Sciences, University of Kent, Canterbury, UK
Optical Coherence Tomography (OCT) has been initially developed as a non-invasive high resolution optical imaging modality for ophthalmology, followed by rolling the technology to other medical fields. OCT has however considerable potential in biosciences as well as in non-destructive testing. The review will present such recent applications in a variety of fields. A method and systems for direct delivery of en-face OCT images will also be presented. The signal conventionally provided by a Fourier Transform or equivalent is replaced by delivery of multiple signals, using an electrical processor for each optical path difference (OPD) in the sample investigated. The principle of operation is termed as master slave (MS) interferometry, where signal from a depth in the sample for a certain OPD in a slave interferometer is selected by setting the same OPD value in a master interferometer. The MS principle enables real time display of several en-face OCT images using ultrafast tunable lasers in downconversion configurations. To this end, I will also present our research on two technologies for ultra-fast tuning lasers for fast acquisition of OCT data: dispersive cavity with dual resonance and time stretch configurations.
Keywords: optical coherence tomography, swept sources, broadband sources, 3D imaging, depth resolved imaging.
[1] A. Gh. Podoleanu, Optical coherence tomography, Journal of Microscopy, 247(3) 209-219, (2012).
[2] A. Gh. Podoleanu, A. Bradu, Master-slave interferometry for parallel spectral domain interferometry sensing and versatile 3D optical coherence tomography, Opt. Express 21, 19324-19338 (2013).
[3] A. M. Jiménez, S. Grelet, V. Tsatourian, P.B. Montague, A. Bradu, A. Podoleanu, 400 Hz volume rate swept-source optical coherence tomography at 1060 nm using a KTN deflector, IEEE Photonics Technology Letters, vol. 34, no. 23, 1277-1280 (2021).
[4] R. Riha, A. Bradu, A. Podoleanu, Dual resonance akinetic dispersive cavity swept source at 900 kHz using a cFBG and an intensity modulator, Optics Letters, vol. 47, no. 16, 4032-4035 (2022).

Luigi Sirleto
Noises investigations and image denoising in femtosecond stimulated Raman scattering microscopy
R. Ranjan^1,2, G. Costa^1,3, M. A. Ferrara¹, M. Sansone³, and L. Sirleto1
¹National Research Council, Institute of Applied Sciences and Intelligent Systems Napoli, Italy
²Department of Biochemistry and Molecular Pharmacology, New York University School of Medicine, New York, USA
³Department of Electrical Engineering and Information Technologies, University “Federico II” of Naples, Italy
In the literature of SRS microscopy, the hardware characterization usually remains separate from the image processing. In this paper, we consider both these aspects and statistical properties analysis of image noise, which plays the vital role of joining links between them. Firstly, we perform hardware characterization by systematic measurements of noise sources, demonstrating that our in-house built microscope is shot noise limited. Secondly, we analyze the statistical properties of the overall image noise, and we prove that the noise distribution can be dependent on image direction, whose origin is the use of a lock-in time constant longer than pixel dwell time. Finally, we compare the performances of two widespread general algorithms, i.e. Singular Value Decomposition (SVD) and Discrete Wavelet Transform (DWT), with a method, i.e. Singular Spectrum Analysis (SSA), which has been adapted for SRS images. In order to validate our algorithms, in our investigations lipids droplets (LDs) have been used and we demonstrate that the adapted SSA method provides an improvement in image denoising[1,2].
[1] R. Ranjan, G. Costa, M. A. Ferrara, M. Sansone, L. Sirleto, Noises investigations and image denoising in femtosecond stimulated Raman scattering microscopy, Journal of Biophotonics. vol. 15, no. 6, e202100379, (2022).
[2] R. Ranjan, G. Costa, M. A. Ferrara, M. Sansone, L. Sirleto, Noise measurements and noise statistical properties investigations in a stimulated Raman scattering microscope based on three femtoseconds laser sources, Photonics, 9(12), 910, (2022).

Anton Stefan – Razvan
Surface roughness and optical characterization of nanoporous silver films synthesized by one-step dealloying
A. R. Stefan¹, E. G. Fu², D. E. Tranca¹, S. G. Stanciu¹, A. Toma³, C. V. Sammut⁴, and G. A. Stanciu¹
¹Center for Microscopy-Microanalysis and Information Processing, University Politehnica of Bucharest, Romania
²State Key Laboratory of Nuclear Physics and Technology, School of Physics, Peking University, P.R. China
³Center for Research and Training in Innovative Techniques of Applied Mathematics in Engineering “Traian Lalescu”, University Politehnica of Bucharest, Romania
⁴Department of Physics, Faculty of Science, University of Malta, Msida, Malta
Surface roughness and nano-topography in nanoporous silver (NPS) films are investigated as a function of dealloying agent. The nanoporous films are analyzed by atomic force microscopy and near field optical microscopy. IT is found that the nano-roughness formed on the surface of the films affects local properties of the film at a great scale. Detailed metrological quantification based on the autocorrelation function (ACF), height-height correlation function (HHCF), power spectral density function (PSDF), Minkowski connectivity and fractal analysis are proposed for the characterization of the nanoscale surface topography. Certain characteristics such as the accumulation of silver atoms are observed on the surface of the films and a mechanism based on the interaction between the dealloying agents and the surface is proposed for the explanation of the experimental behavior. In addition, appropriately designed experiments are conducted, and they confirm the presence of this mechanism.

Denis Tranca
Applications of phasor data analysis on scattering scanning near-field optical microscopy investigations
D. E. Tranca, R. Hristu, S. G. Stanciu, and G. A. Stanciu
Center for Microscopy-Microanalysis and Information Processing, Politehnica University of Bucharest, Romania
Investigations by using scattering scanning near-field optical microscopy (s-SNOM) usually result in acquisition of a pair of two images: amplitude and phase, which hold complementary information about the optical properties of the investigated samples. Phasor diagrams are graphical ways of complex data display and represent an alternative to classical amplitude-phase images for displaying the data contained in the s-SNOM images. In this work we propose some applications and directions for rapid analysis of s-SNOM data displayed by means of phasor diagrams based on investigations performed on different sample types: biological, organic, and inorganic materials. Our analysis demonstrates practical uses for phasor diagrams to extract valuable qualitative information from s-SNOM images.

Zeev Zalevsky
Super-resolved imaging behind scattering medium
E. Israeli, A. Sanjeev, R. Salahudeen Rafeeka, G. Chen, and Z. Zalevsky
Bar-Ilan University, Ramat-Gan, Israel
Time multiplexing is a super-resolution technique that sacrifices time to overcome the resolution reduction obtained because of diffraction. There are many super resolution methods based on time multiplexing, but all of them require a-priori knowledge of the time changing encoding mask, which is projected on the object and used to encode and decode the high-resolution information. In this paper, we present a time multiplexing technique that does not require the a priori knowledge on the projected encoding mask. The concept includes illuminating the object positioned behind scattering medium, through the scattering medium. This generates illumination of the object with speckle patterns. The patterns themselves are not a-priori known but the same projected pattern can be preserved and shifted by using the memory effect of the scattering medium. By properly capturing larger number of low-resolution images encoded with the projected time-shifting speckle patterns, a high-resolution image can be reconstructed after applying proper decoding algorithm. The paper includes both numerical as well as experimental validation of the proposed novel imaging concept.
Keywords: time multiplexing, super-resolution, scattering medium, speckle patterns projection.

OWW invited presentations

Ernesto Ciaramella
Intra-satellite optical wireless communications in relevant environments
G. Cossu, L. Gilli, N. Vincenti, V. Bresciani, E. Pifferi, V. Schena, and E. Ciaramella, Scuola Superiore Sant’Anna, Istituto TeCIP, Pisa, Italy
We present approach, design and preliminary tests of the TOWS study, which successfully demonstrated an innovative approach to optical wireless communication in spacecrafts. The developed hardware can realize optical wireless connections among different units by means of MIL-STD 1553 signals, which is the most common type of intra-satellite data bus. The same optical transceivers are flexible and can be used in quite different relevant application scenarios.

Jian Chen
Modelling of optical communication over lighting infrastructure with ultra-wide spectral carrier clusters
Jian Chen¹, Jun Wang¹, Wenjing Sun¹, Anliang Cai¹, and Changyuan Yu²
¹School of Telecommunications and Information Engineering, Nanjing University of Posts and Telecommunications, China
²Department of Electronic and Information Engineering, The Hong Kong Polytechnic University, Kowloon, Hong Kong
The flourishing lighting industry has taken the full visible light spectra upon which the communication services will be only provided as value-added. On the basis of better satisfying human visual system, high-efficiency and energy-saving, such auxiliary communication is simultaneously carried by prerequisite ultra-wide optical spectral cluster in lighting process. Novel modelling of optical communication over lighting are thus established for the purpose of analyzing simultaneous modulation and wideband detection of the signal. The model is far beyond the assumption of single wavelength or multiplexed wave as the carrier. It avoids too simple and unrealistic extension of fiber optics or wireless communication theories for characterizing optical communication over lighting. It is expected to provide theoretical and technical basis on mobile VLC which perfectly comparable with the evolved lighting infrastructure.

Giulio Cossu
Design challenges in high throughput WDM-FSO systems for satellite communications
G. Cossu, V. Spirito, M. Ninos, and E. Ciaramella, Scuola Superiore Sant’Anna, Istituto TeCIP, Pisa, Italy
The key technology to provide Terabit/s links in space is the Free Space Optics (FSO) with Wavelength Division Multiplexing (WDM). This work reports and explains how to elaborate a link budget for WDM-FSO feeder links, i.e., links that connect an Optical Ground Station to a satellite. Designing these links is a challenging task, since the optical beams travel also through the turbulent atmosphere adding several penalties. The effects along the propagation are addressed and discussed, estimating all the impairments based on analytic and stochastic models. Then, we determined the system parameters that can provide the expected performance.

Ivan Djordjevic
Covert optical communication over turbulent terrestrial free-space optical link
V. Nafria and I. B. Djordjevic, University of Arizona, Tucson USA
Unlike traditional secure communication methods, denying unauthorized access to the content of the transmitted message, the covert communication prevents detection of the transmission attempt in the first place. In this invited paper, we review our recent activities on covert free-space optical (FSO) communication activities at the University of Arizona (UA). At UA we have established a 1.5 km-long FSO communication link between Optical Sciences (OSC) Meinel and ECE Department buildings. We use an EDFA as an ASE noise source for covert communication and perform the BPSK signaling over the FSO link at multi-Gb/s data rates. To deal with the atmospheric turbulence effects we use the adaptive optics. Different strategies to enable covert communication operating in strong turbulence regime will be presented at the conference.

Andrew Ellis
Advanced digital signal processing for high-capacity mode-division multiplexed free-space optical communications
Zhouyi Hu¹, Zhaozhong Chen², Yiming Li¹, D. M. Benton¹, A. A. I. Ali^{1, 3}, M. Patel¹, M. P. J. Lavery², and A. D. Ellis¹
¹Aston Institute of Photonic Technology, Aston University, Birmingham, UK
²James Watt School of Engineering, University of Glasgow, UK
³Now with Lumensisty Ltd, Romsey, UK
Spatial modes provide a potential dimension to boost the capacity of free-space optical (FSO) communication systems. Various modal basis sets can be used. For a given aperture size, complete orthogonal modal basis sets can provide higher capacity compared to incomplete modal basis sets, but are more sensitive to FSO channel impairments, such as atmospheric turbulence. In this invited paper, we review our recent progress in using advanced digital signal processing algorithms for the implementation of high-capacity mode-division multiplexed FSO communication systems when employing complete modal basis sets. Besides turbulence, the relatively high inter-mode crosstalk from a commercial multiplexer/demultiplexer has been taken into account. By employing adaptive loading at the transmitter side and/or advanced multiple-input multiple-output detection algorithms at the receiver side, record-high single-wavelength transmission data rates and spectral efficiency have been achieved over both turbulence-free and turbulent FSO links, where all key devices are commercially available.
Keywords: atmospheric turbulence, digital signal processing, free-space optics, mode-division multiplexing, multiple-input multiple-output, optical wireless communication.

Vincenzo Petruzzelli
Integrated optical phased arrays for on-chip communication
G. Calò, G. Bellanca, M. Barbiroli, F. Fuschini, V. Tralli, D. Bertozzi, and V. Petruzzelli, Politecnico di Bari, Italy
Chip Multiprocessors (CMPs) exploiting the potentialities of parallel computing are the state-of-the-art solution to face the constant need of increasing computing system efficiency. As the number of cores in chip multiprocessors continues to scale up, the efficient interconnection of these cores is becoming a major challenge to avoid communication bottleneck and to meet the high bandwidth, low-power and low-latency requirements which, actually, cannot be matched by traditional point-to-point connections through dedicated electrical links. The realization of efficient on-chip interconnections is one of the most important challenges. To overcome the communication bottleneck of these multichip systems, in this work we propose a new approach based on the use of optical wireless routers. These routers can be integrated with an existing Optical Network on Chip as an alternative to ring-based routing matrices with the aim to increase the overall efficiency of the network. In particular, different configurations of on-chip optical wireless interconnections are proposed. These configurations exploit transmitting and receiving Optical Phased Arrays (OPAs) made of integrated dielectric antennas.

Henrique Salgado
Sigma-delta modulation for enhanced underwater optical communication systems
J. H. Araújo, J. S. Tavares, and H. M. Salgado
INESC TEC, Faculdade de Engenharia, Universidade do Porto, Portugal
This paper presents an experimental investigation of Sigma-Delta Modulation (SDM) as a means of improving the performance of underwater optical communication systems. The study considers the impact of the key parameters of SDM, including quantization noise, and oversampling ratio, on the system’s signal-to-noise ratio, bandwidth, and bit error rate. The results of this study provide insights into the design and optimization of SDM-based underwater optical communication systems, paving the way for future research in this field.

Scott Watson
Blue lasers for optical wireless communication
S. Watson¹, S. P. Najda², P. Perlin^2,3, T. Suski², L. Marona^2,3, M. Leszczynski^2,3, S. Stanczyk², D. Schiavon^2,3, T. J. Slight⁴, and A. E. Kelly¹
¹James Watt School of Engineering, University of Glasgow, UK
²TopGaN Ltd, Warsaw, Poland
³Institute of High Pressure Physics PAS, Warsaw, Poland
⁴Sivers Photonics Ltd, Blantyre, UK)
Distributed feedback (DFB) lasers based on gallium nitride (GaN) have been fabricated and characterised for use in optical wireless communications. These devices find applications in free space visible light communication, but also play a fundamental role in underwater and space environments due to the low loss transmission at blue wavelengths. Devices have shown Gbit/s performance making them ideal candidates for low-cost, high speed data transmission.

Changyuan Yu
Multi-user visible light communication and positioning system based on multiplexing technology
Zhongxu Liu and Changyuan Yu
Department of Electronic and Information Engineering, The Hong Kong Polytechnic University, Kowloon, Hong Kong, China
Visible light communication and positioning (VLCP) is a promising technology for constructing a multi-functional wireless network that provides simultaneous high-speed communication and high-precision positioning functions. To simultaneously transmit various and complex visible light communication (VLC) and visible light positioning (VLP) signals of multiple users, multiplexing technologies are necessarily adopted in VLCP systems. In this paper, we first review and analyze the VLCP system designs based on conventional multiplexing technologies, including time division multiplexing, frequency division multiplexing, and code division multiplexing. Then, we propose a multi-user VLCP system based on the dual-domain multiplexing scheme, where the VLC and VLP signals of multiple users are effectively integrated and transmitted through multiplexing the time and code resources. The proposed method can make full use of transmission resources to offer simultaneous VLC and VLP functions for multiple users.
Keywords: visible light communication and positioning, visible light communication, visible light positioning, multiplexing technology.

PAM invited presentations

Kyungwon An
Superradiant quantum heat engine
Kyungwon An, Department of Physics and Astronomy, Seoul National University, Korea
A superradiant state is a special phase-correlated quantum state of atoms capable of undergoing superradiance immediately without a time delay. By employing a superradiant state of atoms in a cavity, we have recently realized a photonic quantum heat engine, where the atoms traversing the cavity serve as a heat reservoir and the photons act as an engine medium exerting radiation pressure on the mirrors. Our engine operates between a thermal state and a superradiant state of reservoir atoms at the same reservoir temperature. In our experiment, the effective engine temperature went up to 150,000K because of the large ergotropy transfer from the reservoir through superradiance, resulting in the engine efficiency as high as 98%.

Guoping Lin
Exploring Kerr frequency comb generation with Yttria Stabilized Zirconia (YSZ) crystalline microcavities
Guoping Lin, Harbin Institute of Technology, Shenzhen, China
Microcavity Kerr frequency comb devices have been emerging as promising compact comb sources for a wide range of applications. Considering the oxide crystalline material platform, yttria-stabilized zirconia (YSZ) has a high refractive index of 2.1 at the telecom wavelength and a Kerr nonlinear coefficient similar to that of the silicon nitride platform. Here, we fabricated sub-millimeter size YSZ crystalline microcavities with Q factors above ten million and explored Kerr frequency comb generation at the telecom wavelengths with YSZ.

PhotoMAN invited presentations

Juan Pedro Fernandez-Palacios
Investigation of mid-term migration scenarios to multi-band solutions in metropolitan networks
J. P. Fernández-Palacios¹, F. Arpanaei^1,2, J. M. Rivas-Moscoso¹, J. A. Hernández², and D. Larrabeiti²
¹Telefónica Research and Development, Madrid, Spain
²Department of Telematic Engineering, Universidad Carlos III de Madrid, Madrid, Spain
The evolution toward beyond-5G/6G services and applications requiring very high bandwidths will put ever-growing pressure on deployed optical networks to provide the spectral resources needed to accommodate such traffic loads. This is particularly true for the metro/regional segments, where expected traffic CAGR exceeding 40%, primarily driven by CDN traffic confined to the network segments closer to the end users, will push the fiber capacity to its fundamental limits on a number of “hot” links in the short to medium term, irrespective of the use of spectrally efficient modulation formats, especially suited for short-haul transmission. It is therefore critical to evaluate migration scenarios to expand spectral resources beyond the extended C-band (4.8 THz) mainly in use today. In this paper, we conduct multi-homed edge-to-core routing, modulation-level and spectrum-assignment simulations over Telefónica reference metropolitan networks, considering bandwidth-variable coherent transmission with per-channel capacity of 100-400 Gbps in 50 GHz and link-by-link C+L-band migration, while ensuring optimal GSNR performance. Results show that the rollout of L-band equipment over a reduced number of links can efficiently extend the lifespan of current networks, guaranteeing congestion-free operation with minimal intervention, and can be a suitable transitional capacity-stretching solution prior to undertaking more disruptive multi-fiber deployments.
Keywords: multi-band, spectrum assignment, network migration, metropolitan networks.

PICAW invited presentations

Mario Nicola Armenise
Flexible photonic integrated circuits: A new paradigm to process data on-board satellites
M. N. Armenise, A. di Toma, G. Brunetti, N. Saha, and C. Ciminelli
Optoelectronics Laboratory, Politecnico Di Bari, Italy
Photonic Integrated Circuits (PICs) are becoming an enabling technology suitable for a large range of applications such as Space and biomedicine. PICs deal with light signals exploiting photonic basic building blocks. Their attractiveness is mainly related to the capability to manage analog signals without A/D conversion [1]. NewSpace Economy sets several constraints mainly in terms of reliability and flexibility of on-board systems, taking into account the need for small size and low weight, low propagation losses, low power consumption, immunity to electromagnetic disturbances, high processing speed, wide bandwidth, and radiation resistance. Reconfigurable PICs are one of the most promising technologies to fulfil all those requirements. In particular, system flexibility could be achieved by means of programmable or tuneable Application-Specific PICs (ASPICs) [2]. A tuneable PIC should be tailored according to the targeted applications. It exploits different physical effects, e.g. thermo-optic effect, electro-optic effect, or phase-changing materials, to optimize its functionalities also reconfiguring itself in relation to the user demands or external environment. The main bottlenecks of this approach are the need for specific design and optimization each time, the recursive designing costs, and the lack of multitasking. On the other hand, a programmable PIC exploits the same chip to perform several functions, even targeted to different applications. Although the latter approach ensures larger flexibility, the main issues are the high power consumption related to the tuning of different elements at the same time, and lower performance than ASPIC (e.g. insertion loss, wavelength precision, limited free spectral range) [3-5]. Here, both approaches for systems flexibility are carefully reviewed, rating their limits and potential developments, also evaluating the tuning mechanisms and technological challenges. The suitability of the aforementioned systems for Space applications is also critically analysed, aiming at highlighting the main functionalities needed to process data on-board.
Keywords: Photonic Integrated Circuits, tuneable, programmable, Space.
[1] A. Macho-Ortiz, D. Pérez-López, J. Azaña, and J. Capmany, Analog programmable-photonic computation, arXiv preprint arXiv:2203.14118 (2022).
[2] G. N. Tzintzarov, S. G. Rao, and J. D. Cressler, Integrated silicon photonics for enabling next-generation space systems, MDPI Photonics, vol. 8, no. 4, p. 131 (2021).
[3] W. Bogaerts and A. Rahim, Programmable photonics: An opportunity for an accessible large-volume PIC ecosystem, IEEE Journal of Selected Topics in Quantum Electronics, 26(5), 1-17 (2020).
[4] J. Capmany, I. Gasulla, and D. Pérez, The programmable processor, Nature Photonics, 10(1), 6-8 (2016).
[5] W. Bogaerts, D. Pérez, J. Capmany, D. A. Miller, J. Poon, D. Englund, and A. Melloni, Programmable photonic circuits, Nature, 586(7828), 207-216 (2020).

Jonathan Bradley
Tellurite-coated silicon nitride waveguides for active, passive, and nonlinear photonic integrated circuits
H. M. Mbonde¹, B. L. Segat Frare¹, N. Singh², M. Sinobad², T. Wildi², C. N. Naraine¹, P. Torab Ahmadi¹, B. Hashemi¹, M. A. Méndez-Rosales¹, H. C. Frankis¹, D. B. Bonneville¹, K. Miarabbas Kiani¹, R. Wang¹, J. N. Westwood-Bachman³, C. Horvath³, M. Aktary³, R. Mateman⁴, A. Leinse⁴, J. H. Schmid⁵, P. Cheben^5,6, P. Mascher¹, A. P. Knights¹, T. Herr², F. X. Kärtner^2,7, and J. D. B. Bradley¹
¹Department of Engineering Physics, McMaster University, Hamilton, Canada
²Center for Free-Electron Laser Science, Deutsches Elektronen-Synchrotron, Hamburg, Germany
³Applied Nanotools Inc., Edmonton, Canada
⁴LioniX International BV, Enschede, The Netherlands
⁵National Research Council Canada, Ottawa, Canada
⁶Center for Research in Photonics, University of Ottawa, Canada
⁷Department of Physics, Universität Hamburg, Germany
We present on active rare-earth-doped, low-loss passive, and nonlinear integrated photonic devices on wafer-scale silicon nitride platforms coated with highly nonlinear tellurite glass. We demonstrate waveguide amplifiers and lasers, high-Q-factor microresonators, and tailored group velocity dispersion between the normal and anomalous regimes enabling efficient supercontinuum sources. These devices represent promising building blocks for monolithic active-passive-nonlinear photonic integrated circuits with applications including communications, quantum information, precision metrology, imaging, and sensing.

Onur Düzgöl
On the training of photonic neural networks considering physical limitations
O. Düzgöl, VPIphotonics, Berlin, Germany
Electronically controlled Photonic Integrated Circuits (PIC) represent powerful hardware solutions for deep learning applications due to their high-speed and wide-bandwidth features. The accuracy of such photonic neural networks might be significantly limited if the training considers only the ideal system performance. It is crucial to account for the realistic physical constraints of the PIC during network training to guarantee high performance. Constraints could originate from fabrication tolerances, electrical and optical noise sources, bandwidth limitations, etc. This work presents a novel simulation technique for the schematic-aware training of photonic deep neural networks.

Alex Fuerbach
Mid-infrared integrated photonics
A. Fuerbach, T. Fernandez, S. Gross, M. Withford, B. Johnston, and T. Gretzinger, School of Mathematical and Physical Sciences, Macquarie University, Sydney, Australia
We report on our research into the fabrication of fiber-coupled photonic chips via femtosecond laser direct inscription in mid-infrared compatible glasses. We believe that this work represents a major step towards the development of future all-integrated and field-deployable spectroscopy systems in the important molecular fingerprint region. Potential applications range from atmospheric trace-gas detection to defence and medicine.

Marco Grande
Design and optimization of broadband optical duplexer and triplexer couplers
A. Thottoli¹, A. S. Vorobev^1,2,3, G. Biagi^2,4, S. ladanza^5,6, G. Magno¹, L. O’Faolain^2,3, and M. Grande¹
¹Department of Electrical and Information Engineering, Politecnico di Bari, Bari, Italy
²Centre for Advanced Photonics and Process Analysis, Munster Technological University, Cork, Ireland
³Tyndall National Institute, Cork, Ireland
⁴PolySenSe Lab, Physics Department, University of Bari, Italy
⁵Laboratory of Nano and Quantum Technologies, Paul Scherrer Institut, Villigen, Switzerland
⁶IBM Research Zurich, Switzerland
On-chip optical combiners with high coupling efficiency can be fully exploited in both multiple gas/liquid sensing devices and telecommunication applications. In this paper, we will review the enabling technologies and discuss the basic operating characteristics of ultra-broadband optical couplers. The design and preliminary fabrication results of optimized optical duplexers and triplexers based on angled multimode interference (AMMI) and directional coupler (DC) configurations will be also detailed.

Haroldo Hattori
Opto-electronic components based on 2D and refractory materials
I. Al-Ani, K. As’Ham, S. Akter, S. Abdo, Ziyuan Li, and H. T. Hattori, School of Engineering and Information Technology UNSW, Canberra, Australia
In this article, we highlight our current work on optoelectronic devices based on 2D and refractory materials. We initially present our past work on nano-antennas based upon refractory materials and show how they can handle higher fluences than noble metals. We then show how refractory ceramics can be applied to ultraviolet and visible photodetectors based on refractory carbides/borides which can potentially be integrated to silicon carbide power electronic devices. Finally, we exploit 2D dichalcogenides and show how to achieve perfect absorbance and efficient strong coupling in the materials, when combined with nanostructures such as nano-cylinders and meta-gratings.

Kambiz Jamshidi
Numerical modelling and characterization of active silicon ring resonators
K. Jamshidi¹, M. Catuneanu¹, S. Dev¹, Menglong He¹, A. Zarif1, H. Vithalani¹, H. S. Duranoglu Tunc¹, A. Shetewy¹, Shiyao Fang¹, D. Heydari², R. Hamerly^3,4, and H. Mabuchi²
¹Integrated Photonics Devices Group, Chair of RF and Photonics, Technische Universität Dresden, Germany
²E. L. Ginzton Laboratory, Stanford University, Stanford, USA
³Physics and Informatics Laboratories, NTT Research Inc., Sunnyvale, USA
⁴Research Laboratory of Electronics, MIT, Cambridge, USA
Silicon ring resonators are important components that can be fabricated using photonic IC (PIC) technologies and have found several applications in the realization of high-speed modulators, all-optical filters, reservoir computing, and photon pair generation [1-3], etc. Several nonlinearities like thermal, free-carrier, Kerr, and two-photon absorption affect the performance of these resonators. The dynamical model of ring resonators is necessary to characterize the fabricated rings and to use the proper model for the desired application [4-6]. This paper will discuss recent progress in static and dynamic modeling of ring resonators. These models are used to characterize the active silicon ring resonators which were previously designed and fabricated.
[1] Chaoxuan Ma et al., Silicon photonic entangled photon-pair and heralded single-photon generation with CAR> 12,000 and g (2)(0)< 0.006, Optics Express 25.26 (2017): 32995-33006.
[2] Shi Li et al., Micro-ring resonator based photonic reservoir computing for PAM equalization, IEEE Photonics Technology Letters 33.18 (2021): 978-981.
[3] M. I. Hosni, et al., Low Power, Compact integrated photonic sampler based on a silicon ring modulator, IEEE Photonics Journal 14.4 (2022): 1-6.
[4] R. Hamerly, et al., Conditions for parametric and free-carrier oscillation in silicon ring cavities, Journal of Lightwave Technology 36.19 (2018): 4671-4677.
[5] M. Borghi, et al., On the modeling of thermal and free carrier nonlinearities in silicon-on-insulator microring resonators, Optics Express 29.3 (2021): 4363-4377.
[6] D. Gray, et al., Thermo-optic multistability and relaxation in silicon microring resonators with lateral diodes, Physical Review Applied 14.2 (2020): 024073.

Andrew Katumba
Using Bayesian techniques to accelerate the design of silicon photonics reservoirs
A. Katumba^1,2, J. Mikelson¹, M. P. Matovic¹, J. Dambre², and P. Bienstman²
¹Makerere University, Kampala, Uganda
²Ghent University, Ghent, Belgium
Silicon photonics reservoirs have shown incredible promise as high-speed, energy-efficient neuromorphic processors for optical communications networks. However, achieving high performance on practical tasks tends to be both computationally expensive and storage intensive. In this work we employ Bayesian techniques to i) optimize reservoir hyper-parameters and ii) reduce the number of expensive, physical propagation results required to obtain an accurate estimate on the task with a small number of evaluations. We will use the case of numerical simulations of silicon photonics reservoir signal equalization in a 56 Gbaud PAM-4 100 km transmission system and report symbol and bit level performance metrics with appropriate error bounds.

Kenji Kintaka
Research progress on cavity-resonator-integrated guided-mode resonance mirror for Gaussian beam
K. Kintaka¹, A.Watanabe², J. Inoue², and S. Ura²
¹National Institute of Advanced Industrial Science and Technology, Ikeda, Japan
²Kyoto Institute of Technology, Japan
A guided-mode resonance filter integrated in a waveguide resonator on a reflective substrate can present highly efficient reflection with a steep reflection-phase change. Recent research work on improvement of characteristics of the device for small-diameter Gaussian beam will be introduced and discussed.

Sylwester Latkowski
Standardization and automation of test processes in the production flow of integrated photonics
S. Latkowski, D. Pustakhod, X. Leijtens, and K. Williams
Institute for Photonic Integration, Eindhoven University of Technology, The Netherlands
Global technology roadmaps for semiconductor electronics (HIR) and integrated photonic systems (IPSR-I) widely highlight demands for increased automation and standardization of electronic-photonic testing across the production flow. Test processes at all stages, including front-end, back-end, outsourced semiconductor assembly and test (OSAT) suppliers, module, and system integrators are deemed to be one of the top contributors to the manufacturing costs of integrated photonics. Current developments of test processes towards Test-as-a-Service, and standardization efforts carried out at Photonic Integration Technology Center and TU/e will be presented.

Alessio Lugnan
Silicon ring resonator with phase-change material as a plastic dynamical node for scalable all-optical neural networks with synaptic plasticity
A. Lugnan¹, S. Garcia-Cuevas Carrillo², J. Song², S. Aggarwal³, F. Brückerhoff-Plückelmann⁴, W. H. P. Pernice⁴, H. Bhaskaran³, C. D. Wright², and P. Bienstman¹
¹Photonics Research Group, INTEC Department, Ghent University – imec, Belgium
²Department of Engineering, University of Exeter, UK
³Department of Materials, University of Oxford, UK
⁴Department of Physics, University of Münster, Germany
Synaptic plasticity, that is the ability of connections in neural networks to strengthen or weaken depending on their input, is a fundamental component of learning and memory in biological brains. We present a numerical and experimental investigation of an integrated photonic plastic node, consisting of a silicon ring resonator enhanced by phase-change materials (GST). This all-optical device is capable of dynamical nonlinear behaviour, multi-scale volatile memory, non-volatile memory and multi-wavelength operations. We discuss its employment as a building block in scalable all-optical dynamical neural networks that can adapt to their input via synaptic plasticity.

Christos Riziotis
Design and fabrication challenges of integrated optical circuits for quantum computing applications
C. Riziotis, National Hellenic Research Foundation, Theoretical and Physical Chemistry Institute, Athens, Greece
The paper will discuss current design and fabrication challenges for the development of silica-on-silicon optical circuits defined by direct laser writing techniques, for quantum computing and sensing applications. Such silica-based laser written circuits platform allow a high degree of customization and fabrication flexibility enabling the demonstration of high performance optimized devices compatible for lossless interconnection with high optical networks. Key demanding issues such as novel integration approaches of single photon emitters with waveguides, and multiwavelength qubits generation combined with on-chip processing capabilities will be covered.

David Rowe
Group IV mid-infrared photonic devices and applications
D. J. Rowe, L. Reid, Chen Wei, C. J. Stirling, C. J. Mitchell, Han Du, Xingzhao Yan, D. T. Tran, Yangbo Wu, M. Banakar, Yanli Qi, A. Osman, Ke Li, J. Soler Penades, Longqi Zhou, K. M. Groom, J. Heffernan, C. G. Littlejohns, M. Nedeljkovic, and G. Z. Mashanovich
Optoelectronics Research Centre, University of Southampton, UK
We present our recent results on mid-infrared photonic devices, including component optimisation, circuit design and their application to sensing. We show the performance of an on-chip FTIR microspectrometer implemented in silicon-on-insulator. A self-referenced switching sensor in germanium-on-silicon (GoS) improves noise rejection by a factor of 11 compared to a regular waveguide sensor. We demonstrate waveguides with single-moded guidance over an octave of frequency at mid-infrared wavelengths to enable on-chip spectroscopy by suppressing higher-order modes. We apply a noise model to evaluate the performance of our waveguide sensors for therapeutic drug monitoring. Flip-chip bonding has been used to integrate quantum cascade lasers onto a GoS platform and we report further advances in coupling efficiency, structural integrity, process design and real-time laser monitoring. Final, we discuss recent progress on detectors, included bolometers and defect-mediated methods.

Alejandro Sánchez-Postigo
Enhancing the performance of waveguide-integrated superconducting nanowire single-photon detectors using subwavelength grating metamaterials
A. Sánchez-Postigo, C. Graham-Scott, and C. Schuck, Institute of Physics, University of Münster, Germany
Photonic integrated circuits hold great promise for scaling sensing and communication schemes to large system size. Their performance can further be enhanced by integrating devices with functionalities for quantum technology, such as superconducting nanowire single-photon detectors (SNSPDs). The measurement capabilities of SNSPDs include leading photon counting performance in terms of detection efficiency, dark count rates, and time accuracy (jitter). However, it is challenging to optimize all of these parameters simultaneously in a single device. Here we show how additional design freedom for detector performance optimization can be achieved by embedding SNSPDs into subwavelength gratings. These periodic planar structures enable the synthesis of metamaterials with tailorable optical properties, which we exploit for enhancing the absorption efficiency of ultrashort waveguide-integrated SNSPDs that favor high timing accuracy and low noise operation.

Isaac Suárez
Waveguide amplifiers and lasers based on FASnI₃ perovskite thin films
I. Suárez¹, H. P. Adl², V. S. Chirvony², J. Sánchez-Díaz³, R. S. Sánchez³, I. Mora-Seró³, and J. P. Martínez-Pastor²
¹Escuela Técnica Superior de Ingeniería, Universidad de Valencia, Spain
²UMDO, Instituto de Ciencia de los Materiales, Universidad de Valencia, Spain
³Institute of Advanced Materials (INAM), Universitat Jaume I, Castelló, Spain
The integration of optical functionalities in flexible substrates has become in an important trend in the optoelectronics community. However, the sophisticated technology to fabricate suitable optical architectures in a flexible substrate limits its demonstration to extremely few reports, which becomes even more challenging for active devices, where the appropriate integration of a material with high efficiency of emission is also necessary. In this work, a FASnI₃ (FA, formamidinium) lead-free perovskite thin films are incorporated in a flexible polyethylene terephthalate (PET) substrate and cladded by a polymethylmethacrylate(PMMA) thin film. The structure conforms a planar waveguide where the geometrical parameters (i.e. thicknesses of the films) are properly chosen to: (i) allow the single mode propagation at the photoluminescence (PL) wavelength, (ii) provide an optimum excitation of the FASnI3 by end-fire coupling the pump beam, (iii) enhance the light-matter interaction in the semiconductor and with it the optical gain, (iv) provide preferable direction for the emitted light and a direct outcoupling. As a result, amplified spontaneous emission is demonstrated with an extremely low threshold, about 1 µJ/cm², and a strong polarization anisotropy preferable to the transverse electric (TE) polarization. Moreover, the device exhibits narrow lasing lines (< 1 nm) caused by the formation of random cavity loops in the polycrystalline grains. The operation of the device is analyzed under bending conditions demonstrating that the figures of merit can be tuned with the curvature radius. The proposed device represents an important step towards the development of future cheap and green flexible/wearable technology.

David Thomson
High efficiency and high-speed silicon optical modulators
D. J. Thomson, W. Zhang, M. Ebert, K. Li, B. Chen, S. Liu, W. Cao, F. Meng, X. Yan, H. Du, M. Banakar, D. T. Tran, C. G. Littlejohns, A. Scofield, G. Yu, R. Shafiiha, A. Zilkie and G. T. Reed
Optoelectronics Research Centre, University of Southampton, UK
Optical modulators built in a CMOS compatible silicon photonics platform allow the potential for high data rate communication at low cost. Here our recent progress in high efficiency and high-speed silicon optical modulators is presented, including mechanisms for enhancing the performance of devices beyond previous limitations.

PNPA invited presentations

Stéphane Calvez
Nonlinear conversion in Cavity-Resonant Integrated Grating Filters
S. Calvez1, A. Monmayrant¹, O. Gauthier-Lafaye¹, E. Popov², and A.-L. Fehrembach²
¹LAAS-CNRS Toulouse, France
²Fresnel Institute, Marseille, France
In this presentation, we will review our recent progress in nonlinear conversion in grating-coupled Fabry-Pérot planar microcavities also known as Cavity-Resonant Integrated Grating Filters. Having established that enhanced second harmonic generation is obtained in these resonators, we will discuss the design and experimental demonstration of technical implantations allowing the achievement of critical coupling and improved conversion efficiencies.

Francesco De Lucia
Poled fibers for nonlinear photonics: Recent advances and future perspectives
F. De Lucia¹, N. Englebert¹, P. Parra-Rivas¹, C. Mas Arabí¹, R. Bannerman², M. I. M. A. Khudus², S.-P. Gorza¹, G. Brambilla², J. Gates², P. Sazio², and F. Leo¹
¹Service OPERA-Photonique – Université libre de Bruxelles, Brussels, Belgium
²Optoelectronics Research Centre, University of Southampton, UK
Silica fibers thermally poled possess a non-null second order nonlinear susceptibility and can consequently be exploited for the realization of parametric processes usually prohibited, such as for example second harmonic generation or parametric down conversion. In this talk we present their most recent applications, ranging from high harmonics generation to the implementation of an all-fiber optical parametric oscillator, and discuss some future perspectives of what we still consider a reliable technological platform for nonlinear photonics applications.

Carlos Alonso-Ramos
Optomechanical and nonlinear applications in silicon photonics
P. Nuño Ruano¹, J. Zhang^1,2, T. T. D. Dinh¹, D. González-Andrade¹, X. Le Roux¹, M. Montesinos-Ballester¹, C. Lafforgue¹, D. Medina-Quiroz¹, D. Benedikovic³, P. Cheben^2,4, S. Edmond¹, D. Bouville¹, N. D. Lanzillotti-Kimura¹, D. Marris-Morini¹, E. Cassan1, L. Vivien¹, and C. Alonso-Ramos¹
¹Université Paris-Saclay, CNRS, Centre de Nanosciences et de Nanotechnologies, Palaiseau, France
²National Research Council Canada, Ottawa, Canada
³University Science Park, University of Zilina, Slovakia
⁴Dept. Electronics, Carleton University, Ottawa, Canada
Periodically patterning silicon with a subwavelength pitch opens new degrees of freedom to control the propagation of light and sound in silicon photonic circuits with unprecedented flexibility. In this invited presentation, we will show our most recent results on the use suspended silicon waveguides for supercontinuum generation in the near-IR and mid-IR. We will also discuss our recent demonstrations of subwavelength engineering of photons and phonons in suspended and non-suspended silicon optomechanical cavities.

Concita Sibilia
Linear and nonlinear optical properties of Zno-ZnWO4 eutectic composites
C. Sibilia¹, G. Leahu¹, R. Li Voti¹, E. Petronjievic¹, M. C. Larciprete¹, M. Centini¹, A. Belardini¹, and D. Pawlak²
¹Dept SBAI, University of Roma La Sapienza, Italy
²Ensemble3 – Center of Excellence, Warsaw, Poland
Many different optical interesting and unusual properties of eutectics [1] ZnO/ZnWO₄ have been studied ranging from linear up to nonlinear optical properties in the visible range. The optical linear properties evidencing a strong polarization dependence of transmitted and reflected signal have been analyzed [2]. For example, the photodeflection method utilized for those sample was able to put into evidence the excitonic resonance in the blue region. Also, the nonlinear optical behavior was studied looking at the Second Harmonic generation: we used a set-up based on a pulsed Ti:Sapphire laser with 130 fs pulse duration, wavelength of 800 nm and repetition rate of 1 kHz as a pump light source. The polarization of the fundamental beam at the laser’s output was in p-state and it can be tuned by means of a rotating a half-wave plate at 800 nm. In order to suppress the SHG signal generated from the half-wave plate, a long pass filter was placed after the plate. The sample was placed on a rotational stage which enables tuning of the angle of incidence α. The light coming out of the sample was then filtered by a short pass filter and set to p or s state by a polarization analyzer before the detector. With this set-up the intensity of s or p SHG signal at the output as a function of the input polarization or α was detected and the corresponding conversion efficiency was estimated. The conversion efficiency was attributed to a phase matching condition enhancement due to the effective dispersion low of the eutectic compound [3,4]. The complex geometry of the eutectic composite reveals peculiar properties both in the visible and in the IR ranges acting as natural polarizing filters opening the way to new interesting photonics applications.
[1] D. A. Pawlak et al., Advanced Functional Materials 20, 1116-1124 (2010).
[2] P. Osewski et al., Advanced Optical Materials 8,1901617 (2020).
[3] C. J. Spengler, S. O’Hara, App. Optics vol. 3, no. 9 (1964).
[4] P. Osewski et al., Sci. Rep. 7, 45247 (2017).

Misha Sumetsky
SNAP platform: New ultraprecise fabrication methods and devices
M. Sumetsky, Aston Institute of Photonics Technologies, Aston University, Birmingham, UK
SNAP platform enables exceptionally precise fabrication of microresonators and microresonator circuits at the optical fibre surface with the subangstrom and, potentially, picometer fabrication precision. Here, the recently developed experimental approaches in SNAP technology and recently invented new SNAP devices are reviewed. The new approaches include fabrication of optical microresonators by lithographic methods, annealing in a flame, slow cooking, fibre bending, and fibre side-coupling. The new devices include microwave photonic filters, optical frequency comb generators, and bat microresonators.

Quantum Photonics invited presentations

Anthony Bennett
Quantum light emission from colour centres in aluminium nitride
A. Bennett, Cardiff University, UK

Adrien Bensemhoun
Bright multimode entanglement out of a SiN microring
A. Bensemhoun¹, V. D’Auria¹, M. Melalkia¹, G. Esposito¹, Y. Désières², S. Guerber², Q. Wilmart², K. Roux², S. Olivier², A. Zavatta^5,6, C. Gonzalez-Arciniegas³, O. Pfister³, A. Martin¹, J. Etesse¹, L. Labonté¹, G. Patera⁴, and S. Tanzilli¹
¹Université Côte d’Azur, CNRS, Institut de Physique de Nice (INPHYNI), UMR 7010, Nice,France
²Université Grenoble Alpes, CEA LETI, Grenoble, France
³Department of Physics, University of Virginia, Charlottesville, USA
⁴Université Lille, CNRS, PhLAM – Physique des Lasers Atomes et Molécules, Lille, France
⁵Istituto Nazionale di Ottica, Florence, Italy
⁶LENS and Department of Physics Astronomy, University of Firenze, Italy
We investigate, in continuous variable regime, multimode entanglement among different frequency components generated in a Silicon Nitride (SiN) micro-ring above its oscillation threshold. Entangled spectral modes at the micro-ring output form a frequency comb and generated in an extremely compact configurations (micro-rings with radius of about ten micrometers). The multimode structure opens up the possibility of connecting multiple users to a quantum network and/or increasing channel capacity across a set of users and can be exploit for quantum computing. In this work, we study multimode quantum states generated by four-wave mixing pumped by a continuous wave laser. In the regime of continuous variables, some pioneering works, all based on the SiN platform, have been reported, showing bi-partite quantum correlations in intensity or among field quadratures. Here, we present a theoretical analysis aiming at quantifying quadrature entanglement in different frequency comb regimes and show a transition between bi-partite to multipartite entanglement as a function of increased pump power and of the measurement parameters. In the simulations, multipartite entangled states are considered to be emitted in the telecommunication C-band so as to be compatible with standard optical fibers and off-the-shelf fiber-based components. We also present an experimental setup built to measure intensity correlations that are directly linked to quadratures and highlight multimode entanglement. Results on two mode intensity squeezing will be presented and discussed in the context of multimode dynamics.

Ortwin Hess
Nanoplasmonics as enabler of room-temperature quantum nanophotonic networks
O. Hess^1,2, ¹School of Physics and CRANN Institute, Trinity College Dublin, Ireland, ²The Blackett Laboratory, Imperial College London, UK
Quantum technologies are widely expected to bring a revolution in communications and information technologies in the coming decade allowing, for example, un-paralleled levels of secure communications. For quantum communication, photonic quantum effects have played a central role, but most photonic solutions and systems based on light-matter interaction also require cryogenic environments. Strong coupling of light and matter at the single emitter level is a fundamental quantum resource offering deterministic energy exchange between single photons and a two-level system, and the possibility to achieve single-photon nonlinearities via the anharmonicity of the Jaynes-Cummings ladder. Until recently, however, the conditions for achieving strong-coupling were most commonly met at cryogenic temperatures such that de-coherence processes are suppressed. As a major step forward, we have recently demonstrated room-temperature strong coupling of single molecules [1] and single quantum dots [2] to ultra-confined light fields in plasmonic resonators at ambient conditions. The fact that strong-coupling conditions may be reached at room temperature is of immense interest because it represents a clear route to a practical implementation and use of quantum behaviour in nanophotonic systems and its application in bio-sensing [3]. The talk will discuss how nanoplasmonics can be an enabler of ultrafast room-temperature quantum nanophotonic networks via strong coupling and ultrafast quantum dynamics [4]. We will highlight the physics associated with recently demonstrated room-temperature strong coupling of single molecules in a plasmonic nano-cavity [1] and near-field generated strong coupling of single quantum dots [2] and single quantum emitter Dicke enhancement [5] paving the road towards single-photon quantum nonlinearities. The presentation will also explain near-field enhanced single-photon emission in near-zero index materials [6] and ultrafast multi-partite quantum entanglement [7]. This provides the foundation for unprecedented control over photon number, single photon dynamics, and dynamic multi-photon coherence. These properties are all imperative for the development of next-generation, nanoscale building blocks in ambient-temperature photonic quantum communication technologies. ACKNOWLEDGEMENTS: Supported by the Science Foundation Ireland (SFI) via grants 18/RP/6236 and 22/QERA/3821.
[1] R. Chikkaraddy, B. de Nijs, F. Benz, S. J. Barrow, O. A. Scherman, E. Rosta, A. Demetriadou, P. Fox, O. Hess, and J. J. Baumberg, Single-molecule strong coupling at room temperature in plasmonic nanocavities, Nature 535, 127 (2016).
[2] H. Groß, J. M. Hamm, T. Tufarelli, O. Hess, and B. Hecht, Near-field strong coupling of single quantum dots, Science Advances 4, eaar4906 (2018).
[3] N. Kongsuwan, X. Xiong, P. Bai, J.-B. You, C. E. Png, L. Wu, and O. Hess, Quantum plasmonic immunoassay sensing, Nano Lett. 19, 5853 (2019).
[4] X. Xiong, N. Kongsuwan, Y. Lai, C. E. Png, L. Wu, and O. Hess, Room-temperature plexcitonic strong coupling: Ultrafast dynamics for quantum applications, Appl. Phys. Lett. 118, 130501 (2021).
[5] T. Tufarelli, D. Friedrich, H. Groß, J. Hamm, O. Hess, and B. Hecht, Single quantum emitter Dicke enhancement, Phys. Rev. Research 3, 033103 (2021).
[6] F. Bello, N. Kongsuwan, J. F. Donegan, and O. Hess, Controlled cavity-free, single-photon emission and bipartite entanglement of near-field-excited quantum emitters, Nano Lett. 20, 5830 (2020).
[7] F. D. Bello, N. Kongsuwan, and O. Hess, Near-field generation and control of ultrafast, multipartite entanglement for quantum nanoplasmonic networks, Nano Lett. 22, 2801 (2022).
Keywords: quantum nanophotonic networks, nanoplasmonics, room-temperature strong coupling, single-emitter Dicke enhancement, single photon quantum nonlinearity, quantum entanglement

Marco Liscidini
Efficient generation of squeezed light via spontaneous four-wave mixing in integrated structures
A. Viola, L. Zatti, and M. Liscidini, Università degli Studi di Pavia, Italy
We investigate the use of integrated structures for the efficient generation of squeezed light via dual-pump spontaneous four-wave mixing. We consider the case of ring resonators, in which resonant field enhancement is typically used to greatly increase the efficiency of nonlinear interactions. We show that in these structures the presence of a comb of equally spaced resonances can also lead to the enhancement of parasitic processes that can degrade the quality of the generated light, thus limiting the available squeezing. Here, we discuss possible solutions to this issue, and we introduce a device comprising of a ring resonator and a resonant interferometric coupler able to selectively control the resonant field enhancement. We show that through this structure one can strongly limit the effect of parasitic processes and overcome the intrinsic limitations of a single ring resonator. Finally, we model the effect of nonlinear parasitic processes and provide an analytic expression of the achievable squeezing.

Khaled Mnaymneh
Silicon nitride integrated quantum photonics
K. Mnaymneh, E. Yeung, D. B. Northeast, S. Haffouz, J. Lapointe, P. J. Poole, D. Dalacu, and R. L. Williams
National Research Council Canada, Ottawa, Canada
In this talk, we present our recent work in field-ready quantum technologies. Using silicon nitride as a materials platform for scalable quantum optics, we demonstrate in-plane, high-quality non-classical light from our III-V nanowire sources integrated on pre-fabricated photonic circuits. We conclude with future directions and next steps.

Markus Pollnau
Quantum-optical condition for photons/bosons equivalent to Pauli’s exclusion principle, general differential equation of thermal equilibrium, and novel relation between Boltzmann, Fermi-Dirac, and Bose-Einstein distribution
M. Pollnau, University of Surrey, Guildford, UK
By exploiting Einstein’s rate-equation approach [A. Einstein, Phys. Z. 18, 121 (1917)] to Planck’s law of blackbody radiation [M. Planck, Ann. Phys. 309, 553 (1901)], we obtain a simple relation between the population densities of the two energy levels of the atomic oscillators in the walls of the black body, as assumed by Einstein in his paper from 1917, and the occupation numbers in a photonic excited and ground state. This relation establishes a quantum condition for photons and, more generally, all bosons, which has the same physical relevance as Pauli’s exclusion principle [W. Pauli, Z. Phys. 31, 765 (1925)], the quantum condition for fermions. We then derive a differential equation of thermal equilibrium, which is independent of the nature of particles involved and, hence, of general validity. Simple integration delivers the Boltzmann distribution [L. Boltzmann, Sitzungsber. Kais. Akad. Wiss. Wien Math. Naturwiss. Classe 76, 373 (1877)], which therefore emerges as the most general distribution that quantifies a thermal equilibrium. Exploiting the established quantum conditions for fermions or bosons, simple integration of the same general differential equation of thermal equilibrium delivers the Fermi-Dirac [E. Fermi, Rendiconti Lincei 3, 145 (1926)] and Bose-Einstein [Bose, Z. Phys. 26, 178 (1924)] distribution, respectively. Since these two distributions each require an additional condition, they emerge as special cases of the general Boltzmann distribution. This result is further underlined by the fact that inserting either quantum condition directly into the Boltzmann distribution transforms it directly into either the Fermi-Dirac or the Bose-Einstein distribution. This finding implies that fermions and bosons simultaneously obey both their own specific and the general Boltzmann distribution. The results presented in this paper raise serious questions about the concept of distinguishable classical particles and indistinguishable quantum particles. It would imply that fermions and bosons are simultaneously distinguishable and indistinguishable particles.

Constantin Simovski
Spatial Fano resonance and its implication for a glass microsphere
V. Klimov¹, R. Heydarian², and C. Simovski²
¹Lebedev Physical Institute, Russia
²Aalto University, Finland
The well-known Fano resonance (a rather broad maximum adjacent to a sharp narrow minimum) was initially discovered in quantum mechanics, but, nowadays, it is well known also in classical optics. In optics, it is commonly thought as a kind of resonant frequency dispersion of absorption or extinction cross section of resonant scattering objects. Sometimes, it is also revealed for electric or magnetic polarizabilities of nanoparticles, but, in any case, it is considered as a feature of a parameter and not of a field. However, if we look at the underlying physics of this resonance, we will see that this resonance can nicely refer to the light itself. Really, it results from the interference of a continuum of the object eigenstates with its resonant state. Conventionally, these are either energy states or eigenfrequencies. However, in the diffraction by an optically substantial object, such as a microsphere illuminated by visible light, all non-resonant terms of the Mie expansion form the quasi-continuum in space and can nicely interfere with the resonant multipole field. If this interference is pronounced, we must observe the Fano resonance is space. Moreover, we may engineer this resonance so that the Fano maximum is inside the sphere and the sharp minimum is outside it, in free space. Indeed, for a pronounced interference we need the approximate equivalence of the magnitudes of the resonant mode and the quasi-continuum. For a single plane wave impinging on the sphere this equivalence is not achievable. We have shown that this condition is respected when the sphere is illuminated by a hollow wave beam, e. g. by the 1st order Bessel beam. In this case the spatial Fano resonance is present, and its minimum located behind the sphere is a subwavelength spot, in which electromagnetic field nullifies. Since this region in free space is tiny and cold, it is suitable for trapping not only small nanoparticles but also molecules and atoms. This claim is confirmed by calculations of the operational parameters of the trap. An experimental demonstration of this unique and simple trap would open new doors in optical trapping.

Quantum Communications invited presentations

Gustavo Anjos
An FPGA-based physical layer approach for CV-QKD systems
G. Anjos¹, M. Almeida^1,2, J. Martins^1,2, N. Silva¹, N. Muga¹, and A. N. Pinto^1,2
¹Instituto de Telecomunicações, Aveiro, Portugal
²Department of Electronics, Telecommunications and Informatics, University of Aveiro, Aveiro, Portugal
Quantum key distribution (QKD) provides a secure and effective way of exchanging cryptographic symmetric keys without the possibility of an eavesdropper being undetected. The transmission and detection of the quantum states at the physical layer is the first step to defining a common source of entropy, where both parties will extract a raw key. Over the last few years, continuous variable quantum key distribution (CV-QKD) protocols have become an attractive technology for QKD, providing a low-cost solution that can be easily integrated with the current optical network devices and infrastructure. In this case, the key material is encoded in the phase and amplitude quadratures of the optical field, with coherent detection being employed at the receiver side to recover the raw key. Unlike other QKD technologies, a CV protocol requires complex and highly computationally demanding digital signal processing (DSP) operations. In that sense, parallel computation tools such as field programmable gate arrays (FPGAs) represent a key element for the practical implementation of this quantum technology and to scale its performance in terms of distance and secret key rate indicators. This work presents an FPGA-based implementation of the physical layer of a CV-QKD system. The proposed architecture and employed protocols are described, and hardware implementation aspects are discussed, including resource occupation analysis, configuration parameters, and timing issues. Moreover, the controlling mechanisms needed to synchronize with the post-processing layer, and also to orchestrate the commutation between the calibration and key generation modes are described. The integration of the FPGA with the quantum front-end is also presented.

Ramon Aparicio-Pardo
Quantum entanglement management via reinforcement learning
R. Aparicio-Pardo and A. Cousson, Université Côte d’Azur, CNRS, Sophia Antipolis, France
Abstract: Quantum communications make use of the quantum entanglement as fundamental resource. When two qubits are entangled, their state changes exhibit non-classical correlations, regardless of the physical distance between them, that can be used to design new applications not possible with classical communication, such us quantum key distribution or distributed quantum computation. Unfortunately, quantum entanglement is a probabilistic process strongly dependent on the features of involved devices (optical fibers, lasers, quantum memories, …). The management decisions (i.e., the control policy) to set up and to keep the entanglement as long as possible with the highest quality constitutes a stochastic control problem. This Entanglement Management Problem (EMP) can be modelled as Markov Decision Process (MDP) and solved under the Reinforcement Learning (RL) framework (a form of Machine Learning). In this work, we apply this RL framework to learn an entanglement management policy outperforming the State-of-the-Art policy without requiring models characterizing precisely the involved quantum devices.

Davide Bacco
BB84 decoy-state QKD protocol over long-distance optical fiber
G. Guarda^1,2, D. Ribezzo^2,3, T. Occhipinti⁴, A. Zavatta^4,2, and D. Bacco^4,5
¹European Laboratory for Non-Linear Spectroscopy, Sesto Fiorentino, Italy
²Istituto Nazionale di Ottica del Consiglio Nazionale delle Ricerche, Firenze, Italy
³Universita degli Studi di Napoli Federico II, Napoli, Italy
⁴QTI S.r.l., Firenze, Italy
⁵Universita degli Studi di Firenze, Department of Physics and Astronomy, Firenze, Italy
Quantum key distribution represents one of the most mature and well-studied advances in quantum technologies. Many protocols have been implemented, breaking record distances both employing satellites and fiber-based systems. However, there still are open challenges in achieving long distance links without implementing quantum repeaters. One of the main limiting factors comes from the non-ideality of detection systems, in particular from intrinsic dark counts. As the covered distances increase, the signal decreases in intensity and the noise in the detector prevails, hindering the extraction of a secret key. In this work, we propose the use of high-performance state-of-the-art superconducting nanowire single-photon detectors (SNSPD) showing ultra-low dark count rates to reduce the quantum bit error rate (QBER) in the detection system. The transmitter adopts the well-tested three-state BB84 protocol with the decoy-state method and the signal travels through an optical fiber channel.

Massimo Borghi
Programmable silicon photonic sources of frequency bin entangled qubits and qudits
M. Borghi, N. Tagliavacche, F. A. Sabattoli, H. El Dirani, L. Youssef, C. Petit-Etienne, E. Pargon, J. E. Sipe, M. Liscidini, C. Sciancalepore, M. Galli, and D. Bajoni, Università di Pavia, Italy
In the last few years, photonic quantum architectures based on high dimensional encoding have been developed with applications ranging from quantum computation to secure communication. Photonic qudits can be efficiently prepared due to the wide variety of degrees of freedom that photons possess. For example, quantum optical microcombs in integrated ring resonators generate entangled photon pairs over many spectral modes, which can be manipulated with off-the-shelf fiber optic components. Ideally, those sources should be programmable and have a high generation rate, with the comb lines tightly spaced for the implementation of efficient quantum gates based on electro-optic frequency mixing. While these requirements cannot all be satisfied by a single resonator device, where there is a trade-off between high generation rate and high finesse, a promising strategy is in the use of multiple resonators, each generating photon pairs in specific frequency bins via spontaneous four-wave mixing. Based on this concept we present programmable silicon photonic devices for the generation of frequency bin entangled qubits and qudits, in which bin spacing, qudit dimension, and bipartite quantum state can be reconfigured on-chip. Using small size ring resonators with a radius of tens of microns, we achieve a high brightness (MHz/mW²) per comb line with a bin spacing down to 15 GHz, and fidelities above 85% with maximally entangled Bell states up to a dimension of four. Our results point the way to the efficient generation and manipulation of high dimensional, frequency-bin-encoded multipartite states.

Hans Brunner
CV-QKD design for network integration
H. H. Brunner, C.-H. F. Fung, and M. Peev, Huawei Technologies Düsseldorf GmbH, Germany
Continuous-variable quantum key distribution (CV-QKD) has reached significant maturity. Considerations about how to integrated it into optical communication networks become necessary. As QKD only provides key exchange, this technology cannot take a central role in optical network design but has to adapt to the requirements of the network. In this article compact CV-QKD prototypes with several key features facilitating network integration are presented. Among these features are the coverage of typical metro link losses with automatic adaptation to the channel conditions as well as in-band synchronization to reduce its spectral needs to a single DWDM channel. In many situations, this full C-band tunable channel can simply be connected to a free multiplexer port of an DWDM infrastructure without any interruption of existing traffic. Additionally, any-to-any connectivity can reduce the number of devices, while dynamic protocol switching allows to address different cryptographic requirements. The prototypes as well as their features have been demonstrated in an operational environment.

Goran Djordjevic
Security analysis of quantum key distribution protocol over FSO system influenced by Málaga atmospheric turbulence
G. T. Djordjevic¹ and I. B. Djordjevic²
¹Faculty of Electronic Engineering, University of Niš, Serbia
²University of Arizona, Tucson, USA
In this paper, we consider quantum key distribution protocol that can be applied over terrestrial free space optical links where atmospheric turbulence effects are modeled by general Málaga distribution. Málaga distribution for modeling the atmospheric turbulence channel is appropriate when there is a light line-of-sight component (LOS), as well as scattered components by the eddies on the propagation axis and off-axis eddies. Some other distributions are particular cases of Málaga distribution for specific numerical values of its parameters, and consequently the results presented in this paper are very general. By applying analytical approach, we study the secrecy performance of this system. We evaluate quantum bit error rate and secret key rate. We examine the effect of different channel and receiver parameters on these metrics.

Verónica Fernández
Photonic integrated circuits and components for quantum key distribution
D. Cano, D. Balado, and V. Fernández, Instituto de Tecnologías Físicas y de la Información, CSIC, Madrid, Spain
In this talk, we present designs of photonic integrated circuits and components for applications in quantum communications. The goal is to miniaturize the instrumentation while optimizing the security of various quantum key distribution protocols, such as BB84 with different qubit encodings, and measurement-device-independent protocols (MDI-QKD). The proposed components include diffraction gratings for polarization coupling, on-chip path-polarization interconverters, nanoantennas, and graphene nanocavities for coupling individual photon emitters. We simulate the behavior of the proposed circuits and components, and analyze the quantum key error for different parameters, comparing the advantages of single photons and weak coherent states.

Tawfik Ismail
Feasibility analysis of uplink quantum communication with hap considering beam wandering and weather dependence
N. Alshaer and T. Ismail, National Institute of Laser Enhanced Sciences, Cairo University, Giza, Egypt
The encryption process is essential for ensuring data protection and privacy. However, as computational power grows exponentially, breaking the encrypted data becomes feasible. This leads to insecure data transmission over a public channel. Quantum key distribution is a secure communication mechanism that allows shared parties to exchange encryption keys periodically. Furthermore, it has the ability to detect eavesdropping since the error level becomes higher when she attempts to access the communication channel. This paper studies and analysis the performance of the uplink quantum channel between the ground station and the high-altitude platform system (HAPS). In order to achieve optimal performance, the system parameters, such as modulation variance, receiver aperture, and zenith angle influence, are tuned with consideration to the effects of weather conditions and beam wandering.

Vicente Martin
The Madrid testbed: QKD SDN control and key management in a production network
V. Martin, University Polytechnic the Madrid, Spain

Michał Parniak-Niedojadło
Atomic ensembles as nodes of quantum and classical optical networks
M. Parniak, M. Mazelanik, A. Leszczyński, M. Lipka, W. Wasilewski, M. Jastrzębski, S. Kurzyna, B. Niewelt, J. Nowosielski, S. Borówka, and U. Pylypenko
Centre for Quantum Optical Technologies, Centre of New Technologies, University of Warsaw, Poland
Photons are excellent carriers of information as they can be easily transmitted over long distances. However, in quantum information science we often cannot accept almost any loss of light, and direct amplification is forbidden as it would introduce noise, which would in turn compromise security of the quantum link. This issue led to the invention of quantum repeaters, which may probabilistically repeat a weak quantum signal without introducing noise. Atomic ensembles can serve as physical implementations of quantum repeaters, as they can generate, process and store the optical photons travelling along the link. I will present our recent advances in introducing multiplexing into the atomic-ensemble technology, and our ideas how those systems well known in fundamental physics can be applied in quantum communications. In most recent times a need arises also to connect remote quantum computers, often based on superconducting qubits operating with GHz microwave photons. Our atomic ensembles, when excited to Rydberg states, may serve as interconnects between those microwave devices and optical networks.

Paola Parolari
Integration of the QKD layer in fibre networks using multicore fibres
P. Parolari, A. Gagliano, A. Gatto, P. Boffi, T. Hayashi, A. Mecozzi, C. Antonelli, and P. Martelli
Politecnico di Milano, PoliCom – Dip. Elettronica Informazione e Bioingegneria, Milano, Italy
Uncoupled multicore fibres (MCFs) are a suitable solution for integrating the quantum communication systems in WDM networks. The performance of the QKD layer is in fact impaired by nonlinear effects generated by the classical channels. MCFs allow a smart management of classical and quantum key carriers coexistence, preserving the secret key rate generation thanks to a proper choice of the wavelength-core allocation plan.

Armando Nolasco Pinto
Quantum assisted secure multiparty computation
A. Nolasco Pinto et al., Universidade de Aveiro, Instituto de Telecomunicações, Aveiro, Portugal
We will present our recent advances in the implementation of secure multiparty computation services based on quantum technology. We will also highlight the advantages of using quantum technology in comparison with a fully classical approach.

Matteo Schiavon
High-speed continuous-variable quantum key distribution with advanced digital signal processing
M. Schiavon, Y. Piétri, L. Trigo Vidarte, D. Fruleux, M. Huguenot, B. Gourand, A. Rhouni, P. Grangier, and E. Diamanti, Sorbonne Université, CNRS, Paris, France
Continuous-variable quantum key distribution (CV-QKD) is a promising solution for providing high secure key rates in moderate channel loss regime. A great advantage with respect to discrete-variable (DV) systems is the use of a technology similar to the one use in classical coherent communication, in particular for the detection system, which can operate at room temperature and benefits from an easier integration process. In addition to this, the use of advanced digital signal processing (DSP) techniques developed for classical communication allows for bandwidth-efficient temporal shaping, which optimizes the performance of the CV-QKD system. These techniques applied to the detected signal are also fundamental for using a locally generated local oscillator, correcting frequency and phase differences using frequency-multiplexed pilots generated by the transmitting laser. In this presentation, we will describe how these techniques can be applied to a CV-QKD system and show some recent experimental results obtained by our research group, including results for a receiver based on a Photonic Integrated Circuit (PIC).

Gabriel Senno
On the proper quantification of the randomness produced by QRNGs
G. Senno^1,2, T. Strohm³, and A. Acín^1,4
¹ICFO-Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, Spain
²Quside Technologies S.L., Barcelona, Spain
³Corporate Research, Robert Bosch GmbH, Renningen, Germany
⁴ICREA-Institucio Catalana de Recerca i Estudis Avançats, Barcelona, Spain
An ideal QRNG, such as one that prepares spin-1/2 states in the +Z direction and measures them in the X direction, produces bits that are uniformly random and independent of any pre-existing information. However, the prepared states and the measurements performed in real quantum devices are always imperfect or noisy. This introduces an unavoidable element of stochasticity that leads to an apparent randomness not intrinsic to quantum theory. Operationally, this stochasticity is modeled through correlations with an external observer, Eve, whose goal is to make the best guess about the device’s outcomes. In the quantum information literature, the so-called side information provided to Eve has usually been limited to the state. In this talk, we will present a general framework for the quantification of quantum randomness accounting for arbitrary noise both in the state and in the measurements. Finally, we will report on the recent progress in applying this theoretical framework to Quside’s QRNGs.

Grzegorz Sęk
Towards practical QD-based single photon sources in the telecom range
G. Sęk, Wroclaw University of Science and Technology, Poland
Secure quantum communication requires on-demand bright sources of single photons with ultra-low probabilities of multiphoton events and very good emission extraction efficiency to provide high transmission rates. It is of particular importance to transfer the developments from proof-of-principle experiments at shorter wavelengths to telecom wavelengths for compatibility with the existing low-loss fiber networks, especially for long-haul communication. In that respect, semiconductor nanostructures have been proven as prospective and flexible solid-state platform, which is a mature nanotechnology allowing for scalability and integration. It already enabled realization of many fundamental quantum optics experiments revealing the potential of epitaxial quantum dots for quantum communication and quantum networks applications. Nowadays much effort is devoted to improvement of the emitters’ performance and realization of more practical devices. In this contribution there will be overviewed our recent results on engineering and investigation of the electronic and optical properties of quantum emitters suitable for the 1.3-1.55 µm spectral range, made of two different material systems of InGaAs on GaAs and InAs on InP, and further on development of efficient quantum-dot-based single photon sources within such platforms. For various classes of quantum dot materials there will be discussed the currently achievable single photon emission purity and its temperature stability, always in conjunction with the underlying physics of excitonic complexes confined in such nanostructures or the related fundamental limitations on the side of technology and fabrication. In addition, there will be elaborated the issue of photonic confinement engineering and placing quantum dots in especially designed, spectrally broadband photonic structures of various geometries for controlling the emission rates, linear polarization degree as well as improving the extraction efficiency. Possibility to generate entangled photon pairs for selected examples of telecom quantum dots will also be discussed. Eventually, there will be described a solution for constructing compact, robust, portable and cryogenic-free plug and play fiber-based sources operating at telecom wavelengths.

Nuno Silva
A network server for distributing quantum random numbers
N. A. Silva¹, M. Ferreira^1,2, M. A. Carvalho¹, A. Souto^3,4, N. Paunković³, P. Mateus^2,4, A. Teixeira^1,2, and A. N. Pinto^1,2
¹Instituto de Telecomunicações, University of Aveiro, Portugal
²Department of Electronics, Telecommunications, and Informatics, University of Aveiro, Portugal
³Instituto de Telecomunicações, Lisbon, Portugal
⁴LASIGE, Departamento de Informática, Faculdade de Ciências, Universidade de Lisboa, Portugal
⁵Departamento de Matemática, Instituto Superior Técnico, Universidade de Lisboa, Portugal
Quantum random number generators (QRNGs) based on homodyne detection have a potential to be a cost-effective solution to deploy random numbers at high-speed rates over networks. The new information technologies, such as quantum key distribution, cloud computing, and big data, demands true randomness for those cryptosystems to be secure and private. This is incompatible with known security loopholes of classical pseudo-random number generators. In this work, we discuss our recent advances in the implementation of a vacuum-based QRNG service to be used in a distributed network environment. We will also highlight the advantages of using quantum technologies to generate random numbers in comparison with classical approaches.

Michela Svaluto Moreolo
Efficient solutions for quantum secure communications in future optical networks
M. Svaluto Moreolo, Centre Tecnològic de Telecomunicacions de Catalunya (CTTC/CERCA), Spain
To face the quantum era and the prospect or threat of quantum computing, especially in a disaggregated network environment, the design and implementation of efficient quantum secure communication systems facilitating their integration in the optical network infrastructure is key. Quantum key distribution (QKD) is one of the most promising technologies to ensure long-term security. In particular, continuous-variable QKD results an efficient solution more compatible and suitable to be integrated with conventional optical systems. In this invited talk, quantum secure systems based on QKD for enabling a smooth and sustainable integration in optical networks are introduced, considering the related challenges, towards future secure 6G networks.

Alessandro Zavatta
Advances on the feasibility analysis of underwater optical communications
M. Pinel^1,3,4, S. Cocchi^2,3, C. De Lazzari³, M. Menchetti³, T. Occhipinti³, A. Zavatta^3,4, and D. Bacco^2,3
¹Università degli Studi di Napoli Federico II, Italy
²Department of Physics and Astronomy, Università degli Studi di Firenze, Italy
³QTI S.r.l., Firenze, Italy
⁴Istituto Nazionale di Ottica del Consiglio Nazionale delle Ricerche (CNR-INO), Firenze, Italy
In this work we study the underwater optical channel, making a feasibility analysis on the development of a high-speed communication system with security guaranteed by Quantum Key Distribution (QKD).
In particular, we introduce a new model for the attenuation of the underwater medium which includes the effect of turbulence within the marine environment. We report the performance of the system focusing on the most important figures of merit, such as the Secret Key Rate of the quantum channel and the bit rate of the classical channel at the physical layer as a function of the total link range. We carried out these analyzes depending on various environmental conditions, such as the geographical area, depth, path-loss and turbulence models. The communication protocols are BB84 with time-bin encoding for QKD and baseband On-Off Keying (OOK) modulation for classical data communication for a maximum link range of 100 meters.

Quantum Photonics invited presentations

Eilon Poem
Photon synchronization with a room-temperature atomic quantum memory
O. Davidson, O. Yogev, E. Poem, and O. Firstenberg
Department of Physics of Complex Systems, Weizmann Institute of Science, Rehovot, Israel
Efficient synchronization of single photons that are compatible with narrowband atomic transitions is an outstanding challenge, which could prove essential for photonic quantum information processing. Here, we report on the synchronization of independently-generated single photons using room-temperature atomic quantum memory. The photon source [1,2] and the memory [3,4] are interconnected by fibers and employ the same `ladder’ atomic-level scheme. We store and retrieve the heralded single photons with end-to-end efficiency of 25% and final anti-bunching of g=0.023. Our synchronization process increases the photon-pair coincidence rates by a factor of about 30, reaching over 1000 detected synchronized photon pairs per second. The fidelity of the synchronized photons and their indistinguishability from the unstored photons are quantified by a Hong-Ou-Mandel interference measurement, yielding less than 10% fidelity degradation, due mostly to temporal-shape change during retrieval.
[1] O. Davidson et al., New J. Phys 23, 073050 (2021).
[2] O. Davidson et al., arXiv:2301.06049 (2023).
[3] R. Finkelstein et al., Science Adv. 4, eaap8598 (2018).
[4] O. Davidson et al., arXiv:2212.04263 (2022).

RONEXT invited presentations

Marcelo Abbade
Enhancement of security of inter data centre links with spectral polarization scrambling and phase encoding
M. Pereira Nogueira, P. P. Pareto Junior, I. Aldaya, and M. L. F. Abbade
São Paulo State University, School of Engineering, São João da Boa Vista, Brazil
Encryption is a key technology for providing confidentiality and integrity for communication systems. It is implemented in all upper communication layers by well-established commercial standards. However, the physical layer converts bits to signals, which are not encrypted. This situation generates a harmful security bottleneck that needs to be circumvented. In this work, we propose a new signal encryption scheme for dual polarization optical communication systems that is based on the spectral scrambling of base-band signals of the two orthogonal polarizations. The performance of the new encryption scheme, combined with spectral phase encoding, is analysed by means of computer simulations in the security-sensitive scenario of inter data centres links.

Khouloud Abdelli
Fault monitoring in passive optical networks using machine learning techniques
K. Abdelli¹, C. Tropschug², H. Griesser²,and S. Pachnicke¹
¹Kiel University, Germany
²ADVA Optical Networking, Germany
Passive optical network (PON) systems are susceptible to a wide range of failures, including fiber cuts and optical network unit (ONU) transmitter/receiver failures. Any interruption of service caused by a fiber cut can result in significant financial losses for service providers or operators. In the case of almost equidistant branch terminations, identifying the faulty ONU becomes difficult because the reflections from the branches overlap, making it difficult to distinguish the faulty branch given the global backscattering signal. The complexity of fault surveillance increases with the number of fiber links to be monitored, resulting in less reliable monitoring. To deal with these challenges, we propose in this paper different machine learning (ML) approaches for fault monitoring in PON systems and we validate them using experimental optical time domain reflectometry (OTDR) data.

Marija Furdek
A multi-objective heuristic algorithm for proactive spectrum defragmentation in elastic optical networks
E. Etezadi¹, C. Natalino¹, R. Diaz², A. Lindgren², S. Melin², L. Wosinska¹, P. Monti¹, and Marija Furdek¹
¹Department of Electrical Engineering, Chalmers University of Technology, Gothenburg, Sweden
²Telia AB, Solna, Sweden
One of the main obstacles of efficient resource usage under dynamic traffic in elastic optical networks (EON) is spectrum fragmentation, where fragmented spectrum slots increase the blocking probability of incoming service requests. Proactive spectrum defragmentation approaches deal with this issue by trying to prevent blocking from occurring, typically through periodical reallocation of a fixed number of connections. The connections are commonly selected for reallocation based on their properties such as age, without detailed consideration of the spectrum occupancy states. In this work, we propose a heuristic algorithm for proactive spectrum defragmentation that combines several frag- mentation metrics to find the best connections to re-configure. We analyze the relationship between different fragmentation metrics and the resulting service blocking probability. Simulation results show that the proposed heuristic algorithm outperforms the existing proactive spectrum defragmentation algorithms, achieving lower blocking probability at the same defragmentation overhead.

Anderson Sanches
Analysis of eavesdropping on optical 2-D OCDMA networks
M. Sebastião¹, A. Sanches¹, R. Nóbrega¹, H. Mrabet², I. Glesk³, S. Haxha⁴, A. Jurado-Navas⁵, and T. Raddo⁵
¹CECS-Information Engineering, Federal University of ABC, Santo Andre, Brazil
²Tunisia Polytechnic School, University of Carthage, Tunis, Tunisia
³Faculty of Engineering, University of Strathclyde, Glasgow, UK
⁴Dept. of Electronic Engineering, Royal Holloway University of London, Egham, UK
⁵Dept. of Comm. Engineering, University of Malaga, Spain
Cybersecurity and cyber resilience are becoming crucial for many industries, especially in the era of digital transformation. In this work, we report on the security analysis of the physical layer of OCDMA networks based on 2-D codes such as fast frequency-hopping (FFH). We analyze eavesdropping in OCDMA networks using FFH codes spread in both, time and frequency domains that use quadrature phase-shift keying (QPSK). The analysis is based on a newly derived bit error rate (BER) formula considering the eavesdropper’s partial knowledge of the 2-D code that is needed to replicate the ONU decoder. An analytical formalism for evaluating the BER performance of the network is derived by considering 2-D codes, QPSK modulation format, avalanche photodiode shot noise, thermal noise, and multiple-access interference among optical network units (ONUs). Numerical results show that the intercepted signal is hard to decode and the information retrieved when the eavesdropper makes more than one error in guessing the used ONU code. It is shown the number of simultaneous ONUs substantially affects the eavesdropper’s capability to decode the intercepted signal. The novel 2-D FFH signal encoding is robust against eavesdropper interception. It offers a feasible solution to increase security levels in practical optical networks.

Shabnam Sultana
Resilient control-plane design for T-SDN based optical transport networks
S. Sultana^1,2, R. Romero Reyes¹, K. T. Nguyen¹, and T. Bauschert¹
¹Chair for Communication Networks, Technische Universität Chemnitz, Germany
²highstreet technologies GmbH Berlin, Germany
With the emerging focus on the control plane design of SDN-based networks, numerous studies have solved the controller placement problem with diverse objectives. However, the design of the control plane itself has not been thoroughly studied, especially for Transport (T-SDN) based networks. To close this gap, we proposed in our previous work a heuristic method for the design of a centralized control plane for T-SDN networks. The approach determines the optimal number and placement of control-plane interfaces as well as the routing of the control-plane traffic. The objective is to minimize the cost of the control-plane w.r.t. the number of control plane interfaces and the capacity consumed by the control plane traffic. For that, the assumption was made that only a subset of transport nodes is directly connected to a single central controller through the control interfaces, while the control traffic of the remaining nodes is forwarded via dedicated connections. In this paper, we consider the extended control plane design problem by assuming a distributed T-SDN control-plane consisting of multiple interconnected controllers and extend our method accordingly so as to determine the optimal number and placement of the controllers as well as the optimal routing of the controller-node traffic and the controller-controller traffic considering reliability constraints (i.e., robustness w.r.t. single node or single link failures). The performance of the method is assessed for selected transport network topologies for which we analyse the impact of the cost parameters on the control-plane network design.

SDM-WDM invited presentations

Tiago Alves
On the use of feedforward neural networks to improve the ICXT tolerance in self-coherent MCF systems
T. M. F. Alves, J. L. Rebola, and A. V. T. Cartaxo
Instituto de Telecomunicações-IUL, Iscte – Instituto Universitário de Lisboa, Portugal
In this work, machine learning techniques based on artificial neural networks are investigated to improve the performance of self-coherent short-reach weakly-coupled multicore fibre (WC-MCF) systems. Particularly, a feedforward neural network is proposed to mitigate the performance degradation induced by the random variation of the intercore crosstalk (ICXT) along time in 200 Gb/s quadrature amplitude modulation WC-MCF systems. A product between the skew and the symbol rate much lower than one and a self-coherent receiver based on Kramers-Kronig technique, are considered.
Keywords: Intercore crosstalk, multicore fibres, neural networks, self-coherent receivers, space-division multiplexing.

Adolfo Cartaxo
Limitations induced by core-dependent loss on the intercore crosstalk of concatenated uncoupled multicore fiber systems
J. L. Rebola and A. V. T. Cartaxo
Instituto de Telecomunicações, Iscte – Instituto Universitário de Lisboa, Portugal
We study the effect and performance limitations induced by core-dependent loss (CDL) on the intercore crosstalk of uncoupled multi-core fibers (MCFs). The CDL influence of concatenating a high number of MCF segments and long MCF spans that require amplification will be analyzed and discussed.

Ivana Gasulla
Dispersion-diversity signal processing in space-division multiplexing fibers
S. García, E. Nazemosadat, M. Ureña, and I. Gasulla
Photonics Research Labs, iTEAM Research Institute, Universitat Politecnica de Valencia, Spain
Beyond high-capacity digital communications, space-division multiplexing fibers bring significant benefits to microwave signal distribution and processing, as not only space but also chromatic dispersion are introduced as new degrees of freedom. The key lies in developing new fibers where each individual core/mode is tailored to provide parallel dispersion-diversity signal processing.

Nelson Muga
Self-coherent detection in multicore fiber systems impaired by intercore crosstalk
N. J. Muga¹, T. M. F. Alves^3,4, R. K. Patel¹, A. N. Pinto^1,2, and A. V. T. Cartaxo^3,4
¹Instituto de Telecomunicações, Aveiro, Portugal
²Department of Electronics, Telecommunications, and Informatics, University of Aveiro, Portugal
³Instituto de Telecomunicações, Lisbon, Portugal
⁴Iscte – Instituto Universitário de Lisboa, Portugal
Space division multiplexing transmission, employing multicore fibers, as well as simplified coherent detection technologies have been intensively investigated in recent years to accommodate the demand for energy-efficient short-reach fiber-optic communication systems with extremely high capacity. Indeed, the conjugation of multicore fibers and simplified coherent receivers can be explored as a promising scheme to tackle the problems of capacity constraints in data center networks. This paper presents our recent investigations on the exploitation and optimization of novel simplified coherent detection techniques, e.g. Kramers-Kronig and DC-Value methods, and on the performance assessment of weakly-coupled MCF-based systems employing such new coherent detection receivers.
Keywords: self-coherent receivers, digital signal processing, multi-core fibers, space-division multiplexing, weakly-coupled.

Masatoshi Suzuki
High-capacity and ultra-long-haul transmission over transoceanic distances using coupled and uncoupled 4-core fibers with standard cladding diameter
M. Suzuki, D. Soma, S. Beppu, Y. Wakayama, N. Yoshikane, and T. Tsuritani, Waseda University, Japan
High-capacity transmission experiments using coupled and uncoupled 4-core fibers with standard cladding diameter are discussed. 62.9 Tbit/s and 50.4 Tbit/s transmissions over 9150 km have been achieved with uncoupled and coupled 4-core fibers, respectively. Real-time MIMO processing for coupled 4-core fiber transmission over 7200 km and FIFO less EDFAs for submarine cable systems are also discussed.

João Pedro
Comparison of performance models for software-defined wideband optical networks
J. Pedro, Infinera, Carnaxide, Portugal
Having a fast but still sufficiently accurate quality of transmission (QoT) estimation method is fundamental for efficient and cost-effective optical network planning and operation. However, accurately evaluating the performance of multi-band systems with low/moderate computational complexity is challenging because of the increased impact of the Stimulated Raman Scattering (SRS) effect. The generalized signal-to-noise ratio (GSNR) considers the effect of the additive Gaussian disturbances and the nonlinear interference and is a reasonably accurate estimate of the QoT in coherent multilevel-modulated dispersion uncompensated wavelength division multiplexed optical transmission systems. In this work, we perform a comprehensive comparison of the accuracy and computation time of the main methodologies for GSNR estimation on transmission systems with bandwidths of up to 20 THz, considering also the impact on system capacity on a reference backbone network.

SDM for High-Capacity Transmission invited presentations

Filipe Ferreira
On the scaling of the number of modes in mode division multiplexing systems
F. M. Ferreira, F. A. Barbosa, and R. Yadav
University College London, UK
We review our recent advances on the design of multimode fibres with hundreds of spatial pathways for reduced differential mode delay in the C-band and on the development of adaptable spatial multiplexing techniques to enable scalability of all data pathways.

Norbert Hanik
Optimization of ultra-broadband optical wavelength-conversion in nonlinear multi-modal silicon-on-insulator waveguides
N. Hanik, T. Kernetzky, Yizhao Jia, U. Höfler, R. Freund, C. Schubert, I. Sackey, G. Ronniger, and L. Zimmermann
Technical University of Munich, Germany
Ultra-Broadband Wavelength Conversion is identified as one of the key issues in future high-capacity, flexible optical networks. In this contribution, methods to optimize the design of Multi-Modal high-nonlinear SOI-Waveguides to achieve broadband wavelength conversion between extreme optical wavelength-bands are presented. Finally, measurements and experimental results are discussed that prove ultra-broadband conversion of data signals between different l-bands.

Georg Rademacher
Petabits/s transmission over multimode fibers
G. Rademacher, R. S. Luis, B. J. Puttnam, and H. Furukawa
National Institute of Information and Communications Technology, Japan
Optical fiber transmission systems using space division multiplexing (SDM) over multi-mode fibers (MMFs) potentially offer the highest spatial density, especially considering fibers with the current standard cladding diameter. In this talk, we discuss the principles of SDM transmission in MMFs and report on recent transmission demonstrations, including the transmission of more than 1.5 Peta-bit/s over a 55 mode MMF.

Stefan Rothe
Achieving information security in spatially multiplexed communication systems by harnessing disorder of multimode fibres
S. Rothe, K.-L. Besser, D. Krause, D. Pohle, R. Kuschmierz, N. Koukourakis, E. Jorswieck, and J. W. Czarske
Technical University of Dresden, Germany

Ioannis Roudas
Mode vector modulation: A review
I. Roudas, J. Kwapisz, and E. Fink
Montana State University, Bozeman, USA
The use of multidimensional modulations can significantly reduce the energy consumption of optical networks. In this invited paper, we review Mode Vector Modulation (MVM), a generalized polarization modulation technique for transmission over multimode/multicore optical fibers or free space. MVM, like Polarization Shift Keying (PolSK) and Stokes Vector Modulation (SVM), can be combined with direct detection and is thus appropriate for future high-capacity, short-haul optical interconnects. The MVM transceiver design, the analytical evaluation of the performance of the optically-preamplified MVM direct-detection receiver, the optimization of MVM constellations using geometric shaping, and the associated bit-to-symbol mapping are the main topics of this review. We demonstrate that, in terms of receiver sensitivity, MVM outperforms traditional single-mode, direct-detection-compliant, digital modulation formats by several dB’s, and the SNR gain increases with the number of spatial degrees of freedom.

Pedro Vaz
Single pixel imaging: imaging through scattering medium and other applications
P. G. Vaz and J. Cardoso, LIBPhys, University of Coimbra, Portugal
In this work we will explore the concepts of SPI allied to a mathematical tool called compressive sensing and present a simulation and experimental work of the usage of SPI to reconstruct images of targets hidden in scattering mediums.

SDN-NFV invited presentations

Piero Castoldi
Network programmability for smart factory mobile robotics: The SmartEdge project approach
P. Castoldi¹, L. Esmaeel², F. Paolucci², F. Cugini², and D. Bowden³
¹Scuola Superiore Sant’Anna, Italy
²CNIT, Italy
³DELL, Ireland
In this paper we show how P4-based network programmability is exploited to enable swarm formation and reliable communications in decentralized smart factory scenarios including mobile robots. In band telemetry will be extensively used by all network nodes to provide for dynamic aggregation/disaggregation of connected entities to perform different augmented functions: computing, massive data-delivery, time-sensitive networking.
Keywords: network programmability, network telemetry, edge processing, packet processing.

SWP invited presentations

Trevor Benson
Fiber optic sensor systems without using spectral analysis
T. Benson, George Green Institute for Electromagnetics Research, University of Nottingham, UK
The paper will describe our investigations of FBG systems where a simple measurement of transmitted or reflected power provides a cheaper alternative to specialist interrogators.

Elżbieta Bereś-Pawlik
Simultaneous study of fluorescence and transmission based on a sensor with a doped optical fibre
E. Bereś-Pawlik, George Green Institute for Electromagnetics Research, University of Nottingham, UK

Wilfried Blanc
Tailoring oxide nanoparticles in optical fibers
Zhuorui Lu^1,2, M. Cabié³, M. Guzik⁴, M. Ude¹, T. Neisius³, D. Tosi^5,6, C. Molardi⁵, F. Pigeonneau², and W. Blanc¹
¹Université Côte d’Azur, INPHYNI, CNRS, Nice, France
²MINES ParisTech, PSL Research University, CEMEF – Centre for material forming, Sophia‑Antipolis, France
³Aix Marseille Univ, CNRS, Centrale Marseille, France
⁴Faculty of Chemistry, University of Wrocław, Poland
⁵Nazarbayev University, School of Engineering and Digital Sciences, Nur-Sultan, Kazakhstan
⁶National Laboratory Astana, Laboratory of Biosensors and Bioinstruments, Nur-Sultan, Kazakhstan
Optical fibers containing nanoparticles were proposed twenty years ago to develop new applications in lasers and amplifiers. By encapsulating luminescent ions in the nanoparticles, new emission properties can then appear. However, the particles must be small in size to limit the optical losses by light scattering. More recently, this type of optical fiber has shown a strong potential for application as sensors. These exploit the light scattering properties induced by nanoparticles. Then, the development of these fibers for these different applications depends on our ability to control the characteristics of the nanoparticles in the optical fibers. During this presentation, we will show how the drawing step is a crucial step to achieve this goal.

Pierpaolo Boffi
Fiber interferometric sensors for monitoring the telecom infrastructure integrity
P. Boffi¹, M. Brunero², M. Fasano¹, A. Madaschi¹, J. Morosi², and M. Ferrario²
¹Dipartimento di Elettronica Informazione e Bioingegneria, PoliCom Lab, Politecnico di Milano, Italy
²Cohaerentia s.r.l., Milano, Italy
Fiber interferometric sensors are used for structural health monitoring and for diagnostics and surveillance of the telecom infrastructure integrity. Their capabilities in terms of cost, energy consumption and reduced complexity in system implementation and data processing are shown to demonstrate the sustainability.

Reinhard Caspary
Automatisation steps for laser direct writing
R. Caspary, Cluster of Excellence Phoenix D, Leibniz University Hannover, Germany
Two-photon polymerisation (TPP) is an additive manufacturing tool based on laser direct writing with sub-wavelength resolution. It has received enormous attention in recent years because it enables the production of precision polymer micro-optics without post-processing steps as well as three-dimensional diffractive optical structures. However, TPP is still a lab-technology which requires elaborate and time-consuming alignment steps. This talk will present our approach to automise many of these steps.

Pavel Cheben
Subwavelength-engineered metamaterial devices for integrated photonics
P. Cheben¹, J. H. Schmid¹, P. Ginel-Moreno², S. Khajavi³, R. Korček⁴, W. Fraser³, D. Sirmaci⁵, A. F. Hinestrosa², J. M. Luque-González², D. Pereira-Martín², A. Sánchez-Postigo², A. Hadij-ElHouati², D. Benedikovič⁴, A. Ortega-Moñux², J. G. Wangüemert-Pérez², I. Molina-Fernández², R. Halir², W. N. Ye³, D. Melati⁶, C. Alonso-Ramos⁶, D. González-Andrade⁶, L. Vivien⁶, I. Staude⁵, J. Zhang¹, M. Milanizadeh¹, D.-X. Xu¹, Y. Grinberg¹, R. Cheriton¹, S. Janz¹, S. Wang¹, M. Vachon¹, M. Dado⁴, R. Fernández de Cabo⁷, and A. V. Velasco⁷
¹National Research Council Canada, Ottawa, Canada
²University of Malaga, Malaga, Spain
³Carleton University, Ottawa, Canada
⁴Dept. Multimedia and Information-Communication Technologies, University of Zilina, Slovakia
⁵Institute of Solid State Physics, Friedrich-Schiller-University Jena, Germany
⁶Centre de Nanosciences et de Nanotechnologies, CNRS, Universite Paris-Saclay, Palaiseau, France
⁷Instituto de Óptica Daza de Valdés, Consejo Superior de Investigaciones Científicas (CSIC), Madrid, Spain
Incorporating subwavelength grating metamaterials in nanophotonic waveguides has opened new degrees of freedom to control light propagation on a photonic chip. In this invited contribution, we will present our recent advances in development of subwavelength-engineered metamaterial devices for silicon photonics, including fiber-chip couplers, nanophotonic waveguides with controlled anisotropy, resonant waveguides, complex spectral filers and nanoantennas for Optical Phased Arrays (OPAs).
[1] P. Cheben, D-X. Xu, S. Janz, A. Densmore, Subwavelength waveguide grating for mode conversion and light coupling in integrated optics, Opt. Express 14(11), pp. 4695-4702 (2006).
[2]. P. Cheben, P. J. Bock, J. H. Schmid, J. Lapointe, S. Janz, D.-X. Xu, A. Densmore, A. Delâge, B. Lamontagne, T. J. Hall, Refractive index engineering with subwavelength gratings for efficient microphotonic couplers and planar waveguide multiplexers, Opt. Lett. 35(15), pp. 2526-2528 (2010).
[3] P. Cheben, R. Halir, J. H. Schmid, H. A. Atwater, D. R. Smith, Subwavelength integrated photonics, Nature 560(7720), 565–572 (2018).
[4] R. Halir, A. Ortega-Moñux, D. Benedikovic, G. Z. Mashanovich, J. G. Wangüemert-Pérez, J. H. Schmid, Í. Molina-Fernández, P. Cheben, Subwavelength-grating metamaterial structures for silicon photonic devices,” Proc. IEEE 106(12), 2144–2157 (2018).
[5] J. M. Luque-González, A. Sánchez-Postigo, A. Hadij-ElHouati, A. Ortega-Moñux, J. G. Wangüemert-Pérez, J. H. Schmid, P. Cheben, Í. Molina-Fernández, R. Halir, A review of silicon subwavelength gratings: building break-through devices with anisotropic metamaterials, Nanophotonics 10(11), pp. 2765–2797 (2021).

Caterina Ciminelli
Lab-On-Chip for liquid biopsy: A new strategy for the detection of biochemical targets
C. Ciminelli, P. Colapietro, G. Brunetti, and M. N. Armenise
Optoelectronics Laboratory, Politecnico di Bari, Italy
In the last decades, cancer incidence has enormously risen, becoming the leading cause of death in developed countries and the most significant threat and challenge to human health. For these reasons, the biomedical research community is looking for non-invasive diagnostic tools for early screening, diagnosis, prediction of prognosis, early detection of relapse, and follow-up of cancer diseases [1]. Until these purposes, Predictive, Preventive, and Personalized Medicine (PPPM) has become the future challenge in oncology research aiming at new tools and technologies capable of detecting disease at an earlier stage, reducing adverse drug reactions, and improving the selection of new biochemical targets for drug discovery. In this context, a new and powerful non-invasive diagnostic tool, offering the possibility of reliable analysis and diagnosis of diseases from several biological fluids is liquid biopsy [2]. The use of this technology has many advantages over traditional methods, such as reducing substantially time, costs, consumption, risks, and failure rates of clinical trials for new treatments [3]. The capability of performing liquid biopsy by using Lab-On-Chip technologies allows to minimize invasiveness and risks. [4] Here, we review Lab-On-Chip (LoC)s, designed to achieve a system for Personalized Medicine capable of performing detection, capture, and analysis of cancer liquid biomarkers (ctDNA, cfDNA, CTCs, exosomes, EVs, etc.)[5]. The overview is focused on the photonic sensing section that could ensure high specificity and sensitivity of the system to a selected biomarker and remarkable limit-of-detection (LOD) [6]. In particular, we provide an overview of photonic sensor technologies by describing their main application in the field of biosensing for Personalized Medicine applications, critical and comprehensive evaluations regarding the prospects of the LoC operating platform, and optimization methods for its future applications.
[1] J. Marrugo-Ramírez, M. Mir, J. Samitier, Blood-based cancer biomarkers in liquid biopsy: A promising non-invasive alternative to tissue biopsy, International Journal of Molecular Sciences, 19(10), 2877 (2018). [2] F. Ferrara, S. Zoupanou, S. Primiceri, E. Z. Ali, M. S. Chiriacò, Beyond liquid biopsy: Toward non-invasive assays for distanced cancer diagnostics in pandemics, Biosensors and Bioelectronics, 196, 113698 (2022). [3] G. Li, W. Tang, F. Yang, Cancer liquid biopsy using integrated microfluidic exosome analysis platforms, Biotechnology Journal, 15(5), 1900225 (2020).
[4] J. Sierra, J. Marrugo-Ramirez, R. Rodriguez-Trujillo, M. Mir, J. Samitier, Sensor-integrated microfluidic approaches for liquid biopsies applications in early detection of cancer, Sensors, 20(5), 1317 (2020).
[5] L. Gorgannezhad, M. Umer, M. N. Islam, N. T. Nguyen M. J. Shiddiky, Circulating tumour DNA and liquid biopsy: Opportunities, challenges, and recent advances in detection technologies, Lab on a Chip, 18(8), 1174- 1196 (2018).
[6] M. C. Estevez, M. Alvarez, L. M. Lechuga, Integrated optical devices for Lab-On-a-Chip biosensing applications, 6(4), 463-487 (2021).

Antonio Díez
Modal analysis of acoustic resonances in an optical fiber: All-optical excitation and detection
L. A. Sánchez, C. A. Álvarez-Ocampo, M. Delgado-Pinar, A. Díez, J. L. Cruz, and M. V. Andrés, Universidad de Valencia, Burjassot, Spain
Opto-mechanical interactions in optical fibers based on Forward Brillouin Scattering (FBS) can lead to a new paradigm for the optical fiber sensing technology, since it allows monitor the surroundings of the fiber without requiring light interaction with the fiber outer medium. Point and distributed sensing schemes have been demonstrated based on FBS. FBS consists on the interaction of an optical signal (the “probe”) with opto-excited transverse acoustic mode resonances (TAMRs) of the optical fiber. TAMRs are typically excited via electrostriction by an optical beam that propagates in the fiber (the “pump”). The development of applications based on this nonlinear effect requires accurate knowledge of the properties of such acoustic modes. In this work, different all-optical approaches for the excitation and detection of TAMRs in optical fibers will be presented and discussed.

Antonella D’Orazio
Guided mode resonance-based transparent metasurfaces for selective multi-color reflection
G. Magno, M. Grande, O. Gauthier Lafaye, and A. D’Orazio
National Nanotechnology Laboratory, CNR-Istituto Nanoscienze, Università del Salento, Lecce, Italy
Metasurfaces enable precise and efficient control over light’s angular-spectral properties, making them crucial for developing augmented reality displays for information visualization. In this contribution, we will focus on the design of transparent metasurfaces that use guided mode resonances to achieve polychromatic selective reflection, specifically for wearable augmented reality systems. These metasurfaces may be valuable in the realization of near-eye visual aids in support of individuals with cognitive impairment issues.

Iker García
Partial least squares and partial least squares-discriminant analysis to detect and quantify adulterations in virgin olive oil using optical methods of analysis
D. Castro^1,2, M. C. Ortiz¹, S. Sanllorente¹, I. García², I. Ayesta³, M. Azkune⁴, and J. Zubia⁵
¹University of Burgos, Dep. Chemistry, Spain
²AOTECH (Advanced Optical Technologies S.L.), Escuela Ing. de Bilbao, Spain
³University of the Basque Country, UPV-EHU, Dpto. de Matemática Aplicada, Escuela de Ingeniería de Bilbao, Spain
⁴University of the Basque Country, UPV-EHU, Dpto. de Ingeniería Electrónica, Escuela de Ingeniería de Bilbao, Spain
⁵University of the Basque Country, UPV-EHU, Dpto. de Ingeniería de Comunicaciones, Escuela de Ingeniería de Bilbao, Spain
Due to its high nutritional value, olive oil (OO) is more expensive than most of other vegetable oils, making it the most common edible oil to be adulterated by many merchants or oil suppliers in small percentages in order to obtain economic benefits. These fraudulent practices become more sophisticated every day, which gives rise to the necessity of the implementation of new more innovative and efficient methodologies. For that reason, in this work, the great advantages of some optical methods of analysis combined with chemometrics are used to study the possibilities they present in the determination of adulterants in OO [1-6]. In this work, the presence of five different adulterants (vegetable oils) in OO has been evaluated using different spectroscopic techniques (UV-Vis, NIR and Raman spectroscopy) by applying chemometric methods. One the one hand, the percentage of adulterants was calculated using Partial Least Squares (PLS). In addition, qualitative classification models (PLS-Discriminant Analysis) have been proposed to distinguish between adulterated and unadulterated samples of intense OO. Using these techniques, it is possible to classify between unadulterated samples of OO and those that have been adulterated, obtaining almost a hundred percent both for sensitivity and specificity. Within the adulterated, it is also possible to identify which is the vegetable oil (adulterant) in the sample. A good estimation of the adulterant percentage in OO was also achieved, obtaining the best results when UV-Visible spectroscopy was used.
[1] X. Meng, et al., Rapid detection of adulteration of olive oil with soybean oil combined with chemometrics by Fourier transform infrared, visible-near-infrared and excitation-emission matrix fluorescence spectroscopy: A comparative study, Food Chemistry, 405, 134828 (2023).
[2] P. Fang, H. Wang, X. Wan, Olive oil authentication based on quantitative β-carotene Raman spectra detection, Food Chemistry, 397, 133763 (2022).
[3] I.uisánchez, G. Rovira, M. P. Callao, Multivariate qualitative methodology for semi-quantitative information. A case study: Adulteration of olive oil with sunflower oil, Analytica Chimica Acta, 1206, 339785 (2022).
[4] J. Zhang, H. Sun, W. Lu, Recent advances in analytical detection of olive oil adulteration. ACS Food Science and Technology, 2(3), 415-424 (2021).
[5] S. A. Ordoudi, O. Özdikicierler, M. Z. Tsimidou, Detection of ternary mixtures of virgin olive oil with canola, hazelnut or safflower oils via non-targeted ATR-FTIR fingerprinting and chemometrics, Food Control, 142, 109240 (2022).
[6] S. A. Ordoudi, L. Strani, M. Cocchi, Toward the non-targeted detection of adulterated virgin olive oil with edible oils via FTIR spectroscopy and chemometrics: Research methodology trends, gaps and future perspectives, Molecules, 28(1), 337 (2023).

Jian-Jang Huang
Electrical manipulation of plasmonic relaxation and the application of voltage-modulated plasmon resonance to biosensing
K. Barman¹, Syu-Cing Ma¹, R. Gupta¹, N. A. P. Ondevilla², Liang-Yun Lee¹, Hsien-Chang Chang^2,3, and Jian-Jang Huang^1,4
¹Graduate Institute of Photonics and Optoelectronics, National Taiwan University, Taipei, Taiwan
²Department of Biomedical Engineering, National Cheng Kung University, Tainan, Taiwan
³Medical Device Innovation Center, National Cheng Kung University, Tainan, Taiwan
⁴Department of Electrical Engineering, National Taiwan University, Taipei, Taiwan
This talk reveals two studies on electrical controlled plasmonic responses, one for understanding the plasmon-phonon interactions and the other for demonstrating high-sensitivity EC (electrochemical)-SPR biosensors. In the first part, we experimentally study the effect of voltage controlled surface acoustic waves on localized surface Plasmon (LSP), which unveils exceptional properties of plasmon-phonon interaction. The experiment was conducted by depositing Gold nanoparticles on an X-cut LiNbO₃ to generate plasmonic oscillation, and fabricating an interdigital transducer monolithically to create surface acoustic wave pulses. The interaction between amplitude acoustic wave and plasmonic oscillation affects different plasmon dynamics and relaxation gradients, leading to a systematic change in LSP absorption. Second, we designed and investigated a novel voltage modulated optical biosensor based on a hybrid plasmonic and electrochemical phenomenon. The SPR (surface plasmonic resonance) was generated from a thin layer of gold nanohole array on a glass substrate. The optical response under various voltage bias conditions were tested using the target analyte, C-Reactive Protein (CRP). We observed that SPR response is concentration-dependent and can be modulated by varying DC voltages or AC bias frequencies. The phenomenon is due to spatial re-distribution of electron concentration at the metal-solution interface. Our proposed voltage actuated sensor is permissible for various future optoelectronic integration for plasmonic and electrochemical sensing.

José Javier Imas
Optical fiber sensors based on lossy mode resonances (LMRs): Fundamentals and recent developments
J. J. Imas, I. Del Villar, C. R. Zamarreño, and I. R. Matías, Electrical, Electronic and Communications Engineering Dept., Public University of Navarre, Pamplona, Spain
Lossy mode resonance (LMR)-optical sensing technology has consolidated in the last years in the field of the resonance-based sensors, which rely on the utilization of a thin film that affects the propagation of the light through the waveguide, thus generating a resonance. Optical fibers have been the most commonly employed waveguide for the development of LMR-based sensors, including applications such as refractive index sensing, gas detection, humidity sensing, pH sensing or biosensing, among others. In this work, the fundamentals of LMR-based optical fiber sensors are reviewed, as well as some of the main lines of research that are currently being pursued in order to improve their performance: development of multisensing platforms on fiber to simultaneously measure several variables, and increase of the resolution by either improving the sensitivity or the figure of merit (FOM) of the LMR based sensor.
Keywords: optical fiber, sensors, thin-films

Brana Jelenković
Squeezed light by FWM in alkali vapor: Generation and application
M. Ćurčić, D. Arsenović, F. Krajinić, B. Jelenković
Institute of Physics Belgrade, Serbia
We present the method for generating amplitude squeezed light (ASL) from twin photon pairs obtained using four way mixing (FWM) in alkali vapors [1], The dependence of ASL on the pump and probe laser detuning, and on the vapor density, obtained in potassium vapor using double-Λ atomic scheme, will be compared with the analytical models. Obtained agreement in certain ranges of FWM parameters, and disagreement in others, will be discussed. Quantum correlated and entangled photon pairs produced by FWM, or by other methods like SPDC, have been proven in many successful applications. Taking properties of quantum light, quantum sensing and quantum imaging has overcome performances done by classical light, increasing measuring sensitivity by lowering noise below standard quantum limit, SQL. One way of sub SQL images exploits time and mode correlation between twin beams in a differential scheme for noise reduction. We present method of using two-correlated photons microscopy, such as shown in [2], and explain when it will be advantageous over classical two-photon spectroscopy.
[1] M, Ćurčić and B. Jelenković, Enhanced intensity difference squeezing with a low gain off-resonant four-wave-mixing in potassium vapor, Opt. Communications 533, 129301 (2023).
[2] T. Li et al., Squeezed light induced two-photon absorption fluorescence biomarkers, Appl. Phys. Lett. 116, 254001 (2020).

Bhupesh Kumar
Disorder enhanced-photonic crystal based on-chip spectrometer
B. Kumar and S. Schulz
SUPA, School of Physics and Astronomy, University of St. Andrews, Fife, UK
Spectrometers are commonly used for various purposes such as chemical and biological sensing and characterizing light sources. However, traditional grating-based spectrometers are large and expensive. To reduce the size, the effective path length must be increased while maintaining a small footprint. This can be achieved through the use of multiple light scattering in a random structure. However, current disorder-based speckle spectrometers have low efficiency and poor signal-to-noise ratios due to high optical losses [1]. To overcome this issue, the controlled disorder is superimposed on a photonic crystal to increase wavelength separation and suppress out-of-plane scattering[2,3,4], leading to improved performance. The device is fabricated using electron beam lithography on a Silicon on Insulator (SOI) wafer. Simulation results show that a combination of disorder and periodicity enhances throughput by 30% compared to only disorder, without compromising spectral resolution. Future plans include optimizing hyper uniform disorder-based configurations for enhanced throughput and higher resolution.
[1] B. Redding et al., Nat. Photon. 7, 746 (2013).
[2] J. P. Vasco and S. Hughes, ACS Photonics ,6 (11), 2926-2932 (2019).
[3]. L. O’Faolain et al., Opt. Express 18, 27627 (2010).
[4] J. Li et al., Photonic Nanostruct. 10, 589 (2012).

Igor Meglinski
Spin and orbital angular momenta in biomedical diagnosis and tissues characterisation
I. Meglinski^1,2,3, I. Lopushenko³, A. Sdobnov³, and A. Bykov³
¹College of Engineering and Physical Sciences, Aston University, Birmingham, UK
²Aston Institute of Photonics Technologies, Aston University, Birmingham, UK
³Optoelectronics and Measurement Techniques, University of Oulu, Finland
We explore the potential of structured vortex laser beams, known also as shaped light with orbital angular momentum (OAM), for diagnosis of cells and cells cultures, as well as for quantitative characterization of biological tissues. The structured vortex beams contains a spin contribution, conditioned by the polarization of the electromagnetic fields and an orbital contribution, related to their spatial structure. When the shaped light propagates in a homogeneous transparent medium, both spin and orbital angular momenta are conserved. In order to study a conservation of spin and orbital angular momenta of the shaped light propagation in a homogeneous transparent medium we have built a Mach-Zehnder-like interferometer featuring spatial light modulator (SLM) for generating Laguerre-Gaussian (LG) light beams with different momenta. The LG beam passes through a tissue sample and the interference with reference plane wave is detected on the camera. We show that when the LG beam propagates through normal and cancerous tissue samples the OAM is preserved with the noticeably different phase shift – twist of light. We also demonstrate that the twist of light is up to ∼ 1000 times more sensitive to the refractive indices changes within the tissue samples and, therefore, has a high potential to revolutionize the current practices of tissue diagnosis, e.g. histology examination. The results of our experimental studies are well agreed with the results obtained with newly developed by Monte Carlo code developed in-house. Finally, we conclude that the application of OAM for biomedical diagnosis offers fascinating opportunities for both new fundamental biological studies and practical clinical applications.

Jean-Michel Nunzi
Advanced photodetectors, sensors and energy harvesting devices
J.-M. Nunzi, Queen’s University, Quebec, Canada
Several approaches are currently explored to build devices exploiting size-effects in nano-sciences. Self-assembling emerges as a master bottom-up technique to enable the applications of nanomaterials into the real world. Among these applications, image sensing and processing requires capabilities that are beyond the technology of current image sensors, such as automated color-based quality inspection systems operating under varying levels of illumination [1] or laser-based satellite communication systems using parallel optical processing functions [2]. I will describe the recent outcomes of our network of collaborative research aimed at exploiting the benefits of organic [3], perovskite [4], graphene [5] and plasmonic photodetectors [6,7] for sensing [8], detecting, and harvesting light and solar energy.
[1] R. D. Jansen-van Vuuren, J.-M. Nunzi, S. N. Givigi, Frontiers in photosensor materials and designs for new image sensor applications, IEEE Sensors J. 21, 11339 (2021).
[2] I. M. Kislyakov et al., Nonlinear optical fullerene and graphene based polymeric 1D photonic crystals: Perspectives for slow and fast optical bistability, J. Opt. Soc. Am. B 38 C198-C209 (2021).
[3] E. V. Verbitskiy et al., Pyrimidine-based push-pull systems with a new anchoring amide group for dye-sensitized solar cells, Electronic Materials 2, 142–153 (2021).
[4] L. L. Wang et.al., Double-layer CsI intercalation into an MAPbI3 framework for efficient and stable perovskite solar cells, Nano Energy 86, 106135 (2021).
[5] S. Aynehband, M. Mohammadi, R. Poushimin, J.M. Nunzi, A. Simchi, Efficient FAPbI3-capped PbS-quantum dot graphene-based phototransistors , New J. Chem. 45, 15285–15293 (2021).
[6] D. Salem, M. Shalabi, F. Souissi, F. Nemmar, M. Said Belkaid, M. Aamir, J. M. Nunzi, Ag nanoparticle-based efficiency enhancement in an inverted organic solar cell, Eur. Phys. J. Appl. Phys. 90, 30201 (2020).
[7] S. M. A. Mirzaee, O. Lebel, J.M. Nunzi, Simple unbiased hot-electron polarization-sensitive near-infrared photo-detector, ACS Appl. Mater. Inter. 10, 11862-11871 (2018).
[8] M. Aamir, M. Shahiduzzaman, T. Taima, J. Akhtar, J. M. Nunzi, It is an all-rounder! On the development of metal halide perovskite-based fluorescent sensors and radiation detectors, Adv. Opt. Mater. (2021).

Giovanni Pellegrini
Photonic multilayers for broadband and large area superchiral surface waves
G. Pellegrini¹, E. Mogni², J. Jil-Rostra³, F. Yubero^2,3, G. Simone^2,4, S. Fossati⁵, J. Dostálek^5,6,7, R. Martinez Vázquez⁸, R. Osellame⁸, M. Celebrano², M. Finazzi², and P. Biagioni²
¹Dipartimento di Fisica,Università degli studi di Pavia, Italy
²Dipartimento di Fisica, Politecnico di Milano, Italy
³Instituto de Ciencia de Materiales de Sevilla, CSIC-Universidad de Sevilla, Spain
⁴School of Mechanical Engineering, Northwestern Polytechnical University Xi’an, Shaanxi, China
⁵Biosensor Technologies, AIT-Austrian Institute of Technology GmbH, Tulln an der Donau, Austria
⁶FZU-Institute of Physics, Czech Academy of Sciences, Prague, Czech Republic
⁷Laboratory for Life Sciences and Technology (LiST), Faculty of Medicine and Dentistry, Danube Private University, Krems, Austria
⁸Istituto di Fotonica e Nanotecnologie (IFN)-CNR, Milano, Italy
Chirality is omnipresent in chemistry and of paramount importance in the modern pharmaceutical industry. Chiroptical analysis techniques allow for a flexible and low-cost molecular structure characterization, but their limited sensitivity prevents on-chip integration. We overcome these limitations by introducing the concept of superchiral surface waves, and design photonic multilayers capable of a two orders of magnitude chiral signal enhancement compared to standard techniques [1–3]. We design structures displaying broadband spectral operation over arbitrarily large areas and compatibility with lab-on-a-chip setups. The structural and optical characterizations of the realized platforms shows excellent agreement with the design [4]. We finally adopt optimization and machine learning techniques to design multilayers operating from the ultraviolet to the near infrared regime, with great flexibility in terms of adopted materials. These findings pave the way towards the integration of chiroptical techniques with microfluidic networks, enriching the widespread lab-on-chip technology with new functionalities.
[1] G. Pellegrini, M. Finazzi, M. Celebrano, et al., Chiral surface waves for enhanced circular dichroism, Phys. Rev. B 95:241402 (2017).
[2] G. Pellegrini, M. Finazzi, M. Celebrano, et al., Surface-enhanced chiroptical spectroscopy with superchiral surface waves, Chirality 30:883–889 (2018).
[3] G. Pellegrini, M. Finazzi, M. Celebrano, et al. Superchiral surface waves for all-optical enantiomer separation, J. Phys. Chem. C 123:28336–28342 (2019).
[4] E. Mogni, G. Pellegrini, J. Gil-Rostra, et al., One-dimensional photonic crystal for surface mode polarization control, Advanced Optical Materials 10:2200759 (2022).

Alexander Quandt
Basic theoretical and numerical concepts of photovoltaics
A. Quandt, School of Physics, NRF-DST Centre of Excellence in Strong Materials and Materials for Energy Research Group, University of the Witwatersrand, Johannesburg, South Africa
Solar cell simulations have become an essential tool for the development of novel types of photovoltaic devices. Many of the standard software packages currently in use are very mature numerical tools. They are easy to understand and easy to apply. This led to a development, where simulations make up for a good fraction of the literature about photovoltaics, and they even tend to substitute more and more of the experimental work and the practical development of real working devices. I would like to give an overview of the basic theoretical and numerical concepts underlying solar cell simulations. Then I will discuss some typical examples to point out the advantages, but also the practical limitations of standard photovoltaic device simulations. Furthermore, I will suggest several promising theoretical and numerical extensions, which could change the current focus of the field towards more fundamental aspects of light-matter interactions, rather than using solar cell simulations only as a virtual tool to explore variations in the key device components of standard types of solar cells.

Giuseppe Rizzelli
Early-warning debris flow and avalanches detection system based on optical fiber polarization sensing
G. Rizzelli¹, S. Pellegrini², S. Aiassa³, F. Antolini³, A. Insana⁴, M. Barla⁴, and R. Gaudino²
¹Links Foundation, Torino, Italy
²Dipartimento di Elettronica e Telecomunicazioni, Politecnico di Torino, Italy
³Geosolving srl, Torino, Italy
⁴Geotechnical and Building Engineering, Politecnico di Torino, Italy
Landslides, avalanches and debris flows are common hazards in the mountain environment that can endanger people and infrastructures. The existing monitoring systems in the geotechnical field are often unsuitable for real-time applications, such as early-warnings of the aforementioned events [1]. We present an optical fiber system [2-3] able to give an alarm when some anomalous event is detected [4]. Experiments have been carried out on a reduced scale model of the slope of a mountain, showing that state of polarization monitoring [5] is a reliable way to early-detect anomalous vibrations.
[1] M. Hürlimann, V. Coviello, C. Bel, X. Guo, M. Berti, C. Graf, J. Hübl, S. Miyata, J. B. Smith, and H.-Y. Yin, Debris-flow monitoring and warning: Review and examples, Earth-Science Reviews, vol. 199, p. 102981 (2019).
[2] L. Schenato, A review of distributed fibre optic sensors for geo-hydrological applications, Applied Sciences, vol. 7, no. 9 (2017).
[3] I. Di Luch, P. Boffi, M. Ferrario, G. Rizzelli, R. Gaudino, and M. Martinelli, Vibration sensing for deployed metropolitan fiber infrastructure, Journal of Lightwave Technology, vol. 39, no. 4, pp. 1204–1211 (2021).
[4] S. Aiassa, F. Antolini, M. Barla, A. Insana, R. Gaudino, G. Rizzelli Martella, and S. Pellegrini, A new real-time debris flow and avalanches detection system based on optical fiber sensing, in Proceedings of the 8th International Conference on Debris Flow Hazard Mitigation (2023).
[5] A. Mecozzi, M. Cantono, J. C. Castellanos, V. Kamalov, R. Muller, and Z. Zhan, Polarization sensing using submarine optical cables, Optica, vol. 8, no. 6, pp. 788–795 (2021).

Marco Saldutti
Lasing threshold in nanolasers with extreme dielectric confinement
M. Saldutti, Yi Yu, and J. Mørk, DTU Fotonik, Department of Photonics Engineering, Technical University of Denmark, Lyngby, Denmark
Today, most of the energy in computer chips is wasted for data communications through electrical wires. Not only does ohmic heating hamper further miniaturization and integration, but it also limits the data processing speed. On the other hand, on-chip optical interconnects are advantageous in terms of energy consumption and bandwidth, thus being a real keystone for information and communication technologies with higher energy efficiency and more complex functionalities. However, this dense integration of electronics and photonics requires new semiconductor lasers, with ultra-small footprint, low noise and reduced energy consumption. Nanolasers based on emerging dielectric cavities with deep sub-wavelength optical confinement may offer unprecedented light-matter coupling rate, near-unity spontaneous emission factor and ultra-low threshold current. However, the extreme dielectric confinement encountered in these nanolasers calls for a reconsideration of the standard approach to identifying the lasing threshold. In this presentation, we discuss a new threshold definition, valid all the way from the macro to the nanoscale and reflecting the recycling process that photons undergo in nanolasers with extreme dielectric confinement. By utilizing a Langevin approach and a more fundamental stochastic simulation scheme, we discuss quantum noise and photon statistics in relation to this generalized threshold definition.

Salvador Sales
Real-time monitoring systems using fiber optic sensors
S. Sales, D. Barrera, J. Madrigal, D. Maldonado-Hurtado, and V. Hernández-Ambato
ITEAM Research Institute, Universitat Politècnica de València, Spain
Fiber optics Sensors are widely used today. We will present our latest developments to monitor real-time systems in applications ranging from civil engineering to medical or aerospace applications. Our sensors can monitor temperatures ranging from cryogenic temperatures to very high temperatures (over 2000 K).

Markus A. Schmidt
Flexible light manipulation through nanophotonics interfaced with optical fibers
M. A. Schmidt^1,2, ¹Max Planck, Erlangen, ²Institute for Photonic Technology, Jena, Germany
Here I will report on dielectric nanostructures interfaced with optical fibers and demonstrate their capabilities on the examples of achromatic light focussing and optical trapping. Both topics involve implementation of nanostructures on fibers through 3D nanoprinting. This has allowed for (i) the realization of an achromatic metasurface-based lens interfaced to a SMF-28, used for wavelength- and polarization-independent light focussing across the entire telecommunication range, and for (ii) trapping microspheres and bacteria with only one single-mode fiber containing a nanoprinted holographic metalens with a record-high numerical aperture of 0.88.

Vincenzo Luigi Spagnolo
Latest advances in quartz enhanced photoacoustics spectroscopy for environmental and industrial applications
A. Zifarelli, G. Menduni, M. Giglio, A. Sampaolo, P. Patimisco, Hongpeng Wu, Lei Dong, and V. Spagnolo, Technical University of Bari, Italy
Environmental monitoring, as well as safety and security, and industrial applications demand for real time and in-situ solutions capable to unambiguously identify and quantify chemical analytes composing the investigated samples. Starting from the basic physical principles governing the quartz tuning fork physics, I will review the main results achieved by exploiting custom QTFs in QEPAS sensing for real-world applications.

Łukasz Szostkiewicz
From smart materials for space industry to soil temperature gauges for climate change monitoring: A review of new applications of distributed optical fiber sensors
Ł. Szostkiewicz, InPhoTech sp. z o.o, Ołtarzew, Poland
Distributed optical fiber sensors (DOF’s) are usually associated with strain and temperature measurements of long linear constructions. Within this paper we demonstrate how alterations in sensing schemes and application of specialty optical fibers allow to broaden the applications of DOF’s. One of those is an multi line underground temperature monitoring in arctic environment which demonstrates the possibility to remotely interrogate multiple sensing fibers with centimeter spatial resolution. We will also discuss the possibilities of distributed optical fiber sensing embedded in composites and metal alloys.
Keywords: distributed optical fiber sensors, specialty optical fibers.

Mikhail Vasilevskiy
Can graphene plasmons be efficiently generated in a non-linear optical process?
M. I. Vasilevskiy, University of Minho and International Iberian Nanotechnology Laboratory, Braga, Portugal
Resonant interaction of two optical beams, with adjusted frequencies and wavevectors, mediated by graphene surface plasmons (SPs) was demonstrated experimentally several years ago by measuring the differential reflectance of the probe beam. However, the understanding of these results requires much larger second-order optical conductivities of graphene than calculations based on standard perturbation theory approaches can yield. We shall discuss this contradiction and physical processes beyond the coherent frequency-difference generation of SPs that can be involved here, namely, hot-electron effects and the feasibility of the all-optical generation of coherent graphene plasmons.

Aiguo Wu
Nanoparticles for optical sensing detection, tumor imaging and therapy in biomedicine
Aiguo Wu, Cixi Institute of Biomedical Engineering, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, China
Photoactive or photofunctional nanoparticles are widely used in many research fields such as storing, transporting, analyzing, sensing, imaging, and therapy. Particularly, there are so many applications in biomedicine based on photoactive or photofunctional nanoparticles. In this presentation, we will discuss some progress in optical sensing applications based on noble metal nanoparticles for detection of various types of cations/anions, small organic molecules, and cancer cells [1-3]; a various of biomedical applications in tumor imaging, therapy and therapeutic visualization based on different kinds of metal oxide nanoparticles for example iron oxide nanoparticles, titanium oxide nanoparticles, zinc oxide nanoparticles and their nanocomponents with metal nanoparticles etc. [4-10].
[1] F. Q. Zhang, L. Y. Zeng, Y. X. Zhang, H. Y. Wang, and A. G. Wu, Nanoscale, 3, 2150-2154 (2011).
[2] Y. X. Gao, X. Li, Y. L. Li, T. H. Li, Y. Y. Zhao, and A. G .Wu, Chem. Commun., 50, 6447-6450 (2014).
[3] J. Lin, O. U. Akakuru, and A.G. Wu, View, 2, 20200146 (2021).
[4] Z. Y. Shen, T. X. Chen, X. H. Ma, W. Z. Ren, Z. J. Zhou, G. Z. Zhu, A. Zhang, Y. J. Liu, J. B. Song, Z. H. Li, H. M .Ruan, W. P. Fan, L. S. Lin, J. Munasinghe, X. Y. Chen, and A. G. Wu, ACS Nano, 11, 10992-11004 (2017).
[5] Z. Y Shen, J. B. Song, Z. J. Zhou, B. C. Yung, M. A. Aronova, Y. Li, Y. L. Dai, W. P. Fan, Y. J. Liu, Z. H. Li, H. M. Ruan, R. D. Leapman, L. S. Lin, G. Niu, X. Y. Chen, and A. G. Wu, Adv. Mater., 30, 1803163 (2018).
[6] C. Liu, J. Xing, O. U. Akakuru, L. J. Luo, S. Sun, R. F. Zou, Z. S. Yu, Q. L. Fang, and A. G. Wu, Nano Lett., 19, 5674-5682 (2019).
[7] Z. Q. Jiang, B. Yuan, Y. J. Wang, Z. N. Wei, S. Sun, O. U. Akakuru, Y. Li, J. Li, A. G. Wu, Nano Today, 34,100910 (2020).
[8] X. W. Xu, J. Lin, Y. H. Guo, X. X. Wu, Y. P. Xu, D. H. Zhang, X. Z. Zhang, Y. J. Xie, J. Wang, C. Y. Yao, J. L. Yao, J. Xing, Y. Cao, Y. Y. Li, W. Z. Ren, T. X. Chen, Y. Ren, A. G. Wu, Biosensors and Bioelectronics, 210, 114305 (2022).
[9] H. Du, F. Yang, C. Y .Yao, W. H Lv, H. Peng, S. G. Stanciu, H. A. Stenmark, Y. M. Song, B. Jiang, A. G. Wu, Biomaterials, 2022, 291,121868.
[10] H. Du, F. Yang, C. Y. Yao, Z. C. Zhong, P. H. Jiang, S. G .Stanciu, H. Peng, J. P. Hu, B. Jiang, Z. H. Li, W. H. Lv, F .Zheng, H. A. Stenmark, and A. G. Wu, Small, 18, 220166 (2022).

THzP invited presentations

Samira Mansourzadeh
New opportunities open by advances in table-top high-power broadband terahertz sources
S. Mansourzadeh, T. Vogel, C. Millon, M. Khalili, R. Löscher, and C. J. Saraceno, Ruhr-Universität Bochum, Germany
The “terahertz” frequency range extends from about 100 GHz to 30 terahertz (THz). Long unexplored because of the difficulties of their generation, giving the well-known term “terahertz gap”; there is now a various explored way to generate them: plasma, optical rectification in organic and inorganic crystals, photoconductive antenna. We are developing high-power, broadband, and high dynamic range laser-based THz sources. These sources operate within the range of MHz / hundreds of kHz of repetition rate. This enables applications like THz time domain spectroscopy or pump-probe spectroscopy to be massively accelerated. Application fields such as the investigation of water molecular dynamics or THz imaging benefit enormously from these sources. In particular, samples with large absorption index in the THz range have been very difficult to characterize so far. Our high- power sources often make an efficient investigation with simultaneously high signal strength possible.

Daniel Mittleman
Conformal leaky-wave antennas for terahertz networks
H. Guerboukha, R. Shrestha, J. Neronha, Zhaoji Fang, and D. M. Mittleman
School of Engineering, Brown University, Providence, USA
We explore the performance of curved leaky-wave antennas in the terahertz range. We identify two distinct regimes in which the far-field emission pattern varies relative to that of a planar leaky-wave antenna. We show that a curved multi-aperture leaky-wave antenna can be used for agile far-field beam forming, and demonstrate high-gain wireless links at gigabit-per-second data rate with low bit error rate, in multiple directions simultaneously. This work lays the foundation for the implementation of terahertz leaky-wave structures in conformal geometries.

Mauro Pereira
Superlattices: From nonequilibrium Green’s functions to medical physics and integrated photonics applications
M. F. Pereira^1,2, V. Vaks³, V. Anfertev³, and H. Zafar²
¹Department of Physics, Khalifa University of Science and Technology, Abu Dhabi, UAE
²Department of Condensed Matter Theory, Institute of Physics, Czech Academy of Sciences, Czech Republic
³Institute for Physics of Microstructures of RAS, Nizhny Novgorod, Russia
In this talk we will summarize our recent theoretical and experimental studies of different types of superlattices. We start with a summary of the predictive theory used to simulate giant control of THz nonlinearities and demonstrate its validity per direct comparison with experiments [1-3]. Next the same semiconductor superlattices are used for the detection of nitriles, showing potential as diagnostic method for cancer patients treated with chemotherapy. In the second part of the talk, we focus on compact and broadband adiabatically bent superlattice-waveguides with negligible insertion loss and ultra-low crosstalk. Our numerical simulations also predict accurately the experiments based on a silicon-on-insulator platform. The approach is applicable to other waveguide geometries and integrated photonic platforms [5-6].
[1] M. F. Pereira et al., Sci Rep 10, 15950 (2020).
[2] V. Vaks et al., Sci Rep 12, 18117 (2022).
[3] M. F. Pereira, Nanomaterials 12, 1504 (2022).
[4] H. Zafar et al., in IEEE Journal of Selected Topics in Quantum Electronics, doi: 10.1109/JSTQE.2023.3241617.
[5] H. Zafar et al., Opt. Express 30, 10087-10095 (2022).
[6] H. Zafar et al., AIP Advances 10, 125214 (2020).

Jasmin Smajic
Plasmonic antennas for the reception of millimeter and THz waves
J. Smajic, H. Ibili, T. Blatter, M. Baumann, B. Vukovic, and J. Leuthold
Institute of Electromagnetic Fields, ETH Zurich, Switzerland
On-chip systems comprising a plasmonic THz antenna with an integrated electro-optical modulator are a very promising solution for sensing or future high-speed wireless communication links. In this context, we will present a modeling and simulation method for the optimization of THz-antennas. The model is capable of revealing the influence of the integrated modulator to the antenna parameters and its field enhancement capabilities essential for electro-optical modulation. Ultimately, we will present an in-detail antenna optimization approach for a given modulator design based on the accurate antenna’s equivalent circuit that eliminates the need for computationally very expensive 3-D FEM antenna simulations.

VLC invited presentations

Véronique Georlette
Li-Fi and Visible Light Communication for Smart Cities and Industry 4.0: Challenges, research and market status in 2023 (Tutorial)
V. Georlette and V Moeyaert, Electromagnetism and Telecommunications Dept., University of Mons, Belgium
The development of technologies that use cellular Radio Frequency (RF) networks to transmit information wirelessly has increased dramatically over the last decade. These technologies include mobile phones, tablets, connected gadgets and the Internet of Things (IoT). The simultaneous use of all these devices quickly saturates the available network. As the RF spectrum resource is limited and regulated, it is important to find alternative connectivity. To reply to this shortage of wireless connectivity, Li-Fi (Light Fidelity) and Visible Light Communication (VLC) are good candidates. Li-Fi is the high data rate bidirectional application of VLC. VLC uses visible and infrared light to transmit data wirelessly. Over the last decade, interest in VLC grew in the scientific community and on the market. However, most scientific works and products are focused on the indoor environment. The external environment for VLC applications, which would be very relevant for smart cities as well as some industrial applications, is very little covered in the literature. This tutorial aims to present the advances of these technologies and their relevance in these two environments. As opposed to the indoors, the quantity of particles in the air in outdoor and some industrial environments is more important. Depending on the environment in which the system is deployed, the optical signal may be more or less impacted. Indeed, whether it is indoor or outdoor, the attenuation and the disturbance applied to the signal are different. The primary impactors on outdoor VLC equipment, which increase the medium’s total attenuation, are mainly weather variability and the interactions between the light wave and particles in the atmosphere. These particles include dust, fog, and the possible presence of smoke due to fire or pollutants which cause phenomena such as scattering and absorption. A third effect to consider is the reflection of the optical signal on certain surfaces and their interference on the receiver’s end. After a general state of the art of VLC and Li-Fi, this tutorial provides an overview of these phenomena and how they can be studied and mitigated. Afterward, the latest technological innovations are presented. Then, a market review will present the main challenges that Li-Fi and VLC technologies face for their massive deployment for private consumers and private companies. For instance, there is no single standard for Li-Fi and VLC. This makes it hard for manufacturers of end devices and light manufacturers to comply with just one norm. Furthermore, this technology has not reached its maturity level yet. As VLC requires the use of LEDs as its emitter’s front-end and since they were adopted a relatively short time ago, it makes this technology relevant but still needs some time for the light market to stabilize itself. Nevertheless, VLC and Li-Fi have a bright future ahead and this tutorial will conclude with practical examples of their use in smart cities and smart industries.

WAOR invited presentations

Redha Alliche
PRISMA-v2: A cloud overlay network extension
R A. Alliche¹, T. Da Silva Barros¹, R. Aparicio-Pardo¹,and L. Sassatelli²
¹Université Côte d’Azur, CNRS, Inria, I3S, France
²Université Côte d’Azur, CNRS, I3S, Institut Universitaire de France, France
In this paper, we present PRISMA-v2, a new release of PRISMA, a Packet Routing Simulator for Multi-Agent Reinforcement Learning. PRISMA-v2 brings a new set of features. First, it allows simulating overlay network topologies, by integrating virtual links. Second, this release offers the possibility to simulate control packets, which allows to better evaluate the overhead of the network protocol. Last, we integrate the modules along with the core (ns-3) to a docker container, so that it can be run in any machine or platform. PRISMA-v2 is, to the best of our knowledge, the first realistic overlay network simulation playground that offers to the community the possibility to test and evaluate new network protocols.

Samael Sarmiento
Low-cost all-optical switching nodes for ultra-dense optical metro-access networks
S. Sarmiento and J. A. Lázaro, Altran Innovación, Barcelona, Spain
Optical metro-access networks (OMANs) must enable connectivity among 5G-based radio stations, edge datacentres, businesses, and home users. In such a heterogeneous scenario, greater scalability, higher levels of dynamic connectivity and flexibility, reduced end-to-end latency, and increased energy efficiency are required. Mesh-based ultra-dense wavelength division multiplexing (u-DWDM) OMANs using reconfigurable optical switching nodes are a promising solution. However, the designs of traditional optical switching nodes relay on wavelength-selective switches (WSSs), which provide high network reconfigurability only at a high cost, making them prohibitive for OMANs. Moving away from this design approach, we proposed a novel cost-effective and energy-efficient design based on a modular DWDM structure for reconfigurable optical add-drop multiplexer (ROADM) and optical cross-connects (OXC) nodes compatible with mesh-based u-DWDM OMANs. Results show that proposed solutions can provide performance close to that of WSS-based OXCs but with a switching node cost reduction of one order magnitude.

Helio Waldman
A minimal idleness algorithm for spectrum assignment on a single elastic link under dynamic traffic
H. Waldman, R. Campos Bortoletto, and V. Ferreira de Sousa
Dept. of Communications, FEEC/Unicamp, Campinas, Brazil
Short Abstract: This paper presents an analytical derivation of an optimal spectrum assignment algorithm that minimizes spectral resource idleness in a single elastic link. The algorithm is aware of the requestable connection sizes and rates thereof. This knowledge enables the calculation, for each possible void size and assignment policy, of the expected idle slot-time integral until the void is either fully occupied or coalesced into a new void by the termination of a neighboring connection. Idleness minimization may then be obtained by comparison among all possible on-arrival assignment policies when starting at each possible void size. Since the number of policies grows exponentially with the number of requestable connection sizes, a scalability issue is identified and its mitigation is discussed.

Krzysztof Walkowiak
Performance analysis of multilayer optical networks with time-varying traffic
A. Knapińska¹, P. Lechowicz¹, S. Spadaro², and K. Walkowiak¹
¹Wroclaw University of Science and Technology, Poland
²Universitat Politècnica de Catalunya, Barcelona, Spain
In this paper, we examine a multilayer packet-over-optical network. The packet layer is used to provision time-varying traffic, i.e., traffic that changes over time (day) due to the different popularity of various services and applications at different times of the day. In turn, the optical layer provides a virtual topology of lightpaths transmitting aggregated requests from the packet layer. The proposed algorithm allows to establish traffic in both analyzed layers and utilizes cross-layer information what enables traffic grooming. In addition, traffic prediction provided by ML algorithms is applied to improve routing and grooming decisions. The main objective of this paper is to make a comparison of various transceiver models in a multilayer optical network provisioning time-varying traffic. In more details, the key goal of is to examine what are the potential benefits of updating the transceivers to new models offering better performance in terms of spectral efficiency and transmission reach. We present and discuss results of extensive simulations run on a representative network topology with realistic physical assumptions and under diversified dynamic time-varying traffic patterns. As the main performance metric, we use bandwidth blocking probability (BBP). In addition, we estimate and 1% threshold of BBP defined as the maximum traffic that can be provisioned in the network with BBP not greater than 1%, which is a commonly acceptably threshold for BBP. Furthermore, we report other metrics including spectrum usage and number of reallocations.

WeInTel invited presentations

Molka Gharbaoui
Intent-based networking: Current advances, open challenges, and future directions
M. Gharbaoui, B. Martini, and P. Castoldi, Scuola Superiore Sant’Anna, Pisa, Italy
5G and beyond networks aim at provisioning a variety of services with different characteristics that require complex network configuration operations, which increases the risk of human error. This brings the necessity for the design and implementation of a flexible and programmable architecture that allows for an easy and automated network configuration, thus paving the way for self-managing and self-optimizing networks. In this context, Intent-based Networking (IBN) is emerging as a novel approach that facilitates network management and automates the implementation of network operations required by applications. The aim is to use a simple declarative approach while unburdening applications to deal with technology-specific low-level networking directives. The objective of the paper is three folds: first reviewing the current advances in the IBN architecture and its building blocks; second discussing the open issues and challenges that still need to be addressed to further improve it and third presenting some future directions to overcome those challenges.

Carmen Mas Machuca
Long-term capacity planning in flexible optical networks
C. Mas Machuca, Technische Universität München, Germany
Operators are continuously analyzing the most efficient solution to cope with their increasing demands in terms of investments, spectrum efficiency, over- and under-provisioning, etc. This talk will propose and compare different alternatives for operators to increase the capacity of flexible optical core networks.

Hailey Shakespear-Miles
Dynamic subcarrier allocation for P2MP connections
H. Shakespear-Miles, M. Ruiz, and L. Velasco Universitat Politècnica de Catalunya Barcelona, Spain
This paper details a solution for dynamically allocating subcarriers in a point-to-multipoint connection in the upstream direction. Using Digital Subcarrier Multiplexing a single carrier can be divided into several subcarriers. An ILP was used to dynamically allocated subcarriers in various traffic scenarios allowing for an increased number of edge nodes serviced. Significant capital and energy cost reductions were shown in comparison to traditional methods.

Michela Svaluto Moreolo
Photonic and quantum communication technologies for optical networks evolution
M. Svaluto Moreolo, L. Nadal, J. M. Fabrega, and J. Vílchez
Centre Tecnològic de Telecomunicacions de Catalunya (CTTC/CERCA), Spain
The role of photonic technologies and optical communications, including quantum communications, is particularly relevant to address the societal challenges posed by 6G networks and for a sustainable network evolution. This work focuses on recent advances in programmable multi-dimensional (spectrally and spatially multiplexed) transmission systems and adaptive high-capacity (multi-Tb/s) photonic transceivers to address a sustainable capacity scaling and the need of future optical networks. In particular, it is discussed how to enable high-performance, flexibility, agility, cost/power efficiency and security, promoting an optimal resource usage. To address security aspects, quantum key distribution is considered in coexistence with classical/conventional systems.