WinPhoS’ expertise proceeds along the complete chain from device and circuit technology up to systems and networks. Our main research interests are currently focused on:

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Beyond 5G/6G Networks

Beyond 5G (B5G) and 6G networks are expected to encompass a plethora of different technologies in the optical and wireless domains of the transport and access network segments, including different frequency bands, such as millimeter Wave (mmWave) and THz, to operate in synergy with the traditionally used sub-6 GHz spectrum. This, on the one hand, requires developing hardware technologies that support high-capacity fiber-wireless transmissions with beamsteering capabilities and spectral efficient transport schemes. At the same time, the introduction of Network Function Virtualization (NFV) combined with the Software Defined Networking (SDN) paradigm of network control act as key enablers for unparalleled network flexibility towards the efficient management of disparate resource types (i.e., communication, computational and storage). In such a heterogeneous environment comprising a “network of networks”, cross-layer resource allocation strategies and end-to-end protocols for optimized network performance and high scalability become very challenging.

Our group is actively involved in research on highly heterogeneous B5G/6G network architectures spanning all network segments (core, transport X-haul, access), deploying energy-efficient integrated photonic solutions interfaced with millimeter wave phase array antennas and utilizing a distributed computational infrastructure, with emphasis on the development of optimal and low complexity resource allocation schemes in the fiber-wireless domain for traffic routing, scheduling and QoS prioritization. Our activities include the design, implementation and evaluation of algorithms and protocols leveraging system-level simulation tools and FPGA development as well as their integration with open source network management and orchestration tools. In addition, our group has a vast experience in testing and validation of Fiber-Wireless solutions including mmWave and THz antenna prototypes.

References:

1. M. Gatzianas, A. Mesodiakaki, G. Kalfas, and N. Pleros, "Energy-efficient Joint Computational and Network Resource Planning in Beyond 5G Networks" in Proc. IEEE Global Telecommunications Conference (GLOBECOM 2021), Dec. 2021.
2. A. Mesodiakaki, P. Maniotis, M. Gatzianas, C. Vagionas, N. Pleros and G. Kalfas, "A Gated Service MAC Protocol for Sub-Ms Latency 5G Fiber-Wireless mmWave C-RANs" in IEEE Transactions on Wireless Communications, vol. 20, no. 4, pp. 2502-2515, Apr. 2021, doi: 10.1109/TWC.2020.3042762.
3. G. Kalfas, et al., "Next Generation Fiber-Wireless Fronthaul for 5G mmWave Networks" IEEE Communications Magazine, vol. 57, no.3, pp. 138-144, Mar. 2019.
4. A. Tsakyridis, et al., "Reconfigurable Fiber Wireless IFoF Fronthaul With 60 GHz Phased Array Antenna and Silicon Photonic ROADM for 5G mmWave C-RANs" IEEE Journal on Selected Areas in Communications, vol. 39, no. 9, pp. 2816-2826, Sep. 2021.

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Integrated Photonics

In the course of the years past, integrated photonics promised an exciting breakthrough through the development of photonic chips capable of controlling the light in a plethora of applications expanding from biological or chemical sensors and optical computing up to data communications.

Our research group is actively operating in the area of integrated photonics through the involvement in several EU projects towards the development of integrated transceiver modules, photonic interconnects and electro-optic switches, optical memories and biosensor devices. Our studies extend from the design and characterization of passive integrated photonic components, i.e. grating couplers, multimode interference structures, ring-resonator based devices, arrayed waveguide gratings, routing elements, de/multiplexers and waveguide frontends, to the design of optical interfaces for active/passive devices for several material platforms and technologies.

References:

1. Chatzianagnostou E., Ketzaki D., Dabos G., Tsiokos D., Weeber J.-C., and Miliou A., "Design and Optimization of Open-cladded Plasmonic Waveguides for CMOS Integration on Si3N4 Platform" Plasmonics, (2018). [Link]
2. S. Pitris, G. Dabos, C. Mitsolidou, T. Alexoudi, P. De Heyn, J. Van Campenhout, R. Broeke, G. T. Kanellos, and N. Pleros, "Silicon photonic 8 × 8 cyclic Arrayed Waveguide Grating Router for O-band on-chip communication" Optics Express, vol.26, pp.6276-6284 (2018). [Link]
3. G. Dabos, A. Manolis, A.L. Giesecke, C. Porschatis, B. Chmielak, T. Wahlbrink, N. Pleros, and D. Tsiokos, "TM grating coupler on low-loss LPCVD based Si3N4 waveguide platform" Optics Communications, 405, pp.35-38 (2017). [Link]
4. D. Ketzaki, K. Vyrsokinos and T. Alexoudi, "InP and Polymer waveguide frontend designs for beam transforming applications" to appear in proceedings of International Conference on Transparent Optical Networks, ICTON (2019).
5. D. Ketzaki, D. Chatzitheocharis, C. Calò, C. Caillaud, A. Delga and K. Vyrsokinos, "Si-rich Nitride Waveguides for the formation of Back-End-Of-Line Interfaces with III-V Optical Sources on Silicon" to appear in proceedings of SPIE Photonics West (2019).

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Plasmonics

Plasmonics is a rapidly developing field that studies elementary polar excitations bound to metal surfaces. Plasmonic technology offer a new class of components with enhanced optical performance at ultra-small footprints. Current research efforts focus on bringing plasmonics in wafer scale CMOS lines to demonstrate low-cost fabrication of compact modules in the ever-growing areas of data communications and bio-sensing.

Our research group has been actively involved in the field of plasmonics towards the development of integrated, on-chip, low energy electro-optic switches and ultra-sensitive biosensors.

References:

1. G. Dabos, A. Manolis, S. Papaioannou, D. Tsiokos, L. Markey, J.-C. Weeber, A. Dereux, A. L. Giesecke, C. Porschatis, B. Chmielak, and N. Pleros, "CMOS plasmonics in WDM data transmission: 200 Gb/s (8 × 25Gb/s) transmission over aluminum plasmonic waveguides" Opt. Express vol. 26, pp. 12469-12478, 2018 [Link]
2. G. Dabos, A. Manolis, D. Tsiokos, D. Ketzaki, E. Chatzianagnostou, L. Markey, D. Rusakov J.-C. Weeber, A. Dereux, A. L. Giesecke, C. Porschatis, T. Wahlbrink, B. Chmielak, and N. Pleros, "Aluminum plasmonic waveguides co-integrated with Si3N4 photonics using CMOS processes" Scientific Reports, vol. 8, no. 1, art. no. 13380, 2018 [Link]
3. S. Papaioannou, D. Kalavrouziotis, K. Vyrsokinos, J.-C. Weeber, K. Hassan, L. Markey, A. Dereux, A.Kumar, S. I. Bozhevolnyi, M. Baus, T. Tekin, D. Apostolopoulos, H. Avramopoulos and N. Pleros, "Active plasmonics in WDM traffic switching applications" Scientific Reports, vol. 2, art. no. 652, 2012 [Link]

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Optical RAM

Memory functionalities still remain the stronghold of electronics, forming a fundamental bottleneck in computing and routing engines, widely known as “Memory Wall”. Aiming to resolve the long memory access latencies and slow-bandwidths dictated by electronic memories, WinPhos members have been the first to demonstrate an all-optical static RAM cell capable of storing and retrieving light at will by exploiting optical non-linear switching mechanisms, while by thorough theoretical and experimental investigations of various photonic integration platforms and architectural optimizations, the fastest reported RAM and CAM cells to date were also demonstrated. This on-going research activity aims at laying down the architectural and technological principles for scaling up to complete optical cache hierarchies for fast fetching of computing data and address look-up table architectures for low-latency router look-up functionalities.

References:

1. N. Pleros, D. Apostolopoulos, D. Petrantonakis, C. Stamatiadis, and H. Avramopoulos, "Optical static RAM cell", IEEE Photon. Technol. Lett. vol. 21, no. 73, pp. 73-75, Jan. 2009. [Link]
2. C. Vagionas, P. Maniotis, S. Pitris, A. Miliou, N. Pleros, "Integrated Optical Content Addressable Memories (CAM) and Optical Random Access Memories (RAM) for Ultra-Fast Address Look-Up Operations" Appl. Sci. 2017, 7(7), 700, DOI: 10.3390/app7070700 [Link]
3. T. Alexoudi, D. Fitsios, A. Bazin, P. Monnier, R. Raj, A. Miliou, G. T. Kanellos, N. Pleros and F. Raineri, "III–V-on-Si Photonic Crystal Nanocavity Laser Technology for Optical Static Random Access Memories", IEEE Journal Selected Topics in Quant. Electronics, vol. 22, no. 6, 4901410, Nov-Dec. 2016 [Link]

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Neuromorphic Computing

Artificial neural networks are inspired by the biological neural networks that constitute human brain, leading the researchers to design new computing platforms. Recently, custom ASICs have been designed to operate as neural network accelerators in order to surpass the limitations of traditional Von-Neumann architectures, achieving an outstanding performance in terms of power consumption and speed. However, silicon photonics having the credentials for achieving high bandwidths, have already been used to implement photonic units towards ultra-fast neural networks accelerators.

Our research group has recently demonstrated a Sigmoid optical thresholder layout capable to perform as activation unit in a single neuron, as well as a complete photonic artificial neuron based on the Sigmoid activation unit.

References:

1. G. Mourgias-alexandris, A. Tsakyridis, T. Alexoudi, K. Vyrsokinos, and N. Pleros, "Optical Thresholding Device with a Sigmoidal Transfer Function" to appear in Proceedings of Photonics in Switching and Computing (2018).
2. G. Mourgias-alexandris, A. Tsakyridis, N. Passalis, A. Tefas, and N. Pleros, "Experimental demonstration of an optical neuron with a logistic Sigmoid activation function" to appear in Proceedings of Optical Fiber Communication Conference (2019).

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Optical Switching

The massive increase of data that have to be processed in modern Data Centers (DCs) and High-Performance Computers (HPCs) is constantly pushing the limits of the underlying network infrastructure, with the currently employed switching equipment failing to provide the required performance credentials in a cost- and energy-efficient envelope. In this context optical switching solutions emerge to offer high-throughput and ultra-low latency, while at the same time translating the proven energy and cost advantages of optics into respective benefits at system-level.

Our research group has been actively involved in the exploration of diverse optical switching technologies, within the context of the several EU and national research projects. Our research studies cover a broad range of the DC network hierarchy, starting from small-scale on-board switching solutions and reaching up to switching architectures for thousands of nodes.

References:

1. N. Terzenidis, M. Moralis-Pegios, G. Mourgias-Alexandris, T. Alexoudi, K. Vyrsokinos and N. Pleros, "High-Port and Low-Latency Optical Switches for Disaggregated Data Centers: The Hipoλaos Switch Architecture [Invited]", Journal of Optical Communications and Networking, vol. 10, no. 7, p. B102, 2018. [Link]
2. M. Moralis-Pegios, N. Terzenidis, G. Mourgias-Alexandris, M. Cherchi, M. Harjanne, T. Aalto, A. Miliou, K. Vyrsokinos and N. Pleros, "Multicast-Enabling Optical Switch Design Employing Si Buffering and Routing Elements", IEEE Photonics Technology Letters, vol. 30, no. 8, pp. 712-715, 2018. [Link]
3. N. Terzenidis, M. Moralis-Pegios, C. Vagionas, S. Pitris, E. Chatzianagnostou, P. Maniotis, D. Syrivelis, L. Tassiulas, A. Miliou, N. Pleros and K. Vyrsokinos, "Optically-Enabled Bloom Filter Label Forwarding Using a Silicon Photonic Switching Matrix", Journal of Lightwave Technology, vol. 35, no. 21, pp. 4758-4765, 2017. [Link]

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Optical Interconnects

The amount of data generated nowadays by 4G/5G applications, cloud computing and the Internet of Things is constantly fueling the need for faster and energy-efficient optical interconnections in Data Centers (DC) and High Performance Computing (HPC) systems.

Current research focuses first on how high-performance photonic components will be developed and integrated towards high-speed, high-density and energy-efficient Transceivers and Routing/Switching modules and second how they can be exploited to build novel interconnect architectures for DCs and HPCs.

Our research group has been involved in the development of interconnection architectures exploiting Arrayed Waveguide Grating Router modules for wavelength-routed passive interconnection schemes targetting a broad spectrum of DC interconnection levels ranging from board-to-board up to rack-to-rack connectivity.

References:

1. S. Pitris et al., "A 40 Gb/s Chip-to-Chip Interconnect for 8-Socket Direct Connectivity Using Integrated Photonics" in IEEE Photonics Journal, vol. 10, no. 5, pp. 1-8, Oct. 2018. [DOI: 10.1109/JPHOT.2018.2873673] [Link]
2. T. Alexoudi et al., "Optics in Computing: from photonic Network-on-Chip to Chip-to-Chip Interconnects and Disintegrated Architectures" in Journal of Lightwave Technology. [DOI: 10.1109/JLT.2018.2875995] [Link]
3. N. Terzenidis, M. Moralis-Pegios, G. Mourgias-Alexandris, K. Vyrsokinos, and N. Pleros, "High-port low-latency optical switch architecture with optical feed-forward buffering for 256-node disaggregated data centers" Opt. Express 26, 8756-8766 (2018). [DOI: 10.1364/OE.26.008756] [Link]

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Biosensors

WinPhoS has identified the strong potential of integrated photonics and plasmonics in biomedical applications. In this context, winphos has launched a focus area in optical biosensors for point-of-care diagnostics demonstrating already impressive proof of concept results. We combine a low loss silicone nitride PIC platform with plasmonic waveguides in a novel multi-channel biosensing platform integrated on a chip with extreme sensitivities at a low fabrication cost. WinPhos is committed to further researching novel biosensing concepts and experiments using integrated photonics and plasmonics based on noble and CMOS-compatible metals aiming at disrupting point of need diagnostics and personalized medicine.

References:

1. Evangelia Chatzianagnostou, Athanasios Manolis, George Dabos, Dimitra Ketzaki, Amalia Miliou, Nikos Pleros, Laurent Markey, Jean-Claude Weeber, Alain Dereux, Bartos Chmielak, Anna-Lena Giesecke, Caroline Porschatis, Piotr J. Cegielski, Dimitris Tsiokos, "Scaling the Sensitivity of Integrated Plasmo-Photonic Interferometric Sensors" ACS Photonics [Link]

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Optical Phased Arrays

Optical phased arrays (OPAs) have recently drawn significant research attention due to their promising capabilities of non-inertial optical beam forming and steering delivering a variety of 3D sensing, imaging, illumination, ranging and optical communication applications. By manipulating the specific spatial distribution of the amplitudes and phases emitted from individual optical antennas, OPAs can form the desired radiation patterns through far-field interference.

Our research group is actively involved in the field of OPAs towards the development of compact integrated beam steering, LIDAR circuits as well as integrated wavefronts for hybrid switching systems.

References:

1. T. Alexoudi, D. Ketzaki, D. Chatzitheocharis, D. Alexandropoulos, R. Santos, M. Halter, T. Lamprecht, K. Vyrsokinos, "Low-loss polymer waveguide-based frontend for beam transforming in InP/polymer platform" in 24th OptoElectronics and Communications Conference (OECC), 8817710, Jul. 2019. [Link]
2. D. Ketzaki, G. Patsamanis, T. Lamprecht, K. Vyrsokinos, T. Alexoudi, "Waveguide frontend designs for beam transforming applications" in International Conference on Transparent Optical Networks (ΙCTON 2019), 8840423, Jul. 2019. [Link]
3. G. Patsamanis, T. Alexoudi, D. Chatzitheocharis, K. Vyrsokinos, and D. Ketzaki, "Optical Beam Shaping through SiN-Based Waveguide Arrays Towards WSS Front-Ends" in International Conference on Transparent Optical Networks (ICTON 2020), Mo.E5.4, Jul. 2020.