Charoula Mitsolidou

Digital Optical Physical-Layer Network Coding for mm-Wave Radio-Over-Fiber Signals in Fiber-Wireless Networks

We demonstrate a digital Optical Physical-layer Network Coding (OPNC) for mm-wave fiber-wireless signals modulated with up to 2.5 Gb/s On/OFF Keyed (OOK) data. The proposed OPNC concept uses an all-optical XOR gate comprising a Semiconductor Optical Amplifier-Mach Zehnder Interferometer (SOA-MZI) with SOAs being driven at low moderate electrical currents in order to perform the all-optical encoding between the OOK envelopes of the data, ignoring the high-frequency Sub-Carrier (SC) signal. In this scheme, network coding is performed on-the-fly at the central office and the resultant packet is broadcasted at the client nodes, where the decoding takes place. We demonstrate experimental results of OPNC using OOK data signals modulated on a 10 GHz SC with the aid of a second all-optical XOR gate for the decoding process at the clients site, reporting error-free performance for both synchronous/asynchronous data packets. The scenario of all optical encoding for 60 GHz SC frequencies followed by electrical decoding at the end-users is evaluated via PHY-layer simulations. Going a step further and considering the network level, we present a performance improvement on the network throughput by using the proposed network coding.

Optical Physical-Layer Digital Network Coding for 2.5-Gb/s RoF-Based FiWi Networks

We demonstrate the first digital optical physical-layer network coding (OPNC) scheme for 2.5-Gb/s ON/OFF keyed (OOK) subcarrier modulated (SCM) signals suitable for the application in fiber-wireless networks. The proposed OPNC scheme employs all optical XOR logic gates that rely on cross-phase modulation-based Semiconductor Optical Amplifier (SOA) Mach-Zehnder interferometers to perform encoding and decoding operations. The proposed encoding and decoding scheme is targeting deployment at the central office and the clients site at the remote antenna units, respectively. Proof of concept verification is experimentally demonstrated for 2.5-Gb/s OOK-SCM data using a 10-GHz subcarrier. Both synchronous and asynchronous operations are evaluated, achieving error free operation.

All-Optical Tag Comparison for Hit/Miss Decision in Optical Cache Memories

An all optical multi-wavelength tag comparator unit followed by a semiconductor optical amplifier-read access gate (SOA-RAG) is presented for all-optical cache memory architectures. Proof-of-principle operation of the Tag Comparison (TC) circuit as a dual-bit tag-comparison stage is presented by exploiting cross-phase modulation-based XOR logic gates based on SOA-Mach-Zehnder interferometers (SOA-MZIs), in order to decide upon a cache hit or cache miss operation, while the two SOA-MZI outputs control the ON/OFF cross-gain-modulation of the SOA-RAG unit. Experimental error free operation is demonstrated for a 8 × 10-Gb/s wavelength division multiplexing (WDM) formatted optical word signal and a 4 × 10-Gb/s WDM tag.

First demonstration of all-optical digital network coding in radio over fiber networks

We propose and experimentally demonstrate the first all optical digital network coding between OOK-NRZ Subcarrier Modulated (SCM) signals for Radio over Fiber (RoF) networks using a Semiconductor Optical Amplifier-Mach Zehnder Interferometer (SOA-MZI) as an XOR encoder. Successful encoding and decoding is demonstrated for 1 Gb/s data on a 10 GHz sub-carrier for synchronous and asynchronous NRZ data.

All-optical digital physical-layer network coding for DPSK mm-wave Radio-over-Fiber networks

We demonstrate the first all-optical digital physical-layer network coding (AOPNC) for Differential Phase Shift Keyed (DPSK) Sub-Carrier Modulated (SCM) signals in mm-wave Radio-over-Fiber (RoF) networks. AOPNC is performed at the Central Office (CO) by employing a Delay Interferometer (DI) for phase-to-amplitude conversion, two Semiconductor Optical Amplifier-Mach Zehnder Interferometers (SOA-MZIs) performing the XOR and XNOR operation between the OOK converted signals and a third SOA-MZI for the phase regeneration of the encoded phase-formatted XOR signal. Encoding and decoding are evaluated via simulations for 2.5 Gb/s NRZ-DPSK data modulated on 60 GHz SC for both synchronous and asynchronous operation.

DPSK-demodulation based on ultra-compact micron-scale SOI platform

We present the error-free demodulation of a 10Gb/s DPSK-signal based on a novel Delayed Interferometer with ultra-small footprint. The device is fabricated on thick um-scale SOI platform and exhibits similar dimension with nanophotonic based DIs.

Heterogeneous 60 GHz / 5 GHz broadband optical wireless systems supporting dynamic bandwidth allocation

We present our recent work in developing and demonstrating a fully converged heterogeneous high-throughput 60 GHz / 5 GHz optical wireless transmission system that allows for dynamic bandwidth allocation towards supporting Cloud RAN architectures. In addition to modulation/demodulation of the baseband optical signals, this system is responsible for the conversion of the optical phase modulated low frequency sub-carriers signals into higher frequency wireless signals and their transmission into the air. Finally, its design is capable of supporting Medium-Transparent MAC protocol mechanisms allowing for a seamless interplay between optical and wireless.

Optical interconnect and memory components for disaggregated computing

High-performance server boards rely on multi-socket architectures for increasing the processing power density on the board level and for flattening the data center networks beyond leaf-spine architectures. Scaling, however, the number of processors per board and retaining at the same time low-latency and high-throughput metrics puts current electronic technologies into challenge. In this article, we report on our recent work carried out in the H2020 projects ICT-STREAMS and dREDBox that promotes the use of Silicon Photonic transceiver and routing modules in a powerful board-level, chip-to-chip interconnect paradigm. The proposed on-board platform leverages WDM parallel transmission with a powerful wavelength routing approach that is capable of interconnecting multiple processors with up to 25.6 Tbps on-board throughput, providing direct and collision-less any-to-any communication between multiple compute and memory sockets at low-energy 50 Gbps OOK line-rates. We demonstrate recent advances on the Si-based WDM transceiver, cyclic AWGR router and polymer-based electro-optical circuit board key-enabling technologies, discussing also potential applications in disaggregated rack-scale architectures. We also demonstrate our recent research on optical RAM technologies and optical cache memory architectures that can take advantage of the on-board interconnect technology for yielding true disintegrated computing resolving both power and memory bandwidth bottlenecks of current computational settings.

5G Small-Cell Networks Exploiting Optical Technologies with mmWave Massive MIMO and MT-MAC Protocols

Analog optical fronthaul for 5G network architectures is currently being promoted as a bandwidth- and energy-efficient technology that can sustain the data-rate, latency and energy requirements of the emerging 5G era. This paper deals with a new optical fronthaul architecture that can effectively synergize optical transceiver, optical add/drop multiplexer and optical beamforming integrated photonics towards a DSP-assisted analog fronthaul for seamless and medium-transparent 5G small-cell networks. Its main application targets include Urban and Hot-Spot Area networks, promoting the deployment of mmWave massive MIMO Remote Radio Heads (RRHs) that can offer wireless data-rates ranging from 25 to 100 Gb/s and beyond depending on the fronthaul technology employed (e.g. spatial or wavelength division multiplexing transport). Small-cell access and resource allocation is ensured via a Medium-Transparent (MT-) MAC protocol that enables the transparent communication between the central office and the wireless end-users or the access cells via V-band massive MIMO RRHs.

High-throughput and low-latency 60GHz small-cell network architectures over radio-over-fiber technologies

Future broadband access networks in the 5G framework will need to be bilateral, exploiting both optical and wireless technologies. This paper deals with new approaches and synergies on radio-over-fiber (RoF) technologies and how those can be leveraged to seamlessly converge wireless technology for agility and mobility with passive optical networks (PON)-based backhauling. The proposed convergence paradigm is based upon a holistic network architecture mixing mm-wave wireless access with photonic integration, dynamic capacity allocation and network coding schemes to enable high bandwidth and low-latency fixed and 60GHz wireless personal area communications for gigabit rate per user, proposing and deploying on top a Medium-Transparent MAC (MT-MAC) protocol as a low-latency bandwidth allocation mechanism. We have evaluated alternative network topologies between the central office (CO) and the access point module (APM) for data rates up to 2.5 Gb/s and SC frequencies up to 60 GHz. Optical network coding is demonstrated for SCM-based signaling to enhance bandwidth utilization and facilitate optical-wireless convergence in 5G applications, reporting medium-transparent network coding directly at the physical layer between end-users communicating over a RoF infrastructure. Towards equipping the physical layer with the appropriate agility to support MT-MAC protocols, a monolithic InP-based Remote Antenna Unit optoelectronic PIC interface is shown that ensures control over the optical resource allocation assisting at the same time broadband wireless service. Finally, the MT-MAC protocol is analysed and simulation and analytical theoretical results are presented that are found to be in good agreement confirming latency values lower than 1msec for small- to mid-load conditions.