Tb/s transmission matching the requirements of future beyond 5-G mobile systems and high-throughput services in the future sustainable metro/access network is demonstrated. An innovative photonic transmitter module of a bandwidth/bitrate variable transceiver has been designed and developed integrating multiple directly modulated long-wavelength InP vertical cavity surface emitting lasers (VCSELs) in a silicon-photonics platform. Multicarrier direct modulation of each VCSEL combined with dense WDM multiplexing with a modular approach provides flexibility in the transported capacity to match dynamic bandwidth allocation, fine granularity, and scalability according to a pay-as-you-grow scheme. The use of VCSELs directly modulated with discrete multitone (DMT) signals is a sustainable technological solution in terms of cost, power consumption and footprint. Moreover, the adoption of multi core fibers (MCFs) allows to also use the space dimension for multiplexing, perfectly matching the proposed modular approach and coping with the mobile systems increasing throughput in an effective way. Here we experiment the propagation over 129 km, including 21 km of a 7-core MCF, with 57 Gb/s capacity per DMT -modulated VCSEL channel and 25 GHz WDM spacing, demonstrating more than 1.2 Tb/s total throughput thanks to the proposed modular solution.

We experimentally demonstrate a 5G digital fronthaul network that relies on multi-adaptive bandwidth/bitrate variable transceivers (BVTs) and an autonomic software-defined networking (SDN) control system for partially-disaggregated wavelength division multiplexing (WDM)/space division multiplexing (SDM). Transmission of 256-QAM 760.32 MHz orthogonal frequency-division multiplexing (OFDM) radio signal is performed, with a total radio transmission capacity of 5.667 Gb/s. Digitized signal samples are carried as a 22.25 Gb/s digitized radio-over-fiber (DRoF) data stream and transmitted over a WDM/SDM infrastructure including 40-wavelength 100-GHz arrayed waveguide gratings (AWGs) and 19-core fiber. The autonomic SDN controller deploys a control loop for the multi-adaptive OFDM-based BVTs that monitors the per-subcarrier signal to noise ratio (SNR) and assigns the optimal constellation based on the actual signal degradation. An error vector magnitude (EVM) below the targeted 2.1% is achieved while setting up connections in less than 5 s.

ITU-T Recommendation G.694.1 defines normative DWDM frequency grids, each being a reference set of values that correspond to allowed nominal central frequencies, obtained using a fixed channel spacing (e.g., 12.5 GHz, 25 GHz, 50 GHz or 100 GHz). This rigid, grid-based approach does not seem well adapted for data rates beyond 100 Gb/s, is particularly inefficient when a whole wavelength is assigned to a lower rate optical path, and is not flexible enough for multi-rate systems . Consequently, the next generation of optical networks will require a flexible, highly efficient and adaptive management of the optical spectrum, along with advanced optical modulation schemes that efficiently use allocated spectrum slots, and recent progress on optical network technology justifies research on both new optical transmission systems as well as the applicability of control and management frameworks to such networks. We design and deploy a GMPLS control plane for flexible optical networks with coherent optical orthogonal frequency-division multiplexing (O-OFDM) transmission; we detail its functional architecture, which combines a centralized entity that performs path routing and modulation assignment, with a distributed spectrum allocation. The centralized entity (i.e., a path computation element) uses pre-configured static path characterizations, based on exhaustive OFDM transmission simulations, when performing dynamic path computation in line with GMPLS constrained shortest path mechanisms. The distributed spectrum allocation assigns frequency ranges (slots) to connection requests, by using dynamic signaling procedures and applying slot assignment policies. We summarize the control plane protocol extensions involved in the main functional aspects: routing and topology dissemination, path computation, signaling and resource reservation. We experimentally validate and evaluate the integrated centralized PCE and GMPLS control plane in a control plane testbed, obtaining key performance indicators such as path setup latency and blocking probability for different frequency slot assignment policies.

We present a recursive approach to implement the Discrete Hartley Transform in the optical domain by using a passive fiber network of asymmetric couplers, without phase shifters. The optical implementation of Discrete Cosine Transform is also derived, resulting in effective and flexible tools for optical data compression and signal processing.