Metro area network (MAN) connectivity is rapidly evolving towards a much more dense, complex and diverse scenario to be dynamically addressed with flexible cost-efficient and high-capacity technology and architecture solutions, dealing with an even more open and disaggregated paradigm. In this work, sliceable bandwidth/bitrate variable transceiver (S-BVT) architectures adopting modular approach and suitable photonic technologies (such as VCSEL), enabling to efficiently and dynamically exploit both spectral and spatial dimensions, are discussed, considering design, implementation, cost and flexibility aspects. Recent numerical and experimental results are reported, showing how to enable scalability towards supporting multi-Tb/s connectivity in flexible and dynamic large MAN.
The high capacity demand, to support broadband services and everything-to-internet connectivity is pushing the limits of both access and metro networks, requiring the adoption of novel strategies for the optical transceiver modules. This represents an opportunity for the adoption in these network scenarios of novel photonic technologies based on single-mode vertical cavity surface emitting lasers (VCSELs) at long wavelengths. On one hand, the access network evolution requires a line rate increase beyond 10 Gb/s, targeting 50 Gb/s propagation in passive optical networks (PONs) over a few tens of kms in standard single mode fiber (SSMF) with simple, cost effective and energy efficient transceivers. On the other hand, the future metropolitan area network (MAN) will need to handle multi-Tb/s traffic in a very dynamic scenario, over variable distances up to hundreds of kms while promoting sustainability, reducing the CapEx and OpEx costs and power consumption. Both needs can be fulfilled by adopting VCSEL direct modulation with multicarrier modulation formats such as discrete multitone (DMT), in combination with distinct transmitter architectures and receiver solutions to support different aggregate capacity requirements and transmission reaches. In any case DMT with bit/power loading enables flexible rate and adaptive distance for metro network applications and link adaptation and PON resource usage optimization for future access networks. In this work, we report our recent results on the adoption of VCSEL technology in both scenarios, with special focus on the receiver and transmitter adopted architectures.
This article provides insight on two of the most relevant applications driving the design of the future MAN: the implementation of 5G by means of C-RAN (Cloud - Radio Area Network) and the deployment of edge computing. The work addresses important questions such as the target latency budget for future MANs, the target bandwidth requirements for 2020-2030 induced by 5G midhaul and fronthaul traffic, and describes how optical and electronics layers can co-operate to meet the QoS targets of C-RAN and edge computing traffic. In the process, we identify the key architectural elements to meet the challenges of these applications in a cost-effective way.
Innovative photonic solutions designed and developed in the H2020 research project PASSION are presented for the future metropolitan area network (MAN) supporting different aggregated data traffic volumes and operating at heterogenous granularities. System performance evaluated both by simulations and experimentation regarding the proposed vertical cavity surface emitting laser (VCSEL) -based modular sliceable bandwidth/bitrate variable transceiver (S-BVT) are shown in realistic MANs organized by hierarchical levels with the crossing of multiple nodes characterized by new switching/aggregation technologies. The capabilities and challenges of the proposed cost-effective, energy-efficient and reduced footprint technological solutions will be demonstrated to face the request of huge throughput and traffic scalability.
The information technologies (ITs)-communications infrastructure convergence is key to future optical networks for achieving an automated orchestration of IT, optical and cloud resources. To cope with this challenge, transmission systems need to be agile, programmable, and capable of transmitting large amounts of data, while covering data center and metropolitan networks. This work addresses transmission solutions using coherent detection combined with either direct or external modulation, with special focus on flexible, high capacity and cost/energy-efficient systems. The proposed technological solutions are evaluated in terms of throughput, and programmability and interaction with the control plane.
The use of vertical cavity surface emitting laser (VCSEL) at long wavelengths, especially if characterized by large bandwidth or tunable capability, is appearing as an attractive technology for the implementation of advanced transceivers to be used in optical metro networks at 100G and beyond.
In this work, we report recent promising results on the adoption of different types of VCSEL for the sliceable bandwidth/bitrate variable transceiver (S-BVT) design. Special attention will be devoted to technological aspects and challenges, focusing on the added value of exploiting novel photonic technologies for the implementation of costeffective transceivers, suitable for future optical metro networks targeting high capacity and flexibility.
SOA-based wavelength conversion is obtained in an interferometric device exploiting two synchronous cascaded conversion processes in a SLALOM followed by a nonlinear filter. An accurate analysis and experimental eye-diagrams demonstrate significant signal quality improvement.
Extremely high is nowadays researchers' interest towards amplification techniques alternative to Erbium Doped Fiber Amplifiers (EDFA); driving force is the exploitation of new and larger fiber optic communication bandwidths. While EDFA gain relies on population inversion in an active material and thus amplification bandwidth is directly related to the doping ion energy levels, well known effects such as Raman and third order nonlinear susceptibility in optical fiber allow amplification not subject to this constraint. In optical parametric amplification, in particular, bandwidth shape and spectral collocation are determined by the choice of pump wavelength and power. Thus almost every spectral region can be reached provided that proper pump is available. We present a detailed analysis of optical parametric amplification in standard communication fiber, discussing different operation regime according to pump wavelength placement with respect to fiber zero dispersion wavelength. In particular attention is paid to the optical parametric amplifier gain bandwidth and saturation. We evidence that a key OPA project parameter is the relative phase between interacting waves, i.e., pump, signal and idler. This parameter not only allows comprehension of gain dynamics in the amplifier, but also can be controlled by engineering the nonlinear medium to improve OPA performances. Experimental verifications are also presented to validate the proposed analysis.
We present the analysis of reshaping capabilities of an all- optical threshold circuit. The device is based on SOA's XGM with two amplifiers in a feedback configuration. Simulations and experimentations of the threshold behavior are proposed and commented.
A programmable optical bistable device, based on a ring fiber optic circuit in which is inserted an optical amplifier, is presented. The optical amplifier has the purpose both to obtain the bistable duration and to reset the device by means of the loop gain compression effect.
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