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.
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.
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.
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.
A new optical backplane solution is proposed for high-capacity ICT apparatus. A modular, scalable and full-mesh bandwidth-upgradable optical interconnection between optoelectronic boards is guaranteed thanks to an optimized layout of standard MM 12-fiber ribbons which divides the overall backplane into several independent optical sub-circuits. The novel automated assembly procedure of fiber ribbons inside sub-circuits with a robotic work-cell is described. System validation of the optical backplane performed with commercially available MM 12-fiber transceivers @10Gb/s proved the feasibility of the proposed solution for future optical interconnections with terabit overall capacity.
We will show the capabilities of optical modes known as optical vortices in order to perform mode-division multiplexing
(MDM) propagation with a different approach. In particular, we will propose optical vortices not only as an alternative
way to increase the fiber capacity, but also as a cost-effective and “green” solution able to reduce power dissipation in
high capacity systems with respect to solutions based on coherent detection and computationally complex digital MIMO
processing, employed in MDM with usual LP modes.
Two different proposals based on the all-optical spatial mode demultiplexing and on a non-linear MIMO receiver can
allow to employ direct detection and to exploit optical vortices in very simple systems useful for short and medium
distances links, where the cost reduction and energy sustainability are mandatory.
Temperature measures on overhead power lines are shown thanks to a Raman-based fiber optic distributed sensor.
Monitoring performance on optical ground wires is compared to typical electric measurement in field. A large number of
measurement cycles are performed over multiple days under various weather conditions. Monitoring performance on
phase conductors is also evaluated and compared to electric measurement in realistic environment simulating solar
irradiation and natural wind ventilation both on unloaded and loaded conductors.
Exploitation of integrated-optic capabilities in terms of compactness and low-cost are demonstrated in distributed
temperature sensing experimentation. Design and characterization of an integrated-optic circuit in SiON technology with
high index contrast suitable for Raman-based fiber sensor are presented.
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.
An optical wireless system useful for short metropolitan distance connections is proposed. Differently from other apparata described in literature or commercially available, our solution is completely transparent to third window telecommunication channel thanks to standard single mode optical fiber interfaces, without any electro-optic conversion. Such a system guarantees the high performances required to optical communication networks (BER, SNR and so on) without link fault and bit broadening penalties. System characterization and BER performances at 10Gbit/s, also in presence of 1.55micrometers multi-wavelength signal, are presented for connections up to 200m building-to-building roof distance. The implemented transmitter and receiver devices are compact in dimensions, very low cost and can find application not only in metropolitan network links in case of digging impediments due to time, license and cost constraint, but also in disaster recovery and local extraordinary high-bandwidth demand.
A detailed experimental and theoretical analysis of multi- channel XPM-based wavelength conversion in standard communication fibers. Dispersion impact is taken into account and comparison with FWM based conversion technique is also offered.
Preliminary experimentation of angle-multiplexed high- efficiency volume holograms at 1550 nm is presented. It exploits two-color technique by recording digital bytes at 488 nm in iron-doped lithium niobate and retrieving them in near infrared. The stored database constitutes a first holographic memory for optical fiber communication systems.
A 2 X 2 optical switch performing bidirectional cross-bar on optical communication signals at 1550 nm is presented and experimented. The switch is based on electro-optic effect in bulk CdTe crystals. Operation is totally independent by input state of polarization of the optical beams to be addressed. The proposed free-space architecture grants high compactness, reliability and fast response time compared with common switching solutions.
A novel device able to perform a real-time recognition of a temporal stream of optical bits at the communication wavelength of 1550 nm is presented. First experimentation with byte streams at 2.5 Gbit/s coming from a standard transmission line shows the capability of the device to produce the recognition optical signal in a PRBS continuous data flux.
A digital volume holographic database in iron-doped lithium niobate to be read out by a multi-wavelength signal in the near infrared is here successfully performed, thanks to so- called two-color technique. Three 4-bit digital words have been recorded via angle multiplexing at 488 nm and retrieved at 1550 nm by a 200 GHz-WDM (Wavelength Division Multiplexing) beam.
Header Error Control in all-optical ATM switching nodes is discussed. An architecture of an error detection subsystem is designed suitable for free-space parallel optical implementation.
Optical byte recognition using volume holographic correlator is presented. The storage of 256 multiplexed holograms is performed and the phase-coded byte discrimination in real- time is experimented.
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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