Programmable filterless network architecture based on optical white boxes

We propose and evaluate a novel architecture enabling high-capacity, resource efficient and agile elastic optical networks. It is based on sliceable bandwidth-variable transponders and optical white box switches which route optical signals without filtering them. Instead of using active filtering components, each node is equipped with an optical white box based on a programmable optical switch that serves as an optical backplane. It provides interconnections between input/output ports and passive splitters and couplers. Due to signal broadcast and the absence of filtering (so-called drop-and-waste transmission), some of the signals appear on unintended links which can lead to an overhead in spectrum usage. To address this issue, we formulate the problem of signal routing, modulation format and spectrum assignment in programmable filterless networks based on optical white boxes as an integer linear program (ILP) with the objective to minimize the total spectrum usage. Simulation results indicate that our proposed solution obtains a beneficial tradeoff between component usage and spectrum consumption, using a drastically lower number of active switching elements than the conventional networks based on hard-wired reconfigurable add/drop multiplexers, and lowering the maximum used frequency slot by up to 48% compared to existing passive filterless networks

Space continuity constraint in dynamic Flex-Grid/SDM optical core networks: An evaluation with spatial and spectral super-channels

Space Division Multiplexing (SDM) appears as a promising solution to overcome the capacity limits of single-mode optical fibers. In Flex-Grid/SDM optical networks, nodes offering full interconnection between input/output fiber ports and spatial channels, typical SDM-Reconfigurable Optical Add/Drop Multiplexer (SDM-ROADM) referred to as independent switching with lane support (InS with LC support), require very complex and expensive node architectures. Alternative designs have been proposed to relax their requirements, such as those realizing Joint-switching (JoS) by switching one spectrum slice across all spatial channels at once. In this work, we evaluate the benefits of a cost-effective SDM-ROADM architecture that makes a trade-off between (i) performance in terms of network throughput and (ii) architectural complexity by forcing the Space Continuity Constraint (SCC) end-to-end, that is, along the connection physical path. The performance and architectural complexity of such a SDM-ROADM solution are compared in dynamic Flex-Grid/SDM scenarios against benchmark networks based on InS with LC support and JoS SDM-ROADMs, under both spatial and spectral super-channels. We quantify the network throughput when scaling the spatial multiplicity from 7 to 30 spatial channels, considering Multi-Fiber (MF) as well as Multi-Core Fiber (MCF) SDM solutions. The obtained results reveal that differences in terms of network throughput employing InS without LC support SDM-ROADMs is merely up to 14% lower than InS with LC support SDM-ROADMs, while the network CAPEX can be dramatically reduced by 86%. In contrast, networks employing InS without LC support SDM-ROADMs carry up to 40% higher throughput than JoS ones, whereas the network CAPEX can be raised up to 3×. This paper also analyses the spatial multiplicity impact on both network metrics (throughput and CAPEX).Peer ReviewedPostprint (author's final draft

Assessment of Flex-Grid/MCF optical networks with ROADM limited core switching capability

The majority of the research studies on Flex-Grid over multi-core fiber (Flex-Grid/MCF) networks are built on the assumption of fully non-blocking ROADMs (FNB-ROADMs), able to switch any portion of the spectrum from any input core of any input fiber to any output core of any output fiber. Such flexibility comes at an enormous extra hardware cost. In this paper, we explore the trade-off of using ROADMs that impose the so-called core continuity constraint (CCC). Namely, a CCC-ROADM can switch spectrum from a core on an input fiber to a chosen output fiber, but cannot choose the specific output core. For instance, if all fibers have the same number of cores, the i-th core in the input fibers can be just switched to the i-th core in the output fibers. To evaluate the performance vs. cost trade-off of using CCCROADMs, we present two Integer Linear Programming (ILP) formulations for optimally allocating incoming demands in Flex-Grid/MCF networks, where the CCC constraint is imposed or not, respectively. A set of results are extracted applying both schemes in two different backbone networks. Transmission reach estimations are conducted accounting for the fiber’s linear and non-linear effects, as well as the inter-core crosstalk (ICXT) impairment introduced by laboratory MCF prototypes of 7, 12 and 19 cores. Our numerical evaluations show that the performance penalty of CCC is minimal, i.e., below 1% for 7 and 12-core MCF and up to 10% for 19-core MCF, while the cost reduction is large. In addition, results reveal that the ICXT effect can be significant when the number of cores per MCF is high, up to a point that equipping the network with 12-core MCFs can yield superior effective capacity than with 19-core MCFs.Peer ReviewedPostprint (author's final draft

OSNR-aware control of optical white boxes on elastic optical networks

Asia Communications and Photonics Conferene (ACP) © OSA 2016 Results of optical white boxes on Elastic Optical Networks with adaptive modulation format and symbol rate simulations demonstrate that synthesized nodes improve capacity under low loads while preserving performance of existing ROADMs for higher loads

Key performance indicators for elastic optical transponders and ROADMs:the role of flexibility

Flexible optical networks will provide the required service diversity to manage unpredictable traffic patterns and growth. However, a key challenge is to quantify flexibility in order to indicate the associated performance of individual components and subsystems required to support networks and correlate it with other figures of merit. Measurable key performance indicators will aid the process towards the design and deployment of cost effective and efficient optical networks. Moreover, the design and placement of network elements within a network influences the resultant network-wide flexibility and performance. In this paper, we highlight critical design parameters for key optical components, optical transmission and switching subsystems using flexibility as an additional figure of merit. We derive models to measure the flexibility of key optical components, optical transmission and switching subsystems based on entropy maximization. Using these models, we evaluate flexibility and design trade-offs of the presented enabling technologies with other key performance indicators such as spectral efficiency, lightpath reach, total capacity, normalized cost, connectivity and others. This study provides an advanced and more informed set of design rules that quantify and visualize the different degrees of flexibility of enabling technologies and associated performance based on required specification and/or functionality