Search

Future optical core networks realizing Flex-Grid and Space Division Multiplexing (Flex-Grid/SDM) will be key to effectively cope with the rapid growth of the Internet traffic, thanks to their superior capacity and spectrum utilization flexibility. Specifically about SDM, the spatial dimension can be considered either fixed or flexible. The goal of this work is two-fold. Firstly, it aims at quantifying the capacity (in terms of throughput) of Flex-Grid/SDM networks assuming either a fixed or a flexible spatial dimension. To this end, we scale up the spatial multiplicity from 7 to 30 spatial channels, considering Multi-Fiber (MF) and Multi-Core Fiber (MCF) solutions. Secondly, it also aims at analyzing the throughput scalability in these networks versus their hardware requirements, especially from the transponder requirements point of view. The obtained results show that, for a 4.3× spatial multiplicity scaling factor, the throughput of spatially fixed Flex-Grid/SDM networks scales up to 3.5×. Conversely, when the spatial dimension is considered flexible, throughput can be pushed up to a 5× factor for both MF and MCF solutions. However, a long-term realization of spectrally-spatially flexible optical networks (SS-FONs) requires up to 9.6× more laser sources and 2.7× electronic complexity (per required connection) in the transponders compared to spatially fixed Flex-Grid/SDM networks. Furthermore, SS-FONs enable different options for assigning the spectral and spatial resources to traffic demands. In this sense, another contribution of this work is the introduction of a novel methodology that trades network throughput for transponder (the major network equipment cost in SDM networks) complexity reduction.

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).