Design and Assessment of FM-MCFs-Suited SDM-ROADMs With Versatile Spatial Group Configurations and Unified QoT Estimator

Abstract

In this paper, we focus on the design of different node architectures suitable for Few-Mode Multi-Core Fibers (FM-MCFs) based networks. Both dimensions, core and mode, open different possible ways to group spatial channels depending on the physical impairments of the Space-Division Multiplexed (SDM) optical fibers. Moreover, the channel switching across a group of cores/modes at once and the end-to-end routing are not only mandatory aspects for certain spatial channels, but also recommendable in order to reduce the node complexity/cost. Thus, we propose various SDM-capable node architectures based on versatile and homogeneous spatial group configurations. Then, a unified physical-layer-aware Quality of Transmission (QoT) estimator is formulated to not only evaluate these node architectures in a simulation tool, but also validate them in a real experimental environment using a stateful Path Computation Element (PCE) as a central controller. The obtained resultsdisclose that the cost-efficient node design parameter, namely, the size of the spatial group , depends on both the network and traffic profile size. Specifically, for a national optical backbone network equipped with a homogeneous and hexagonally arranged 6-weakly-coupled modes and 7-weakly-coupled cores fibers, equals 6, while for a continental backbone network, can raise up to 14. In any case, we demonstrate that the cost-benefit tradeoff in node design must be analyzed in detail in order to meet the huge traffic volumes of the next years.

Partial-MIMO Based Mode-Group Transmission and Routing in a Field-Deployed 15-Mode Network: Throughput, DSP Resources and Network Flexibility

“…As previously introduced, in MGDM multiple spatial modes, characterized by similar effective refractive indices, can be organized as a whole super-channel, the MG. In FMFs, the independent MGs are characterized by a weak or even negligible IGXT [10], while the spatial modes belonging to the same MG are strongly coupled, owing to their almost identical propagation constants. The MGDM solution permits to adopt a partial-MIMO approach, in which the processing is applied on a MG basis just on the degenerate modes belonging to the same MG.…”

“…An alternative approach is mode-group division multiplexing (MGDM) [9], where the spatial modes of the same mode group (MG), strongly coupled, constitute a single modal super-channel. MGDM could represent a suitable solution for metropolitan networks, considering that the inter-group crosstalk (IGXT) remains limited or even negligible among different MGs for sufficiently short distances [10]. In such a scheme, the transmission is performed only within specific MGs that are distant enough to neglect or tolerate the IGXT [11].…”

“…In this case, the partial MIMO processing at the receiver side can be applied to each transmitted MG separately, to recover just the degenerate modes belonging to the same MG, thus yielding to a substantial reduction of the required resources. Moreover, this solution allows also routing applications over short and medium reach scenarios [10], [12], where the IGXT is low or even negligible. The different MGs, in fact, can be handled independently, improving the granularity in switching and enabling multi-hop routing in both spectrum and space dimensions.…”