Theoretical analysis of long-haul systems adopting mode-division multiplexing

In this paper, we modify the Gaussian noise model (GN-model) to address the nonlinearity effects in few-mode fibers. Closed-form expressions for the nonlinear interference power in birefringent few-mode fibers (FMFs) are derived and the effect of differential mode group delay (DMGD) is investigated. Moreover, the nonlinearity accumulation through propagation in multiple-spans fiber and the birefringence effect are considered. In addition, we discuss the effect of the DMGD on the fiber nonlinearity in systems adopting mode-division multiplexing (MDM). The results show that the DMGD management degrades the system performance in weak coupling regime because the nonlinear interference is enhanced. However, strong coupling-based transmission outperforms weak coupling transmission regardless of the DMGD effect in the weak coupling regime. On the other hand, by taking the DMGD effect into account, the system performance in weak coupling regime is better than that in strong coupling regime. Furthermore, the impact of the nonlinearity on the maximum reach is discussed

Design and assessment of FM-MCFs-suited SDM-ROADMs with versatile spatial group configurations and unified QoT estimator

In this article, we focus on the design of different node architectures suitable for few-mode multi-core fibers (FMMCFs) 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 results disclose that the cost-efficient node design parameter, namely, the size of the spatial group G, 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, G equals 6, while for a continental backbone network, G 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.This work was supported by the Spanish Project AURORAS under Grant RTI2018-099178-B-I00.Peer ReviewedPostprint (author's final draft