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.