Investigation of LP- and Vector-Modes for the Analysis of Space-Division Multiplexed Systems in the Nonlinear Regime

Space-division multiplexing in multimode fibers is a very promising approach to overcome the shortcoming of capacity in long-haul optical transmission systems. In this paper, we present an analysis of different mode representations in multimode fibers. We resume the properties and the interrelations of linearly polarized and vectorial modes. We take a look at the coupled nonlinear Schrödinger equation and Manakov equations for strongly coupled mode groups. The nonlinear coupling coefficient of the Manakov equation is investigated for both mode bases, in order to verify if the approximated linearly polarized modes are a valid representation for the analysis of nonlinearities in space-division multiplexed systems. Even though the effective mode areas differ considerably between LP- and vector modes, the simulated coupling coefficient shows a good agreement between both models. The results indicate that the mode basis does not affect the nonlinear parameter. For the analysis the field distributions of the modes are numerically calculated with a vector finite difference modesolver. Finally the simulated results are verified analytically.