Nonlinear Gaussian Noise Model for Multimode Fibers With Space-Division Multiplexing

Space-division multiplex has become a promising approach to overcome future capacity shortages in long-haul optical transmission systems. In this paper, we present an analytical approach to calculate the nonlinear interference between signals that travel in different fiber modes of a multimode fiber SDM system. We discuss several simplifications based on intra- and intermodal four-wave mixing theories, and compare the analytical model with simulations in an exemplary few-mode fiber transmission system with three and six spatial modes. To generate a deep understanding of the impact of intermodal nonlinear signal distortions, we focus our analysis on the relative strength of intra- and intermodal nonlinearities. A good agreement between the analytical model and numerical simulations is found, making the model an easy-to-use tool to estimate the overall nonlinear distortion in space-division multiplexed transmission systems with multimode fibers.