Nonlinear Compensation for Digital Coherent Transmission

This chapter describes a universal postcompensation scheme to compensate all deterministic impairments in fiber called digital backward propagation (DBP). To understand how DBP works, it looks in detail how the electric field of the signal propagates in the forward direction in fiber, which is governed by the nonlinear Schrodinger equation. Nonlinear compensation for multiple fiber segments with the same accumulated dispersion is performed in a single step in dispersion‐folded DBP, resulting in orders‐of‐magnitude savings in computation. In terms of computational load, it might be worthwhile to consider dispersion‐folded DBP not only for installed dispersion‐managed systems but also for future transmission systems. It is possible for a dispersion‐managed transmission system using dispersion‐folded DBP to outperform a dispersion‐unmanaged transmission system using electronic dispersion compensation, both of which are within the realm of current DSP capability.