The Memory-Enhanced Gaussian Noise (MEGN) Model for Fiber-Optic Channels

TL;DR

The paper introduces the Memory-Enhanced Gaussian Noise (MEGN) model, extending the EGN model to account for symbol energy correlations in fiber-optic channels, validated through simulations and experiments.

Contribution

It provides a rigorous mathematical derivation of a memory extension of the EGN model that explicitly includes symbol energy correlations.

Findings

Normalized NLI power estimations with less than 5% error

Model validated across various symbol rates and distances

Framework for optimizing correlated modulation schemes

Abstract

The enhanced Gaussian noise (EGN) model is widely used for estimating the nonlinear interference (NLI) power accumulated in coherent fiber-optic transmission systems. Given a fixed fiber link, under the assumption that transmitted symbols are independently and identically distributed (i.i.d.), the EGN model establishes that the NLI power depends on time-invariant signal statistics, i.e., the second-, fourth-, and sixth-order moments of the symbols, which are determined by the modulation format and its probability distribution. However, recent advances in coded modulation have sought to mitigate NLI by introducing controlled temporal correlations among transmitted symbols, thereby violating the i.i.d. assumption underlying the EGN model. Among these correlations, symbol energy correlations are believed to exert the most significant influence on NLI. This work presents a rigorous mathematical derivation of a memory extension of the EGN model that explicitly accounts for symbol energy correlations, referred to as the MEGN model. The proposed MEGN model is validated through both numerical simulations and transmission experiments. Normalized average NLI power estimations with less than 5% errors across a wide range of symbol rates and transmission distances are reported. The model also provides a theoretical framework for analyzing and optimizing optical transmission systems employing temporally correlated modulation schemes.