Analytic Models for the Capacity Distribution in MDG-impaired Optical SDM Transmission

TL;DR

This paper develops analytical models to describe the capacity distribution in multi-mode optical SDM systems affected by mode-dependent loss and gain, extending previous single-mode results to systems with more than two modes.

Contribution

It introduces new analytic expressions for capacity distribution in systems with arbitrary mode counts, using Gaussian approximations and correlation fitting, filling a gap in existing research.

Findings

Analytical models match simulation results across various scenarios.

Provides capacity distribution expressions for systems with more than two modes.

Enhances understanding of capacity variability in MDL/MDG-affected optical systems.

Abstract

In coupled space-division multiplexing (SDM) transmission systems, imperfections in optical amplifiers and passive devices introduce mode-dependent loss (MDL) and gain (MDG). These effects render the channel capacity stochastic and result in a decrease in average capacity. Several previous studies employ multi-section simulations to model the capacity of these systems. Additionally, relevant works derive analytically the capacity distribution for a single-mode system with polarization-dependent gain and loss (mode count D = 2). However, to the best of our knowledge, analytic expressions of the capacity distribution for systems with D > 2 have not been presented. In this paper, we provide analytic expressions for the capacity of optical systems with arbitrary mode counts. The expressions rely on Gaussian approximations for the per-mode capacity distributions and for the overall capacity distribution, as well as on fitting parameters for the capacity cross-correlation among different modes. Compared to simulations, the derived analytical expressions exhibit a suitable level of accuracy across a wide range of practical scenarios.