Raman amplification and ISRS in SDM links: Analytical evaluation and closed-form models for optical transmission

TL;DR

This paper develops closed-form models for Raman amplification and ISRS in SDM optical links, accounting for mode coupling and inter-modal effects, validated by simulations and applicable to experimental estimation.

Contribution

It introduces novel analytical expressions for DRA and ISRS in SDM fibers supporting coupled mode-groups, including mode coupling and non-linear effects.

Findings

Models show excellent agreement with simulations.

Pump and fiber configurations significantly influence gain and MDG.

Proposed routines enable experimental estimation of Raman profiles.

Abstract

In optical communications, the Raman effect is exploited for its lasing properties in distributed Raman amplification (DRA) and leads to spectral distortions through inter-channel stimulated Raman scattering (ISRS). In single-mode fibers, these effects are well understood and modeled, but equivalent closed-form expressions for arbitrarily coupled space-division multiplexing (SDM) links are lacking. In this work, we expand upon previous literature by providing closed-form expressions modelling DRA and ISRS in common SDM fiber designs that support arbitrarily-coupled degenerate mode-groups, incorporate mode coupling, and accounting for inter-modal non-linear effects, showing excellent agreement with simulations. The derived formulas are then applied to representative scenarios, illustrating how distinct pump and fiber configurations influence gain and mode-dependent gain (MDG). Finally, we describe suggested routines for experimentally estimating the Raman response profiles of SDM fibers.