Closed-form Expression for the Power Profile in Wideband Systems with Inter-channel Stimulated Raman Scattering

TL;DR

This paper derives an approximate closed-form expression for the power profile in wideband fiber-optic systems affected by inter-channel stimulated Raman scattering and fiber loss, enabling more efficient system design and optimization.

Contribution

It introduces a novel closed-form formula for the power profile considering ISRS and fiber loss, validated against numerical solutions, and provides an inverse expression for power pre-emphasis.

Findings

High accuracy of the formula for single-span and multi-span links

Effective inverse expression for target OSNR profiles

Enhanced understanding of power distribution in wideband systems

Abstract

Wideband systems experience significant inter-channel stimulated Raman scattering (ISRS) and channel-dependent losses. Due to the non-uniform attenuation profile, the combined effects of ISRS and fiber loss can only be accurately estimated using numerical methods. In this work, we present an approximate closed-form expression for the channels' power profile accounting for these combined effects. We validate the proposed expression against numerical solutions in the case of CLU transmission, showing high accuracy for both single-span and multi-span fiber-optic links. Additionally, we derive an inverse expression, formulated as a function of the output power, which can be utilized to target a desired optical signal-to-noise ratio (OSNR) profile through pre-emphasis of the launched channel powers.