The Gaussian Noise Model in the Presence of Inter-channel Stimulated Raman Scattering

TL;DR

This paper introduces a Gaussian noise model that accurately accounts for inter-channel stimulated Raman scattering and frequency-dependent effects in optical fiber systems, validated by simulations and applicable to wide bandwidth transmissions.

Contribution

The paper presents a novel semi-analytical Gaussian noise model incorporating ISRS effects, with a simplified analytical version for specific cases, validated against numerical simulations.

Findings

Maximum deviation of 0.1 dB between model and simulations

Up to 2 dB change in nonlinear interference due to ISRS

Model applicable to 10 THz bandwidth systems

Abstract

A Gaussian noise (GN) model is presented that properly accounts for an arbitrary frequency dependent signal power profile along the link. This enables the evaluation of the impact of inter-channel stimulated Raman scattering (ISRS) on the optical Kerr nonlinearity. Additionally, the frequency dependent fiber attenuation can be taken into account and transmission systems that use hybrid amplification schemes can be modeled, where distributed Raman amplification is partly applied over the optical spectrum. To include the latter two cases, a set of coupled ordinary differential equations must be numerically solved in order to obtain the signal power profile yielding a semi-analytical model. However for lumped amplification and negligible variation in fiber attenuation, a less complex and fully analytical model is presented which is referred to as the ISRS GN model. The derived model is exact to first-order for Gaussian modulated signals and extensively validated by numerical split-step simulations. A maximum deviation of $0.1$~dB in nonlinear interference power between simulations and the ISRS GN model is found. The model is applied to a transmission system that occupies an optical bandwidth of $10$~THz, representing the entire C+L band. At optimum launch power, changes of up to $2$~dB in nonlinear interference power due to ISRS are reported. Furthermore, comparable models published in the literature are benchmarked against the ISRS GN model.