Transmission stability and Raman-induced amplitude dynamics in multichannel soliton-based optical waveguide systems

TL;DR

This paper investigates the stability and amplitude dynamics of multichannel soliton-based optical systems, revealing how nonlinear couplers can significantly enhance transmission stability by suppressing radiative sidebands compared to single-fiber systems.

Contribution

It introduces a simplified predator-prey model for Raman-induced amplitude dynamics and demonstrates its accuracy in predicting soliton behavior in multichannel optical waveguides.

Findings

Stable oscillatory amplitude dynamics at short-to-intermediate distances

Transmission destabilization due to radiative sidebands at larger distances

Nonlinear waveguide couplers significantly improve transmission stability

Abstract

We study transmission stability and dynamics of pulse amplitudes in $N$-channel soliton-based optical waveguide systems, taking into account second-order dispersion, Kerr nonlinearity, delayed Raman response, and frequency dependent linear gain-loss. We carry out numerical simulations with systems of $N$ coupled nonlinear Schr\"odinger (NLS) equations and compare the results with the predictions of a simplified predator-prey model for Raman-induced amplitude dynamics. Coupled-NLS simulations for single-fiber transmission with $2 \le N \le 4$ frequency channels show stable oscillatory dynamics of soliton amplitudes at short-to-intermediate distances, in excellent agreement with the predator-prey model's predictions. However, at larger distances, we observe transmission destabilization due to resonant formation of radiative sidebands, which is caused by Kerr nonlinearity. The presence of linear gain-loss in a single fiber leads to a limited increase in transmission stability. Significantly stronger enhancement of transmission stability is achieved in a nonlinear $N$-waveguide coupler due to efficient suppression of radiative sideband generation by the linear gain-loss. As a result, the distances along which stable Raman-induced dynamics of soliton amplitudes is observed are significantly larger in the waveguide coupler system compared with the single-fiber system.