Raising the stimulated Brillouin scattering threshold power by longitudinal compression gradient in a fiber amplifier

TL;DR

This paper introduces a novel method using a longitudinal strain gradient to significantly increase the threshold power for stimulated Brillouin scattering in optical fibers, supported by analytical modeling and experimental validation.

Contribution

It presents a new approach to enhance SBS threshold power through strain engineering, with analytical expressions and experimental confirmation of the effect.

Findings

SBS threshold power increased by about 3 times in passive fibers

SBS threshold power increased by about 2 times in amplifying fibers

Analytical predictions match experimental results in passive fibers

Abstract

We demonstrate and analyse a novel approach to enhance the threshold power of stimulated Brillouin scattering (SBS) in optical fibers, using a longitudinal compressive strain gradient. We derive analytical expressions for the power spectral density of the backscattered Stokes wave in the general case of passive and amplifying optical fibers, by considering the strain and optical power distributions. Our method provides an accurate prediction of the SBS gain spectrum, that we illustrate with a quantitative comparison between measurements and calculations of the SBS Stokes spectra, before and after applying the compression gradient. Our experimental results demonstrate the successful enhancement of the SBS threshold power by a factor of about 3 for the passive fiber and 2 for the amplifying fiber. The enhancement that we manage to calculate in the case of the passive fiber is in perfect agreement with the experimental result.