Optimized modulation formats for suppression of stimulated Brillouin scattering in optical fiber amplifiers

Abstract

Laser linewidth broadening through phase modulation is an effective way of suppressing stimulated Brillouin scattering (SBS) [1]. However, several applications require laser linewidth to be as narrow as possible. These contradicting requirements call for phase modulation formats that allow for suppression of SBS while maintaining the laser power within a tolerable optical bandwidth. Previously, we have reported on the optimization of phase modulation for single-frequency laser to get nearly equal amplitude spectral components within the given optical bandwidth [2]. In Ref. [2] the spectral line spacing is assumed to be large compared to the intrinsic Brillouin gain bandwidth and there is no interference among the corresponding Brillouin Stokes waves. A more robust SBS model is required to obtain fully optimized phase modulation formats if the spectral spacing is small. In the present work, we implement a SBS finite difference model based on the work of Ref. [3].