Temporal characteristics of the light output from optical fibers with PRBS-modulated laser injection

Pseudo-random binary sequence (PRBS) phase modulation is an effective method to promote the stimulated Brillouin scattering (SBS) threshold of high-power narrow linewidth fiber lasers. Most studies focus on the subjects of PRBS pattern selection, filter parameter optimization, threshold promotion, etc. In this paper, the temporal characteristics of the light output from optical fibers with PRBS modulated laser injection are investigated theoretically. We found that serious temporal fluctuations, i.e., high intensity pulses, existed in the output laser and backward Stokes light, even though the time-averaged backward Stokes power is only 1% of the input laser power. Based on the transient three wave coupling equations, through exploring the influence of clock rate and PRBS pattern, we demonstrate that this phenomenon arises from the long dwell times in PRBS patterns. Finally, modified PRBS patterns are proposed to significantly eliminate the intense pulses without decreasing the original SBS threshold. (C) 2022 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement

Automated summary

This paper investigates the temporal characteristics of the light output from optical fibers with PRBS modulated laser injection and finds significant temporal fluctuations. Based on the exploration of clock rate and PRBS pattern, it is demonstrated that these fluctuations arise from the long dwell times in PRBS patterns. Finally, modified PRBS patterns are proposed to eliminate intense pulses.