Experimental study on the influence of backward ASE on SBS process in single-frequency amplifier

摘要

We have constructed an all-fiber single-frequency amplifier system and an additional all-fiber amplifiedspontaneous emission (ASE) source system to simulate the effect of generated backward ASE on stimulated Brillouinscattering (SBS) in master oscillator power amplification (MOPA) system. By injecting the artificial ASE sourcebackward into the Yb-doped MOPA system directly and measuring the evolutions of SBS threshold power with theincreasing ASE power level, we can get the changes of SBS process during the amplification. Effects of counterpropagatingASE on SBS threshold decreasing were obvious: When there was no counter-propagating ASE beinginjected, the backscattered power started to rise very slowly. However, with the added artificial ASE increasing, thebackscattered power departed from linear quite early. And the SBS threshold power was reduced to different levels withdifferent power level of additional ASE. As the artificial counter-propagating ASE power increased from 0 to 275.9mW,the SBS threshold power was correspondingly dropped down from 4.75W to 3.35W. The 30% reduction of the SBSthreshold can be a siginificant influence in a single-frequency fiber amplifier.