为了达到布里渊光时域分析(BOTDA)系统双通道激光源的布里渊频移要求, 设计了一个光纤布里渊频移器, 放置在其探测脉冲通道, 使探测光与另一通道的扫频光具有布里渊频移差(约11.2 GHz)。通过分析频移器的输出光谱线宽窄化原理, 利用光纤中激发的布里渊增益谱结合一定的环形腔结构形成窄线宽的布里渊斯托克斯光谱输出, 且分析了环形腔频移器的受激布里渊散射阈值和光-光转换效率两个性能指标及其影响因素。采用1551 nm窄线宽光源, 对实际搭建的9 km单模光纤布里渊频移器进行了实验验证, 结果表明：频移器的受激布里渊散射阈值为2.3 mW, 布里渊频移对应的波长改变约为0.1 nm, 此时的定向耦合器耦合比为0.4, 光-光转换效率为49%。所设计的光纤布里渊频移器能达到布里渊光时域分析系统光源的技术指标, 降低了系统的复杂性和成本。

In order to meet the Brillouin frequency shift requirement of dual channel laser source for Brillouin optical time domain analysis(BOTDA) system, an optical fiber Brillouin frequency shifter is designed and placed in the probe pulse channel to make Brillouin frequency shift difference(about 11.2 GHz) between the probe pulse light and the frequency scanning light in another channel. By analyzing the frequency shifter output spectral linewidth narrowing principle, the Brillouin Stokes spectral output with narrow linewidth is formed by combining optical fiber stimulated Brillouin gain spectrum and specific ring cavity structure. The two performance indexes, including threshold of stimulated Brillouin scattering of ring cavity frequency shifter and light-light conversion efficiency, and their influence factors are analyzed. An experimental device of Brillouin frequency shifter with a seed source of 1551 nm and 9 km single mode fiber is set up. The experimental results indicate that the threshold value of stimulated Brillouin scattering is 2.3 mW and the wavelength change corresponding to the Brillouin frequency shift is about 0.1 nm, when the coupling ratio of directional coupler is 0.4 and light-light conversion efficiency is 49%. This optical fiber Brillouin frequency shifter meets the basic light source technical indexes of BOTDA system, which reduces the complexity and the cost of the system.