提出一种基于反馈光纤环（FFL）的窄线宽单纵模布里渊激光器（BFL），主腔是由光环形器构成的单通谐振腔，长度从传统单纵模BFL的10 m扩展并优化至50 m，FFL的光纤作为激光器主要增益介质，为了获得单模运行，则将其长度选为传统单纵模BFL的光纤长度10 m。通过理论分析，相对于传统的单纵模窄线宽BFL，基于FFL的BFL阈值和线宽都可以得到改善。实验中，与两组不同长度单模光纤进行对比分析，优化了基于FFL的BFL环长，同时将系统置于保温盒中，消除外界对系统的干扰，最终获得的阈值为99 mW，边模抑制比提高了45 dB，1 h内输出功率波动为0.8 dB的单纵模布里渊激光，利用延时干涉的方法，测得线宽约为3.23 kHz，与理论分析值相符。

A novel narrow linewidth single longitudinal mode (SLM) Brillouin fiber laser (BFL) based on the feedback fiber loop (FFL) is proposed. The main single pass ring is constructed by an optical circulator and a 50 m single mode fiber (SMF) whose length is extended from 10 m of traditional BFL to 50 m used as laser gain medium. In order to guarantee the SLM operation, the FFL is configured with a 10 m SMF of traditional BFL. By theoretical analysis, threshold and linewidth of FFL-based BFL are better than those of traditional SLM BFL. In experiments, ring length is optimized by contrast with other two group different length SMFs. The system is enclosed in temperature control system so that environment disturbance is reduced. The SLM BFL with 99 mW threshold, 45 dB sidemode suppression and 0.8 dB power fluctuation in 1 h is obtained. 3.23 kHz linewidth is measured by delay interference method.