构建全光纤环形腔放大器，对重复频率在10~50 kHz范围、脉宽数百纳秒的调Q脉冲进行多程放大。本实验研究未对脉冲放大程数进行控制，讨论了脉冲多程放大的增益特性及脉冲时域波形演变特性：该放大系统自动改变脉冲重复频率。实验得到多程放大增益相对于单程放大的增益，最大可提高7 dB以上。研究结果表明，对于重复频率在10kHz及以下的脉冲，采用环形腔多程放大将显著提高放大器的转换效率和信号增益。实验研究为更低重复频率的脉冲实现全光纤再生放大打下基础。

Based on the all-fiber ring-cavity multi-pass pulse amplifier, pulses of Q-switched with a few hundred nanosecond duration and repetition rate of 10~50 kHz range are amplified. Although the number of pass is not controlled, some important phenomena such as characteristics of gain and time domain evaluation in multi-pass amplification are acquired, and the output frequency of pulse is changed by the ring-cavity multi-pass amplifier. A gain of 7 dB higher than that of single pass amplification is obtained. Experimental results demonstrate that signal gain and conversion efficiency can be greatly enhanced by using ring cavity multi-pass amplification for a pulse repetition rate of 10 kHz or lower than that. The results can be helpful to investigation on all-fiber regenerative amplifier.