在高功率主振荡功率放大激光器(MOPA)中,放大的自发辐射(ASE)及其引起的 自激振荡对激光器输出光特性有显著影响。理论分析了自激振荡与光纤端面 反射率的关系。基于自行设计的MOPA光纤激光器系统,实验研究了自激振荡 与增益光纤长度、抽运光功率和信号光功率之间的关系,并根据实验结果归 纳出MOPA光纤激光器的输出特性曲线。结果表明放大级的放大倍数介于 10～15之间时,输出光谱中自激振荡光所占的比例最小。实验结果为优 化MOPA光纤放大器、提高输出激光的信噪比提供了一定参考。

In high power master oscillation power amplification (MOPA) laser, the amplified spontaneous emission (ASE) and induced self-excited oscillation have significant effects on output characteristics of lasers. Relationship between the self-excited oscillation and fiber end surface reflectivity is analyzed theoretically. Based on the self-designed MOPA fiber laser system, relationships between the self-excited oscillation and gain fiber length, pump power, signal power are investigated experimentally. According to the experimental results, the output characteristic curves of MOPA fiber laser are summarized. Results show that when the amplification stage ranges from 10 to 15, the proportion of self-excited oscillation light in output spectrum is the smallest. Experimental results provide a reference for the optimization of MOPA fiber amplifier and improvement of signal to noise ratio of output laser.