超窄线宽激光器随机发生的跳模现象，作为一种干扰或噪声，是降低光学相干检测系统性能的重要因素。为了有效检测单纵模超窄线宽激光器的模式稳定性，提出一种基于光纤M-Z干涉仪的超窄线宽激光器跳模检测方法，该方法通过在干涉仪内引入相位生成载波(PGC)外调制技术，将激光器跳模过程中光源相干性的变化转化为干涉仪相干度的突变，从而实现对整个跳模过程的实时监测。实验结果表明，该方法在检测灵敏度上有明显优势，能够有效监测跳模的持续时间、模式竞争随时间演化的动态过程等跳模细节，尤其适合用于短直腔激光器的跳模检测，并且能为光纤激光器跳模现象的预测与主动抑制提供重要参考。

As one type of disturbance or noise, random mode hopping of ultra-narrow line-width lasers is a significant factor that debases the performance of optical coherence detection system. In order to detect the mode stability characteristics of single-longitudinal-mode lasers with ultra-narrow line-width, a new method for detecting mode hopping based on fiber Mach-Zehnder interferometer with externally modulated phase generated carrier(PGC) is proposed. It transforms the entire mode hopping process to the visibility change of interference waveform so as to achieve real-time observation. The experimental results show that this method has such high sensitivity that it can be used to capture the duration and the dynamic process of mode competition effectively, especially for lasers with short linear cavity. Besides, this method will play an important role in the prediction and active suppression of mode hopping in fiber lasers.