研究了一种长基线激光干涉仪的在线稳定性监测技术，可用于纳米量级的位移和振动测量。构建了一个臂长22 m的激光干涉仪用于位移和振动测量。基于相位生成载波(PGC)解调技术，通过在相位调制载波中增加已知频率、固定幅值的指示信号，利用指示信号的幅度变化，实现激光干涉仪的工作状态监测，以及测量环境的变化与波动的指示。实验结果表明，加入已知幅度频率的指示信号可以实现激光干涉仪在线运行状态的监测。该方法的优点是没有增加硬件负载，可实现激光干涉仪的在线稳定性监测，简化了干涉仪调试过程，提高了运行效率。

On the Basis of the long-baseline laser interferometer, an online stability monitoring technique is studied for nanoscale displacement and vibration measurement. A laser interferometer with 22 m arm is built to measure displacement and vibration. Based on phase generated carrier (PGC) demodulation technique, an indication signal with known frequency and fixed amplitude is added. Working condition monitoring of laser interferometer, measurement of environmental changes and fluctuation indication can be realized by the variation of the amplitude of indication signal. Experimental results show that online condition monitoring of the laser interferometer can be achieved by adding a known indication signal. This method can carry out online stability monitoring of laser interferometer without extra hardware load, which can simplify the debugging process of interferometer and improve the running efficiency.