零差相干激光通信系统具有高速率及远距离传输的特性，在星间高速激光通信骨干网中占有重要地位。分析了光学锁相环的工作原理并建立了相应的数学模型，得到了光学锁相环的开环及闭环传递函数，推导了误差传递函数，分析了环路带宽的影响因素。分析了锁相环路中的相位噪声误差，建立了误差因素、探测灵敏度以及环路带宽之间的关系。分析得到锁相环的优化带宽为1.5 MHz，测试了接收机的误码率。当通信速率为5 Gbit/s、调制方式为二进制相移键控时，得到接收机的接收灵敏度为-41.4 dBm，误码率为10-7。

A homodyne coherent laser communication system has the characteristics of high speed and long-distance transmission, and it plays an important role in the establishment of inter-satellite high-speed laser communication network. The operating principle of optical phase-locked loop is analyzed, and the corresponding mathematical model is established. The open-loop and closed-loop transfer functions of optical phase-locked loop are obtained. The error transfer function is derived. The influencing factors on loop bandwidth are analyzed. The phase noise error of phase-locked loop is analyzed， and the relationship among error factor, detection sensitivity and loop bandwidth is established. The optimized bandwidth of phase-locked loop is 1.5 MHz, and the bit error rate of the receiver is tested. The receiving sensitivity of -41.4 dBm and the bit error rate of 10-7 are obtained when the communication rate is 5 Gbit/s and the modulation mode is binary phase shift keying.