在相干体制下，二进制相移键控(BPSK)信号调制的零差接收机可实现理论上的最高灵敏度，是星间相干光通信的研究和应用重点。零差接收机要求本振波和信号波严格相位同步，常用的相位同步技术是光学锁相环(OPLL)。阐述了光学锁相环的基本原理，介绍了近20年来光学锁相环的发展，在此基础上总结了各种类型锁相环的性能和适用范围。回顾了欧洲国家在星间相干光通信计划中通信终端使用光学锁相环的情况。最后对光学锁相环技术进行了总结，对该技术的前景进行了展望。

Homodyne binary phase shift keying(BPSK) receivers can achieve the best sensitivity theoretically， so becomes the research and application focus of inter-satellites coherent optical communications. Homodyne receivers require the local oscillating laser and the signal wave to oscillate synchronously， and optical phase locked loop(OPLL) is the most efficacious phase synchronous technology. We survey the principle of OPLL， and introduce the development of OPLL in recent twenty years. Basis on this，the characteristics and applicability of each OPLL type are discussed. Applications of OPLL in international representative research of inter-satellites coherent optical communications are reviewed. In the end we summarize the OPLL technology and give the prospect.