基于瑞利散射效应的相干探测光时域反射技术（COTDR）因具有高动态范围、高灵敏度等特性，而成为超长距离连续分布式传感监测的重要手段。在介绍COTDR技术的原理和发展现状基础上，对COTDR传感系统的设计及关键技术包括抑制相干衰落噪声、提高传感速度以及多机理融合传感系统等进行了研究，并对COTDR在超长通信线缆链路监测、温度和应变传感等方面的应用进行了探讨。

The coherent optical time domain reflectometry (COTDR) based on Rayleigh scattering is an important technique for the monitoring of ultra-long fiber link, for its high dynamic range and sensitivity. The principle and development of COTDR is introduced. The design method and key techniques such as the coherent fading noise suppression, measurement speed enhancement and multi-functions fusion system structure are discussed. And several important applications of COTDR are given, including ultra-long communication optical fiber link monitoring and distributed temperature/strain sensing.