研究了基于瑞利散射的高性能定量检测分布式光纤传感技术。在相位敏感光时域反射计(Φ -OTDR)的基础上，用窄线宽激光器和微波电光调制实现对光频移的精确控制，构成直接检测相干光时域反射计(COTDR)传感系统。通过分析光频移产生的传感光纤瑞利散射光干涉图样的变化，得到了传感量(温度或应变)的定量信息。对直接检测COTDR 传感系统进行了理论分析，并进行了COTDR 工作过程和散射信号相关特性的仿真分析，验证了高分辨率分布式光纤传感原理。在此理论分析基础上，采用微波电光调制得到了可变光频移，组建了直接检测COTDR实验系统，实现了25 km 分布式光纤温度传感实验，可测量到25 km 光纤末端0.1 ℃的温度变化。

A high-performance quantitative detection distributed optical fiber sensing technology based on Rayleigh scattering is proposed and studied. Based on the phase-sensitive optical time-domain reflectometer (Φ -OTDR), a direct detection coherent optical time-domain reflectometer (COTDR) sensing system is set up, by combining the narrow-linewidth laser with microwave electro-optical modulation to obtain optical frequency-shift precisely. The sensing quantity (temperature or strain) can be obtained from the change of the Rayleigh scattering light interference pattern generated by the frequency shift of the light source. The sensing principle of the direct-detecting COTDR system is studied, with simulating and analyzing the COTDR sensing process and the correlation characteristics of the scattering signals. On the basis of theoretical analysis, the direct- detecting COTDR experimental system is built, and 25 km distributed optical fiber temperature sensing experiment is realized. The experiment results show that the COTDR experimental system can measure the temperature change of 0.1 ℃ at the end of the 25 km sensing fiber.