单模光纤中的布里渊散射光相对于入射光有一定的频移，该频移量与单模光纤所处环境的温度呈线性关系。根据这种线性温度敏感特性, 布里渊光时域反射计(BOTDR)作为一种分布式光纤布里渊传感系统，可对铁路既有线上的光缆温度分布进行监测。分别定位和测试水泥包覆、铁管包覆、土壤直埋这三种铺设方式的路段，获得温度变化曲线，温度变化量分别为10，8，6 ℃, 温升速率分别为10，8，1 ℃/h。实验结果表明，系统能够反映管线中的温度变化趋势以及变化速率，可用于铁路既有线的温度安全监测。

The Brillouin frequency shift is linearly related to the temperature change along the single-mode fiber. Based on the linear temperature sensitivity, the Brillouin optical time-domain reflectometry (BOTDR), as one of the distributed optical fiber Brillouin sensing system, can realize detection of temperature distribution along the existing fiber cable in the railway communication system. Three kinds of cables with different cablecasting styles, including cement cladding, iron piping and directly buried laying, are positioned and tested, and temperature change curves are obtained. Temperature variation for the three kinds of fibers is 10, 8, and 6 ℃, respectively, and the temperature rising rate is 10, 8, and 1 ℃/h, respectively. The experimental results show that the BOTDR sensing system can reflect the trend and the rate of temperature change, and can be used for on-line temperature monitoring on railway communication fiber cables.