在布里渊光时域分析仪(BOTDA)中，需要检测由脉冲激励光和直流连续探测光的非线性作用产生的受激布里渊散射信号。根据激励光和探测光采用的不同频差，可分为激励光频率高于探测光的增益型和激励光频率低于探测光的衰减型。由于受激布里渊散射作用引起的功率损失影响，增益型BOTDA的传感距离和信噪比(SNR)受到一定限制。对于衰减型布里渊光时域分析，进行了增益型和衰减型传感模式的性能分析比较，并以100 km传感系统为例进行了系统研究。研究结果表明，衰减型BOTDA具有更好的传感距离和检测精度，在同样传感距离下衰减型的最差检测信噪比比增益型高10 dB以上，因此更适合于长距离分布式光纤传感器。

In the system of Brillouin optical-fiber time-domain analysis (BOTDA), stimulated Brillouin scattering signal which produced by the interaction of pulse pump and DC continuous wave (CW )probe light should be detected. According to the frequency difference between two optical waves, BOTDA systems can be made as two types. One is the gain-mechanism, whose frequency of the pump pulse light is higher than the CW probe, and the other is the loss-mechanism, whose frequency of the pump pulse light is lower than the CW probe. In the gain-mechanism BOTDA, the sensing distance and the signal-to-noise ratio (SNR) are limited for the loss of pulse pump by the Brillouin interaction. The loss-mechanism BOTDA is studied by comparing the gain-mode BOTDA. The scheme of 100 km′s loss-mechanism BOTDA is set as the sensing system. It is found that the loss-mechanism BOTDA has better sensing distance and detecting performance than the gain-mechanism, and the worst SNR of the loss-mechanism is above 10 dB larger than the gain gain-mechanism under the same distance. So, the loss-mechanism BOTDA is a better choice for the long-range distributed optical-fiber sensing.