激光器频率漂移对相位敏感光时域反射计性能影响研究

针对激光器频率漂移对相位敏感光时域反射计(-OTDR)的性能影响,文中采用后向瑞利散射的一维脉冲响应模型对其进行了理论分析。在实验室测试中,搭建了臂长差为100 m 的非平衡MZ干涉仪来实时监测激光器的频率漂移;并通过测试三种不同频率漂移的激光器下的 -OTDR 系统性能验证了理论分析的正确性。理论分析及实验结果表明,激光器的频率漂移是引起 -OTDR 曲线波动的重要因素,频率漂移越大,其引起的 -OTDR 曲线波动就越大;当频率漂移高达几百MHz/min时,在时域上已难以区分出是频率漂移引起的扰动还是入侵事件引起的扰动,但仍能在频域中将频率漂移噪声分辨出来。

Influences of frequency drift of laser source on phase sensitivity optical time domain reflectometer

The influences of frequency drift of laser source on phase sensitivity optical time domain reflectometer(-OTDR) was investigated. One-dimensional pulse-response model of Rayleigh backscattering in a single-mode fiber was employed to analyze the trace-to-trace fluctuations induced by frequency drift. In laboratory test, an unbalanced Mach-Zehnder interferometer (MZI) with path-length difference of 100m was employed to monitor the frequency drift real-time, and the performances of -OTDR system using three lasers with different frequency drift rate were compared to testify the theoretical analysis. Both the theoretical and the experimental results show that the frequency drift of laser source is an important source for the fluctuations of -OTDR waveform, and the trace-to trace fluctuations increase as the growing of frequency drift. Moreover, it is difficult to distinguish the fluctuations induced by frequency drift and the fluctuations induced by intrusion event in time-domain when the frequency drift is up to several hundreds of MHz/min. However, the differences between them are more evident in frequency-domain. The conclusion is useful for choosing laser sources and improving the performance of -OTDR.