Yuan Quan, Wang Feng, Liu Tao, Liu Yu, Zhang Yixin, Zhong Zhen, Zhang Xuping
Opt Express. 2019 Feb 4;27(3):3664-3671. doi: 10.1364/OE.27.003664.
The frequency-drift of laser source is a crucial factor for influencing the performance of the phase-sensitive optical time domain reflectometer (Φ-OTDR). It induces signal fluctuation and severely limits the measurement capacity for low frequency. In this paper, a twice differential method is proposed to compensate for the influence of the laser-frequency-drift in Φ-OTDR. It uses the differential signal between two points on the sensing fiber as a reference signal and then subtracts the reference signal from the main signal to obtain the final result. In the experiment, the signal fluctuation induced by laser-frequency-drift is decreased by more than 95%. A vibration with a 0.1 Hz frequency on a 6 km sensing fiber is detected with 10 m spatial resolution and sensitivity is estimated to be 5.9 nε. With this method we also successfully measured the process of a stepper motor stretching a fiber section. This method will expand the scope of application of Φ-OTDR in the fields, which require high sensitivity and low frequency response.
激光源的频率漂移是影响相敏光时域反射仪（Φ-OTDR）性能的关键因素。它会引起信号波动，并严重限制低频测量能力。本文提出了一种二次差分法来补偿Φ-OTDR中激光频率漂移的影响。该方法将传感光纤上两点之间的差分信号用作参考信号，然后从主信号中减去参考信号以获得最终结果。实验中，由激光频率漂移引起的信号波动降低了95%以上。在一根6 km的传感光纤上，以10 m的空间分辨率检测到了频率为0.1 Hz的振动，灵敏度估计为5.9 nε。利用该方法，我们还成功测量了步进电机拉伸光纤段的过程。该方法将扩大Φ-OTDR在需要高灵敏度和低频响应的领域中的应用范围。
