激光器频率漂移对相位敏感光时域反射计扰动定位精度的影响

Influences of the Frequency Drift of the Laser on Location Precision of the Phase-Sensitive Optical Time-Domain Reflectometry

基于多波干涉原理,建立了基于相位敏感光时域反射计(OTDR)的光纤分布式扰动传感器(FDDS)光路系统数学模型,研究了激光器频率漂移对相位敏感OTDR定位精度的影响机理。仿真结果表明:激光器的频率漂移是导致传感器定位精度和信噪比降低的关键因素,当激光器的频率漂移分别高于25 MHz/min和30 MHz/min时,依据移动平均和有扰动减无扰动定位方法以及移动平均和移动差分算法得到的传感器信噪比低于2dB,定位算法失效。采用频率漂移速率分别为3MHz/min和190 MHz/min的激光器进行实验,实验结果表明:频率漂移速率为3MHz/min的激光器通过所述的两种定位方法得到的定位误差均为100m;频率漂移速率为190MHz/min的激光器无法实现扰动的定位。研究结论为激光器的选型以及提高传感器的定位精度提供了理论指导。

Mathematic models of the fiber-optic distributed disturbance sensor （FDDS） based on the phase-senstive optical time-domain reflectometry （OTDR） are established and the influences of the frequency drift of the laser on the sensor are simulated and experimented based on multiple-wave theory. The simulation results demonstrate that the frequency drift of the laser is a critical factor that results in the reduction of the positional accuracy of sensor and the signal-to-noise ratio （SNR）. The SNR is less than 2 dB by moving averaging and subtraction of the traces with disturbances from traces without disturbances and by moving averaging and moving differential method when the frequency drifts of the laser are larger than 25 MHz/min and 30 MHz/min, respectively. It means that the two location methods fail to locate the disturbance. Experiments are made with lasers with frequency drifts of 3 MHz/min and 19 MHz/min, respectively. The experimental results show that the location errors with the two location techniques are both 100 m when the laser with a frequency drift of 3 MHz/min is utilized. In contrast, it fails to locate the disturbance when the frequency drift of the laser is 190 MHz/min. The investigation results are helpful to select the laser source and improve the location precision of the sensor.