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中国物理学会期刊

基于动态标定的拉曼分布式光纤测温系统研究

CSTR: 32037.14.aps.74.20241652

Research on Raman distributed fiber temperature measurement system based on dynamic calibration

CSTR: 32037.14.aps.74.20241652
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  • 拉曼分布式光纤测温系统基于拉曼斯托克斯(Stokes)散射光和反斯托克斯(anti-Stokes)散射光功率进行温度解调, 拉曼散射光功率直接影响测温精度. 系统中激光脉冲功率以及雪崩光电探测器增益均可能出现随机变化, 从而导致获取的拉曼散射光功率波动, 因此本文提出一种基于动态标定的拉曼分布式光纤测温系统方案, 通过设置温度标定单元并结合提出的功率校正算法, 消除标定单元的温度的动态变化对拉曼散射光功率的贡献, 再基于先前标定的数据, 分别将拉曼Stokes散射光和拉曼anti-Stokes散射光功率校正到同一激光脉冲功率及雪崩光电探测器增益水平, 从而提升系统的测温精度. 系统采用50 ns的激光脉冲, 在4.6 km长的单模光纤上开展测温试验, 结果显示: 在35—95 ℃的测温区间, 基于传统的温度解调算法, 测温偏差为–5.8—1.0 ℃, 均方根误差为4.0 ℃, 而基于动态标定的校正算法, 测温偏差为–0.8—0.9 ℃, 均方根误差为0.5 ℃. 本文提出新的拉曼分布式光纤测温系统具备拉曼散射光功率动态校正功能, 有工程推广价值.

     

    Distributed optical fiber temperature measurement system is widely used in the fields of substation, power cable, natural gas transmission pipeline and other temperature measurement systems. It can continuously measure the temperature information at each location along the sensing direction. Raman distributed optical fiber temperature measurement system demodulates the temperature information based on Raman Stokes scattered light and anti-Stokes scattered light power, and the Raman scattering light power directly affects the temperature measurement accuracy. So, it is a challenging task to control the hardware of the system to ensure the feasiblity of the Raman sacttering signals. The laser pulse power, and the gain of avalanche photodetector may vary randomly in the system, resulting in fluctuations in the acquired Raman scattered light power data. Therefore, a scheme of Raman distributed fiber temperature measurement system based on dynamic calibration is proposed in this work, and by setting up the temperature calibration unit and combining the proposed power correction algorithm and previous calibration data, the Raman Stokes scattering light and Raman anti-Stokes scattering light power are calibrated at the same laser pulse power level and avalanche photodetector gain, thereby improving the temperature measurement accuracy of the system. For the performance demonstration of the new scheme, the experimental system adopts 50-ns laser pulse to carry out temperature measurement experiments with a 4.6-km long single-mode fiber. The results show that in the temperature measurement range from 35 ℃ to 95 ℃, based on the traditional temperature demodulation algorithm, the temperature deviation measured is in the range from –5.8 ℃ to 1.0 ℃, and the root mean square error is 4.0 ℃, and by the dynamic calibration algorithm, the deviation of deviation measured is within –0.8 ℃ to 0.9 ℃ and the root mean square error is 0.5 ℃. Therefore, the novel Raman-type distributed optical fiber temperature measurement system proposed in this work has the function to dynamically correct the Raman-type scattered light power to suppress the influence caused by instability of the key devices such as pulsed laser and avalanche photodetector and improve the temperature measurement accuracy, which is valuable in practical engineering applications.

     

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