基于多频相干光时域反射计的光纤温度分布测量

Measurement of Fiber-optic Temperature Distribution Based on Multi-frequency Coherent Optical Time Domain Reflectometry

摘要:

提出了一种基于瑞利散射的多频相干光时域反射温度测量方法,采用相位调制产生多频探测光,可有效地提高传感光纤的受激布里渊散射阈值,降低系统中的相干瑞利噪声,提高系统信噪比;当按光源频率和相位调制器调制频率的变化量之比等于二频率之比对二者进行同时调节时,可实现光纤温度的高精度分布式测量.理论研究了多频相干光时域反射计的传感机理,利用MATLAB仿真比较了采用单频和多频光源时传感系统的性能.结果表明,在系统信噪比为5dB和扫频范围为3GHz时,系统可达到空间分辨率为1m、最大测量误差为0.005℃的性能指标.

Abstract:

A method for distributed temperature measurement based on multi-frequency coherent optical time domain reflectometer (COTDR) is proposed,which can effectively increase the threshold of stimulated Brillouin scattering (SBS),reduce the coherent Rayleigh noise (CRN),and improve the signal to noise ratio in the system.The multi-frequency probe light is obtained by phase modulation,and when both the frequency of laser and modulation frequency of phase modulator (PM) change in a manner that the rate between changes of these two frequencies are equal to the ratio between these two frequencies,the high accurate measurement of temperature distribution can be realized with the proposed system.The sensing mechanism of multi-frequency COTDR is studied theoretically and the performance of the system is compared with that of conventional sensing structure using single-frequency probe light by Matlab simulation.The results show that the distributed temperature measurement with a spatial resolution of 1m and a maximum error of 0.005℃ can be realized by the proposed system with a signal to noise ratio of 5dB and a sweeping bandwidth of 3GHz .