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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。
A time-domain reflectance temperature measurement method based on Rayleigh scattering for multi-frequency coherent light is proposed. Phase modulation is used to generate multi-frequency probe light, which can effectively increase the stimulated Brillouin scattering threshold of sensing fiber and reduce the coherence in the system Rayleigh noise, improve the system signal to noise ratio; when the light source and phase modulator modulation frequency ratio of the change is equal to the ratio of the two frequencies to adjust the two simultaneously, the fiber temperature can be highly accurate distributed measurement. The sensing mechanism of multi-frequency coherent optical time-domain reflectometer was studied theoretically, and the performance of the sensing system when using single-frequency and multi-frequency light sources was compared by MATLAB simulation. The results show that the system achieves the performance index of 1m spatial resolution and maximum measurement error of 0.005 ℃ when the system SNR is 5dB and the sweep range is 3GHz.