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针对斯托克斯光和反斯托克斯光的本质损耗、附加损耗使分布式光纤温度传感器产生测温误差的问题, 通过对分布式光纤温度传感器的温度解调原理的研究, 提出了拟合斯托克斯光与反斯托克斯光之间衰减差的方法实现温度自补偿, 以此减小测温误差. 以传感光纤上不同位置的两部分作为参考段和测温段, 参考段的光信号作为测温段拟合多阶衰减差和解调温度的参量, 通过引入多阶拟合结果解调温度, 减小因斯托克斯光和反斯托克斯光的本质损耗、附加损耗导致的温度误差, 实现温度的初步修正. 改变光纤上同一位置的温度, 取3组不同温度值及对应信号值计算引入拟合衰减差前后的瑞利噪声, 分析了瑞利噪声与光纤长度和温度的关系, 通过引入拟合衰减差消除瑞利噪声, 减小了斯托克斯光和反斯托克斯光的本质损耗、附加损耗导致的瑞利噪声误差, 实现温度的再次修正. 分析比较多阶衰减差拟合结果对测温误差以及消除瑞利噪声的影响, 获得最优拟合阶次. 在拟合因参考段的附加损耗而导致的测温段的附加误差后, 通过拟合结果进行温度补偿, 完成了最终温度修正. 实验结果表明, 在30—90 ℃, 引入一阶线性拟合结果的温度修正效果最好, 经过三次修正后, 测温误差从10.50 ℃降低至0.90 ℃.The temperature error caused by the essential loss and the additional loss of Stokes light and anti-Stokes light widely exist in the distributed optical fiber temperature sensor (DTS). According to the temperature demodulation principle of the DTS, a method of fitting the attenuation difference between Stokes light and anti-Stokes light is proposed, which can realize the temperature self-compensation to reduce the temperature measurement error. Two parts at the different positions of the sensing fiber are regarded as the reference section and the temperature measuring section, respectively. The optical signal of the reference section is used as a parameter when demodulating the temperature and fitting the attenuation difference, and the attenuation difference between the Stokes light and the anti-Stokes light is multi-order fitted by the optical signal of the temperature measuring section, then the multi-order fitting results are used to demodulate the temperature for reducing the temperature error caused by the essential loss and additional loss of the Stokes light and anti-Stokes light, in order to implement the preliminary correction of the temperature. Three groups of the different measuring temperature values at the same position of the optical fiber as well as their corresponding signal values are taken in calculation for eliminating the Rayleigh noise, and the relationship of Rayleigh noise with fiber length and temperature are analyzed, and thus further calculating the Rayleigh noise based on the fitting attenuation difference. The influence of the multi-order attenuation difference on the error in temperature measurement and that on the elimination of the Rayleigh noise are compared with each other, and the Rayleigh noise error caused by the essential loss and additional loss of the Stokes light and anti-Stokes light are reduced, then the temperature is corrected again by eliminating the Rayleigh noise. The effect of the multi-order attenuation difference fitting result on the temperature measurement error and on the elimination of Rayleigh noise are analyzed and compared with each other, then the optimal fitting order is obtained. After fitting the additional error at the temperature measurement section that is caused by the additional loss at the reference section, the temperature compensation is carried out by the fitting result, then the final temperature correction is completed. The experimental results show that the temperature correction effect is best by using the first-order linear fitting results in a temperature range of 30－90 ℃, and the temperature measurement error is reduced from 10.50 ℃ to 0.90 ℃ after being corrected three times.
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