深圳大学学报理工版

传统分布式光纤传感系统采用固定噪声基底计算散射光强度.但在分布式拉曼测温系统中,由于雪崩光电二极管(avalanche photo diode,APD)光接收机工作时的温度和偏压等因素会导致基底微小改变; 而由于拉曼散射光远弱于瑞利散射光,在长距离的温度解调时这个微小的改变对解调结果的影响尤为明显.为解决此问题,提出动态噪声差分算法的方法,即将菲涅尔反射峰后的基底噪声的平均值作为此散射光的动态噪声基底,实现对APD光接收机的噪声基底的动态测量.在拉曼自解调实验系统中,发现由于接收机工作时的温度和偏压等因素的微小改变导致光接收机的噪声基底存在6.62 mV的波动,且噪声基底波动导致测温精度随距离的上升而恶化; 采用动态噪声基底的方法可消除噪声基底波动对测温结果的影响,将有效传感距离从3.0 km延长至11.5 km,同时在10.4 km处实现了0.61 ℃的测温不确定度和1.58 ℃的测温精确度,可为分布式拉曼传感长距离测量提供参考.

Fixed ground noise is always used to calculate the intensity of the backscattering in traditional distributed optical fiber sensing system. In the Raman distributed temperature sensor(RDTS), the ground noise will be influenced by the change of the working temperature and bias voltage of optical receiver based on avalanche photo diode(APD). Raman scattering light is the weakest one among three kinds of backscattering light. This means the tiny change of the ground noise will affect the results of temperature measurement, especially in long distance sensing system. In order to solve this problem, we propose a method of dynamic noise difference algorithm for RDTS. By using the average value of dark current noise which is behind Fresnel reflection as the dynamic ground noise, we dynamically obtain the actual ground noise of the optical receiver based on APD. In self-demodulation RDTS, the ground noise of optical receiver is about 6.62 mV. And as the distance increases, the temperature accuracy becomes worse and worse due to the ground noise fluctuation. When the influence of the ground noise fluctuation on the measure results is eliminated by dynamic noise difference algorithm, the effective sensing distance increases from 3 km to 11.5 km. And the uncertainty of 0.61 ℃ and the temperature accuracy of 1.58 ℃ are obtained over a 10.4 km sensing fiber. A RDTS with a long sensing distance is achieved by this method.

引言
1 自解调实验装置及原理
2 APD光接收机基底噪声
3 接收机基底波动对测温结果的影响
4 测量结果及分析
5 结语

图1 分布式光纤拉曼自解调实验装置<br/>Fig.1 The experiment of distributed optical fiber sensor based on self-demodulation

图1 分布式光纤拉曼自解调实验装置
Fig.1 The experiment of distributed optical fiber sensor based on self-demodulation

图2 拉曼后向散射和光接收机噪声基底<br/>Fig.2 Raman backscattering and basic noise of optical receiver

图2 拉曼后向散射和光接收机噪声基底
Fig.2 Raman backscattering and basic noise of optical receiver

图3 基底波动对解调结果的影响<br/>Fig.3 The result influenced by basic noise fluctuation

图3 基底波动对解调结果的影响
Fig.3 The result influenced by basic noise fluctuation

图4 测温结果整体分布<br/>Fig.4 The overall-distribution of the temperature measurement results along the fiber

图4 测温结果整体分布
Fig.4 The overall-distribution of the temperature measurement results along the fiber

表1 不同测温位置的测温结果(P=0.68)<br/>Table 1 The measure result at different test zones(P=0.68)℃

表1 不同测温位置的测温结果(P=0.68)
Table 1 The measure result at different test zones(P=0.68)℃

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引言

1 自解调实验装置及原理

2 APD光接收机基底噪声

3 接收机基底波动对测温结果的影响

4 测量结果及分析

5 结语

期刊信息

备注