利用反卷积提高布里渊光纤传感系统空间分辨率的研究

发布时间：2019-06-13 18:21

【摘要】：由于分布式布里渊光纤传感系统能够根据布里渊中心频移测量传感光纤中不同位置处应力或温度的变化而在道路桥梁的健康监测中有广泛地应用。传统的布里渊光时域分析(BOTDA,Brillouin Optical Time Domain Analysis)系统使用矩形脉冲作为泵浦光,连续光作为探测光,对探测光进行扫频,记录传感光纤中产生的受激布里渊散射信号,通过布里渊增益谱的中心频移来确定传感光纤不同位置温度或应力的变化。传感距离越长,所需泵浦脉冲越宽,空间分辨率越低。在长距离传感的情况下保有高空间分辨率的BOTDA系统将会拥有广泛的应用空间。本文提出了基于反卷积方法提高BOTDA系统的空间分辨率,在不增加实验装置复杂性的前提下,只需打入一次泵浦脉冲并通过反卷积数值方法来消除泵浦脉冲对散射信号的展宽。具体内容如下:首先,利用受激布里渊散射三波耦合方程仿真得到不同受力情况下的斯托克斯光,并利用已知的泵浦光与斯托克斯光进行反卷积,研究反卷积方法提高空间分辨率的可行性及极限。其次,搭建了BOTDA实验平台,为研究反卷积方法将重叠峰分辨开来的极限,设计了传感光纤中两段受力,其中间隔一段不受力的结构,观察并采集了不同受力大小及受力间隔下的散射信号及泵浦信号。利用现有算法对对实验数据进行处理,得到略次于仿真结果的反卷积结果。最后,实验结果显示:在输入脉冲观测准确的条件下可以使用反卷积方法来消除泵浦脉宽对信号造成的展宽,在输入脉冲观测不准确的条件下可以使用时域锐化方法。两种方法都能够将空间分辨率提高1.75倍以上。
[Abstract]:Because the distributed Brillouin optical fiber sensing system can measure the stress or temperature at different positions in the sensing fiber according to the Brillouin center frequency shift, it has been widely used in the health monitoring of roads and bridges. The traditional Brillouin optical time domain analysis (BOTDA,Brillouin Optical Time Domain Analysis) system uses rectangular pulse as pump light and continuous light as probe light, sweeps the detected light, records the stimulated Brillouin scattering signal produced in the sensing fiber, and determines the temperature or stress change of the sensing fiber at different positions by the center frequency shift of Brillouin gain spectrum. The longer the sensing distance is, the wider the pump pulse is and the lower the spatial resolution is. The BOTDA system with high spatial resolution under the condition of long distance sensing will have a wide range of application space. In this paper, a deconvolution method is proposed to improve the spatial resolution of BOTDA system. without increasing the complexity of the experimental device, it is necessary to break in the pump pulse once and eliminate the broadening of the scattering signal by the deconvolution numerical method. The concrete contents are as follows: firstly, the Stoke light under different forces is simulated by using the stimulated Brillouin scattering three-wave coupling equation, and the feasibility and limit of improving the spatial resolution by using the known pump light and Stokes light are studied. Secondly, the BOTDA experimental platform is built. In order to study the limit of distinguishing overlapping peaks by deconvolution method, two segments of force in sensing fiber are designed, in which the structure is not subjected to force at intervals. The scattering signals and pump signals under different stress sizes and stress intervals are observed and collected. The existing algorithms are used to process the experimental data, and the deconvolution results, which are slightly inferior to the simulation results, are obtained. Finally, the experimental results show that the inverse convolution method can be used to eliminate the broadening of the signal caused by the pump pulse width under the condition that the input pulse observation is accurate, and the time domain sharpening method can be used under the condition that the input pulse observation is inaccurate. Both methods can increase the spatial resolution by more than 1.75 times.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN253

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