光纤光栅传感OFDR解调关键技术研究

发布时间：2018-01-11 03:20

本文关键词：光纤光栅传感OFDR解调关键技术研究　出处：《电子科技大学》2015年硕士论文　论文类型：学位论文

【摘要】：光纤光栅传感因波长编码、测量范围广、抗电磁干扰、长期稳定性好、耐腐蚀,尤其是能阵列复用等优点,在工程结构、石油化工、电力系统等诸多领域的监测中有着十分广泛的应用,是目前最为成熟的光纤传感器。但受光源谱宽与传感器带宽的限制,无法实现高密度传感器阵列复用。将光频域反射计(OFDR)技术应用于光纤光栅传感解调是实现高密度阵列复用最为有效的方法。针对高密度光纤光栅传感系统,论文主要对OFDR的光源特性、光路结构及解调算法中的关键技术进行了研究。论文主要研究工作如下:1.阐述了OFDR的基本原理,推导了OFDR的理论模型,对影响其动态范围、空间分辨率的各种因素进行了分析和讨论。建立了相位噪声理论模型,仿真分析了其在不同的光源相干长度和连接器反射率下对拍频信号的影响。进一步讨论了OFDR系统抑制光谱偏振衰落的方法。2.开展了光纤光栅传感系统OFDR解调算法设计与特性分析。对影响拍频信号的非线性调谐效应进行了分析,并总结了其补偿方法。通过理论推导,讨论了辅助干涉仪触发采样法中调谐光源扫频速率与光路时延间的匹配条件。3.仿真分析验证了非均匀傅里叶变换(NUFFT)和三次样条插值算法能够消除非线性调谐效应,改善系统空间分辨率,并提出采用加汉明(hamming)窗FFT的三次样条插值法,减小信号能量的扩散,进一步提高系统空间分辨率。4.开展了高密度光纤光栅传感OFDR解调实验。一方面,编写了基于NUFFT和加窗三次样条插值补偿算法的信号处理软件,实现空间分辨率1cm的OFDR系统。另一方面,进一步编写了光纤光栅波长偏移量的解调算法,并开展了温度解调实验。OFDR系统成功解调了不同温度下光纤光栅的波长偏移量,通过与光谱分析仪实际测试结果对比,验证了解调算法的正确性。在4个波长一致、间隔为15cm弱反射的光纤光栅传感器阵列上,不增敏的情况下,获得温度灵敏系数9.83/Cpm?。实验结果表明该OFDR系统能够应用于高密度光纤光栅传感的解调。
[Abstract]:Fiber Bragg grating (FBG) sensing has many advantages such as wavelength coding, wide measurement range, anti-electromagnetic interference, good long-term stability, corrosion resistance, especially the ability of array reuse, etc., in engineering structure, petrochemical industry. Power system and other fields of monitoring have a very wide range of applications, is the most mature optical fiber sensor, but limited by the spectral width of light source and sensor bandwidth. Unable to implement high density sensor array multiplexing. OFDR (Optical Frequency Domain reflectometer). Fiber Bragg grating sensing demodulation is the most effective method to realize high density array multiplexing. This paper mainly studies the characteristics of OFDR light source, optical circuit structure and the key technology of demodulation algorithm. The main research work of this paper is as follows: 1. The basic principle of OFDR is expounded. The theoretical model of OFDR is derived, and the factors affecting its dynamic range and spatial resolution are analyzed and discussed, and the theoretical model of phase noise is established. The effects of coherent length of light source and reflectivity of connector on the beat frequency signal are simulated and analyzed. The method of suppressing spectral polarization fading in OFDR system is further discussed. 2. Fiber Bragg grating sensing system is developed. Design and characteristic analysis of OFDR demodulation algorithm. The nonlinear tuning effect affecting beat frequency signal is analyzed. And summarized its compensation method. Through the theoretical derivation. The matching conditions between the frequency sweep rate of the tuned light source and the optical path delay in the trigger sampling method of the auxiliary interferometer are discussed. 3. The simulation results verify the nonuniform Fourier transform (NUFFT). And cubic spline interpolation algorithm can eliminate the nonlinear tuning effect. The spatial resolution of the system is improved and the cubic spline interpolation method with hamming window FFT is proposed to reduce the diffusion of signal energy. Further improve the system spatial resolution. 4. The high-density fiber grating sensing OFDR demodulation experiment is carried out. On the one hand. The signal processing software based on NUFFT and cubic spline interpolation compensation algorithm is developed to realize the OFDR system with spatial resolution of 1cm. Furthermore, the demodulation algorithm of wavelength offset of fiber grating is compiled, and the temperature demodulation experiment. OFDR system successfully demodulates the wavelength offset of fiber grating at different temperature. The correctness of the demodulation algorithm is verified by comparing with the actual test results of the spectrum analyzer. In the case of four fiber Bragg grating sensor arrays with the same wavelength and 15cm interval weak reflection, the sensitivity is not increased. The temperature sensitivity coefficient is 9.83% Cpm? The experimental results show that the OFDR system can be applied to demodulation of high density fiber grating sensor.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN761;TN253

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