基于伪随机序列调制的BOTDR传感系统研究

发布时间：2018-04-05 18:07

本文选题：分布式光纤传感器　切入点：布里渊散射　出处：《燕山大学》2014年硕士论文

【摘要】：基于布里渊光时域反射(Brillouin Optical Time Domain Reflectometry, BOTDR)的分布式光纤传感技术是一种利用自发布里渊散射的测量技术，其测量的参数作为光纤位置长度的函数，它可以连续测量整个光纤长度上沿光纤路径分布的外部物理参量，并使同时获取被测参量的空间分布状况以及其随时间变化状态成为可能。相比于传统的测量仪器，具有全面的连续性，远距离，大容量，无损检测和网络智能等优点。然而由于自发布里渊散射光极其微弱，BOTDR系统中空间分辨率和动态范围两大性能指标相互制约。因此，本文在深入分析BOTDR系统传感机理的基础上，提出将伪随机序列应用于传感系统中，以提高系统测量的信噪比并获得较好的测量效果。首先，介绍了分布式光纤传感技术的分类和基于Brillouin散射的分布式光纤传感技术的国内外发展现状；介绍了光纤中的三种散射效应，推导了Brillouin频移、散射谱强度与温度、应变的定量关系，介绍了BOTDR系统的信号检测原理，并重点阐述了相干检测原理，并给出了系统的性能参数指标。其次，提出采用伪随机序列编码技术来改善Brillouin分布式光纤传感系统的信噪比。介绍了伪随机序列的概念和产生机理，并就产生的伪随机序列进行性质仿真验证。最后将m序列应用于BODTR系统，通过仿真分析m序列对系统信噪比的影响。再次，将m序列应用于BOTDR光纤传感系统，设计了编码光脉冲模块和散射信号采集与相关解调处理模块。通过理论分析和实验研究，证明与单脉冲探测方案相比，该方案可以显著提高BOTDR光纤传感系统的信噪比。验证了采用m序列改善系统性能的可行性。最后，设计了一套基于编码光脉冲和相关解调的BOTDR分布式光纤传感系统，并对其各个子系统进行了阐述。通过分布式温度测量实验证明与单脉冲探测方案相比，该方案可以在不降低空间分辨率的前提下有效降低测试系统噪声。
[Abstract]:The distributed optical fiber sensing technology based on Brillouin Optical Time Domain reflectometry (BOTDR) is a measurement technique based on self-published Brillouin scattering.It can continuously measure the external physical parameters along the path of the fiber and make it possible to obtain the spatial distribution of the measured parameters and the variation of the parameters with time at the same time.Compared with traditional measuring instruments, it has the advantages of overall continuity, long distance, large capacity, nondestructive testing and network intelligence.However, the spatial resolution and dynamic range of the self-issued Brillouin scattering light are restricted to each other in the BOTDR system.Therefore, on the basis of deeply analyzing the sensing mechanism of BOTDR system, this paper proposes to apply pseudorandom sequences to the sensing system to improve the signal-to-noise ratio (SNR) of the system and obtain better measurement results.Firstly, the classification of distributed optical fiber sensing technology and the development status of distributed optical fiber sensing technology based on Brillouin scattering are introduced, three scattering effects in optical fiber are introduced, the frequency shift of Brillouin, the intensity and temperature of scattering spectrum are derived.The quantitative relationship of strain, the principle of signal detection in BOTDR system is introduced, the principle of coherent detection is expounded, and the performance parameters of the system are given.Secondly, pseudorandom sequence coding technique is proposed to improve the signal-to-noise ratio of Brillouin distributed optical fiber sensor system.The concept and mechanism of pseudorandom sequence are introduced, and the properties of pseudorandom sequence are verified by simulation.Finally, m sequence is applied to BODTR system, and the influence of m sequence on SNR is analyzed by simulation.Thirdly, the m sequence is applied to the BOTDR optical fiber sensing system, and the coded optical pulse module and the scattering signal acquisition and correlation demodulation processing module are designed.The theoretical analysis and experimental study show that the proposed scheme can significantly improve the signal-to-noise ratio (SNR) of the BOTDR optical fiber sensing system compared with the monopulse detection scheme.The feasibility of using m sequence to improve system performance is verified.Finally, a BOTDR distributed optical fiber sensing system based on coded optical pulse and related demodulation is designed, and its subsystems are described.The experimental results of distributed temperature measurement show that compared with the monopulse detection scheme, the proposed scheme can effectively reduce the noise of the test system without reducing the spatial resolution.
【学位授予单位】：燕山大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TP212;TN911.3

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