外差BOTDA中相位解调系统的设计与实现
发布时间：2018-09-06 13:01
【摘要】：本文在综述布里渊光时域分析(BOTDA)技术研究现状的基础上,论述了自发布里渊散射(SPBS)和受激布里渊散射(SBS)的作用机理,根据受激布里渊散射的作用机理,分析了布里渊频移受温度和应变影响的特性,研究了布里渊频移与光纤温度和应变的对应关系。介绍了传统的直接检测BOTDA系统原理和可以同时检测布里渊幅度和相移的外差BOTDA系统原理,对比分析了两种系统,推导了受激布里渊散射作用传输函数和两种系统输出信号的信噪比表达式。在分析外差BOTDA系统的基础上,深入研究了布里渊相位的解调方法,设计了模拟相位解调系统和数字相位解调系统。在Simulink系统中搭建了模拟相位解调系统模型,仿真实现了对射频信号和本振信号的相位差提取。针对模拟相位解调系统中由于正交解调模块AD0105B中的硬件结构、系统中AOM的频率不稳定性引起的误差提出了相应的解决办法。使用Labview软件搭建了数字相位解调仿真平台,在此平台上使用过零检测法、相关检测法以及I/Q正交检测法实现了对相位差信息的提取,并在不同噪声条件下分析了三种方法的性能:小噪声条件下,过零检测法受噪声影响较大,相关检测法、I/Q正交检测法基本不受影响,保持较好的解调精度;大噪声条件下,过零检测法受噪声影响很大,丧失解调能力,相关检测法发生边缘漂移现象,解调精度降低,I/Q正交检测法受影响较小,依然保持较高的解调精度。后期针对三种数字解调算法提出了相应的优化方案:在过零检测法中,加入叠加平均过程,实现在噪声环境中提取高精度相位差信息;在相关检测法中,提出迭代相关检测方案,极大的提高了算法的抗噪声能力,适用于低信噪比信号中精确提取相位信息。在I/Q正交检测法中,对数据进行全相位预处理过程,解决了I/Q正交检测法检测非整周期序列时存在的频谱泄露问题。
[Abstract]:Based on the review of the research status of Brillouin optical time domain analysis (BOTDA) technology, the mechanism of self-releasing Brillouin scattering (SPBS) and stimulated Brillouin scattering (SBS) is discussed in this paper, according to the mechanism of stimulated Brillouin scattering. The effect of temperature and strain on Brillouin frequency shift is analyzed, and the relationship between Brillouin frequency shift and fiber temperature and strain is studied. This paper introduces the principle of traditional direct detection BOTDA system and heterodyne BOTDA system which can detect Brillouin amplitude and phase shift simultaneously. The transfer function of stimulated Brillouin scattering and the expression of signal-to-noise ratio of the output signals of the two systems are derived. Based on the analysis of heterodyne BOTDA system, the method of Brillouin phase demodulation is studied, and the analog phase demodulation system and digital phase demodulation system are designed. An analog phase demodulation system model is built in Simulink system, and the phase difference between RF signal and local oscillator signal is extracted by simulation. This paper presents a solution to the error caused by the frequency instability of AOM in the analog phase demodulation system due to the hardware structure of the quadrature demodulation module (AD0105B) and the frequency instability of the AOM in the system. The digital phase demodulation simulation platform is built with Labview software. The zero-crossing detection method, the correlation detection method and the I / Q orthogonal detection method are used to extract the phase difference information on the platform. At the same time, the performance of three methods is analyzed under different noise conditions: under the condition of small noise, the zero crossing detection method is greatly affected by noise, the correlation detection method I / Q orthogonal detection method is basically unaffected, and the demodulation accuracy is better under the condition of large noise. The zero-crossing detection method is greatly affected by the noise and loses the demodulation ability. The correlation detection method has the phenomenon of edge drift. The demodulation accuracy is reduced and the I / Q quadrature detection method is less affected, and the demodulation accuracy is still high. In the later stage, three digital demodulation algorithms are proposed: in the zero-crossing detection method, the superposition average process is added to extract the high-precision phase difference information in the noise environment, and in the correlation detection method, the phase difference information is extracted in the noise environment. An iterative correlation detection scheme is proposed, which greatly improves the anti-noise ability of the algorithm and is suitable for extracting phase information accurately in low SNR signals. In the I / Q orthogonal detection method, the whole phase preprocessing process of the data is carried out, which solves the spectrum leakage problem in the detection of non-integer periodic sequences by the I / Q orthogonal detection method.
【学位授予单位】：华北电力大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TP212
本文编号：2226426
[Abstract]:Based on the review of the research status of Brillouin optical time domain analysis (BOTDA) technology, the mechanism of self-releasing Brillouin scattering (SPBS) and stimulated Brillouin scattering (SBS) is discussed in this paper, according to the mechanism of stimulated Brillouin scattering. The effect of temperature and strain on Brillouin frequency shift is analyzed, and the relationship between Brillouin frequency shift and fiber temperature and strain is studied. This paper introduces the principle of traditional direct detection BOTDA system and heterodyne BOTDA system which can detect Brillouin amplitude and phase shift simultaneously. The transfer function of stimulated Brillouin scattering and the expression of signal-to-noise ratio of the output signals of the two systems are derived. Based on the analysis of heterodyne BOTDA system, the method of Brillouin phase demodulation is studied, and the analog phase demodulation system and digital phase demodulation system are designed. An analog phase demodulation system model is built in Simulink system, and the phase difference between RF signal and local oscillator signal is extracted by simulation. This paper presents a solution to the error caused by the frequency instability of AOM in the analog phase demodulation system due to the hardware structure of the quadrature demodulation module (AD0105B) and the frequency instability of the AOM in the system. The digital phase demodulation simulation platform is built with Labview software. The zero-crossing detection method, the correlation detection method and the I / Q orthogonal detection method are used to extract the phase difference information on the platform. At the same time, the performance of three methods is analyzed under different noise conditions: under the condition of small noise, the zero crossing detection method is greatly affected by noise, the correlation detection method I / Q orthogonal detection method is basically unaffected, and the demodulation accuracy is better under the condition of large noise. The zero-crossing detection method is greatly affected by the noise and loses the demodulation ability. The correlation detection method has the phenomenon of edge drift. The demodulation accuracy is reduced and the I / Q quadrature detection method is less affected, and the demodulation accuracy is still high. In the later stage, three digital demodulation algorithms are proposed: in the zero-crossing detection method, the superposition average process is added to extract the high-precision phase difference information in the noise environment, and in the correlation detection method, the phase difference information is extracted in the noise environment. An iterative correlation detection scheme is proposed, which greatly improves the anti-noise ability of the algorithm and is suitable for extracting phase information accurately in low SNR signals. In the I / Q orthogonal detection method, the whole phase preprocessing process of the data is carried out, which solves the spectrum leakage problem in the detection of non-integer periodic sequences by the I / Q orthogonal detection method.
【学位授予单位】：华北电力大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TP212
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