外差检测BOTDR温度和应变传感技术研究.pdf

华北电力大学硕士学位论文
摘要
本文介绍了基于布里渊散射的温度和应变传感研究现状,分析了光纤中
的布里渊散射特性以及对温度和应变的传感理论,建立了布里渊散射频移和强
度与光纤中温度和应变的对应关系。利用布里渊散射和瑞利散射强度之比来消
除光纤损耗所带来的影响,从而修正布里渊散射强度的相对变化量,为外差检
测 BOTDR 温度和应变传感技术奠定了理论基础。对外差检测 BOTDR 传感系统
和信号处理方案进行了研究,并对下变频子系统中频率综合器模块的控制进行
了重点研究。根据频率综合器的控制要求,设计了微波频率综合器的控制软件
使其能够输出所要求的频率分量。采用了将 Golay 互补序列应用于 BOTDR 光
纤传感系统的方法,通过对 Golay 互补序列的时域和频域特性进行理论分析,
设计了基于 Max+plus II 平台的 Golay 互补序列产生逻辑电路,并进行了仿真分
析,设计产生了码元长度可变、码元宽度可调的高速率 Golay 互补序列,同时
对应用 Golay 互补序列的 BOTDR 传感系统从信噪比、动态范围和测量时间上
进行了分析,并对传感系统从时域和频域的角度进行了 Matlab 仿真,结果表明
调制成 Golay 互补序列的光脉冲较单脉冲传感系统在系统信噪比、温度和应变
分辨率等方面能够改善系统的性能。搭建了部分实验系统,完成了基于 AOM
光脉冲调制的前向光路时域波形测试。


关键词:布里渊散射;BOTDR;外差检测;Golay 互补序列
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华北电力大学硕士学位论文
Abstract
The research condition of temperature and strain sensing based on Brillouin
scattering has been introduced in this thesis. The characteristics and the sensing
mechanism of temperature and strain based on Brillouin scattering in optical fiber have
been analyzed, and the temperature and strain dependences of Brillouin frequency shift
and intensity have been founded. The ratio of the Brillouin scattering light power and
Rayleigh scattering light power is used to eliminate the impact of optical loss to
compensate the Brillouin scattered light power variation, and to establish the design
theory of BOTDR based temperature and strain sensor system using heterodyne
detection. Sensing system and signal processing based on heterodyne detection have
been studied. The microwave frequency synthesizer in down converter subsystem has
been studied in detail. The method of applying plementary sequences in
Brillouin sensing system has been used. A high speed plementary code
with a variable length and adjustable width is designed based on Max+plus II
according to the principle of plementary sequences, and waveform
simulation has been done. In the meanwhile, the performance of BOTDR sensing
system applying plementary sequences is analyzed from the signal to
noise ratio,