光纤光栅解调系统中长距离光延迟效应补偿方法研究

发布时间：2018-09-13 09:51

【摘要】：光纤布喇格光栅(FBG,Fiber Bragg grating)传感器具有体积小、波长编码、复用能力强等特性,为机械装备状态监测与损伤识别提供了新的传感途径并已展现出巨大学术价值和广阔应用前景。基于扫频激光源的FBG解调系统能够满足机械装备监测对大容量传感、高速率采集和高波长分辨率的要求。然而在进行远距离传感解调时,光信号往返传输耗时产生光延迟效应致使系统出现波长解调误差、检测波峰“周期旋转”与排列“乱序”问题,解调系统因定位传感器失败而无法正确获得所需物理量信息。本文分析光延迟效应产生原因并提出相应波长校准算法和波峰辨别方法,主要工作内容如下:(1)分析了基于扫频激光源的FBG解调系统光延迟原因,总结所产生的问题。解调系统通过时域波峰检测时刻的测量来标定波长,而该时刻被光信号往返传输耗时所滞后,解调波长出现误差,检测波峰因出现“周期旋转”与排列“乱序”而无法确定其与传感器的对应关系。(2)改进了解调系统并提出波长校准方法。解调系统增加解调速率调节模块实现多种解调速率间快速切换,增加光源使能模块抑制干扰光。利用两个不相同的解调速率数据,通过计算得到FBG对应梳妆区间和延迟校准参数。消除光延迟误差,实现实时校准解调。(3)提出了同距离和异距离两种部署方式下的波峰辨别方法。同距离部署时主要影响因素为“周期旋转”,异距离则是因FBG光缆距离间差异巨大。利用四个不同解调速率数据之间的关系,结合波长校准方法,辨别出一个扫描周期内检测波峰与传感器的对应关系并消除波长误差。(4)对波长校准与波峰辨别进行了充分实验验证。实验中利用多种长度光缆、多个解调速率以及不同FBG部署方式来模拟真实工程应用场景;利用高分辨率示波器和光谱仪进行数据补偿。观察实验现象,对比数据验证校准与辨别效果。实验数据表明,波长校准方法使得波长误差保持在10pm以下;波峰辨别方法在同距离和异距离部署时均能够正确找到检测波峰与传感器的对应关系。该方法能够消除光延迟所产生的问题,保证解调数据正确、完整。同时,该方法对应用场景中光缆长度、光栅部署、环境等因素导致的光延迟变化具有自适应能力。对比传统方案,本文所提方法具有精度高、灵活性好的优点。特别适用于基于扫频激光源的FBG解调系统进行远距离高速大容量解调,保障了机械装备监测与故障诊断系统的正常运作。
[Abstract]:Fiber Bragg grating (FBG) sensor has the characteristics of small size, wavelength encoding and strong multiplexing ability. It provides a new sensing way for condition monitoring and damage identification of mechanical equipment and has shown great academic value and broad application prospects. However, in the long-distance sensing demodulation, the time-consuming optical signal round-trip transmission results in the wavelength demodulation error, the detection peak "periodic rotation" and the arrangement "disorder" problem, and the demodulation system can not be corrected due to the failure of the positioning sensor. The main work is as follows: (1) The reason of optical delay in FBG demodulation system based on swept-frequency laser source is analyzed, and the problems are summarized. The demodulation system is marked by the measurement of peak detection time in time domain. When the wavelength is fixed, the time is delayed by the time consuming of optical signal round-trip transmission, and the demodulation wavelength has errors. The corresponding relationship between the detection peak and the sensor can not be determined because of "periodic rotation" and "disorder arrangement". (2) Improve the understanding and modulation system and propose wavelength calibration methods. Using two different demodulation rate data, the corresponding dressing interval and delay calibration parameters of FBG are calculated. The error of light delay is eliminated, and the real-time calibration and demodulation are realized. (3) The peak identification methods for the same distance and different distance are proposed. The main factor affecting the distance deployment is "periodic rotation" and the difference between FBG cable distances is enormous. Using the relationship between the four different demodulation rate data and the wavelength calibration method, the corresponding relationship between the detection peak and the sensor in a scanning period is identified and the wavelength error is eliminated. (4) Wavelength calibration and the peak are eliminated. In the experiment, a variety of lengths of fiber optic cables, multiple demodulation rates and different FBG deployments are used to simulate the real engineering application scenarios; high-resolution oscilloscope and spectrometer are used to compensate the data. The experimental phenomena are observed and compared with the data to verify the calibration and discrimination effect. This method can eliminate the problem of optical delay and ensure the correctness and integrity of demodulation data. At the same time, the length of optical cable, grating deployment and ring in the application scene can be ensured by this method. Compared with the traditional scheme, the proposed method has the advantages of high precision and good flexibility. It is especially suitable for FBG demodulation system based on sweep laser source for long-distance, high-speed and large-capacity demodulation, which ensures the normal operation of mechanical equipment monitoring and fault diagnosis system.
【学位授予单位】：武汉理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN253

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