基于超短光纤光栅阵列的分布式多参量传感机理与方法研究

A novel distributed sensing method based on ultra-short weak fiber Bragg grating (wFBG) array is proposed for simultaneous measurement of vibration and static parameters (temperature, strain etc) which are hard to achieve with conventional distributed sensing system based on interference .The method takes advantage of both interferometry and wavelength detection. By detecting the interference of lights reflected from two adjacent gratings with path-match interferometer, high sensitive distributed vibration sensing will be achieved. On the other hand, By examine the central wavelength of the optical pulse reflected by ultra-short wFBG array with a dispersion method, static temperature/strain information of each sensor element are obtained. Distributed optical fiber sensing network based on ultra-short wFBG array will be the research object of the project. The main purposes of the research are listed as follow. Phase induced fading, polarization induced fading and optical spectrum mismatch are serious problem in distributed sensing systems based on ultra-short wFBG array. The impact of random phase noise, phase fluctuation caused by wFBG peak-wavelength drift on the measurement sensitivity will be investigated in order to achieve high-sensitivity dynamic vibration detection. Fast demodulation methods and techniques based on fiber dispersion effect for large scale wFBG array with identical peak wavelength will be studied. The intrinsic crosstalk caused by multiple reflections in wFBG array will be analyzed,and its impact on the detecting accuracy will be evaluated. Measurement mechanism of long-distance sensing based on wFBG array with Raman distributed amplification will be analyzed both theoretically and experimentally. The aim of the research is to realize hybrid interrogation of wFBG array for high-sensitivity distributed vibration detection and quasi-distributed temperature/strain measurement. Above studies have obvious scientific significance and practical application value for promoting the development of the multi-parameter, long distance, high-sensitivity fiber distributed sensing technology.

本项目将超短光纤光栅阵列引入到分布式振动探测系统中，一方面利用匹配干涉仪测量相邻光栅干涉信号的相位变化可以进行高灵敏分布式振动信号探测，另一方面还能通过基于色散原理的波长测量方法获取超短光纤光栅的中心波长，从而解决干涉型光纤分布式传感方法难以测量静态/准静态物理量的问题，达到动态振动和静态应变、温度等同时测量的目的。本项目将以基于超短光纤光栅阵列的分布式光纤传感网络为研究对象，重点解决：基于匹配干涉的分布式振动传感中的相位衰落、偏振衰落和光谱失配问题；基于色散原理的光纤光栅阵列波长检测方法与地址查询技术；光纤光栅阵列中多次反射带来的串扰与噪声对系统探测灵敏度等参数的影响；基于拉曼分布式放大的长距离传感技术等。本研究旨在实现干涉型分布式动态传感与点式准静态传感的融合，为多参数、长距离、高灵敏的光纤分布式传感研究提供理论与技术参考。

本项目针对在许多应用领域中需要对振动、应变、温度等动态参量与准静态参量进行分布式监测的需求，研究基于超短光纤光栅阵列的多参量分布式传感方法和机理。获得了基于超短光纤光栅阵列的动/静态结合的光纤传感理论与方法；研究了大规模光纤光栅阵列中多次反射带来的串扰对系统性能了影响，提出了基于传输矩阵的改进剥层算法以提高系统测量精度；研究了基于弱光纤光栅阵列的分布式传感系统中偏振衰落问题，提出了基于I/Q解调的偏振不敏感解调方法；研究了基于弱光纤光栅阵列的分布式传感系统中的信号处理方法，提出基于卷积神经网络的特征信号识别与分类方法。研制了基于上述成果的分布式传感系统样机一套,能够同时进行基于相干检测的高灵敏分布式振动探测和基于波长检测的静态物理量监测，并应用到深圳市供电局的高压电缆的局部放电和温度异常检测项目中。在上述研究基础上发表10篇学术论文，申请5项国家发明专利，其中4项获得授权，培养了1名博士研究生和7名硕士研究生。