基于微波强度差分响应的全同光纤光栅传感网络构建与解调新方法

At present, the identical grating network with the advantages of high multiplexing ability and low cost has been widely concerned at home and abroad. But the factors including the fluctuation of light power, can influence the accuracy of the intensity demodulated results. In addition, the signal-to-noise ratio is reduced in the existing identical grating sensor network, due to the low spectral density from the light source power, the various phenomenon and effects induced by the cascade gratings. Aiming at these problems, this project proposes a demodulation method for fiber Bragg grating sensor based on the microwave differential responses. The corresponding identical grating sensor network is constructed through the optimization of sensing light source, the design of grating spectrum, the compatibility with network multiplexing technique. The sensing demodulation effects, including large-scale access, high resolution locating, high signal-to-noise ratio, fast process speed and anti-interference character, can be expected. The project will establish the theory analysis model of the transformation from the grating wavelength shift to the microwave differential responses, study the interference mechanism for the demodulation results from the fluctuation of light power, the unstable modulation, grating spectral shadow effect, the grating reflection attenuation. It also will analyze the optical noises induced by the light signal scattering, multipath interference, dual wavelength simultaneous detection, explore the corresponding suppressing method. At last, the project will verify the demodulation scheme based on the microwave differential method, carry out the performance test and analysis of identical grating network. It will promote the application and development of fiber grating sensing network.

目前全同光纤光栅传感网络以其高复用、低成本的优势得到了国内外广泛关注。但现有网络中由于光源功率波动等因素会影响以强度方式进行解调的结果准确性。此外由于光源功率谱密度不高，各种光栅级联效应和现象还会降低解调信噪比。针对这些问题，本项目提出一种基于微波强度差分响应的光纤光栅解调方法，结合传感光源优化、全同光栅谱型设计、融合网络复用技术来构建相应的全同光栅传感网络，期望获得大容量接入、高精度定位、高信噪比接收、快速解调和强抗干扰能力的传感解调效果。项目将建立光栅波长漂移向微波强度差分响应转换的理论分析模型，研究入射光强波动、调制不稳定、光谱阴影效应、光栅反射衰减现象对微波强度差分解调结果的干扰机理，分析信号光散射、多路径反射、双波长同时检测串扰现象所带来的光学噪声形成机制，探索相应噪声抑制方法，验证实现微波强度差分响应的解调方案，实验测试全同光栅网络传感解调效果，推动光纤光栅传感网络应用与发展。

目前全同光纤光栅传感网络以其高复用、低成本的优势得到了国内外广泛关注。但现有网络中由于光源功率波动等因素会影响以强度方式进行解调的结果准确性。此外由于光源功率谱密度不高，各种光栅级联效应和现象还会降低解调信噪比。针对这些问题，本项目研究了一种基于微波强度差分响应的光纤光栅解调方法。通过优化传感光源波长数目和工作方式、结合全同光栅高斯滤波谱型设计、融合网络时分复用技术来构建相应的全同光栅传感网络。项目建立了光栅波长漂移向微波强度差分响应转换的理论分析模型，研究了入射光强波动、光栅反射衰减现象对微波强度差分解调结果的干扰效果，分析了全同光栅反射率和带宽大小对于光谱阴影效应和多路径反射的影响，从理论上探讨了传感网络最大可接入容量，指出了抑制噪声提升信噪比的途径。实验上验证了微波强度差分响应的解调方案并测试了全同光栅网络传感解调效果，在矢量网络分析仪微波扫描9kHz到1GHz频带下，在0到2000ε应变变化范围内实现了0.0034 dB/ε应变灵敏度和0.1 m的FBG定位精度。在2dB的输入光功率波动下，强度解调结果变化量小于0.02 dB，表现出很好的功率波动免疫性。理论上依据此方法搭建的解调系统最高可以实现-0.27 dB/nm的传感灵敏度，19400 FBG的复用数量以及覆盖3298 m的传感距离。项目研究还将解调领域扩展到时域解调上，将时域解调结果和微波解调结果进行了对比分析，在两个波长信道20个级联弱反光栅阵列中，进行了快速的静态应变测量，具有~ 0.54db /μƐ高平均灵敏度，并且其宽动态范围超过3000μƐ。信道切换时间大约为10 ms，总网络解调时间约为50ms。最后探讨了可调离散波长信道的单芯片直调激光器以及可调谐混沌光源等传感光源在光栅传感网络解调中的应用可行性。在本项目支持下，共申请中国发明专利3项，获得授权2项，发表SCI收录文章15篇，培养博士与硕士研究生3人。依托本项目申请并获批一项国基金国际(地区)合作与交流项目。