超声脉冲介入光纤光栅复用理论与方法研究

Fiber Bragg gratings (FBG) have been widely used in industry and military fields because of their light weight, corrosion and electromagnetic interference resistance, easy multiplexing and so on. However, the existing fiber grating network is limited by the bandwidth resources, the positioning accuracy and other factors. On the basis of the previous researches on the aircraft load spectrum measuring and intelligent skin monitoring, this subject puts forward a kind of large capacity multiplexing theory of densely distributed fiber Bragg gratings. The research is mainly concerned on the scientific problem of the selection and addressing about the FBGs by the ultrasonic pulses. Through the study of ultrasonic pulse modulation on fiber gratings, the time-division multiplexing technologies of the densely distributed FBGs are discussed, and the mechanism of the selection and addressing function of the ultrasonic pulses about the FBGs with the same parameters is formulated. The law of the forming and propagation of super flat ultrasonic pulses is revealed under complicate mechanical constraints in the fibers and the decoupling method of the micro strain and the quantities to be measured is established. High speed acquisition of spectral signal and the packaging technology based on micro-texture are to be realized. The subject will provide solutions for local area high density and large capacity optical fiber sensing taking into account the system capacity, density and accuracy, and will lay a theoretical basis for the application of fiber grating sensing technologies in equipment fault precision diagnosis, health monitoring of intelligent materials, three-dimensional shape perception, etc..

光纤光栅因其纤细质轻、耐腐蚀、抗电磁干扰、易于复用等优点已经广泛应用于工业及军事领域。然而现有光纤光栅网络受带宽资源、定位精度等因素限制，传感容量和密度难以提高。本项目在飞机载荷谱测试、智能蒙皮监测等前期研究基础上，提出一种超声介入的大容量密集分布光纤光栅的复用理论。围绕“超声脉冲对光栅的选择和寻址”这一科学问题，通过研究超声脉冲对光纤光栅的调制作用，探索空间密集分布光纤光栅的时分复用问题，阐明超声脉冲对同参数光纤光栅的寻址与选择原理，揭示复杂机械约束条件下高平坦超声脉冲在光纤中的传播规律，建立超声脉冲应变与待测量解耦方法，突破光谱信号高速捕捉技术和基于微织构的光纤光栅封装支撑技术，同时兼顾系统容量、密度和精度，为局部区域高密度大容量光纤传感提供解决方案，为光纤光栅传感在设备故障精密诊断、智能材料健康监测、三维形状感知等领域的应用奠定理论与技术基础。

光纤光栅传感系统已广泛应用于土木工程、电气电子、医疗科学等领域。为进一步提高光纤光栅的复用密度，同时降低解调系统的成本，本项目提出一种基于超声脉冲介入的光纤光栅复用解调技术，将超声脉冲纵波导入光纤，对标准光纤光栅串进行调制，使各光栅的中心波长依次产生暂态红移或蓝移，从而实现对传感光谱的扫描，并利用光电探测器对光谱信号进行采集，通过一定寻峰算法对光纤光栅传感器中心波长进行精确解调。.项目对超声脉冲在光纤中传播时的色散、散射及损耗特征进行了理论研究，基于傅立叶模式耦合理论分析了超声脉冲对光纤光栅的调制作用，并基于多种超声脉冲的仿真对超声脉冲的波形参数进行了优化。研究了超声脉冲激励器件以及器件与光纤之间的匹配问题，设计了超声脉冲介入光纤光栅解调系统，并对所涉及的超声脉冲激励电路、超声脉冲聚能器、光纤导入匹配结构、光电探测宽带跨阻放大电路、信号采集电路等关键技术进行了研究。设计并实现了超声脉冲介入的光纤光栅解调样机系统，包括标准匹配光栅串的光路设计和基于光电探测器的多通道光谱信号采集系统设计等。最后搭建实验系统对超声脉冲介入下的光纤光栅密集复用方法进行了实验验证，结果表明本项目所提出的超声脉冲介入式解调系统，超声脉冲导入光纤后，可对光纤光栅产生明显调制作用，波长精确匹配的双光栅串可在超声脉冲作用下产生波长步进式调节的窄带探测光，实现对被测光纤光栅的有效解调，同时兼具低成本、高分辨率等优点。