高性能光纤布拉格光栅应变传感器的飞秒激光加工研究

光纤布拉格光栅(FBG)具有体积小、耐腐蚀、抗电磁干扰、波分复用能力强等优点，在应变测量中备受青睐。飞秒激光刻写的光栅折射率调制量大、无需载氢、耐高温性好(大于1000℃)，为高性能FBG应变传感器的制造提供新方法，但依然面临应变灵敏度低、温度交叉灵敏度、蓝宝石光栅(SF-FBG)光谱特性差等技术难题。基于此，本项目设计新型光栅结构，采用飞秒激光扫描加工方法，提高加工可控性，实现传感性能优化。主要内容包括：建立光栅结构特征-模式耦合机理-应变传感规律之间的关系模型；设计并优化光纤表面微结构FBG、新型倾斜光栅(TFBG)和预应力SF-FBG器件的结构参数；选择合适的激光加工工艺，实现光谱可控制造；分析不同工艺参数器件的应变传感规律和预应力SF-FBG高温应变特性；利用碳纳米管涂层方法提高微结构FBG和TFBG的应变灵敏度。本项目提出的新结构设计和增敏方法，具有重要学术价值和应用前景。

Fiber Bragg grating (FBG) has unique advantages such as small volume, corrosion resistance, immunity against electromagnetic interference, and excellent wavelength division multiplexing capability, which is very popular in strain measurement. The gratings induced by femtosecond laser show a large refractive index modulation, require no hydrogen loading, and have a high temperature resistance of more than 1000 ℃, which provides a new method for the manufacture of high-performance FBG strain sensors. However, the FBG sensors still face some technical challenges such as low strain sensitivity, temperature cross-sensitivity, and poor spectral quality of SF-FBG. Based on these problems, this project has designed a new grating structure and proposed a femtosecond laser scanning inscription method to enhance the controllability of grating manufacturing and optimize sensing performance of the sensors. The main content is as follows: establishing a model to demonstrate the relation among grating parameters, coupling mode theory, and strain sensing law; designing and optimizing the structural parameters of the fiber surface micro-structured assisted FBG sensor, the novel TFBG sensor and the prestressed SF-FBG sensor; choosing the suitable laser processing parameters to achieve the controllable manufacturing of the spectrum; analyzing the strain sensing laws of the sensors with different processing parameters and the high temperature strain sensing characteristics of prestressed SF-FBGs；improving the strain sensitivity of micro-structured FBG and novel TFBG by using the carbon nanotube coating method. The novel construction and sensitization method proposed in the project show significant academic value and application prospect.