光纤光栅压力计及其传感特性的研究

Study on the Fiber Bragg Grating Pressure Gauges and Its Performance

设计了一种基于悬臂梁结构的光纤布拉格光栅(FBG)压力传感器,采用应变片作为悬臂梁,将垂直压力转换成轴向应力.FBG固定在悬臂梁上,将应力转换成中心波长的漂移.通过半导体激光器斜边检测法检测FBG波长的移动.研究了FBG栅区长度和特征反射光谱宽度的关系,选择并制作了栅区长度为1 mm的FBGs作为传感器,确保FBG中心波长漂移时,半导体激光的波长仍在FBG的反射光谱区域内,扩大了传感器的动态范围.在悬臂梁双侧设计了FBGs对结构,利用这对FBGs对环境温度相应系数相同的特性,消除环境温度波动对压力测量的影响.在实验中改变FBGs对的温度,测量了它们对温度的响应并利用温度消敏算法获得传感器的温度不敏感性能.提出了FBG压力传感器的空分复用技术,利用多个光纤耦合器和光电探头(PD)阵列组成传感网络.上述的压力传感网络技术在边坡、基坑等土木工程结构安全监控领域具有实用价值.

A Fiber Bragg Grating（ FBG） based pressure sensor is designed; the cantilever is made of a strain gauge and it can convert the vertical pressure into axial stress. The FBG which is fixed on the cantilever converts the stress into a center wavelength shift. By using the edge detection method with the help of a laser diode,the wavelength shift of the FBG can be detected. The relationship of the FBG length and its bandwidth is studied. After the comparison,the FBGs with 1 mm length is chosen and fabricated as the sensor,ensuring when the FBG＇s center wavelength shift,the wavelength of the laser diode is still in its reflection spectrum region,in order to enlarge the dynamic range of the sensor. Two FBGs are designed to be fixed on both sides of the cantilever. According to the feature of the same temperature coefficient,the variation of the ambient temperature to the pressure measurement can be eliminated. The temperature of the FBGs pair in the experiment is changed,and their temperature response and the performance after applying temperature insensitivity algorithm are tested. The spatial division multiplexing technology of the FBG based pressure sensors is proposed; by using optical fiber couplers and a photo detector（ PD） array,the sensor networks has been demonstrated. The mentioned pressure sensing network technology is practical in the field of civil engineering such as landslide and foundation monitoring.