基于LPFG微弯特性的高精度位移检测系统

High-Precision Displacement Detection System Based on LPFG Bending Characteristics

在研究长周期光纤光栅(LPFG)温度及微弯特性的基础上,通过引入聚合物温度增敏封装后的光纤布拉格光栅(FBG)作为解调滤波器,搭建了温度自补偿微位移检测系统.将LPFG粘贴于试件上进行微弯测试,在固定波长处,其插入损耗的变化与弯曲度变化呈线性关系.为解决LPFG带宽宽、谐振波长难以精确测量的问题,选择特定波长的FBG作为滤波器,实现了位移检测系统的功率化解调.同时,对FBG利用聚合物进行了温度增敏封装,使其温度灵敏度与LPFG尽量相同,消除了温度对系统的影响.试验结果表明,传感系统输出的光功率与微位移呈良好的线性关系,位移灵敏度为2μW/mm,分辨力为0.5×10-2mm.所设计的系统结构简单、灵敏度高、线性度好,不受外界温度干扰.

Temperature compensation micro-displacement detection system was built based on the analysis of the temperature and micro-bend characteristics of long period fiber grating （LPFG）. Polymer-packaged temperature sensitization fiber Bragg grating（FBG） was used as a filter in the demodulation system. The relationship between insertion loss and curvature was studied through gluing the LPFG onto an experimental laminate sample. Due to wide bandwidth, resonant wavelength is difficult to capture. The problem is solved by introducing a wavelength-set FBG as the system demodulation filter. In addition, the FBG was packaged using polymer to make the resonant wavelength temperature sensitivity similar to that of LPFG. The temperature influence in system is then eliminated. The experimental results show that there is a linear relationship between the output power detected by the photo-detector and the displacement. The displacement sensitivity is 2 μW/mm. The displacement resolution is 0.5×10-2 mm. It is promising to be used in displacement measurement since the demodulation has many characteristics, such as simple structure, high sensitivity and good linearity.