双头管封装光纤Bragg光栅低温传感试验研究

Experimental study on the double-head tube packaging fiber Bragg grating at cryogenic temperature

提出并设计了一种用于低温环境下测量温度的光纤布拉格光栅(FBG)双头管式封装结构,探究了涂覆层材料和封装形式对光纤Bragg光栅传感器低温传感稳定性和精度的影响。同时,试验研究了封装长度对双头管式传感器中心波长与温度的关系,通过多次重复试验测定了传感器低温灵敏度和重复性误差。研究结果表明:由于高折丙烯酸酯涂覆层具有较高的热膨胀系数,因此在77~273 K液氮环境中其增敏效果相对于聚酰亚胺和裸光纤更为显著;采用双头管封装后,FBG中心波长与温度具有高度线性关系,且能有效解决无封装裸FBG易受荷载扰动特性;适当提高封装长度有利于提高封装体系灵敏度系数。重复试验结果表明,所设计的双头管式封装FBG低温传感器灵敏度可达14~20 pm/K,测试误差和灵敏度优于传统FBG低温传感器。

A cryogenic temperature sensor with FBG double-head tube package form was designed and studied in the current study.The effects of coating materials and packaging forms on the stability and accuracy of the proposed fiber Bragg grating at cryogenic temperature were experimentally investigated.The effects of packaging length and correlations between central wavelength and temperature were further revealed.The sensitivity and repeatability error of cryogenic temperature sensors were calibrated through a series of repeated tests.The experimental results demonstrated that owing to the relatively higher thermal expansion coefficient,the high refractive acrylic coating FBG presented better sensitization properties than the Polyimide and bare optical fiber in liquid Nitrogen environments(77~273 K).The central wavelength displayed promising linear correlations with environmental temperature with double-head tube packaging,which could also mitigate the vibration-induced disturbance.In addition,the increase in package length is beneficial in enhancing the sensitivity of FBG sensors.The sensitivity of designed low temperature sensor can reach up to 14~20 pm/K,which is superior to traditional FBG sensors.