对三维光纤布拉格光栅(FBG)应变传感器的温度补偿问题进行研究,设计了新型温度补偿膜片,并采用参考光纤法对传感器进行温度补偿。实验发现,未经老化处理的裸纤在30~40 ℃之间会出现温度拐点,致使温度灵敏系数降低,所以封装之前必须进行老化处理。通过有限元热力分析可知,新型温度补偿膜片在-10~50 ℃之间自身的最大微应变约为0.073 με,受热膨胀系数失配的影响较小,系统的可靠性较高。同时悬臂梁式的缓存结构可使温度补偿光纤在测量过程中不受外界复杂环境的影响,在origin中拟合温度补偿膜片与应变测量传感膜片联合补偿的结果,修正之后线性度可以达到0.9999以上,满量程精度约为0.05%。

We present a novel technique of temperature compensation for 3-dimensional fiber Bragg grating (FBG) strain sensor, and design a temperature compensation diaphragm for temperature compensation of the strain sensor by using reference optical fiber compensation method. Experiment results demonstrate that bare fiber without aging process can appear inflection temperatures between 30 ℃ to 40 ℃, which results in the decrease of the temperature sensitivity coefficient. So we must make aging process firstly before encapsulation to improve the sensitivity of the sensor. Based on the finite element thermal analysis, it is found the designed temperature compensation diaphragm's maximum strain is about 0.073 με when the temperature is increased from -10 ℃ to 50 ℃, which demonstrates the thermal expansion coefficient mismatch has less influence on the diaphragm and this system has high temperature reliability. Besides, sensing accuracy of the fiber sensor is improved by the design of cantilever structure, which makes the sensing immune to the complex environment. We fit and revise the results of joint compensation between temperature compensated diaphragm and the strain sensing diaphragm by the origin. The results show that the sensing linearity can reach more than 0.9999, and the full range accuracy is about 0.05%.