The Influence of Thermal Expansion Coefficient of FBG Packaging Material on Temperature Sensing Accuracy

Abstract

The package technology of fiber grating temperature sensor is the key to promote its engineering. In this paper, the characteristics of thermal expansion coefficient of 304 austenitic stainless steel were discussed, the relationship between thermal expansion coefficient and temperature was studied. The influence of linear thermal expansion coefficient on FBG temperature sensing formula was analyzed, a quadratic polynomial fitting method was proposed to modify the FBG temperature coefficient encapsulated in the channel steel column, and the verification system was build. Experimental results show that, under the same temperature, the measured central wavelength of the sensor is greatly different from the wavelength value obtained under the fixed thermal expansion coefficient. The higher the temperature is, the greater the difference is,and it reaches 0.075 nm at 100 ℃ with the temperature deviation of 2.58 ℃. The measured value is basically consistent with the wavelength value obtained under linear thermal expansion coefficient, and the degree of quadratic polynomial fitting is 0.999 9. Therefore, considering the variation characteristics of thermal expansion coefficient of packaging materials, and adopting the quadratic fitting method will greatly improve the measurement accuracy of the sensor, which is suitable for the occasions with high accuracy requirement on temperature measurement.