The Improvement of Temperature Sensitivity by Eliminating the Thermal Stress at the Interface of Fiber Bragg Gratings

Abstract

This article uses polydimethylsiloxane (PDMS) to package an improved fiber Bragg grating (FBG) temperature sensor. Unlike the structure of PDMS completely enveloping fiber gratings, we utilize microfluidic processing technology to construct a microchannel with a diameter of 150 μm in the area of the fiber gratings. It eliminates the thermal stress on the fiber grating in the radial direction. Through the force analysis of the fiber gratings in the packaged sensor, it can be found that eliminating the radial thermal stress is conducive to improving the axial coefficient of thermal expansion of the fiber gratings. The temperature sensing characteristics of this structure are verified by simulation and experiment. Both theoretical and experimental results have shown that this structure can effectively improve the temperature sensitivity of the sensor. In the experiment, the temperature sensitivity of the packaged sensor is 3.5 times higher than that of the standard fiber gratings. The temperature sensitivity of the sensor is 37.6 pm/°C. It is simple to manufacture, does not pollute the environment, and can accurately monitor the temperature of the complex environment. Therefore, it is an ideal model for temperature monitoring in complex environments such as the ocean and mine.