Characteristics of thermal coefficient of fiber Bragg grating for temperature measurement

A fiber Bragg grating sensor is considered a smart sensor that shows outstanding performance in the field of structural health monitoring (SHM). It has a powerful advantage, especially that of multiplexing, which enables several parameters to be sensed at multiple points by using a single optical fiber line. Among several parameters, the thermal expansion coefficient and thermo-optic coefficient are required to measure temperature. In previous studies, these were considered constant variables. This study shows that two parameters vary with temperature and newly proposes a temperature function for these two parameters. Specifically, these two parameters were defined as a single variable, and then, it was experimentally verified that this variable is a function of temperature. Finally, it was shown that temperature from RT to 100 °C was precisely measured by using the temperature function that was defined through the experiment.