Investigation of the Thermal-Force Coupling and Temperature Compensation of Embedded FBG Strain Sensor

Embedded fiber Bragg grating (FBG) strain sensor is fixed on the measured object when monitoring strain, and the wavelength variation of FBG caused by the thermal strain of the measured object is coupled with the wavelength variation caused by external force. In order to reveal the basic situation of the thermal-force coupling, three embedded FBG strain sensors were prepared. The suspended temperature compensation FBGs and packaged temperature compensation FBGs were arranged inside these sensors. Then, these sensors were placed in the air and reinforced concrete, respectively, to conduct sensing and temperature characteristic experiments. The sensing characteristic experiment proves the effectiveness and good repeatability of the strain measurement of the sensor. The temperature experiments prove that the packaged temperature compensation method is obviously better than the suspended temperature compensation method; and after being embedded in reinforced concrete, these sensors are incompletely suppressed by the thermal expansion of the reinforced concrete, and the temperature sensitivities of three strain FBGs have decreased by 1.594, 1.664, and 1.365 pm/°C, respectively, while the temperature sensitivities of temperature compensation FBGs are basically unchanged.