Fiber Bragg grating temperature-sensor with compensated thermal-sensitivity

초록

Among various kinds of Fiber-optic sensors, FBG sensors are being widely investigated for enhanced SHM scheme that is more robust to environmental perturbations like severe temperature changes. Higher reliability and better flexibility, essential part of those sensors, are highly required in many application fields, especially at high temperature. Generally, the thermal characteristic of FBG sensors are expressed as a term, alpha+ksi, and it is considered as a constant when the temperature change is small enough or negligible during the sensor application. In fact, however, it changes however small it is as the temperature changes, and this finally affects the accuracy of measurement and it becomes more significant as the temperature increases. In this study, the change of thermal sensitivity of FBG sensors is precisely examined under conditions of ultra-high temperature. For the purpose, a thermal test was conducted from room temperature (20oC) to 500oC in a heating furnace using a newly proposed governing equation for the thermal sensitivity of FBG sensors. The experimental results reveal that the thermal sensitivity, alpha+ksi, has average values of approximately 5.8x10-6/oC at 20oC and 9.9x10-6/oC at 500oC and has a non-linear dependency on temperature.