Thermal Characteristics of FBG Sensors for a Long-time SHM in Maglev Systems

초록

Among many kinds of sensors, fiber optic sensors, FBG sensors in particular, can be a good candidate for SHM in maglev systems due to its own advantages such as multiplexing easiness and absolute measurement. Generally, thermal characteristics of FBG sensors are considered as constants when temperature change is negligible. However, they cannot be neglected when FBG sensors are applied to circumstances with temperature changes like a long-time SHM in the field. In this paper, thermal characteristics of FBG sensors are precisely investigated in a thermal chamber for 300 cycles with temperature changes ranging from -20 oC to 60 oC using a new modified governing equation for FBG sensors. From the results, it was successfully shown that thermal characteristics of FBG sensors has a non-linear dependency on temperature and ？？f +？？f varies from 5.97 ？e10-6/oC (-20oC) to 7.36 ？e10-6/oC (60oC) at no thermal cycle. Furthemore, it changes with thermal cycles and the change seems to become severe as cycles increase. For the reason, FBG sensors should be treated carefully under consideration of thermal characteristics when they are applied to circumstances with temperature changes, a long-time SHM in maglev systems in particular.