Temperature characteristics of FBG sensors with different coatings for High Temperature Superconductor Application

Fiber Bragg Grating (FBG) sensors LV one of the promising sensing element for temperature measurement in High Temperature superconductor (HTS) field. The main concern of using FBG sensors for cryogenic temperature sensing is how to increase the low temperature sensitivity caused by the decrease thermal expansion coefficient of silica-glass at low temperatures. This work studied the temperature characteristics of bare FBG and FBG coated with gold and silver for 77-293 K. The temperature characteristics of FBG sensors was studied theoretically and experimentally at first. Then the FBG's thermal response time was evaluated through a sudden temperature change test. Results show that preferable temperature sensitivity can be obtained by the proposed coating materials, and there is a 300 ms response time delay of coated sensors compared with the bare FBG.