Miniature fiber-optic temperature sensors based on silica/polymer microfiber knot resonators

In this paper, we report two fiber-optic temperature sensors based on silica/polymer microfiber knot resonators (SMKR/PMKR). The structures of these sensors are composed of three layers, MgF(2) crystal plate is adopted as the substrate, and the sensing knots are covered by a thin MgF(2) slab to keep it steady and immunity to the environment fluctuations. Experimental results show that the temperature sensitivity of SMKR is approximately 52 pm/ degrees C within 30 degrees C approximately 700 degrees C, while the sensitivity of PMKR is approximately 266 pm/ degrees C within 20 degrees C approximately 80 degrees C. The temporal response of SMKR and PMKR sensors are less than 1 ms and 5 ms, respectively. These microfiber knot resonators can be used as miniature high temperature sensors with fast response. Higher resolution can be anticipated with further improvement of the Q factor of the microfiber knot resonators.