Simultaneous measurement of temperature and refractive index using microfiber knot resonators in Hi-Bi fiber loop mirrors

Abstract

Based on the large evanescent field of microfibers, a novel fiber sensor using a microfiber knot resonator embedded in a Hi-Bi fiber loop mirror is proposed for simultaneous measurement of the temperature and refractive index of solutions. Due to the different responses of the microfiber knot resonator and fiber loop mirror to temperature and refractive index variations, the fiber sensor can measure temperature and refractive index simultaneously by utilizing the sensitivity matrix. The experimental measurements show that the sensitivities of the microfiber knot resonator and the fiber loop mirror to temperature are 5.6 pm/°C and −464.1 pm/°C, respectively. The sensitivity of the microfiber knot resonator to the refractive index of dilute solutions is 116 nm/RIU. The sensor has a higher sensitivity to refractive index variations than LPGs and has potential for use in the field of biochemistry.