High-Sensitivity Temperature Sensor Based on a Coated Single-Mode Fiber Loop

We demonstrate a simple, robust, and highly sensitive temperature sensor based on the resonant excitation of whispering gallery modes in a coated single-mode fiber (SMF) loop that was created by means of bending a standard coated SMF into a loop with a radius of 5 mm. Clear interference fringes were observed in the transmission spectrum of the coated-SMF loop. The resonant wavelength exhibits a linear temperature response at the temperature range from -60° to 10 °C, and a quadratic temperature response at the temperature range from 10° to 140 °C. Moreover, the coated-SMF loop exhibits an ultrahigh sensitivity of up to -5.22 nm/°C at 120 °C, and the sensitivity (i.e., -4.01 nm/°C at 80 °C) is two orders of magnitude higher than that of an uncoated-SMF loop (i.e., 0.04 nm/°C at 80 °C). Hence, such a coated-SMF loop could be used to develop a temperature sensor with a large measurement range from -60° to 140 °C.