High Sensitivity Temperature Sensor Based on Directional Coupler in a Liquid-Filled Tapered Hollow Suspended Dual-Core Fiber

A high sensitivity optical fiber temperature sensor based on a liquid-filled tapered hollow suspended dual-core fiber (HSDCF) is proposed and experimentally demonstrated. The liquid-filled tapered HSDCF constitute a directional coupler. Due to the small distance between cores and the liquid filled in the air hole, resonance coupling occurs between the two suspended cores. The coupling coefficient between the two suspended cores is strongly dependent on the refractive index of the filled liquid, which causes the sensor to be very sensitive to temperature. Experimental results show that the sensor has a high sensitivity of 38.281 nm/°C within the monitorable temperature range of 20–26 °C. Due to the advantages of the high sensitivity, good linear response, and good stability, the proposed sensor has great potential for applications in temperature precision measurement.