Ultrasensitive Temperature Sensor Based on Refractive Index Liquid-Sealed Thin-Core Fiber Modal Interferometers

An ultrasensitive temperature sensor based on a thin-core fiber modal interferometer (TCFMI) is proposed and demonstrated in this paper. After its middle is etched to a thin residual diameter, the TCFMI is sealed in a capillary tube filled with refractive index (RI) liquid. The thermo-optic effect of RI liquid turns the TCFMI into an ultrasensitive temperature sensor with sensitivity up to -22.23 nm/°C at 3.2°C. The sensitivity is over 1000-fold that of the bare TCFMI in air. This proposed temperature sensor is also simple, cost-effective, and suitable for a variety of applications.