High-Sensitivity Loop-Fiber Temperature Sensor Based on Distilled Water Cladding

The study proposed a temperature sensor based on distilled water cladding of the coupling region in the loop-fiber coupler, which was formed by folding a single-mode fiber, melting the taper region with an H
₂
flame, and using two adjacent fibers to obtain the interference in the coupling. Based on thermo-optical effect response and coupling interference principle, with increasing ambient temperature, the refractive index of the distilled water decreased, and the interference spectrum drifted. The experiment explored the relationship between different lengths of taper region and interference spectrum. When the taper region length was 30–35 mm, the interference spectrum improved. Results showed that the maximum sensitivity of the sensor was 151.35 pm/°C and linearity reached 99.99% when the temperature was within the range of 35 °C to 60 °C. Furthermore, we propose a low-cost demodulation scheme. The sensor had high sensitivity, good linearity, good stability, fast response, simple manufacturing process, and low cost. It has potential application value.