Miniaturized High-Sensitivity Temperature Sensor Based on Cascaded Fiber-Optic FPI

In letter, a cascaded fiber-optic Fabry-Perot interferometers temperature sensor with high-sensitivity and small-dimension is proposed and demonstrated. The sensor is fabricated by filling the polydimethylsiloxane (PDMS) and air between two single-mode fiber end-faces located in a section of silica capillary, thus a PDMS-based glue cavity, an air cavity and combined PDMS-air cavity are constructed. Due to the similar optical length between PDMS glue cavity and PDMS-air cavity, the conditions for Vernier effect can be easily satisfied in the sensor fabrication. The temperature sensitivity of proposed sensor is effectively improved in experiment. The research results show that the sensitivity of sensor is enhanced from 2.62 nm/°C to 23.22 nm/°C, which is about 8.86 times than that of the single PDMS-based glue cavity, and the linearity of temperature-dependent wavelength shifts is superior to 0.99 in temperature range of 32~50 °C. The sensor has advantages of high sensitivity, simplicity and easy to fabrication, and the small-dimension merit make it more suitable for point-temperature measurement.