Sensitivity-enhanced temperature sensor with parallel dual fabry-perot interferometers structure based on harmonic Vernier effect

A sensitivity-enhanced temperature sensor with a parallel dual Fabry-Perot interferometers (FPIs) structure based on the harmonic Vernier effect is proposed and experimentally demonstrated. The sensing FPI is fabricated by fusion splicing a multi-hundred-micron long polarization maintaining photonic crystal fiber (PMPCF) tip with a single mode fiber (SMF). The reference FPI is fabricated by inserting two SMFs into the ends of a single-pore capillary. The length of the air cavity in the reference FPI is controlled and optimized to create a harmonic Vernier effect, thereby achieving significant sensitization of the sensor sensitivity and modulation of the amplification factor. Experimental results show that the temperature sensitivity of the single sensing FPI is 11.9 p.m./degrees C from 40 degrees C to 400 degrees C, and the temperature sensitivities of the parallel dual FPIs based on the harmonic Vernier effect are-408.95 p.m./degrees C,-723.23 p.m./degrees C, and-1.93 nm/degrees C, respectively. The proposed sensor has a simple structure, high sensitivity, and excellent stability, making it have certain application prospects in high temperature measurement fields such as aerospace and metallurgy.