Highly sensitive temperature and strain sensor based on fiber Sagnac interferometer with Vernier effect

A novel temperature and strain sensor based on fiber Sagnac interferometer (FSI) with Vernier effect is proposed and demonstrated experimentally. The FSI fabricated by fusion splicing a segment of thin polarization maintaining fiber (TPMF) with a coupler works as sensing. The Vernier effect is generated by cascading a polarization mode interferometer (PMI). The PMI is fabricated by fusion splicing a polarization maintaining fiber (PMF) with a polarizer. The suitable free spectral range (FSR) of the sensor is fabricated based on numerical simulation. The experimental results indicate that with the Vernier effect, the temperature sensitivity can be improved from −1.924 nm/°C to −32.830 nm/°C and the strain sensitivity can be improved from 25.9 pm/με to 407.32 pm/με. The measured amplification factors are about 17 and 16. The good performance of the FSI with the Vernier effect provides a new option in the temperature and strain sensing fields. •A high temperature and strain sensor based on Vernier effect is proposed.•A FSI is cascaded with a PMI to form the sensor.•The sensing FSI–PMI has a linear response in measuring range.•PMI composed of PMF is less sensitive to environmental disturbance than FSL composed of TPMF.