Simplified highly sensitive temperature sensor based on harmonic Vernier effect

A highly sensitive temperature sensor with cascaded polarization maintaining fiber–Sagnac interferometers (PMF–SIs) based on harmonic Vernier effect has been proposed and experimentally demonstrated. Both simulation and experiment results indicate that the fundamental Vernier effect can be achieved through cascading two PMF–SIs with similar free spectral ranges (FSRs) and the first-order harmonic Vernier effect can be further realized by two PMF–SIs possessing FSRs with an approximate multiple relationship. The maximum sensitivity of the cascaded PMF–SIs based on harmonic Vernier effect has be enhanced about 35.5 times compared with that of single PMF–SI, exhibiting a high temperature sensitivity of − 53.3 nm/°C in the temperature measurement range from 30 to 37 °C. The temperature sensor with simple structure and high sensitivity has a great application prospect.