High-Sensitive Temperature Sensor With Cascaded Fabry–Perot Interferometers Based on Enhanced Vernier Effect

In this work, we present a high-sensitivity fiber-optic temperature sensor based on the enhanced Vernier effect. The sensor consists of a cascade of three Fabry–Perot interferometers (FPIs), where FPI1 contains a polydimethylsiloxane (PDMS) cavity, FPI2 contains an air microcavity, and FPI3 contains a PDMS–air hybrid cavity. Since the effective lengths of the PDMS cavity and the PDMS–air hybrid cavity are close to each other, the superposition of the reflection spectra of FPI1 and FPI3 produces the traditional Vernier effect. Due to the thermo-optic effect and thermal expansion effect of PDMS and air, the reflection spectra of FPI1 and FPI3 will vary in the opposite direction with the temperature change, to achieve the enhanced Vernier effect. A temperature sensitivity of −35.45 nm/°C much higher than that of the fiber FPI sensor based on conventional Vernier effect is achieved, in good agreement with the theoretical analysis. The proposed sensor has the advantages high stability, mechanical strength, small size, and low cost, which has a great potential for marine environment detection and bioscience.