High-sensitivity fiber temperature and pressure sensor based on fabry-perot interferometry and Vernier effect

In this work, we propose a novel sensor based on two parallel Fabry-P & eacute;rot interferometers (FPIs) and the Vernier effect, achieving temperature and pressure sensing. Both FPIs utilize the end face of a single-mode fiber as the reflective surface. FPI1 is composed of a single-mode fiber and a thin-core fiber fusion spliced together, with the cavity filled with polydimethylsiloxane (PDMS); FPI2 is made of two segments of single-mode fiber with the cavity filled with ultraviolet (UV) glue. Within the temperature range of 28-40 degrees C, the temperature sensitivities of FPI1 and FPI2 are -0.40 nm/degrees C and 0.49 nm/degrees C, respectively, indicating that the reflection spectra of the two sensors shift in opposite directions as the temperature increases. When the two sensors are connected using a 3 dB coupler and both are employed for temperature sensing, enhanced Vernier effect is achieved, resulting in a sensitivity of -3.38 nm/degrees C. This represents an 8.45-fold and 6.89-fold increase in sensitivity compared to FPI1 and FPI2, respectively. Additionally, FPI2 exhibits sensitivity to pressure; in the range of 0.1-0.7 MPa, the sensitivity of FPI2 reaches 2.73 nm/MPa. When using FPI1 as a reference device and FPI2 as a sensing device, the sensitivity within the same range reaches 20.91 nm/MPa, a 7.65-fold increase compared to FPI2 alone.