High sensitivity temperature sensor based on enhanced Vernier effect through two parallel Fabry–Perot cavities

Abstract

In this paper, an enhanced Vernier effect temperature sensor based on two parallel Fabry–Perot interferometers (FPIs) is proposed and demonstrated experimentally. Among them, F P I 1 is composed of a single-mode fiber (SMF), a quartz capillary, and AB glue filled in the capillary. F P I 2 is formed by filling a capillary with polyimide (PI) solution and inserting two-segment SMF from both sides of the capillary. Since AB glue and PI have good thermal sensitivity, F P I 1 and F P I 2 are highly sensitive to temperature. Due to their different structures, the temperature sensitivity of F P I 1 is negative, and that of F P I 2 is positive. When F P I 1 and F P I 2 with similar free spectral range are connected in parallel, they will act as reference cavities for each other, resulting in an enhanced Vernier effect, which enlarges the sensitivity of the sensor more. In the temperature range of 40°C–58°C, the temperature sensitivity of the sensor is as high as − 13.09 n m / ∘ C , and the fitting coefficient is 0.9974. The experimental results show that in the enhanced Vernier effect sensor structure, only two FPIs with opposite temperature sensitivity are required, which does not increase the difficulty and cost of sensor manufacturing. In addition, the sensor has good stability and repeatability.