High-sensitivity temperature and micro-displacement sensor based on dual Fabry–Perot interferometers and harmonic Vernier effect

Abstract This paper proposes a high-sensitivity temperature and nanoscale displacement sensor based on a parallel configuration of dual Fabry–Perot Interferometers (FPIs) and the harmonic Vernier effect (HVE), and verifies its performance through experiments. In this experiment, two FPIs were designed and fabricated using single-mode fiber (SMF), ultraviolet (UV) adhesive, capillary tubes, and ceramic ferrules. These two FPIs were connected in parallel to form Sensor S. Among them, FPI 1 is composed of a SMF inserted into a ceramic ferrule. The UV adhesive film coated on the end face of the ceramic ferrule enables FPI 1 to exhibit high sensitivity to temperature, thanks to the significant temperature-responsive property of the UV adhesive material. FPI 2 is composed of two segments of SMF inserted into a quartz capillary tube. By adjusting the axial position of one of the fiber segments, the cavity length can be precisely modified, endowing FPI 2 with exclusive sensitivity to micro-displacement. By setting the cavity lengths of the two FPIs to an approximate 2:1 ratio, the HVE is established. Experimental results show that the sensor achieves a temperature sensitivity of 32.674 nm °C −1 and a micro-displacement sensitivity of −0.182 nm nm −1 , both of which are approximately 15 times those of a single FPI. This sensor enables the independent measurement of the two physical quantities, effectively overcoming the problem of cross-interference between temperature and other physical quantities in traditional optical fiber sensors. In addition, it features a simple fabrication process, solves the parameter matching issue in the conventional VE, and thus possesses excellent practical value.