Complex optical fiber sensor based on the Vernier effect for temperature sensing

The Vernier effect is an effective way of magnifying the sensitivity of the sensor for higher resolution sensing. The Fiber-optic cascaded Fabry-Perot Interferometric (CFPI) temperature sensor has been theoretically studied and experimentally investigated in this paper base on Vernier effect. It has been manufactured by a segment of pure silica hollow-core fiber (HCF) fused between two sections single-mode fibers (SMF), where the optical path length of the HCF is similar to that of the terminal SMF. The combination of a fiber Bragg grating (FBG) and a CFPI structure could be used not only obtain the amount of temperature variation but also know the specific value of the temperature. The temperature sensitivity of the sensor was 706.9 pm/°C, which is 76 times higher than that of single one fiber-optic cavity FP temperature sensor. The sensor has a wide range of potential applications such as high-precision temperature sensing and high-temperature monitoring.