A Cladding Corrosion Dumbbell-Shaped Structure Incorporating Eccentric Heterogeneous Fiber Sensor for Simultaneous Measurement of Temperature and Curvature

A cladding corrosion dumbbell-shaped structure incorporating eccentric heterogeneous fiber (EHF) for simultaneous measurement of temperature and curvature is proposed. The cascaded structure of the sensor is a single-mode fiber (SMF)–EHF-SMF, in which a spherical structure is made at both end of the SMF, and the overall structure of the sensor is a dumbbell-shaped structure. When the temperature and curvature change, the length and refractive index of the optical fiber will vary due to thermal and elastic optical effects. By leveraging the corresponding functional relationships and the coefficient matrix method, the dual-parameter matrix equation for temperature and curvature in the sensor can be derived. Due to the characteristics of EHF, the bending direction and effective refractive index difference are different, allowing for directional discrimination. The experimental results show that within the range of $25~^{\circ }$ C– $90~^{\circ }$ C, as the temperature increases, the transmission spectrum of the sensor exhibits a red shift phenomenon, with the highest temperature sensitivity reaching 123.3 pm/°C; in the range of 0–0.73 m ${}^{-{1}}$ , the maximum curvature sensitivity in the x-, $- {x}$ -, and y-directions can reach 13.16 nm/m ${}^{-{1}}$ . Finally, based on the experimental results, the dual-parameter sensing matrix equations in the x, $- {x}$ , and y-directions are obtained. This sensor can achieve curvature and temperature measurement in three different directions and has great potential in the field of dual-parameter sensing. It lays a certain foundation for vector fiber optic sensors and has good research significance.