Ag and ZnO Coated MMF-NCF SPR Fiber Optic Sensor for Simultaneous Measurement of Curvature and Refractive Index

In this article, a novel curvature sensor based on multimode fiber (MMF)-coreless no core fiber (NCF) structure coated with Ag and ZnO films is proposed. The surface plasmon resonance (SPR) effect is excited by the superposition of silver films, and ZnO films effectively modify the SPR valley. The oxide film redshifts the resonance wavelength by 50 nm and increases the transmission depth. In the curvature range of 0~45 m−1, the curvature sensing sensitivity of 0.1632 dB/m−1 is realized. The adjustment function of the SPR base and oxide improves the curvature detection effect of fiber optic curvature sensors. The sensor can also achieve simultaneous refractive index (RI) detection and can adapt to a wide range of RI changes from 1.31 to 1.39 RIU, achieving an RI detection capability of 7600 nm/RIU. The sensor has high sensitivity, high stability, anti-interference, good repeatability, and a depth fluctuation of less than 0.0342 dB. In practical applications, the changes in curvature and RI are often closely related to the properties and structures of substances, so this kind of sensor also has important application value in scientific research in biochemistry, material science, and other fields.