Experimental Study on High Sensitivity Intensity Modulation Curvature Sensor Based on SPR No-Core Fiber

Fiber curvature sensors based on surface plasmon resonance (SPR) have lower curvature detection sensitivity compared to existing curvature sensors. However, they offer advantages that other sensors cannot match, including insensitivity to parameters such as temperature and axial strain. To improve the detection sensitivity of SPR curvature sensors, we propose a no-core fiber (NCF) curvature sensor that measures curvature based on the intensity modulation method. In this curvature sensor, NCF of ZnO/silver film sputtered by a magnetron sputtering method is used as the sensing probe, and multimode fibers (MMFs) are used as the input and output units for optical signals on both sides of the sensing probe. This curvature sensor does not need to cascade other devices to avoid the effect of cross-sensitivity, which meets the current trend of device miniaturization. Due to the excellent light-guiding ability of NCF, the resonance valley excited by the SPR effect is sensitive to small changes in curvature. The experimental results show that the maximum curvature sensitivity of the curvature sensor in the curvature detection range of 0–35 m−1 is 0.4424 dB/m−1 and its linearity can reach 0.95588. This curvature sensor has the advantages of miniaturization, insensitivity to temperature and axial strain, and high curvature sensitivity, providing a new method for fiber SPR curvature sensors.