High Sensitivity Curvature Sensor with Intensity Demodulation Based on Single-Mode-Tapered Multimode-Single-Mode Fiber

A high sensitivity curvature sensor based on single-mode-tapered multimode-single-mode (STMS) fiber structure has been proposed and demonstrated theoretically and experimentally. Due to elastic-optical effect, light field distribution of the STMS structure would be asymmetric when bending is applied, resulting in a profound effect on the transmission characteristics of the STMS structure. The experimental results show a good agreement with the trend of the theoretical predictions. Adopting the intensity demodulation in experiments, an average sensitivity of -21.734 dB/m^-1 over the range of 0.7064 to 1.9129 m^-1 and the maximum sensitivity of -144.876 dB/m^-1 at the curvature of 1.9129 m^-1 have been achieved. Besides, the dependence of temperature on the transmission spectrum of this curvature sensor has been investigated, showing a low temperature cross-sensitivity. Because of these superior properties, this curvature sensor could find useful applications in architecture, mechanical engineering, and medical science.