High-Sensitivity Mach–Zehnder Interferometric Curvature Fiber Sensor Based on Thin-Core Fiber

A simple and compact thin-core fiber (TCF)-based Mach-Zehnder interferometer (MZI) is proposed for curvature measurement. The sensor head is composed by a short section of TCF embedded between two single-mode fibers. The MZI works on the basis of interference between the core mode and cladding mode in TCF. The transmission spectrum of the sensor is analyzed by the fast Fourier transform, which indicates that the interference mainly occurs between LP01and LP018modes propagating in TCF. The experimental results show that the dip wavelengths in transmission spectrum decrease linearly as the curvature increase with a sensitivity of -13.53 nm/m-1. The high curvature sensitivity makes this sensor a candidate for curvature discrimination and measurement in the field of structural deformation, intelligent artificial limb, and mechanical engineering.