Optical fiber hollow ellipsoid for directional bend sensing with a large bending range

Abstract

A micro-fabricated Mach–Zehnder interferometer in optical fiber is demonstrated for bend sensing in four orthogonal directions. The intensity of the resonant dip exhibits a linear response to curvature in a logarithmic unit within a large range from 0 to 9 m−1, and the sensitivities obtained are 0.42 dB/m−1, 0.186 dB/m−1, −0.41dB/m−1, −0.265 dB/m−1, in the directions of 0°, 90°, 180°, and 270°, respectively. The temperature-induced curvature error is only ~0.012 m−1/°C in the bending directions of 0° and 180°. The device is compact, robust and efficient in operation.