Large measurement-range and low temperature cross-sensitivity optical fiber curvature sensor based on Michelson interferometer

Abstract

A large-measurement-range fiber curvature sensor based on Michelson interferometer is proposed and investigated. The sensor is fabricated by sandwiching a bitaper between a single-mode fiber (SMF) and a piece of multimode fiber (MMF), and the MMF end face is multiply discharged to form a fiber sphere. The mode interference is accumulated in the MMF for the bitaper could excite high-order modes and couple them with core mode. The sensor can be defined as a cantilever beam structure, in which the fiber sphere serves as a mass block, while the bitaper and MMF act as cantilever beam. The reflection interference spectrum is sensitive to ambient curvature, so a large-range curvature detection is realized. Experimental results show that the sensor has a sensitivity of −0.6888 nm/m−1 and −1.812 dB/m−1 in the curvature range of 0–12.2894 m−1. The maximum temperature sensitivity is 0.0078 nm/°C and 0.007 dB /°C in the temperature range of 30–150 °C, and the maximum temperature cross-sensitivity is −0.0113 m−1/°C, which could be neglected in the application. The sensor has advantages of low cost, easy fabrication, large curvature detection range, and low temperature cross-sensitivity, making it has broad application prospects in the curvature sensing field.