In-fiber Mach–Zehnder interferometer based on multi-mode fiber and up-taper for curvature sensing

A new type of curvature sensor comprises a stub of multi-mode fiber and an up-taper is proposed and demonstrated experimentally. The whole fabrication process is quite simple and the sensor head is cost effective. Measurement results show that it has a maximum curvature sensitivity of −61.877 nm/m−1 at 1.1718 m−1 (the highest value of reported papers among in-fiber Mach–Zehnder interferometers) and −9.2115 nm/m−1 from 0.865 m−1 to 1.1172 m−1. Temperature sensitivity of 89.01 pm/°C within the range of 20–80 °C has also been achieved, which implies the possibility for measurement of temperature.