Highly sensitive temperature sensor based on a Mach-Zehnder interferometer created in graded index fiber

A Mach-Zehnder interferometer (MZI) based on a graded index fiber (GIF) is proposed and demonstrated for temperature measurement. The device is constructed by splicing a half-pitch GIF between two single mode fibers (SMFs). A microcavity was drilled in GIF near the core and cladding interface. The microcavity and the remaining core of the GIF perform as two interference arms. Such a device exhibits a high refractive index (RI) sensitivity of 24611.54 nm/RIU, and high temperature sensitivity of -12.73 nm/°C with the assistance of high thermo-optic coefficient (TOC) liquids filling the microcavity.