High temperature high sensitivity Mach-Zehnder interferometer based on waist-enlarged fiber bitapers

•This is a novel in-fiber Mach-Zehnder interferometer based on waist–enlarged fiber taper. t has the adventure of compactness and easy fabrication.•The proposed sensor in this paper has a high temperature sensitivity (0.087nm/°C) in the range of 30–1000°C with a good linearity (0.998).•The sensor can figure out the temperature without affected by humidity. An optical Mach-Zehnder interferometer (MZI) composed of a short section of thin-core fiber (TCF) which inserted into a standard single-mode fiber (SMF) with two waist-enlarged bitapers was proposed for high temperature measurement. MZIs with different lengths were fabricated, and the relationship between length and interference period was studied. The fast Fourier transform (FFT) method was used to determine the transmitted spectra of MZIs, and the results indicate that LP01 and LP02 modes are the main modes. The MZI has a high temperature sensitivity of 0.087nm/°C with a good linearity of 99.8% from 30 to 1000°C. Because it has advantages of compact size, easy fabrication, high sensitivity, high mechanical strength and wide sensing range, the MZI can be used for high sensitivity temperature measurement.