High-performance all-fiber Mach-Zehnder interferometer based on D-shaped two-mode fiber coated with polydimethylsiloxane for temperature sensing

•An all-fiber Mach-Zehnder interferometer based on offset fused single mode fiber and partially side-polished two mode fiber is designed and experimentally fabricated.•A method of capillary-packaging and PDMS-filling is proposed for enhancing the temperature sensitivity.•The maximum temperature sensitivity reaches −305.6 pm/°C.•The temperature sensitivity can be controlled by adjusting the polishing depth and the length of polished area.