Simultaneous measurement of refractive index and temperature using multimode microfiber-based dual Mach–Zehnder interferometer

A multimode microfiber (MMMF)-based dual Mach–Zehnder interferometer (MZI) is proposed and demonstrated for simultaneous measurement of refractive index (RI) and temperature. By inserting a section of MMMF supporting a few modes in the sensing arm of the MZI setup, an inline interference between the fundamental mode and the high-order mode of MMMF, as well as the interference between the high-order mode of MMMF and the reference arm, i.e., the dual MZI, is realized. Due to different interference mechanisms, the former interferometer achieves RI sensitivity of 2576.584  nm/RIU and temperature sensitivity of −0.193  nm/°C, while the latter one achieves RI sensitivity of 1001.864  nm/RIU and temperature sensitivity of 0.239  nm/°C, demonstrating the ability to attain highly accurate multiparameter measurements.