Simultaneous measurement of temperature and refractive index with thin-core fiber MZI containing fiber Bragg grating

A thin-core fiber based Mach-Zehnder interferometer (MZI) for simultaneous measurement of temperature and refractive index is demonstrated. It is formed by sandwiching a short section of highly germanium-doped fiber between two single-mode fibers and writing a fiber Bragg grating (FBG) on the germanium-doped fiber. Simultaneous measurement is achieved based on the different responses of the interferometer and the FBG to the two parameters. Experimental results show that temperature sensitivity of 74.2pm/°C and refractive index sensitivity of 6.75nm/RIU are achieved, respectively.