A compact Mach-Zehnder two-mode fiber-optic interferometer for high temperature sensing

A compact high-temperature fiber-optic sensor is demonstrated by fusion splicing a 3.25mm-long two-mode fiber (TMF) between two single mode fibers (SMFs) to form an all-fiber Mach-Zehnder interferometer (MZI). Under optimized splicing conditions, a strong interference is achieved with high extinction ratio (~10dB). Two methods are applied to detect temperature changes from temperature induced wavelength shift and intensity change of a probing light source. Experimental results show the device is capable of monitoring temperature change from 25degC to 425degC with temperature sensitivity of 58pm/degC and 0.45muW/degC with 360muW of input power, respectively, and a theoretical temperature range from 25degC up to 1000degC