Refractive index and temperature sensor based on double-pass in-line Mach-Zehnder interferometer

Abstract

Different from the conventional optical fiber in-line Mach-Zehnder interferometer (MZI), we proposed and demonstrated a novel double-pass in-line fiber taper MZI as a refractive index and temperature sensor in this study. The double-pass MZI is composed of a reflecting mirror, a circulator and an in-line fiber MZI. The attenuation peaks of the double-pass MZI spectra have higher contrasts than the peaks of single-pass spectra. Using our recently proposed spectrum differential integration (SDI) analyzing method, the double-pass MZI sensors' sensitivities can be made nearly twice as large as those of the single-pass ones.