In-line Mach-Zehnder interferometric refractive index sensor based on concatenating two single-mode fiber half-tapers

Abstract

An in-line Mach-Zehnder interferometric refractive index (RI) sensor is demonstrated by concatenating two single-mode fiber (SMF) half-tapers separated by one section of SMF. The cladding modes excited at the first half-taper interferes with the core mode at the second half-taper to generate the interference fringe. Theoretical and experimental results consistently show that the interference fringe shifts toward shorter wavelengths with the external RI sensitivity of 102.3 nm/RIU in the monitoring RI range from 1.333 to 1.413. In addition, the sensing device may endure the axial stress more than 3200 μe with the strain sensitivity of 1.72 pm/μe.