Investigation of an inline fiber Mach-Zehnder interferometer based on hybrid joints of core-offset and peanut-shape for refractive index sensing

Abstract

An inline fiber Mach-Zehnder Interferometer (MZI) that consisted of a standard single-mode fiber sandwiched between a core-offset and a peanut-shape joint is fabricated for the purpose of refractive index (RI) sensing. After one of the core-offset joints is replaced by a peanut-shape joint in an inline fiber MZI with the core-offset pair, the influence of the interference performance caused by the relative offset direction of the two core-offsets is avoided. The RI sensing characteristics under different core-offset displacement and interference arm length are studied. After bending the inline fiber MZI, the interference spectra become more stable, and the RI sensing performance is markedly improved. The RI sensitivity of −167.27 nm/RIU with a resolution of 2.39 × 10-4 RIU is achieved within the measured RI range of 1.333–1.373.