Highly sensitive vector curvature sensor based on a triple-core fiber interferometer

Abstract

A highly sensitive vector curvature sensor based on a triple-core fiber (TCF) interferometer is proposed and demonstrated. The TCF interferometer is composed of a piece of TCF that is fusion spliced to a standard single mode fiber (SMF). A taper is fabricated at the TCF near the TCF-SMF junction to couple the light from the input SMF into the three cores of the TCF and recouple the reflected light from the end of the TCF back to the SMF, which forms a three-beam Michelson interferometer in the TCF. Such a three-beam interferometer has the unique characteristic that its sensitivity is greatly affected by the optical path differences (OPD) and light intensities of the light transmitted in the cores of the TCF. As a result, choosing a TCF with proper refractive index differences between three cores or designing a proper splitting ratio of the TCF taper can effectively enhance the sensitivity of the TCF interferometer. The bending responses of the TCF interferometer were tested in the curvature range of 0-1.305 m−1. Experimental results show that the curvature sensitivities at the opposite bending directions along the cores’ connection are about 91.61 nm/m−1 and -95.22 nm/m−1, respectively.