Fabrication and analysis of microbend fiber sensor using bending-sensitive fiber

Abstract

A bending-sensitive fiber (BSF) is fabricated and analyzed to create a microbend fiber sensor (MFS) with a simple structure. The BSF exhibits a gradual rather than sudden change in the microbend loss, according to a variation in the microbend applied to the BSF. According to the measured refractive index profile of the fabricated BSF, the proposed BSF consists of three different regions: the first core equal to the core of a SMF; the second core that is located around the first core, and whose refractive index is lower than the first core and higher than the cladding; and the cladding. The 3-D finite difference beam propagation method (3-D FD-BPM) is utilized to analyze the characteristics of the BSF. Based on the numerical results using 3-D FD-BPM and the fabricated BSF, a simple MFS with a BSF is created and compared to the MFS with a SMF. In particular, the MFS with the BSF showed a microbend loss from –1 to –20 dB at 1550 nm when the pressure given to the optical fiber is varied from 0 to 0.05 MPa; meanwhile, the MFS with the SMF showed no optical power attenuation.