Bend monitoring and refractive index sensing using flat fibre and multicore bragg gratings

Abstract

A planarized optical fibre designed for two-dimensional bend monitoring and external refractive index sensing is presented. The approach uses two single-mode waveguides each containing a set of spectrally multiplexed Bragg gratings. To achieve sensitivity to bending and external refractive index, the cladding material of the fibre is partially removed through physical machining. This acts to offset the neutral axis, increasing bend sensitivity, and exposes the evanescent field of the guided mode, permitting external refractive index monitoring. Through collective monitoring of the Bragg grating array, real time, multiparameter sensing is attainable, allowing new capability for intelligent monitoring.