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Updated: Jan 25, 2026

A Random-displacement Measurement by Combining a Magnetic Scale and Two Fiber Bragg Gratings
Published on: September 30, 2019
Off-axis ultraviolet-written fiber Bragg gratings for directional bending measurements
Abstract:
Off-axis fiber Bragg gratings are inscribed by ultraviolet irradiation limited to expose only a portion of the fiber core cross section. The coupling to cladding modes is significantly increased, and the amplitude of the cladding mode resonances becomes sensitive to bending in magnitude and direction. Sensitivities ranging from +1.17 dB/m(-1) to -1.25 dB/m(-1) were obtained for bending in different directions relative to the offset direction of the grating, for curvatures from 0 to 1.1 m(-1), a range ideal for the shape sensing of large structures. The bending sensor response is also shown to be independent of temperature and the surrounding refractive index.
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