Distributed curvature sensing using Brillouin scattering and multicore fibres

Abstract

Optical fibre shape sensing refers to the reconstruction of the shape of an object by using the strain measurements induced to the fibre by the bend. By routing an optical fibre through the structure of interest, the strain induced by the bending can be correlated to the radius of curvature of this structure, thus extracting information about its shape. This emerging new technology can be applied to many different fields varying from medical robotics to the health monitoring of structures leading to significant improvements to the quality of life. Multicore fibres are very good candidates for shape sensing thanks to the integrated 3D coordinate system they offer owing to the fixed position of the cores inside their cladding. In this thesis a Brillouin Optical Time-Domain Reflectometry (BOTDR) setup was built to interrogate the multicore optical fibres. BOTDR is a single-ended technique that makes its deployment into the field very practical. To overcome the issue of fibre twist during installation, a D-shaped and a flat, multicore fibre were designed and fabricated for use in shape sensing applications. The fabrication process as well as various ways of handling, cleaving and splicing those novel fibres that present a preferential bend, are analytically described in this work. The D-shaped fibre was used for curvature measurements demonstrating deviations from the real values between 9% and 15%.

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ORCID for Gilberto Brambilla: orcid.org/0000-0002-5730-0499

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