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Proceedings Paper

Type 1A fibre Bragg grating photosensitivity and the development of optimum temperature invariant type I-type IA strain sensors
Author(s): A. George Simpson; Kyriacos Kalli; Lin Zhang; Kaiming Zhou; Ian Bennion
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Paper Abstract

Type 1A fibre Bragg gratings (FBG) form only after the erasure of a standard grating in hydrogenated germanosilicate fibre, under prolonged UV exposure. They are distinct from other grating types as they exhibit a uniquely large increase in the mean index of the core, readily identifiable by a large red shift in the Bragg wavelength. Type 1A gratings can surpass the conventional mean index change by a factor of six with a typical red shift of up to 20nm, interpreted as a mean index increase of up to 1.9x10-2. Importantly, 1A gratings have been shown to exhibit the lowest temperature coefficient of all FBG, which makes them ideal for use as temperature compensated, dual grating sensors. We report on the formation of Type 1A gratings and the correlation between the mean index change of the grating and the growth of a loss band at close to 1400nm that is associated with the formation of OH centres within the fibre. We present annealing data comparing the decay of Type 1 and Type 1A gratings. Finally, we demonstrate a dual temperature compensated strain sensor system, based on two adjoining Type 1 and Type 1A gratings, which have been formed using a common phase mask, yet with central wavelengths many nm apart.

Paper Details

Date Published: 1 September 2004
PDF: 10 pages
Proc. SPIE 5459, Optical Sensing, (1 September 2004); doi: 10.1117/12.545299
Show Author Affiliations
A. George Simpson, Aston Univ. (United Kingdom)
Kyriacos Kalli, Higher Technical Institute (Cyprus)
Lin Zhang, Aston Univ. (United Kingdom)
Kaiming Zhou, Aston Univ. (United Kingdom)
Ian Bennion, Aston Univ. (United Kingdom)

Published in SPIE Proceedings Vol. 5459:
Optical Sensing
Brian Culshaw; Anna Grazia Mignani; Rainer Riesenberg, Editor(s)

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