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Proceedings Paper

Bent tilted fiber Bragg gratings for temperature-independent vibration sensing in vehicles
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Paper Abstract

Fiber grating based techniques have proven themselves as low cost, small size and low weight solutions for sensing strain and/or temperature in various applications, including structural health monitoring of aircrafts, ships and other man-made structures. However, normal fiber gratings are sensitive to both strain and temperature in a manner that is impossible to distinguish from the sensor response. Methods devised to circumvent this problem rely on combinations of gratings with different sensitivity to these two perturbations. Simultaneous measurements on two gratings then provide the necessary information to decode strain and temperature values but this requires special grating configurations and packaging to maximize the differential sensitivity. We will present experimental results of an alternative approach where we use a single very weakly tilted fiber Bragg grating (TFBG), to achieve the same effect. The grating couples light from the fundamental mode guided in the core to a large number of cladding modes, depending on the wavelength of interrogation. We propose and demonstrate a novel configuration in which many high order cladding mode resonances are removed by bonding the TFBG in a pre-bent state on a metal plate. After bonding, only a few low order mode resonances are left and occupy less than 5 nm of bandwidth (thereby allowing multiplexing). These resonances all have the same temperature sensitivity but very different behavior when the plate vibrates, bends or stretches statically. Differential measurements of the resonance power levels and shifts then provide valuable information about the mechanical state of the sensor.

Paper Details

Date Published: 9 October 2007
PDF: 8 pages
Proc. SPIE 6758, Photonics in the Transportation Industry: Auto to Aerospace, 675803 (9 October 2007); doi: 10.1117/12.732863
Show Author Affiliations
Alexei Ivanov, Carleton Univ. (Canada)
Jacques Albert, Carleton Univ. (Canada)

Published in SPIE Proceedings Vol. 6758:
Photonics in the Transportation Industry: Auto to Aerospace
Alex A. Kazemi; Christopher S. Baldwin, Editor(s)

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