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Multiplexed point and stepwise-continuous fibre grating based sensors: practical sensor for structural monitoring?

Xu, Ming Gang, Geiger, Harald and Dakin, John P. (1994) Multiplexed point and stepwise-continuous fibre grating based sensors: practical sensor for structural monitoring? In, Kersey, Alan D. and Dakin, John P. (eds.) Distributed and Multiplexed Fiber Optic Sensors IV. Bellingham, US, Society of Photo-Optical Instrumentation Engineers pp. 69-80. (Proceedings of SPIE, 2294). (doi:10.1117/12.187385).

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We report on recent progress on developing a complimentary pair of optical-fibre-based sensor methods for structural monitoring, for potential application in aerospace composites or civil engineering structures. Particular emphasis is placed on a method for addressing arrays of grating sensors using an acousto-optic tunable filter (AOTF), and on a longer-gauge-length system based on optical-time-domain reflectometry (OTDR). The AOTF possesses the desired frequency-agile capability for random multiplexed access and has a wide tuning range. It is suitable for both dynamic and quasi-static strain sensing. The scheme involves frequency-shift-keying of the RF drive to an AOTF to track the wavelength changes of gratings. We are currently constructing a compact interrogation system based on the concept.
For many sensing applications, it is desirable to have a system able to monitor the average strain over a longer length of the structure. This is being researched using a specially-designed high-resolution OTDR. It enables us to determine the optical path length between partially-reflected points (eg gratings) along the fibre. From the measured optical range of each individual discontinuity, changes in length in each intervening fibre section can be determined. In terms of distance, a resolution equivalent to 100µm over a 5m long fibre section has been achieved within a measurement time of 5sec. Work is being directed towards extending the number of sections monitored, and reducing the measurement time using improved processing algorithms, and to extend performance using communications components.

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Published date: 1994


Local EPrints ID: 77132
ISBN: 9780819416186
PURE UUID: 928e2940-43ba-42e2-9389-99dc693c9bdc

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Date deposited: 11 Mar 2010
Last modified: 18 Jul 2017 23:34

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Author: Ming Gang Xu
Author: Harald Geiger
Author: John P. Dakin
Editor: Alan D. Kersey
Editor: John P. Dakin

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