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Proceedings Paper

Fiber laser hydrophone array
Author(s): David J. Hill; Phillip J. Nash; David A. Jackson; David J. Webb; S. F. O'Neill; Ian Bennion; Lin Zhang
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Paper Abstract

In recent years growing interest has surrounded the development of fiber laser sensors (FLS). This is due to their ultra high sensitivity to temperature and strain as well as their ability to be multiplexed along a single fiber using WDM techniques. It is their extreme sensitivity that has led to them being considered as acoustic pressure sensors rather than standard fiber Bragg gratings. The work presented here describes the development of an array of FLS configured as hydrophones. We discuss the design of the single mode fiber laser used throughout our system; comparing examples based upon distributed Bragg reflectors (DBR) and distributed feedback (DFB). In addition we discuss both the theoretical and experimental acoustic sensitivity enhancements obtained by the application of an elasto-plastic coating to the FLS. The array configuration is described, as is the heterodyne interrogation scheme using an unbalanced Mach-Zehnder interferometer with WDM channel selection. Results from the measurement of the minimal detectable acoustic signal of a bare fiber laser are shown to be -69 dB re.Pa/(root)Hz at 1 kHz when using a 200 m path imbalanced readout interferometer. Further gains in the sensitivity due to the application of various coatings are reported, as is a full characterization of an array of fiber laser hydrophones. Finally we discuss the future research of the FLS, and the areas in which the technology is particularly applicable.

Paper Details

Date Published: 9 December 1999
PDF: 12 pages
Proc. SPIE 3860, Fiber Optic Sensor Technology and Applications, (9 December 1999); doi: 10.1117/12.372963
Show Author Affiliations
David J. Hill, Defence Evaluation and Research Agency Winfrith (United Kingdom)
Phillip J. Nash, Defence Evaluation and Research Agency Winfrith (United Kingdom)
David A. Jackson, Univ. of Kent at Canterbury (United Kingdom)
David J. Webb, Univ. of Kent at Canterbury (United Kingdom)
S. F. O'Neill, Univ. of Kent at Canterbury (United Kingdom)
Ian Bennion, Aston Univ. (United Kingdom)
Lin Zhang, Aston Univ. (United Kingdom)

Published in SPIE Proceedings Vol. 3860:
Fiber Optic Sensor Technology and Applications
Michael A. Marcus; Brian Culshaw, Editor(s)

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