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Proceedings Paper

Fiber laser hydrophone for underwater acoustic surveillance and marine mammals monitoring
Author(s): N. Beverini; S. Firpi; P. Guerrini; E. Maccioni; A. Maguer; M. Morganti; F. Stefani; C. Trono
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Paper Abstract

This work describes the progress in the developing of a hydrophonic sensors array, based on fiber laser technology, tailored for underwater acoustic surveillance of harbors, naval forces, and, in general, of maritime areas of strategic relevance; the same apparatus can also find application for marine mammals coastline surveying, simply addressing a suitable frequency detection band. The sensors are Distributed Bragg Reflectors Fiber Lasers. The laser active medium is an Er+ doped fiber included between two Bragg mirrors that are photo-imprinted through UV radiation on the fiber. The acoustic water pressure variations produce a longitudinal strain on the fiber laser structure with a consequent modulation of the emission wavelength. An in-fiber un-balanced Michelson interferometer transforms the wavelength modulation into phase modulation, enhancing the detection sensitivity. An acousto-optic modulator, mounted on one arm of the interferometer, generates a frequency carrier to allow conventional demodulation techniques. This apparatus has demonstrated a noise-equivalent level of less than 1 mPa/(Hz)1/2 in the 0.5-5 kHz frequency band. Experimentations in marine environment of sensor arrays are in progress, and the first results obtained on a couple of sensors written on a same fiber are presented.

Paper Details

Date Published: 8 February 2011
PDF: 6 pages
Proc. SPIE 7994, LAT 2010: International Conference on Lasers, Applications, and Technologies, 79941D (8 February 2011); doi: 10.1117/12.880973
Show Author Affiliations
N. Beverini, Univ. di Pisa and CNISM (Italy)
S. Firpi, Univ. di Pisa and CNISM (Italy)
P. Guerrini, NATO Undersea Research Ctr. (Italy)
E. Maccioni, Univ. di Pisa and CNISM (Italy)
A. Maguer, NATO Undersea Research Ctr. (Italy)
M. Morganti, Univ. di Pisa and CNISM (Italy)
F. Stefani, Univ. di Pisa and CNISM (Italy)
C. Trono, CNR, Istituto di Fisica Applicata Nello Carrara (Italy)


Published in SPIE Proceedings Vol. 7994:
LAT 2010: International Conference on Lasers, Applications, and Technologies
Vladislav Panchenko; Gérard Mourou; Aleksei M. Zheltikov, Editor(s)

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