Fiber laser hydrophone for underwater acoustic surveillance and marine mammals monitoring

N. Beverini; S. Firpi; P. Guerrini; E. Maccioni; A. Maguer; M. Morganti; F. Stefani; C. Trono

doi:10.1117/12.880973

8 February 2011 Fiber laser hydrophone for underwater acoustic surveillance and marine mammals monitoring

N. Beverini, S. Firpi, P. Guerrini, E. Maccioni, A. Maguer, M. Morganti, F. Stefani, C. Trono

Proceedings Volume 7994, LAT 2010: International Conference on Lasers, Applications, and Technologies; 79941D (2011) https://doi.org/10.1117/12.880973
Event: International Conference on Coherent and Nonlinear Optics (ICONO 2010) and International Conference on Lasers, Applications and Technologies (LAT 2010), 2010, Kazan, Russian Federation

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.

Citation Download Citation

N. Beverini, S. Firpi, P. Guerrini, E. Maccioni, A. Maguer, M. Morganti, F. Stefani, and C. Trono "Fiber laser hydrophone for underwater acoustic surveillance and marine mammals monitoring", Proc. SPIE 7994, LAT 2010: International Conference on Lasers, Applications, and Technologies, 79941D (8 February 2011); https://doi.org/10.1117/12.880973

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