Abstract
We describe a fiber optic hydrophone array system that could be used for underwater acoustic surveillance applications (e.g. military, counter terrorist, and customs authorities in protecting ports and harbors), offshore production facilities or coastal approaches as well as various marine applications. In this paper, we propose a new approach to underwater sonar systems using the voltage-controlled liquid crystals and simple multiplexing method. The proposed method permits measurement of sound under water at multiple points along an optical fiber using the low cost components and standard single mode fiber, without complex interferometric measurement techniques, electronics or demodulation software.
Highlights
Today’s underwater sound detection and mapping technology is based on a complex, large and expensive electrical approach [1]
We describe a fiber optic hydrophone array system that could be used for underwater acoustic surveillance applications, offshore production facilities or coastal approaches as well as various marine applications
The liquid crystal cells consist of two parallel glass substrates separated by a distance d using spacers of control sizes: 5 m for the bulk approaches and 10 m for the fiber optic one
Summary
Today’s underwater sound detection and mapping technology is based on a complex, large and expensive electrical approach [1]. The idea of using an optical fiber as a hydrophone was first published by Bucaro [2]; since various fiber-based sensors have been developed [3,4,5,6,7] These rely either on (1) some interferometric approach including the use of fiber coils and distributed feedback (DFB) fiber-lasers or (2) one of a number of intensity modulation mechanisms, the latter involving physical motion or mechanical effects such as micro bending. Each of these approaches must overcome its own set of problems – including complexity, cost or sensitivity – before truly practical sensors can be produced. This system uses simple demultiplexing of the output light signal based on both amplitude and frequency of light in predefined channels, which are directly linked to the amplitude and frequency of the sound signals measured under water
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