USA As Represented by Secretary of the Navy

Other

W James Trott

Nicholas Lagakos

Jacek Jarzynski

A microbending fiber optic acoustic sensor. A point hydrophone according to a first preferred embodiment of the present Invention includes two opposed pistons which are subjected to an acoustic pressure wave. In response to the pressure wave, the opposed pistons push a pair of deformer plates against an optical fiber to deform the fiber thereby intensity modulating an optical signal passing through the fiber. An extended hydrophone according to a second preferred embodiment of the present Invention includes an optical fiber wound in a helical groove formed in a cylindrical surface. A plurality of parallel axial slots are located in a spaced-apart relationship to each other at positions about the cylindrical surface and are oriented in parallel with the axis of the cylindrical surface. Each axial slot intersects with the helical groove at a plurality of locations and has a depth greater than the depth of the groove. An applied acoustic pressure wave forces the fiber into the axial slots thus deforming the fiber and thereby intensity modulating an optical signal passing through the fiber in response to the acoustic pressure. Depth equalization means are included for each embodiment.

Microbending fiber optic acoustic sensor

A piezoelectric tubular monopole element with zero end displacement which s an omnidirectional sensitivity over the widest possible frequency range. The center section is radially or thickness-poled and the end sections are longitudinally or length-poled. The positive electrodes are connected in parallel and the negative electrodes are connected in parallel for electrical parallel output.

Piezoceramic tubular element with zero end displacement

A broadband directional transducer which provides a beam pattern that is essentially constant for all frequencies above a certain cutoff frequency, an acoustic pressure angular distribution that is virtually independent of the distance from the transducer and no side lobes, includes an array of isophase, omnidirectional electro-acoustic elements on a spherical shell, each element being amplitude-shaded according to the shading function ##EQU1## where n is a positive integer, and .theta. is an angle measured from the axis of the spherical surface to a shaded element.

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Annandale, VA, United States of America

W James Trott