USA As Represented by Secretary of the Navy

Jacek Jarzynski

Nicholas Lagakos

Joseph A Bucaro

Barbara Jarzynski, Legal Representative

W James Trott

A fiber optic hydrophone has a reflective diaphragm having an exposed face and a reflective protected face, at least one transmitting multimode optical fiber having an end spaced apart from the protected face of the diaphragm positioned to emit light toward the diaphragm housing, and a reservoir. A cavity is defined by the diaphragm and the interior surface of the housing. Silicone oil and a compliant elastomeric material with embedded air bubbles are located in the cavity. Ports between the cavity and the reservoir and the reservoir and the exterior of the hydrophone allow static pressure communication between the cavity and the exterior of the hydrophone. The fiber optic probe can have one transmitting multimode optical fiber and six receiving multimode optical fibers, or more or fewer optical fibers. A grating can protect the diaphragm from environmental damage.

Intensity modulated fiber optic hydrophones

A fiber optic sensor for detecting acceleration or displacement includes a fiber optic probe with a multimode transmitting optical fiber, a multimode receiving optical fiber and a edge reflector spaced apart from the fiber probe. The reflector moves in a transverse direction substantially normal to the longitudinal axis of the fiber optic probe, so the amount of light received by the receiving fiber indicates a relative acceleration or a relative displacement of the reflective surface with respect to the fiber probe in the transverse direction of motion of the edge of the reflector. The reflector can be mounted on a cantilever beam. The sensor can have one transmitting fiber, two receiving fiber, and a reflector with two edges, each edge partially covering one of the receiving fibers. A triaxial sensor system has at least two two-fiber sensors.

Fiber optic acceleration and displacement sensors

A strain sensor includes an optical fiber with at least one optical fiber, a reflector body with a reflective surface, a housing affixed to the optical fiber probe and to the reflector body. The reflective surface is spaced apart at a distance d from the ends of the probe's fibers and receives light from the end of the fiber and to reflect at least a portion of the light into the end of the fiber. The housing is attached to the fiber probe at a first end of the housing and attached to the reflector body at a second end of the housing. The housing is affixed to the material to be measured, and in the material causes a change in gap between the fiber end and the reflective surface, modulating the amount of light received in the receiving fiber, detectable by a photodetector connected to the receiving fiber.

Intensity modulated fiber optic strain sensor

A fiber optic pressure sensor includes an optical fiber for transmitting light. The optical fiber has an axis. The fiber optic pressure sensor also includes an etched diaphragm perpendicular to the axis. The diaphragm includes an operative side located at a distance from the optical fiber sufficient to reflect a portion of the transmitted light into the optical fiber. The etched diaphragm includes a semiconductor, a dielectric, and/or a metal.

Fiber optic pressure sensor

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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Bethesda, MD, United States of America

Jacek Jarzynski