USA As Represented by Secretary of the Navy

Aileen M Yurek

Anthony Dandridge

Alan B Tveten

Alan D Kersey

A hydrophone group for shallow towed applications in less than 50 feet of ter. The hydrophone group has a series of hydrophones connected by relatively insensitive fiber optic interconnects. The individual hydrophones are sufficiently sensitive such that the interconnecting optical fiber does not introduce excessive noise. Each hydrophone is basically a sensing fiber wrapped around an air-backed mandrel. Each air-backed mandrel is formed of an extended solid frame substantially non-compliant along a longitudinal axis. The extended solid frame is provided with a channel around the periphery thereof. The channel extends substantially the entire length of the extended solid frame. A flexible outer covering surrounds the extended solid frame. The flexible outer covering is highly compliant in a radial direction extending from the longitudinal axis. The air-backed mandrel has a high frequency mechanical resonance. Each hydrophone is connected in a chain by a plurality of interconnects having a substantially lower sensitivity than each hydrophone.

Hydrophone group design for shallow towed applications

A sensing portion for an interferometric planar hydrophone is disclosed which comprises: a support assembly; a plurality of hollow compliant mandrels mounted to the support assembly in a fixed planar relationship with respect to each other to form a planar configuration; a sensing optical fiber sequentially wound around each of the plurality of mandrels to form a single, serial, optical sensing arm or path between an input position on a first one of the plurality of mandrels and an output position on a last one of the plurality of mandrels; and an acoustically transparent material encapsulating the sensing portion to form a sealed compliant planar hydrophone. In an operational system, an interferometric planar hydrophone is disclosed which comprises: the sensing portion in which the sensing arm is operative to measure a predetermined measurand in a preselected environment and which sensing portion further includes a reference optical fiber environmentally isolated from the predetermined measurand; a light source for transmitting coherent light to both of the sensing and reference optical fibers; and circuitry responsive to light received from the sensing and reference optical fibers for developing an output signal indicative of phase shift differences between the sensing and reference optical fibers to determine the predetermined measurand.

Hydrophone transduction mechanism

An improved inline fiber optic sensor array is achieved by packaging a pllity of fiber optic sensor units such that each fiber optic sensor unit incorporates a complete functional sensor and adjacent fiber optic sensor units are separated by a delay element connected in series between each pair of fiber optic sensor units. Delay elements temporally separate measureand signals received from the individual fiber optic sensor units and permit decoupling of signals produced in response to environmental stress on the non-sensor unit portions of the array.

Inline fiber optic sensor arrays with delay elements coupled between

A fiber optic sensor using the treated coil of optical fiber as a structural support system for the sensor, and a method for making such a sensor.

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Alexandria, VA, United States of America

Aileen M Yurek