Mason & Hanger National, Inc.

Robert J Prenovost

Brian B Crawford

Jeff C Robinson

Judy K Burden

Jimmy L Reil

Aris Tanone

A distributed acoustic sensor utilizing a Fizeau type fiber optic transducer and a distributed acoustic collector to gather and return acoustic disturbances from remote areas in buried, underground, or underwater installations. A light beam from a laser or LED source is transmitted over a fiber to a remote transducer which is coupled to a distributed acoustic collector. The collector may be an extended pipe or tube system filled with an acoustic conducting medium such as air or an appropriate liquid which communicates with the sensing diaphragm in the transducer. An interference beam whose characteristics are a function of the diaphragm motion is created in the transducer and transmitted back over the common single fiber toward the source. An in-line optical coupler/splitter diverts a portion of the returning modulated beam to a photodetector which outputs a proportional electrical signal to an electronic circuit for amplification and analysis.

Distributed acoustic sensor

A distributed fiber optic sensing system for detecting mechanical, acoustic, or ultrasonic disturbances is disclosed. This system is optimized for use as an intrusion detection system in security applications. Light is launched into opposite ends of a sensing fiber loop such that two beams circulate through the loop in opposite directions and then recombine to produce an interference pattern on a photoelectric detector. Disturbances of the sensing fiber loop produce corresponding changes in the interference pattern and thereby the signal level at the detecter. The changes in the electrical signal from the detector are interpreted to provide alarms when the sensing fiber loop is impinged upon by intrusive disturbances, and to provide location of disturbances along the loop. Means are incorporated to decode uniquely coded sonic or ultrasonic signals from personal transmitters borne by authorized personnel approaching the sensing fiber loop. A remotely activated system disturber is affixed to the sensing fiber loop which, when activated by an operator, provides positive confirmation of sensing loop continuity and system operability.

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Huntsville, AL, United States of America

Robert J Prenovost