Litton Systems, Inc.

Bei Sensors & Systems Company, Inc.

Other

Bei Technologies, Inc.

Bei-systron Donner

Michael R Layton

A Douglas Meyer

Bruce A Danver

Dennis P Bevan

Robert H Moore

Steven J Maas

James S Bunn, Jr

G Richard Newell

Timothy R Hilby

Jeffrey D Lastofka

Redundant rate sensor and method in which inertial rate is monitored with a plurality of vibratory sensing elements mounted in a single enclosure, signals from the sensing elements are processed to provide an independent rate output signal for each of the sensing elements, and the independent rate output signals are delivered to a connector which is accessible externally of the enclosure.

Redundant rate sensor and method

A closed loop sensor that utilizes a piezoelectric structure. In one embodiment, drive/non-control electrodes apply drive voltages to the piezoelectric structure and drive/control electrodes apply drive/control voltages to the piezoelectric structure to cause drive mode displacement of the piezoelectric structure and cancel motion induced pickup mode and quadrature displacements of the piezoelectric structure. In another embodiment, pickup/control electrodes detect a pickup signal from the piezoelectric structure corresponding to the motion induced pickup mode and quadrature displacements and apply a control signal to the piezoelectric structure so as to cancel these displacements. In still another embodiment of the invention, an optical sensing device optically senses the motion induced pickup mode and quadrature displacements and control electrodes apply a control signal to the piezoelectric structure so as to cancel them.

Closed loop resonant rotation rate sensor

A closed loop sensor that utilizes a piezoelectric structure. In one embodiment, driven/non-control electrodes apply drive voltages to the piezoelectric structure and drive/control electrodes apply drive/control voltages to the piezoelectric structure to cause drive mode displacement of the piezoelectric structure and cancel motion induced pickup mode and quadrature displacements of the piezoelectric structure. In another embodiment, pickup/control electrodes detect a pickup signal from the piezoelectric structure corresponding to the motion induced pickup mode and quadrature displacements and apply a control signal to the piezoelectric structure so as to cancel these displacements. In still another embodiment of the invention, an optical sensing device optically senses the motion induced pickup mode and quadrature displacements and control electrodes apply a control signal to the piezoelectric structure so as to cancel them.

Rotation rate sensor with optical sensing device

An acceleration insensitive interferometric hydrophone sensor having increased sensitivity comprises a rigid cylindrical support mandrel that is coaxial with and between thin walled sense and reference mandrels. Flanges on the reference and support mandrels form air filled cavities above and below optical reference and sense fiber windings, respectively, that are symmetrically wound on associated mandrels. The walls of the sense and reference mandrels are thin so that they both respond to the same incident acoustic wave signal although 180.degree. out-of-phase. A central collar on the support mandrel provides an acceleration insensitive location for making attachment to the hydrophone. In another embodiment, the reference mandrel is much thicker than the sense mandrel and cavities supporting the sense fiber are caused to operate as acoustic impedance mismatches for rendering the reference fiber winding substantially insensitive to and acoustically decoupling it from an incident acoustic pressure wave signal. In yet another embodiment which does not employ a reference mandrel, the reference fiber is wound around the support mandrel in cavities above the latter that are caused to operate as acoustic mismatches. The junctions of the mandrels are preferably sealed for isolating the wound length of reference fiber and cavities from fluid in which the hydrophone sensor is located.

High performance extended fiber optic hydrophone

The inner surface affixation system and process is a method for affixing wound optical fibers on the inner surface of a hollow cylinder. It is useful, for example, in the manufacture of rigid mandrel-based fiber optic sensors. The optical fibers of a sensor wound on the inner surface are less susceptible to damage than are optical fibers wound on the outside of the mandrel. The process requires that the fibers be supported on a cylinder, which is coated with an adhesive and placed within the sensor mandrel cylinder, at which time the circumference of the supporting cylinder is expanded, causing the fibers to engage the inner surface of the sensor mandrel cylinder. The adhesive is then cured, holding the fibers in place on the inner surface of the sensor mandrel cylinder while the supporting cylinder is contracted and removed from the sensor mandrel cylinder.

Inner surface fiber affixation for manufacturing a sensor mandrel

Two substantially identical optical fiber interferometers, preferably packaged together and exposed to the same parameter to be measured, wherein an increase of the field quantity to be measured causes an increase of the delay time difference of one interferometer and a decrease of the delay time difference of the other interferometer. Demodulator means is connected to the outputs of the interferometers to demodulate the phase-modulated signals from each of the interferometers, and electronic differencing means is connected to receive the demodulated signals from the demodulator means to difference one of the signals from the other to enhance the measured signals relative to the laser-induced noise signals.

Differential fiber optic sensor and method

An improved synthetic heterodyne demodulator circuit. The circuit is arranged to accept the output signal s(t) from an interferometric sensor with large amplitude sinusoidal phase modulation (phase-generated carrier). The phase modulation amplitude is adjusted such that a selected pair of odd and even carrier harmonics are equal. The quadrature signal components are first extracted from the phase-generated carrier using standard homodyne techniques. The quadrature signal components are then used to AM-modulate a pair of equal-amplitude quadrature carrier components at an arbitrary frequency .omega..sub.c, and summed. The result is a conventional PM modulated carrier which can be demodulated using standard FM techniques, followed by integration, to recover with high fidelity the sensed information.

Synthetic heterodyne demodulator circuit

A mismatched path length fiber optic interferometer is optically coupled to an optical fiber and configured to form an omnidirectional acoustic sensor. A second mismatched path length fiber optic interferometer is optically coupled to the optical fiber and configured as a first gradient sensor. A second fiber optic gradient sensor is also optically coupled to the optical fiber. A detector optically coupled to the omnidirectional acoustic sensor and to the gradient sensors converts optical signals output therefrom to electrical signals indicative of the magnitude and direction of changes in an acoustic field. The omnidirectional acoustic sensor may include a length of optical fiber wrapped around the housing while the gradient sensors are mounted inside the housing. The housing perferably has a volume that is adjustable for controlling the buoyancy thereof. Each gradient sensor preferably comprises a pair of mandrels formed to enclose chambers. Optical fiber coils are formed on the mandrels. Both the chambers are filled with a fluid and placed in fluid communication through a tube that defines a sensing axis between the mandrels such that acceleration of the housing along the first sensing axis causes a fluid pressure differential on the first and second optical fiber coils.

Passive fiber optic sensor with omnidirectional acoustic sensor and

A switch-selectable calibration signal is applied to an interferometric sensor channel of fiber optic sensor array for monitoring its operation. A calibration signal is applied at a single physical location to determine the channel scale factors and proper operability of multiple sensors at remote locations in the array. An optical signal input to each interferometric sensor channel in the array, and a compensating interferometer receives optical signals output from the fiber optic sensor array. A signal is applied to the compensating interferometer to form an output signal that simulates signals output from each interferometric sensor in the array. These signals are processed to determine the scale factor of each interferometer in the fiber optic sensor array.

Interferometer calibration for fiber optic sensor arrays

A fiber optic array for detecting and communicating the state of a plurality of spatically remote variables includes a plurality of switchable optical couplers. The couplers are located between fiber optic sense coils that cause responsive phase shifts in optical pulses launched through the array. The couplers are controlled by the parallel outputs of shift registers so that a coupler is only 'on' for the period of time required to couple out a portion of the optical energy of a pulse after passage through the adjacent sense coil and is thereafter shut 'off' to minimize crosstalk between the sensors and to optimize the output optical power.

Fiber optic sensor array

An all fiber optic hydrophone or sensor array has significant size, cost, reliability, and operational advantages over other hydrophone arrays. The array comprises a distributed network of appropriately coiled optical fiber encased in commercially available marine cable. The terminal end of the sensor array preferably contains a modulated miniature solid-state laser diode and photodetector matrix which mate to power and multiplexing electronics. The distributed sensor assembly itself is entirely passive. The hydrophone array comprises an optical signal source and at least one transmitting optical fiber for guiding signals output from the optical signal source. The array further includes a plurality of sensing interferometers coupled to the transmit optical fiber and means for measuring differential changes in the optical path of each sensing interfereometer. The hydrophone array comprises means for superimposing signals output from each sensing interferometer, and a detector for converting optical signals in the receive fiber into electrical signals. The signal processing system in the array includes a compensating interferometer having optical phase modulating means formed in one arm thereof.

Multiplexed fiber optic sensor

A fiber optic sensor array comprises a single transmit optical fiber for guiding an incident optical signal through a plurality of sensing segments in the transmit optical fiber arranged in a series array. The sensor array may includes a single return optical fiber, or the sensors may be arranged in groups with all the member of one group being connected to a corresponding return fiber. Optical couplers formed between the transmit and return optical fibers couple a portion of the incident signal into the return fiber after the signal propagates through each sensing segment. A loop is formed in the transmit fiber at each optical coupler so that the incident signal travels through the sensing segments in one direction and through the return fiber in the opposite direction. The couplers may be identical and may be have either symmertical or asymmetrical coupling coefficients. Asymmetrical couplers may be used to attenuate the intensities of undesired signals that recirculate in the loops of the array.

Fiber optic sensor array and method

Intensity modulated incoherent light is input to an interferometer. The interferometer is preferably formed to have a first arm comprising a first optical fiber and a second arm comprising a second optical fiber. The fibers have an initial optical pathlength difference .DELTA.L.sub.o. The refractive index of a selected one of the optical fibers is determined, and the output of the interferometer is monitored to detect a null signal output with an initial predetermined frequency resolution bandwidth. The initial length resolution is calculated, and the length of one of the fibers is reduced. The frequency resolution bandwidth is then reduced to a new predetermined value, and the frequency providing a null signal output at the new frequency resolution bandwidth is measured. The process is repeated until the pathlength difference becomes a predetermined value.

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Clayton, CA, United States of America

Michael R Layton