USA As Represented by Secretary of the Navy

Gregory H Ames

Roger L Morency

Antonio L Deus, Iii

Jason M Maguire

Christopher M Hansen

David J Moretti

Thomas Joseph Gryk

Jeffrey C Gremillion

Michael Amaral

Paul D Curry

An accelerometer has a substantially linear strain sensor with a transducer joined to the strain sensor. The transducer has a base that provides rigidity perpendicular to a preferred measurement direction. A plurality of outer flaps are joined to the base supporting the strain sensor. The outer flaps are capable of translating acceleration in the predefined direction to strain in the strain sensor. Two centermost flaps are positioned on either side of the center line of the transducer. Struts are joined between a lower portion of one the centermost flap and an uppermost portion of the nearest outer flap. The struts enhance strain by linking outer flap motion to the centermost flaps. Bridges are joined between each two adjacent outer flaps supporting the strain sensor.

Acceleration strain transducer with increased sensitivity

An accelerometer is provided for a fiber optic laser. Strain applied to the fiber optic laser results in an emission wavelength shift. The fiber optic laser is joined to a transducer and extends laterally across said transducer. Acceleration of the transducer in a predefined direction causes strain in said fiber optic laser. The transducer can have many possible designs. There is further provided a system for sensing acceleration which includes a pumping laser and a distributor joined to the fiber optic laser. Return signals from the fiber optic laser are provided to an interferometer and analysis circuitry. In the absence of a transducer, the system can operate as a strain sensor.

Fiber optic laser accelerometer

An accelerometer is provided including a strain sensor with a substantially linear configuration. The strain sensor is mounted on a transducer such that the strain sensor extends laterally across the transducer. The transducer has a base and a plurality of flaps joined at a first end to the base and supporting the strain sensor at a second end. The flaps translate acceleration in a predefined direction to strain in the strain sensor. Further embodiments have flaps defining an interrupted surface with greater height at the center and flaps that have features for enhancing the strain caused by acceleration.

Acceleration strain transducer

An interferometric hydrophone operable for use in surrounding fluid, includes an outer mandrel having an interior open to the surrounding fluid. A sensing optical fiber is wound on the exterior of the outer mandrel. An inner mandrel is positioned in the interior of the outer mandrel. A chamber defined between the inner mandrel and outer mandrel is in communication with the surrounding fluid. The inner mandrel has a sealed gas filled interior. Compression and expansion of the inner mandrel results in compression and expansion of the outer mandrel.

Enhanced sensitivity pressure tolerant fiber optic hydrophone

A thermally compensated fiber Bragg grating package is used with a fiber optic sensor. The package includes a Bragg grating mount connected at each end of a sensor mandrel. An optical fiber is wound around the sensor mandrel and a fiber portion having a Bragg grating therein is wound onto the mount. The mount is made of a rigid material having a negative coefficient of thermal expansion to minimize thermally induced spectral shifts. One example of the material includes zirconium tungstate. A coating material can be used to further adhere the optical fiber to the sensor mandrel and/or to the mount. The mount preferably includes a ramped groove to provide for a smooth transition from the sensor mandrel to the mount.

Thermally compensated fiber bragg grating mount

An interferometric hydrophone is disclosed that comprises a first mandrel defining an interior that is open to surrounding fluid. A sensing optical fiber is wound upon the first mandrel. A second mandrel is positioned in surrounding relationship with respect to the first mandrel. The first and second mandrels define a first chamber therebetween. A case encloses the first and second mandrels and first chamber. The cylindrical case and the second cylindrical mandrel define a second chamber therebetween, which is sealed and filled with gas or vacuum.

Pressure tolerant fiber optic hydrophone

The present invention relates to a fiber optic sensing device having utility as a roll sensor and/or a pitch sensor. The sensing device comprises at least one optical fiber supported in a structure, a movable mass supported within the structure, and at least one detector for detecting changes in tension in the at least one optical fiber due to movement of the movable mass. In the sensor of the present invention, the optical fiber(s) are the only deformable structures, thus maximizing sensitivity.

Fiber optic pitch or roll sensor

The present invention relates to a system for sensing the curvature of a towed hydrophone array and a curvature sensor used in the system. The system has at least two curvature sensors positioned along the length of the array. Each of the curvature sensors comprises a bend member which bends as the array bends, at least one optical fiber within the bend member, and at least one detection device embedded within the at least one optical fiber to detect a change in the strain in the at least one optical fiber.

Fiber optic curvature sensor for towed hydrophone arrays

A system for digitally demodulating optical hydrophone signals is provided. The system includes an optical hydrophone connected to an analog-to-digital converter and further connected to a digital signal processor. Within the digital signal processor, a demodulator is calibrated by a preferred automatic calibration circuit such that mixer frequencies are coherently mixed with the incoming acoustic signals received by the hydrophone. The automatic calibration circuit preferably determines an extreme case of phase offset by following a programmable routine including a series of tests. After the extreme case is detected, the precise phase calibration is known and provided to the demodulator mixer tables. The automatic calibration circuit can be utilized for automatic calibrations of multisensor systems containing large numbers of hydrophones.

Digital signal demodulator calibration system and method for optical hydrophones

The present invention relates to a sensor interrogation system which comprises an optical fiber, at least one sensor containing first and second fiber lasers attached to the optical fiber with the first fiber laser being located spectrally at a first wavelength and the second fiber laser being located spectrally at a second wavelength different from the first wavelength, a pump laser for causing light to travel down the optical fiber so as to cause each of the fiber lasers to lase at its distinct wavelength and generate a distinct laser signal representative of the distinct wavelength, at least one filter for receiving the laser signals generated by the first and second lasers and for transmitting the laser signals from the first and second lasers within a wavelength band, and first and second scanning Fabry-Perot spectrum analyzers for receiving the laser signals for determining the wavelength difference between said fiber lasers.

Multiplexed fiber laser sensor system

An interlink for connecting hydrophone elements to allow a single sensing ber to transition from a first hydrophone element, across the interlink, to a second hydrophone element. The interlink satisfies the dual objective of protecting the sensing fiber during handling system stresses, while desensitizing the sensing fiber along the interlink during operational periods. The interlink has a first end connected to the first hydrophone element, and a second end connected to the second hydrophone element. Between the interlink ends is at least one turn, and the distance traveled along the interlink turns is greater than the linear distance between the interlink ends. The interlink contains a groove that traverses the entire interlink length. Sensing fiber is wound off the first hydrophone element, into the interlink groove that follows the interlink turns, and onto the second hydrophone element. The turns allow the interlink to expand as desired, but the interlink design and material must be chosen to provide sufficient elasticity to return to original form. The sensing fiber may be epoxied to the interlink for greater connectivity.

Interlink for spatially extended hydrophones

An interlink for connecting hydrophone elements that allows a single sens fiber to transition from a first hydrophone element, across the interlink, to a second hydrophone element, while providing a secure connection between hydrophone elements without the disadvantages of mechanical resonances produced by a rigid interlink material. The interlink has a first end connected to a first hydrophone element, and a second end connected to a second hydrophone element. The interlink may be composed entirely of open cell foam, or a more rigid structure that is covered by open cell foam. Sensing fiber transitions from a first hydrophone element, onto the foam interlink, and thence onto a second hydrophone element, with only a change in winding angle. The sensing fiber is not susceptible to a rigid interlink structure and undesirable mechanical resonances.

Reduced mechanical coupling interlink for spatially extended hydrophones

A hydrophone interlink that connects hydrophone elements and allows a sin sensing fiber to transition between hydrophone elements. The interlink has an outer-structure and a contained element. The outer-structure connects the hydrophone elements and has at least one turn such that the distance traveled along the turns exceeds the linear distance between hydrophone elements. The outer-structure material and shape allow temporary interlink stretching and compression during passes through handling sheaves, with memory to allow the interlink to return to its original shape. The outer-structure contains a groove on either end to transition the sensing fiber between the hydrophone elements and the contained element. The contained element is open cell foam that fills the hollow core of the outer-structure. The sensing fiber transitions from a first hydrophone element to immediately enter the feed at the interlink first outer-structure end, whereupon the fiber transitions to the open cell foam and follows the interlink outer-structure structure while remaining on the foam.

Semi-rigid low-noise interlink for spatially extended hydrophones

A device for providing a controlled back-reflection of a preselected port of incident fiber-guided light while minimizing the affect to light continuing down the fiber. The back-reflected light couples to the reverse traveling fiber mode with minimal loss. These devices are used as reflectors in a pulse sampled fiber optic hydrophone array.

Continuous fiber pulse reflecting means

There is presented a fiber-optic connector and a method of making same. The onnector comprises a plurality of ferrules, each of the ferrules having extending centrally therethrough a single optical fiber. The connector further includes structure abutting at least a portion of the ferrules for exercising a radially compressive force on the ferrules for urging the ferrules into a configuration in which said ferrules are coparallel and nested so as to form a stable bundle which in transverse section is substantially axisymmetrical, and retaining the ferrules in the configuration. The connector still further includes alignment structure for angular positioning of said ferrules in said connector in said transverse section about a nominal longitudinal axis of said bundle for registry of the connector with a second connector of complementary configuration.

Growing community of inventors

Wakefield, RI, United States of America

Gregory H Ames