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公开(公告)号：NO20005444A
公开(公告)日：2001-04-30
申请号：NO20005444
申请日：2000-10-27
Applicant: LITTON SYSTEMS INC
Inventor： ROSCIGNO JOHN A , HODGSON CRAIG W , FREDERICK DONALD A , KNAACK WILLIAM C
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公开(公告)号：CA2254251C
公开(公告)日：2001-04-24
申请号：CA2254251
申请日：1998-11-18
Applicant: LITTON SYSTEMS INC
Inventor： HALL DAVID B , BUNN JAMES B , FREDERICK DONALD A , BUNN JAMES S JR
Abstract: The invention is a method for obtaining a measure of the light propagation t ime difference for two light-propagating-media paths. The first step consists of generating two substantially-identical frequency-modulated light waves whereby the frequenc y of the light waves is offset from a reference frequency by a different frequency incremen t for each basic time interval in each of a plurality of groups of three or more basic time interv als. Each frequency increment is the sum of a specified increment and a frequency-modulation-err or increment. The frequency-modulation-error increments associated with the specified incremen ts are independent of each other and unknown. The second step consists of feeding the two light waves into the entry points of two light-propagating-media paths having a light propagation time difference and obtaining a combination light wave by summing the light waves emerging from the exit points of the two light-propagating-media paths. The third step consists of calculatin g an estimated corrected or estimated uncorrected phase measure of the light propagation ti me difference for the two paths for a plurality of groups using only measured properties of the co mbination light wave. 16
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公开(公告)号：CA2199087C
公开(公告)日：2001-02-20
申请号：CA2199087
申请日：1997-03-04
Applicant: LITTON SYSTEMS INC
Inventor： FREDERICK DONALD A , CAPPI JOHN F
Abstract: A fiber optic interferometric sensor for use in a hydrophone system at high pressures includes a reference fiber wrapped around a rigid inner cylinder. A solid layer of compliant material is applied over the reference fiber. The sensing arm of the interferometer is wound over the layer of material applied over the reference fiber. The outer material is sufficiently compliant to provide acoustic sensitivity comparable to that of air-backed hydrophones.
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公开(公告)号：NO20005442D0
公开(公告)日：2000-10-27
申请号：NO20005442
申请日：2000-10-27
Applicant: LITTON SYSTEMS INC
Inventor： FREDERICK DONALD A , CARTER MICHAEL J , FERSHT SAMUEL N , WINSLOW DAVID C
Abstract: A system for sensing subterranean acoustic waves emitted from an acoustic source includes a plurality of laser sources (LS1-LS6), a plurality of subterranean optical sensors (1000), at least one optical detector (D1-D16), and electronics (601). The laser sources each emit light at a different frequency. The subterranean optical sensors are hydrophones (1000) that receive the light and alter the light in response to the acoustic waves. The optical detector (D1-D16) receives the altered light and outputs an electrical signal. The electronics (601) receives the electrical signal and converts it into seismic data format. The hydrophones (1000) are able to operate at pressures of at least 5,000 psi and temperatures of at least 130 degrees Celsius. The hydrophone (1000) may be housed in a cable (1002) having a diameter of less than about 1.5 inches. The hydrophone's sensor preferably includes a reference mandrel (1110), two sensing mandrels (1120), and a telemetry can (1104), all of which are aligned in a coaxial, end-to-end configuration to reduce the profile of the hydrophone (1000). Flexible interlinks (1296) having grooves therein for receiving optical fiber join the mandrels (1110, 1120) together. The reference mandrel (1110) and sensing mandrels (1120) advantageously have hemispherically-shaped endcaps (1264), permitting them to operate at high pressure.
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公开(公告)号：CA2204720C
公开(公告)日：1999-10-26
申请号：CA2204720
申请日：1997-05-07
Applicant: LITTON SYSTEMS INC
Inventor： FREDERICK DONALD A , MANSELL JOHN E , GOLDMAN ROBERT P , MAAS STEVEN J
Abstract: A fiber optic hydrophone is formed as a single interferometer having widely separated interferometer segments formed in each of a pair of optical fibers. The interferometer segments are designed to allow averaging of the effects of local noise sources over a broad area in order to increase the acoustic signal-to-noise ratio. The interferometer segments also allow deployment of the hydrophone around sharp bends. A first optical fiber is formed into a plurality of spatially separated outer coils. A second optical fiber is formed into a plurality of inner coils corresponding to the outer coils. The inner and outer coils are preferably arranged in concentric pairs to form a plurality of sensor segments. A plurality of spacers is arranged such that a spacer is between successive sensor segments. The spacers are formed to guide the outer and inner optical fibers between successive sensor segments such that changes in the physical parameter between the sensor segments produce no phase difference between optical signals guided by the outer and inner fibers. The outer and inner coils are preferably arranged for exposure to the parameter such that changes in the parameter at each sensor segment produce opposite phase changes between the optical signals in the outer coils and the corresponding outer coil.
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Patent Agency Ranking
公开(公告)号：NO985501L
公开(公告)日：1999-05-27
申请号：NO985501
申请日：1998-11-25
Applicant: LITTON SYSTEMS INC
Inventor： HALL DAVID B , FREDERICK DONALD A , BUNN JAMES B , BUNN JR JAMES B
IPC: G01J9/00
Abstract: The invention is a method for obtaining a measure of the light propagation time difference for two light-propagating-media paths. The first step consists of generating two substantially-identical frequency-modulated light waves whereby the frequency of the light waves is offset from a reference frequency by a different frequency increment for each basic time interval in each of a plurality of groups of three or more basic time intervals. Each frequency increment is the sum of a specified increment and a frequency-modulation-error increment. The frequency-modulation-error increments associated with the specified increments are independent of each other and unknown. The second step consists of feeding the two light waves into the entry points of two light-propagating-media paths having a light propagation time difference and obtaining a combination light wave by summing the light waves emerging from the exit points of the two light-propagating-media paths. The third step consists of calculating an estimated corrected or estimated uncorrected phase measure of the light propagation time difference for the two paths for a plurality of groups using only measured properties of the combination light wave.
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公开(公告)号：NO983282L
公开(公告)日：1999-02-01
申请号：NO983282
申请日：1998-07-16
Applicant: LITTON SYSTEMS INC
Inventor： FREDERICK DONALD A , HALL DAVID B
Abstract: A pressure measuring device which utilizes an array of optical, non-acoustic pressure sensors (22) with a laser light source (12) which generates a pulsed light signal into a light transmitting cable (16), wherein the pulsed light signal propagates along the light transmitting cable through the array of optical pressure sensors. A plurality of optical couplers (18) are attached to the light transmitting cable (16) at multiple locations spaced apart from one another in order to branch off at least a portion of the pulsed light each location. Each of the plurality of optical couplers includes a respective optical pressure sensor (22) and a pressure insensitive reflector (26), wherein the branched off portion of the pulsed light signal is transmitted into both the optical pressure sensor (22) and the reflector (26). Each optical pressure sensor (22) reflects a pressure indicating signal back into the optical coupler (18), while the pressure insensitive reflector (26) reflects a reference signal back into the optical coupler. The pressure indicating signal and the reference signal are reflected through the optical coupler (18) into the light transmitting cable as a pair of non-overlapping pulsed signals, which are then retrieved from the light transmitting cable by a signal detector (32) . The retrieved pressure indicating signal is compared with the retrieved reference signal to determine the pressure acting upon the optical pressure sensor.
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公开(公告)号：NO985501D0
公开(公告)日：1998-11-25
申请号：NO985501
申请日：1998-11-25
Applicant: LITTON SYSTEMS INC
Inventor： HALL DAVID B , FREDERICK DONALD A , BUNN JAMES B , BUNN JR JAMES S
Abstract: The invention is a method for obtaining a measure of the light propagation time difference for two light-propagating-media paths. The first step consists of generating two substantially-identical frequency-modulated light waves whereby the frequency of the light waves is offset from a reference frequency by a different frequency increment for each basic time interval in each of a plurality of groups of three or more basic time intervals. Each frequency increment is the sum of a specified increment and a frequency-modulation-error increment. The frequency-modulation-error increments associated with the specified increments are independent of each other and unknown. The second step consists of feeding the two light waves into the entry points of two light-propagating-media paths having a light propagation time difference and obtaining a combination light wave by summing the light waves emerging from the exit points of the two light-propagating-media paths. The third step consists of calculating an estimated corrected or estimated uncorrected phase measure of the light propagation time difference for the two paths for a plurality of groups using only measured properties of the combination light wave.
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公开(公告)号：AU1512197A
公开(公告)日：1997-09-11
申请号：AU1512197
申请日：1997-03-05
Applicant: LITTON SYSTEMS INC
Inventor： FREDERICK DONALD A , CAPPI JOHN F
IPC: G01B9/02 , G01H9/00 , G01V1/18 , G02B6/36 , H04B13/00 , H04R1/44 , H04R23/00 , G01L11/02 , G01B11/22
Abstract: A hydrophone has a fibre optic interferometer with a reference arm (26) formed by a length of optical fibre wound around a rigid mandrel (30) and with constant optical path length, elastic material (42) over the arm, and a concentric sensing arm (24) with a length of optical fibre wound over the material in a coil so that optical path length changes when the hydrophone is exposed to an acoustic field. Optical output signals are passed to a processor to measure acoustic pressure. Preferably, the elastic material is preferably polyurethane, and the sensing arm is encased in further elastic material (44) and spaced from the reference arm. The mandrel is e.g. a solid rod of metal or other rigid material with end flanges, and the reference arm is potted.
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公开(公告)号：NO972783D0
公开(公告)日：1997-06-16
申请号：NO972783
申请日：1997-06-16
Applicant: LITTON SYSTEMS INC
Inventor： FREDERICK DONALD A , GOLDMAN ROBERT P , MAAS STEVEN J , MANSELL JOHN E
IPC: G01H9/00
Abstract: A fiber optic hydrophone (30) is formed as a single interferometer having widely separated interferometer segments (32-35) formed in each of a pair of optical fibers (56-70). The interferometer segments (32-35) are designed to allow averaging of the effects of local noise sources over a broad area in order to increase the acoustic signal-to-noise ratio. The interferometer segments (32-35) also allow deployment of the hydrophone around sharp bends. A first optical fiber (56) is formed into a plurality of spatially separated outer coils (58,90,94). A second optical fiber (70) is formed into a plurality of inner coils (72,92,96) corresponding to the outer coils. The inner (50) and outer coils (72) are preferably arranged in concentric pairs to form a plurality of sensor segments (32-35). A plurality of spacers (40-42) is arranged such that a spacer is between successive sensor segments. The spacers (40-42) are formed to guide the outer (56) and inner (70) optical fibers between successive sensor segments (32-35) such that changes in the physical parameter between the sensor segments (32-35) produce no phase difference between optical signals guided by the outer (56) and inner (70) fibers. The outer (58) and inner coils (70) are preferably arranged for exposure to the parameter such that changes in the parameter at each sensor segment produce opposite phase changes between the optical signals in the outer coils and the corresponding outer coil.
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