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公开(公告)号：GB2227834A
公开(公告)日：1990-08-08
申请号：GB8927540
申请日：1989-12-06
Applicant: LITTON SYSTEMS INC
Inventor： PAVLATH GEORGE A
Abstract: A closed loop fiber optic rotation sensing system prevents the occurrence of instabilities in its feedback signal by modulating the counterpropagating waves with a reference signal and demodulating an electrical signal indicative of the phase difference of two counterpropagating waves with the reference signal. The modulating means is driven to null the phase difference between the counterpropagating waves, and the feedback signal is adjusted to prevent instability. The counterpropagating waves may be either phase modulated or shifted in frequency. The means for modulating the counterpropagating waves may comprise a fiber optic frequency shifter connected to the fiber optic sensing coil and means for applying the reference signal to the frequency shifter. The feedback signal is adjusted with either a pseudo-random or a periodic signal having a zero mean value to prevent instability.
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公开(公告)号：DE3929999A1
公开(公告)日：1990-04-19
申请号：DE3929999
申请日：1989-09-08
Applicant: LITTON SYSTEMS INC
Inventor： PAVLATH GEORGE A
Abstract: Devices and methods for use in integrated optics waveguide circuits containing Y-junctions are presented for intercepting and either absorbing or otherwise removing radiation which has leaked into the substrate in order that such leaked radiation cannot re-enter the waveguide circuit and cause signal errors.
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公开(公告)号：CA1249743A
公开(公告)日：1989-02-07
申请号：CA475915
申请日：1985-03-07
Applicant: LITTON SYSTEMS INC
Inventor： PAVLATH GEORGE A
Abstract: FIBER OPTIC FREQUENCY SHIFTER This invention relates to fiber optic frequency shifters for producing optical signals of a desired frequency range for input to a device such as an optical rotation sensing system. The rotating birefringence is created in a length of fiber optic material, which has the effect of a rotating half-wave plate upon an input optical signal. The length of fiber optic material may have a jacket of either an electrostrictive or a magnetostrictive material formed thereon such that application of an appropriate field to the jacket compresses the enclosed fiber to induce birefringence therein by means of the photoelastic effect. A half-coupler having a block of electro-optically active birefringent material adjacent the interaction region combined with an electrode configuration and circuitry for producing a rotating electric field in the block also produces a rotating half-wave plate frequency shifter. The evanescent field of light propagating in the optical fiber interacts with the rotating birefringence and experiences a frequency shift. The invention also includes feedback circuitry for processing the optical output of fiber optic rotating half-wave plates to maintain the intensity of components in the output signal having the carrier frequency below a threshold value.
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公开(公告)号：DE3475113D1
公开(公告)日：1988-12-15
申请号：DE3475113
申请日：1984-12-03
Applicant: LITTON SYSTEMS INC
Inventor： PAVLATH GEORGE A
IPC: G02B5/30 , G02B6/00 , G02B6/024 , G02B6/10 , G02B6/14 , G02B6/26 , G02B6/28 , G02B6/34 , G02B27/28 , G02F1/01
Abstract: This invention provides apparatus and methods for converting a lightwave of an arbitrary polarization propagating in a single mode optical fiber into a wave having a single linear polarization state. A polarization couples light of an undesired polarization out of the fiber, and a photodetector produces an error signal responsive to light coupled from the fiber. Control circuitry processes the error signal to produce control signals which are input to a polarization of light input to the polarizer to null the error signal. With the error signal maintained at a minimum value the light input to the polarizer and, hence, the light output therefrom is a wave having only the desired linear polarization.
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公开(公告)号：CA1235321A
公开(公告)日：1988-04-19
申请号：CA475907
申请日：1985-03-07
Applicant: LITTON SYSTEMS INC
Inventor： PAVLATH GEORGE A
Abstract: STABLE FIBER OPTIC POLARIZER This invention relates to fiber optic apparatus and methods for polarizing light for use in fiber optic devices, such as rotation sensors. A phase grating formed of alternating layers of dielectrics having different indices of refraction is placed adjacent a half coupler that includes a fiber having a cladding thickness which forms an interaction region. The evanescent field of light of a selected polarization interacts with the phase grating to couple out of the fiber while light of a second selected polarization remains in the fiber.
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Patent Agency Ranking
公开(公告)号：CA1231549A
公开(公告)日：1988-01-19
申请号：CA475914
申请日：1985-03-07
Applicant: LITTON SYSTEMS INC
Inventor： PAVLATH GEORGE A
IPC: G01D5/26 , G01D5/353 , G01D21/00 , G01H9/00 , G01J1/02 , G01J9/00 , G01N21/00 , G01R9/00 , G01R33/032 , G02B6/00 , G02B6/28 , G01N21/17
Abstract: PASSIVE SAMPLING INTERFEROMETRIC SENSOR ARRAYS This invention provides a sensor array using a plurality of fiber optic sensors connected between transmit fibers and receive fibers. The laser transmitter supplies pulses to the transmit fiber and fiber optic couplers couple the pulses from the transmit fiber into the fiber optic sensors. The pulses from the laser transmitter may be frequency chirped or frequency stopped to provide passive sampling of interferometric sensors in addition to intensity sensors, or otherwise frequency modulated. Each sensor is configured to respond to changes in a predetermined physical parameter by altering the shape of the pulse input thereto. Fiber optic couplers couple the sensor output signals into the receive fiber for input to a receiver, which converts the optical signals into electrical signals for input to a processer. A timing reference correlates the sensor output pulses with the sensors.
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公开(公告)号：AU567626B2
公开(公告)日：1987-11-26
申请号：AU5022885
申请日：1985-11-21
Applicant: LITTON SYSTEMS INC
Inventor： PAVLATH GEORGE A
Abstract: @ A gyroscope system includes a coherent light source that supplies counterpropagating waves to a sensing loop through a pair of directional couplers. The polarizations of the waves are controlled so that they traverse identical paths before recombining in one of the couplers to form an interference pattern. Rotation of the sensing loop, a phase modulator and a frequency shifter cause phase changes in the counter propagating waves. A detector monitors the interference pattern of the combined waves and provides a signal to the coherent demodulator that controls the phase modulator. The output of the coherent demodulator is input to a servo loop circuit that drives a voltage controlled oscillator. The output of the voltage controlled oscillator is an oscillatory signal having a frequency equal to the shift in frequency that the counter propagating waves experience in traversing the frequency shifter. The feedback circuitry adjusts the frequency shift to null the phase difference between the counterpropagating waves. The frequency shift is linearly related to the frequency of the signal output from the voltage controlled oscillator. Each cycle of the output of the voltage controlled oscillator corresponds to a fixed angular increment of displacement of the sensing loop. The rotation rate of the sensing loop is a function of the frequency shift and transit time of the waves through the sensing loop. The gyroscope system determines rotation rates and angular displacements over a wide dynamic range by measuring the frequency and zero crossings of the oscillatory output of the voltage controlled oscillator.
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公开(公告)号：AU7136387A
公开(公告)日：1987-08-06
申请号：AU7136387
申请日：1987-04-09
Applicant: LITTON SYSTEMS INC
Inventor： PAVLATH GEORGE A
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公开(公告)号：AU557804B2
公开(公告)日：1987-01-08
申请号：AU3988685
申请日：1985-03-15
Applicant: LITTON SYSTEMS INC
Inventor： PAVLATH GEORGE A
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公开(公告)号：BR8502048A
公开(公告)日：1985-12-31
申请号：BR8502048
申请日：1985-04-30
Applicant: LITTON SYSTEMS INC
Inventor： PAVLATH GEORGE A
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