公开(公告)号：AU556296B2

公开(公告)日：1986-10-30

申请号：AU3208984

申请日：1984-08-20

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.

公开(公告)号：AU4575885A

公开(公告)日：1986-10-09

申请号：AU4575885

申请日：1985-08-05

Applicant: LITTON SYSTEMS INC

Inventor： PAVLATH GEORGE A

IPC: G02B5/30 ,  G02B6/024 ,  G02B6/10 ,  G02B6/28 ,  G02B6/14

公开(公告)号：NO855315L

公开(公告)日：1986-10-02

申请号：NO855315

申请日：1985-12-27

Applicant: LITTON SYSTEMS INC

Inventor： PAVLATH GEORGE A

IPC: H01S3/083 ,  G01C19/64 ,  G01C19/72 ,  G01P9/00 ,  G02F1/01 ,  G01C

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.

公开(公告)号：AU4305185A

公开(公告)日：1986-02-27

申请号：AU4305185

申请日：1985-05-28

Applicant: LITTON SYSTEMS INC

Inventor： PAVLATH GEORGE A

IPC: G02B6/24 ,  G02B6/26 ,  G02B6/28 ,  G02B6/35 ,  G02B6/36 ,  G02B6/38 ,  G02F1/313

Abstract: This invention relates to an electrically switchable fiber optic directional coupler. Two oppositely oriented blocks of an interaction material are placed adjacent the fibers in an evanescent field coupler. Application of an electromagnetic field to the interaction material increases the refractive index of one fiber and decreases the refractive index of the other. The change in refractive indices of the blocks of the interaction material increases the propagation constant of one fiber and decreases that of the other fiber. The coupling of optical signals between the fibers may be varied between zero and 100% by controlling the aplied field to change the propagation constants between values that provide complete cross coupling of light from one fiber into the other and straight through propagation provides an electrically controllable switching action.

公开(公告)号：NO851594A

公开(公告)日：1985-11-26

申请号：NO851594

申请日：1985-04-22

Applicant: LITTON SYSTEMS INC

Inventor： PAVLATH GEORGE A

IPC: G01P9/00 ,  G01C19/64 ,  G01C19/72 ,  G02B6/12 ,  G02F1/01 ,  G02F2/02 ,  G01C ,  G02B

CPC classification number: G02F1/0134 ,  G01C19/721 ,  Y10S359/90

公开(公告)号：DE69808694T2

公开(公告)日：2003-02-27

申请号：DE69808694

申请日：1998-05-20

Applicant: LITTON SYSTEMS INC

Inventor： PAVLATH GEORGE A

IPC: G02B6/02 ,  G02B6/24 ,  H01S3/06 ,  H01S3/17

Abstract: Attenuation of an optical signal (25) at the end (43) of an optical fiber (21) is achieved by positioning a high absorption region (24) at the end of the fiber. A first embodiment teaches a highly doped annulus (24) within a tapered end (5) of the fiber. The highly doped annulus about the light transmitting core (22) serves to absorb light at the end of the fiber. The light transmitting core of the fiber is reduced in diameter due to the tapering, causing the field of light to expand beyond the core. The highly doped annulus is in proximity to the core due to the tapering. The annulus, which is preferably heavily doped with a rare earth such as erbium, absorbs the escaping light in sufficient quantities, both in the initial pass through the tapered region and again upon reflection of the light at the end of the tapered region, such that the attenuation of the reflected light is within acceptable limits without regard to the condition of the fiber's end surface.

公开(公告)号：DE4000800C2

公开(公告)日：1996-03-28

申请号：DE4000800

申请日：1990-01-12

Applicant: LITTON SYSTEMS INC

Inventor： PAVLATH GEORGE A

IPC: G01B9/02 ,  G01C19/72 ,  G01P9/00 ,  G01P3/36

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.

公开(公告)号：CA2003945C

公开(公告)日：1993-06-29

申请号：CA2003945

申请日：1989-11-27

Applicant: LITTON SYSTEMS INC

Inventor： PAVLATH GEORGE A

IPC: G01B9/02 ,  G01C19/72 ,  H01S3/083

Abstract: FIBER OPTIC ROTATION SENSING SYSTEM AND METHOD FOR BIASING A FEEDBACK SIGNAL OUTSIDE A REGION OF INSTABILITY 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.

公开(公告)号：CA1319542C

公开(公告)日：1993-06-29

申请号：CA540817

申请日：1987-06-29

Applicant: LITTON SYSTEMS INC

Inventor： PAVLATH GEORGE A

IPC: G01C19/64 ,  G01C19/72 ,  G01P9/00

Abstract: DUAL FIBER OPTIC GYROSCOPE A fiber optic gyroscope includes a sensing coil formed of ordinary single mode fiber and a module including polarization maintaining optical fibers. A clockwise beam guided by a polarization maintaining fiber passes through a polarizer before being input to the sensing coil. The polarization module includes means for providing an an unpolarized counterclockwise beam to the sensing coil and means for phase modulating a predetermined polarization component. The module also depolarizes the clockwise beam after it has traversed the sensing coil. The clockwise and counterclockwise waves are both unpolarized when they combine in an optical coupler before impinging upon a detector that produces an electrical signal indicative of changes in the interference pattern to indicate rotation of the coil.

公开(公告)号：CA1301894C

公开(公告)日：1992-05-26

申请号：CA590699

申请日：1989-02-10

Applicant: LITTON SYSTEMS INC

Inventor： PAVLATH GEORGE A

IPC: G01C19/72 ,  G01C19/64

Abstract: . APPARATUS AND METHOD FOR PHASE MODULATING OPTICAL SIGNALS IN A FIBER OPTIC ROTATION SENSOR The operating point of a fiber optic rotation sensor is shifted to obtain an increased sensitivity in the measurement of the Sagnac phase shift between counterpropagating beams in a sensing loop. The two counterpropagating optical waves are mixed for detecting interference of the waves to indicate the phase difference between them. The phase of the waves is modulated in accordance with a periodic function having a frequency equal to fs = where t is the transit time for an optical wave in the sensing loop. The interference pattern of the two waves is periodically sampled at a frequency equal to the modulation frequency.