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Showing papers on "Ring laser gyroscope published in 1996"


Book ChapterDOI
01 Jan 1996
TL;DR: The ring laser gyro as discussed by the authors is considered one of the most revolutionary twentieth century developments in the aerospace sensor field and has accumulated millions of successful operational flight hours in both military and commercial aircraft.
Abstract: This chapter introduces the ring laser gyro, which is considered one of the most revolutionary twentieth century developments in the aerospace sensor field. It appeared on the scene in the early 1960s and since then has matured as a dominant product in the aerospace industry, having accumulated millions of successful operational flight hours in military and commercial aircraft.

84 citations


Journal ArticleDOI
TL;DR: In this article, a femtosecond ring laser gyroscope is used to measure the frequency coupling between the counter-propagating pulses inside a femto-condron.
Abstract: Frequency coupling between the counter-propagating pulses inside a femtosecond ring laser gyroscope is studied. It is shown that frequency lock-in results from the counter-propagating pulses overlapping at or near a scattering surface. Nonetheless, the absence of lock-in with a scatterer at the pulse crossing point is demonstrated for the special case of symmetric scattering. The decoupling of the counter-propagating pulses makes possible the measurement of non-reciprocal phase differences of 10−5 and index differences of 10−10 over 1 cm. Besides measuring rotations, applications are found in the measurement of small changes in the index of refraction, and electrical transients on the 100 fs time scale.

48 citations


Patent
31 Oct 1996
TL;DR: A backscatter or secondary wave error reducer for an interferometric fiber optic gyroscope having at least one phase modulator for receiving a square wave bias phase modulation signal and a sine wave carrier suppression modulation signal is presented in this paper.
Abstract: A backscatter or secondary wave error reducer for an interferometric fiber optic gyroscope having at least one phase modulator for receiving a square wave bias phase modulation signal and a sine wave carrier suppression modulation signal. The amplitude of the carrier suppression modulation signal is sufficient to greatly reduce the interference between two sets of backscattered or secondary waves of light originating in the Sagnac loop of the gyroscope. Reduction or elimination of the interference of the two sets of secondary waves reduces or eliminates the secondary wave induced rotation rate sensing error. The frequency of the carrier suppression signal is near or equal to an even harmonic of the proper frequency of the Sagnac loop to reduce the sinusoidal or periodic rotation rate sensing error caused by the carrier suppression modulation signal.

21 citations


Patent
Liu Ren-Young1, Ralph A. Bergh1
28 Jun 1996
TL;DR: In this paper, a gyroscope with three fiber optic loops for sensing rates of rotation in three axes orthogonal to one another is described, where the rotation rate signal processing electronics are shared among the three sensing loops.
Abstract: A gyroscope having three fiber optic loops for sensing rates of rotation in three axes orthogonal to one another. The gyroscope has one or two detectors and one source that is shared among the three fiber optic sensing loop subsystems with a special multi-coupler configuration. Also, portions of the rotation rate signal processing electronics, whether an open or closed loop configuration, are shared among the three sensing loops. The gyroscope may be a single mode optical fiber depolarized configuration or a polarization maintaining optical fiber configuration.

19 citations


Patent
08 Feb 1996
TL;DR: In this paper, a diode-pumped solid-state ring laser gyroscope is used for monaxial or triaxial mesurements, and the limitation and stabilisation of the laser mode is achieved by precise matching of the pumping radiation to the mode volume of the ring laser.
Abstract: The invention concerns a diode-pumped solid-state ring laser gyroscope consisting of a diode-pumped solid-state laser made from a doped crystal or glass in the form of a square or cube for monoaxial or triaxial mesurements; limitation and stabilisation of the laser mode is achieved by precise matching of the pumping radiation to the mode volume of the ring laser. Outcoupling of the laser radiation is done by making the light tunnel through a slit to a dielectric plate which is moved by an actuator. Frequency modulation of the signal is done as required by coupling an acoustic wave into the laser medium or by precise spatial modulation of the diode excitation.

15 citations


Proceedings ArticleDOI
12 Nov 1996
TL;DR: In this article, a production, open-loop fiber optic gyroscope was constructed with only two fiber splices and exhibits performance comparable to the conventional minimum configuration, which can be used for land navigation systems.
Abstract: Further cost reduction of the fiber optic gyroscope is necessary to meet the economic requirements of land navigation systems. We have previously concentrated on the reduction of the number of splices and component improvements in the open-loop, minimum configuration. Now we eliminate non-essential components and splices. The source- detector coupler is not part of the Sagnac interferometer, and serves solely to provide isolation between the broadband optical source and the photodetector. Many commercial laser diodes incorporate a back-facet photodetector to monitor laser intensity. The signal returned from the Sagnac interferometer traverses the laser, is received at this photodetector, and can be distinguished from the laser signal by the bias modulation. Configuring a gyro in this manner eliminates a directional coupler and the separate photodetector, as well as up to three fiber splices in an all-fiber gyroscope. A production, open-loop fiber optic gyroscope has been modified to demonstrate this principal. The gyroscope can be constructed with only two fiber splices and exhibits performance comparable to the conventional minimum configuration.

15 citations


Patent
11 Mar 1996
TL;DR: In this article, the bias bias of a multi-oscillator ring-laser gyroscope was induced by gain medium dispersion effects, and the bias was matched through dispersion equalization to produce a zero induced BIAS G.
Abstract: Based upon the equation, BIAS G α (I DE -I COIL )·(V DE -V OFF ), where BIAS G is the bias of a multi-oscillator ring-laser gyroscope (14) as induced by gain medium dispersion effects, I DE is the proper operating coil current, I COIL is the actual coil current, V DE is the proper path length control operating voltage and V OFF is the actual offset voltage, V DE is matched by path length control offset voltage and/or I DE is matched by proper coil current, to produce a zero induced BIAS G . Matching, through dispersion equalization (DE), is effected by use of clockwise (C) and anticlockwise (A) (or counterclockwise) beams traversing paths with a frame (12). The beams are directed to photodetectors (52, 54) and power meters (56, 58).

13 citations


Patent
03 Jun 1996
TL;DR: In this paper, a mirror for a ring laser gyro includes alternating optical quarterwave regions of SiO2 and ZrO2, and of admixtures of these, and the alternating regions have thicknesses suitable for reflecting a laser beam in a ring gyro.
Abstract: A mirror for a ring laser gyro includes alternating optical quarterwave regions of SiO2 and ZrO2, and of admixtures of these. The alternating regions have thicknesses suitable for reflecting a laser beam in a ring laser gyro. A final coating of ZrO2 and SiO2, and of admixtures of these, is constructed so as to be made substantially of ZrO2 at a bottom portion and so as to have gradually increasing SiO2 content so that the top surface comprises substantially pure SiO2 material.

10 citations


Patent
30 Dec 1996
TL;DR: In this paper, a ring laser gyroscope having an alternating Faraday bias includes mode combining apparatus arranged to cause interference between the modes that propagate within the cavity, which produces two signals indicative of the light intensity in the interference pattern of the combined modes.
Abstract: A ring laser gyroscope having an alternating Faraday bias includes mode combining apparatus arranged to cause interference between the modes that propagate within the cavity. Signal separating apparatus separates a signal indicative of rotation of the frame from other components of the combined intensity signal. The signal separating apparatus produces two signals indicative of the light intensity in the interference pattern of the combined modes. These two signals have a 180° phase difference in corresponding components that are dependent upon the geometric bias caused by the non-planar optical path to produce a rotation signal that is independent of the spatially uniform interference fringes caused by the geometric bias.

10 citations


Patent
09 Feb 1996
TL;DR: In this paper, the bias stability of a ring laser gyro was improved by selecting a secondary transverse mode and controlling the path length of the gyro to maintain the selected mode.
Abstract: Apparatus for improving the bias stability of a ring laser gyro by selecting a secondary transverse mode and controlling the path length of the gyro to maintain the selected mode.

8 citations


Proceedings ArticleDOI
22 Apr 1996
TL;DR: In this paper, a very compact triaxial instrument is described, which takes full advantage of the inherent low random walk and high scale factor linearity of the zero-lock ring laser gyro configuration that Litton has developed over the last decade.
Abstract: A very compact triaxial instrument is described, which takes full advantage of the inherent low random walk and high scale factor linearity of the zero-lock ring laser gyro configuration that Litton has developed over the last decade. The triax instrument is based on a rhombic dodecahedral geometry, which can accommodate three nonplanar ring light paths having orthogonal sensing axes. Component count can be considerably reduced by a discharge layout using a single cathode and two anodes to run all three axes with balanced plasma currents. In addition Litton has used its advanced mirror coating technology to develop antireflection coatings at high incidence angles, which have very low loss. This allows us to use a 'reversed' mirror substrate as a Faraday rotator with external magnets, so greatly simplifying the fabrication of a triax device. The resulting instrument is very well suited for the next generation of pointing and tracking applications with a combination of size, random walk, scale factor, resolution and bandwidth requirements beyond the capabilities of any other current technologies.

Journal ArticleDOI
TL;DR: A mode-locked fiber laser gyroscope is reported that uses a distributed-feedback semiconductor laser amplif ier as the gain medium and the pulse interval could be measured with much-improved accuracy as a function of rotation rate.
Abstract: A mode-locked fiber laser gyroscope is reported that uses a distributed-feedback semiconductor laser amplifier as the gain medium. Stable mode-locked optical pulses were obtained without gain competition, and the pulse interval could be measured with much-improved accuracy as a function of rotation rate. The rms noise equivalent rotation rate was measured to be 0.4deg⁡/h.

Journal ArticleDOI
TL;DR: Guidelines for designing a piezoelectric vibratory gyroscope to be used as an angular velocity sensor are given in this paper. But they do not consider the effects of leakage output.
Abstract: Guidelines are given for designing a piezoelectric vibratory gyroscope to be used as an angular velocity sensor. First, a basic equivalent circuit is given and an approximate equation is derived for sensitivity. Based on the equation, guidelines and issues related to improving sensitivity are discussed. The relationship between the output signal and difference in resonance frequencies of the driving and detecting sides is investigated for cases where the angular velocity is either constant or changing sinusoidally with time. The results are then used to determine the resonance frequencies. Furthermore, a design guideline based on an integral equivalent circuit, which has taken the effects of leakage output into consideration, is discussed and an approach is suggested for supporting the gyroscope. Finally, the performances of various gyroscopes are compared and the utility of a piezoelectric gyroscope as an angular velocity sensor is discussed.

Patent
14 Aug 1996
TL;DR: In this paper, a gyroscope has an optical unit (1) in which a resonant cavity (2) is formed which delimits an optical path of polygonal form and encloses a pressurised gas.
Abstract: The method is applied to a gyroscope which has an optical unit (1) in which a resonant cavity (2) is formed which delimits an optical path of polygonal form and which encloses a pressurised gas. A cathode (k1) is lodged in a cathode chamber (4) in communication with the cavity, which contains two anodes (A1,A2). These anodes are arranged to generate in the cavity two discharge zones (Z1,Z2) which produce two counter propagating laser radiation beams which propagate themselves in a loop closed in the cavity using mirrors placed in each angular region of the optical path. To compensate for the dissymmetry in the optical unit caused by the cathodic chamber an equalising chamber (11), opposite to the cathodic chamber, is in communication with the cavity. The equalising chamber is symmetrically arranged w.r.t the cathodic chamber w.r.t a plane, an axis or a centre of symmetry of the optical unit. The chamber can be heated by electro-magnetic induction.

Journal ArticleDOI
TL;DR: In this paper, the effect of the important mirror parameters, optical loss, scatter and transverse Kerr effect, on gyro performance is defined, and explicit expressions, obtained from the literature and supplemented by new calculations, are given for the expected null-shift, random walk, and scale-factor nonlinearity.
Abstract: A ring laser gyroscope biased by a magneto-optic mirror offers a promising alternative to mechanical dither, for applications requiring no dither and able to tolerate lower performance. The effect of the important mirror parameters: optical loss, scatter and transverse Kerr effect, on gyro performance, is defined. Explicit expressions, obtained from the literature and supplemented by new calculations, are given for the expected null-shift, random walk, and scale-factor nonlinearity; numerical values are listed for a typical magnetic mirror, indicating where improvements are required for potential applications.

Proceedings ArticleDOI
27 Nov 1996
TL;DR: In this paper, a distributed optical fiber stress sensor based on a Sagnac ring construction is described, where the amplitude and frequency of the beat signal is measured by two forward-coupled mode beams.
Abstract: This paper describes a novel configuration of a distributed optical fiber stress sensor based on a Sagnac ring construction. The principle of operation is based on the FMCW technique. The intensity and location of a stress applied to the fiber can be determined simultaneously by detecting the amplitude and the frequency of the beat signal which is produced by two forward-coupled mode beams in the Sagnac ring. The system was found to have a spatial resolution of 1 meter in a sensing range of 50 meters.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Journal ArticleDOI
TL;DR: In this article, a prototype open-loop interferometric fiber-optic gyroscope (IFOG) is presented, where the gyro transfer function is transposed from that of a raised cosine to a sine function using AC modulation, giving maximum sensitivity at rest.
Abstract: This technical note describes the design and fabrication of a prototype open-loop interferometric fiber-optic gyroscope (IFOG). The gyro transfer function is transposed from that of a raised-cosine to a sine function using AC modulation, giving maximum sensitivity at rest. Among various signal processing methods, lock-in principle is used to detect the Sagnac phase shift due to rotation. Initial work is done with bulk-optic components. Finally, all-fiber gyroscope is built using laser diode (1300 nm), PINFET detector, fiber couplers and PZT phase modulator. An effort is made to develop compact IFOG with sensing coil diameter of 10 cm and signal processing card of size 10 x 6.5 sq cm. The present set-up is able to detect the direction of rotation at a rotation rate of 5 x 10/sup -4/ radian per second. Presently, the performance of the set-up is limited by the difficulty in achieving complete reciprocity.

Proceedings ArticleDOI
TL;DR: In this paper, a high-precision goniometer system with a ring laser gyro (RLG) is described and the key techniques for improving the measuring accuracy are analyzed.
Abstract: This presented paper describes a high-precision goniometer system with a ring laser gyro (RLG). The principle of the goniometer is introduced. The key techniques for improving the measuring accuracy are analyzed. As the central element of the goniometer, RLG is investigated, including its error items, such as scalefactor, bias and random walk coefficient. The experimental results are provided.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Patent
09 Aug 1996
TL;DR: In this paper, the authors use a movable mirror for adjustment of the cavity length of the gyroscope laser. The mirror is moved under the effect of a piezo-electric transducer(8) by memorising, during the emission of the radiation, data representing the voltage or control applied to the transducers just before this emission and using the data to control the transducers just after the emission.
Abstract: Includes a movable mirror for adjustment of the cavity length of the gyroscope laser(1). The mirror is moved under the effect of a piezo-electric transducer(8). The method consists of memorising, during the emission of the radiation, data representing the voltage or control applied to the transducer(8) just before this emission and to use the data to control the transducer(8) just after the emission. The data representing the control of the transducer(8) is the voltage applied to the transducer just before the radiation emission, this voltage is stored in a capacitor(C). The voltage being again applied to the transducer after emission ceases. The time constant of the transducer(8) capacity is increased so that the discharge produced during the radiation emission only results in negligible variation of the transducer(8) capacity and therefore the length of the cavity.

Journal ArticleDOI
TL;DR: The techniques of both the open-loop and closed-loop methods are described in detail, which shows the great advantage of the proposed Gyroscope over the to the conventional interferometric fiber-optical gyroscope (I-FOG).
Abstract: A novel interferometric fiber-optic gyroscope with amplified optical feedback by an Er-doped fiber amplifier (EDFA) is proposed and theoretically investigated (the proposed gyroscope is named the feedback EDFA-FOG, FE-FOG in what follows). The FE-FOG functions like a resonant fiber-optic gyro (R-FOG) because of its multiple utilization of the Sagnac loop; however, it is completely different because a low-coherence light source is used. In addition, the gyro output signal is pulsed because the modulation frequency of the phase modulator placed in the Sagnac loop is selected to match the total round-trip time delay of the light, which includes the Sagnac-loop delay plus that of the feedback loop of the fiber amplifier. The sharpness of the output pulse can be adjusted by both the gain of an EDFA and the modulation depth of the phase modulator. When rotation occurs the peak position of the output pulse is shifted as a result of the Sagnac effect. The resolution of the rotation measurement depends on the sharpness of the output pulse. The techniques of both the open-loop and closed-loop methods are described in detail, which shows the great advantage of the proposed gyroscope over the to the conventional interferometric fiber-optical gyroscope (I-FOG).


Proceedings ArticleDOI
12 Nov 1996
TL;DR: In this paper, the results of experimental investigations of a bidirectional Er-doped fiber ring laser for its output power and the rotation rate dependent beat signal are described and demonstrated by using an AM mode-locked EDF laser.
Abstract: We describe the results of experimental investigations of a bidirectional Er-doped fiber ring laser for its output power and the rotation rate dependent beat signal. Enhanced gyroscope beat signal is demonstrated by using an AM mode- locked Er-doped fiber ring laser.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Proceedings ArticleDOI
21 May 1996
TL;DR: In this paper, a distributed optical fiber stress sensor based on a birefringent fiber Sagnac ring was presented. But the system was found to have a reasonable spatial resolution of 1 meter in a sensing range of 50 meters.
Abstract: This paper describes a new distributed optical fiber stress sensor which consists of a birefringent fiber Sagnac ring and whose principle of operation is based on the FMCW technique. The intensity and the location of a stress applied to the fiber can be determined simultaneously by detecting the amplitude and the frequency of the beat signal which is produced by two forward-coupled mode beams in the Sagnac ring. The system was found to have a reasonable spatial resolution of 1 meter in a sensing range of 50 meters.

Patent
20 Feb 1996
TL;DR: In this paper, a photo isolator and a phase modulator are mounted on a gyro to reduce variation of frequency and improve resolution by mounting a photo isolateator and phase modulators for dampening feed back component causing outside a fibering resonator and returning to the fibering resonance.
Abstract: PURPOSE: To reduce variation of frequency and improve resolution by mounting a photo isolator and a phase modulator for dampening feed back component causing outside a fibering resonator and returning to the fibering resonator. CONSTITUTION: A gyro has two pump lasers 12, 14 propagating oppositely in a fibering resonator 18 and a means for coupling pump laser wave to the resonator 18. A coupler 16 for coupling pump laser supply fibers 20, 22 receiving the pump laser wave and arranged to introduce the wave to forward direction and the resonator 18 is included in the gyro. Laser light beam is coupled with the supply fibers 20, 22 for piling the laser light beam from Brillouin ring laser wave propagating oppositely in the resonator 18 and taken out to the supply fibers 20, 22 through the coupler 16 and propagated to return direction reverse from the forward direction. A waveguide path net for piling up the taken out beam includes a phase modulator 40 and carry wave is restrained and a flux is largely damped in a direction toward the resonator 18.

Book ChapterDOI
01 Jan 1996
TL;DR: In this paper, the authors describe the principle of operation and the main properties of the interferometric fiber optic gyro (IFOG) which has been a principal departure from the well-paved road of spinning mass gyros.
Abstract: This chapter describes the principle of operation and the main properties of the interferometric fiber optic gyro (IFOG) which, along with the ring laser gyro (RLG) introduced in the next chapter, has been a principal departure from the well-paved road of spinning mass gyros. Both are based on a fundamental law of physics, namely, the universal constancy of the speed of light in vacuum underlying relativity. The laser gyro is not really a gyro in the classical Newtonian sense of conservation of momentum, but, it takes advantage of the ‘inertia’ of light as will be explained below. The technology has evolved along two principal paths: The RLG, being a closed-path optical oscillator, is active, while the IFOG, which draws its light energy from an external source, is a passive interferometer.

Proceedings ArticleDOI
13 Feb 1996
TL;DR: In this paper, the authors investigated the mechanism that determines backscattering light from mirrors and diaphragms influence on intensity and frequency difference of the traveling-wave in ring laser.
Abstract: We have investigated the mechanism that determines backscattering light from mirrors and diaphragms influence on intensity and frequency difference of the traveling-wave in ring laser. It is shown, that the connection of the counter waves has diffractional as well as interferention nature and is defined by parameters of the resonator mirrors and diaphragms as well as by their disposition as to the amplifying medium. Using the latter, the methods and the devices that allow us to decrease the influence of the static zone of the waves locking in on the output characteristics in 10 - 20 times have been created. The microprocessor systems for laser gyroscope generation regime support and stabilizing its parameters during exploitation were fulfilled. It is shown experimentally that a laser gyroscope with such systems has a null drift 0.005 degree/hour and a random walk 0.003 degree/sqrt (hour).© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Patent
13 Dec 1996
TL;DR: In this paper, a new concept of gyroscope utilizing self-modulation is introduced in a frame of a solid state ring type laser, which includes a base, a laser pumping source, an active medium, a focussing unit, a detector, a magnet and a cover.
Abstract: A new concept of gyroscope utilizing self-modulation is introduced in a frame of a solid state ring type laser. The inventive solid state ring laser system includes a base, a laser pumping source, an active medium, a focussing unit, a detector, a magnet and a cover, wherein the magnet having an appropriate magnetic field strength to distinguish the direction of rotation and to increase the sensitivity. In the inventive gyroscope, a direct sensing of rotation is made by measuring the self-modulation frequency without complex signal processing by using a frequency counter.

Patent
28 Aug 1996
TL;DR: In this article, a laser gyroscope comprising two ninety degree turning prisms optically connected was constructed, and a non-reciprocal gain layer structure was grown on the hypotenuse face of one prism.
Abstract: A laser gyroscope comprising two ninety degree turning prisms optically connected. A non-reciprocal gain layer structure is grown on the hypotenuse face of one prism.


Patent
12 Mar 1996
TL;DR: In this article, a multiple oscillator ring laser gyroscope with high resolution was used to avoid aliasing by using a chirped sampling frequency and a high velocity filter to sample the output of an angular velocity sensor.
Abstract: PURPOSE: To provide a multiple oscillator ring laser gyro scope with high resolution to avoid aliasing by using a chirped sampling frequency and a high velocity filter to sample the output of an angular velocity sensor. CONSTITUTION: A measured angle θ is input to a gyro scope 22, sampled by using a chirped sampling frequency Fs (velocity) from a sampling frequency modulator 46 and integrated by angular velocity integrator 26. To make the output of the gyro scope 22 zero with a sampler and a quantizer 30, it is quantized with a delay conversion coefficient (1-Z- ). The signal Δθ is input to a high velocity filter 24 and filtrated by a movement averaging filter 32 and then sampled at a velocity Fs for a high velocity N sample integrator 34 by a data sampler 36. The output of the high velocity filter 24, as an increment angle Δθ improved in resolution, is sampled at Fs/N by a sampler 38, resulting in super high resolution.