Abstract: The field of the invention is that of solid-state laser gyros. One of the major problems inherent in this technology is that the optical cavity of this type of laser is by its nature highly unstable. To reduce this instability, the invention proposes to introduce controlled optical losses into the cavity that depend on the polarization direction by placing in the cavity an optical assembly comprising a polarizing element, a first element exhibiting a reciprocal effect that acts on the polarization of the wave and a second element exhibiting a nonreciprocal effect that also acts on the polarization of the wave, at least one of these two effects being variable, and to electronically slave these losses to the difference in intensity between the counterpropagating modes. Several devices are described that implement either fixed reciprocal effects combined with variable nonreciprocal effects, or vice versa.

Abstract: A new high-performance, compact microgyroscope is implemented using a microlaser such as a microsphere laser or a microdisc laser that can be easily reduced in size. The microgyroscope includes a pumping unit for inputting pumping light for optical pumping, at least one microsphere or microdisc for oscillating a laser beam by performing optical pumping using light received from the pumping unit, an output coupler for receiving the oscillated laser beam from the microsphere or microdisc, and a photodetector for calculating a beat frequency due to interference between beams output from the output coupler to measure rotation. The pumping unit and the output coupler are constructed using a tapered optical fiber.

Abstract: A semiconductor ring laser gyro comprises: A semiconductor ring laser gyro comprises: a closed optical circuit, the closed optical circuit comprising a plurality of reflection members; a semiconductor laser element disposed in the closed optical circuit and emitting laser light from each end thereof, the semiconductor laser element having a luminous region with a width that is at least ten times as large as a wavelength of the laser light; and a pair of optical systems for forming a shape of the laser light emitted from each end of the semiconductor laser element.

Abstract: A method and apparatus for reducing the thermal induced errors in an IFOG system. The apparatus including a highly thermally conductive material configured to encapsulate a waveguide of an interferometric fiber optic gyroscope (IFOG). The highly thermally conductive material more evenly distributes thermal changes encountered by a sensing coil of the IFOG thereby substantially reducing errors in the IFOG system.

Abstract: Proposed optical device is based on counter-propagating optical fields within at least one nested waveguide-cavity loop, where the part of the waveguide loop is fold into the external waveguide loop. The nesting is performed using at least one waveguide crossing section. The invention may be used in Sagnac interferometer to measure various physical parameters, including rotation rate, electric current and mechanical perturbations. The invention also addressed a measurement method of such non-reciprocal parameters of interest. Optionally, the cavity includes a gain element, and the device operation may be switched discretely or gradually between passive and active regimes, thus changing the measurement characteristics.

Abstract: Interference in a rotation rate detector signal of an interferometric fiber-optic gyroscope from a bias phase modulator signal may be reduced or substantially avoided by transmitting one or more off-frequency signals having a frequency other than the eigenfrequency of the gyroscope towards a bias phase modulator, generating the bias phase modulator signal having a frequency substantially equal to the eigenfrequency of the gyroscope, and driving the bias phase modulator with the bias phase modulator signal.

Abstract: An fiber-optic interferometric rotation sensor device has a laser source combined with an optical fiber. These are configured to cause interference between a beam from the laser source and a beam coming from the optical fiber. The laser source includes an optical cavity having a gain lasing medium. The sensor device includes, along the path of the beam output by the laser cavity, a beam splitter device associated with a mirror, wherein the beam split off from the beam output by the laser cavity is sent into one of the ends of the optical fiber and directed from the other end toward the gain lasing medium to form a nonlinear mirror. The splitter device is followed by a detector.

Abstract: A fiber optic gyroscope including an optical circulator in the path of said first and second beams for providing polarized first and second beams of identical polarization. A phase modulator couples the first and second beams to the first and second end respectively of the fiber loop, and couples for receiving the return first and second beams from the second and first ends respectively of the fiber loop. First and second photodiodes are coupled to the optical circulator for receiving the optical signal from the first and second return beams.

Abstract: Methods and apparatus are provided for reducing output noise of optical gyros. The apparatus includes a sensing system for circulating counter-propagating light beams and producing an output light beam, a coupler having multiple ports and supplying an input light beam to the sensing system, a first detector coupled to the coupler for detecting a rotation rate based on the output light beam, a second detector coupled to the coupler for detecting noise based on the input light beam, and at least one optical device coupled to one of the ports of the coupler. The optical device is configured to reduce a spectral mismatch between the input light beam received by the second detector and the output light beam received by the first detector.

Abstract: An integrated module for a fiber optic gyroscope system includes a fiber optic sensing coil arranged to sense rotations about a sensing axis via the Sagnac effect comprises a substrate, an optical waveguide formed on the substrate, a light source comprising a doped waveguide formed on the substrate. The light source and the optical waveguide are arranged to produce counterpropagating light waves in the fiber optic sensing coil. The light source may be formed as a rare earth doped polymer waveguide or as a rare earth doped glass waveguide.

Abstract: This application describes designs, implementations, and techniques for controlling propagation mode or modes of light in a common optical path, which may include one or more waveguides, to sense a sample.

Abstract: According to one aspect of the present invention, a method for calibrating a fiber optic gyroscope is provided. A method is provided for calibrating a fiber optic gyroscope. First and second portions of light from a first light source are propagated through a fiber optic line in respective first and second directions. A first voltage that causes a predetermined phase shift between the first and second portions of the light from the first light source is calculated. First and second portions of light from a second light source are propagated through the fiber optic line in the respective first and second directions. A second voltage that causes the predetermined phase shift between the first and second portions of the light from the second light is calculated. A difference between the first voltage and the second voltage is then calculated.

Abstract: Systems and methods for performing vibration error suppression in a fiber optic gyro sensor. An example system includes a light source, a sensing loop assembly, a photo detector, and a processing component. The light source generates a light signal that is then modulated by the sensing loop assembly and applied to a fiber optic coil in the assembly. The photo detector receives a modulated light signal that is an output of the sensing loop assembly (coil) and generates an analog signal. The processing component converts the generated analog signal into a modulated digital signal, determines an average of the modulated digital signal, determines an intensity modulation amplitude based on the determined average of the modulated digital signal, and re-scales the modulated digital phase signal based on the determined intensity modulation amplitude.

Abstract: Methods and apparatus provide for birefringent waveguides suitable for optical systems exhibiting polarization dependence such as interferometer sensors including Sagnac interferometric fiber optic gyroscopes (IFOG). The waveguides, for some embodiments, may offer single polarization performance over lengths of about a kilometer or more due to polarization dependent attenuation. According to some embodiments, the waveguides incorporate a pure silica core for resistance to radiation-induced attenuation (RIA).

Abstract: A method and device are presented for use in determining a rate of rotation of an object. The device comprises a light guide comprising an arrangement of a plurality of coupled optical resonators arranged along a curvilinear optical path. This allows for determining a change in at least one of the light phase and frequency affected by the light propagation through the curvilinear path during the device rotation, said change being indicative of the rotation rate of the light guide.

Abstract: This invention discloses to a type of fiber gas lasers and fiber ring laser gyroscopes based on these fiber gas lasers. The fiber gas lasers comprise of excitation gases, optical resonator and excitation source, etc. The optical resonator is made by connecting two selected arms of a single mode fiber coupler to the two ends of hollow-core fiber to form a ring resonator. The hollow-core of the fiber is filled with excitation gases to act as gain medium. The fiber laser is simple to construct, lower cost, and has adjustable size and good amplification performance. The fiber ring laser gyroscopes based on this novel type of gas lasers can be applied on robotics, automobile navigation, etc.

Abstract: A technique for operating an interferometric fiber optic gyroscope (IFOG) exploits digital intensity suppression to improve gyro performance. The IFOG includes an optical portion configured to provide an optical signal, a photodetector configured to convert the optical signal to a photodetector output signal and an electronics portion configured to provide a gyro output based upon the photodetector output signal. The photodetector output signal is quantized to create a digitized representation of the optical signal. An intensity scaling value is determined based upon the digital representation of the optical signal, and the photodetector output signal is adjusted based upon the intensity scaling value to create a scaled photodetector output signal. The digital representation of the optical signal is then digitally reconstructed as a function of the scaled photodetector output signal and the intensity scaling value.

Abstract: In accordance with at least one embodiment of the present invention, a system includes a gyroscope and a flight vehicle operatively connected to the gyroscope. The gyroscope includes a length of fiber optic cable arranged in loop and configured to surround an interior loop region. The gyroscope further includes a control unit configured to send and receive light through the fiber optic cable and measure a rate of rotation of the gyroscope. A portion of the flight vehicle is located within the interior loop region.

Abstract: According to one aspect of the present invention, a fiber optic gyroscope is provided. A substrate has a silicon layer formed over an insulating layer, a waveguide formed within the silicon layer having a main optical channel, first and second splitters coupled at opposing ends of the main optical channel, first and second segments coupled to the first splitter, and third and fourth segments coupled to the second splitter. A fiber optic coil has a first end coupled to third segment of the waveguide and a second end coupled to the fourth segment of the waveguide. A light source is coupled to the first segment of the waveguide to emit light into the waveguide. A photo-detector coupled to the second segment of the waveguide to capture at least some the light and detect interference therebetween.

Abstract: A method for determination of/compensation for the bias/random walk errors induced by the light source in fiber-optic Sagnac interferometers employing a modulation method for stochastically independent shifting of the operating point to the points of highest sensitivity. A reference beam is output from the light beam emitted from the light source of the interferometer and passed to the fiber coil to produce a proportional reference intensity signal. Such signal is demodulated with the demodulation pattern of the rotation rate control loop to demodulate the rotation rate intensity signal (proportional to rotation rate). The demodulated reference intensity signal measures the bias/random walk errors to be determined. Demodulation of the reference intensity signal is simultaneous with that of the rotation rate intensity signal so that components of the reference and rotation rate intensity signals (each resulting from light components simultaneously emitted from the light source) are identically demodulated.

Abstract: A method for forming an interferometer is disclosed. The method involves forming a ring interferometer and a fiber optic gyroscope on a single semiconductor substrate.

Abstract: A system and method for recovering lost data in an electronic gyroscope sensor system are disclosed, which use a linear adaptive predictive technique for determining what data was lost by the gyroscope sensor system during a disruptive interval involved. More precisely, a system and method for recovering lost data in a fiber optic gyroscope sensor system are disclosed, which continuously predicts “N” future samples of sensor data and stores the last known good “L” sensor values and the calculated “L” coefficients in a non-volatile memory. In the event that the fiber optic gyroscope sensor system becomes inoperable (e.g., due to a temporary loss of power to the gyroscope or other cause of electromechanical failure), and once the gyroscope sensor system resumes operation (e.g., power is reapplied), the stored “L” coefficients are retrieved from the non-volatile memory, and are used to calculate the data lost by the fiber optic gyroscope sensor system during the inoperative period involved.

Abstract: An optical phase modulator comprising a plurality of non-polarizing waveguides having a layered stack including a core between at least one layer of cladding material, wherein the core is constructed of electro-optic material(s), wherein the layers of cladding materials having lower indices of refraction than the core for guided mode, wherein the layer of cladding material having higher indices of refraction than the core for non-guided mode, a substrate dimensioned and configured to integrate a plurality of optical components, wherein the optical components include a plurality of non-polarizing waveguide(s), a waveguide having a non-polarizing non-modulating region and a non-polarizing modulating region, coupler/splitter(s), electrode(s), a waveguide configuration including a first non-polarizing waveguide, a second polarizing waveguide and a third waveguide, and at least two optical fiber pigtails where one is coupled to a second and third waveguide.

Abstract: A fiber optic gyroscope (FOG) includes a sensing coil with a particular magnetic sensitivity magnitude and direction with respect to the geometric axis of the sensing coil. The FOG also includes a plurality of magnetic compensators. Each magnetic compensator is fabricated so as to have a particular magnetic sensitivity magnitude and direction, the magnitude being comparable to that of the sensing coil, with large tolerances relative to the magnitude and direction. The compensators are positioned relative to one another and to the sensing coil such that the combined magnetic sensitivities of the compensators cancel the magnetic sensitivity of the sensing coil.

Abstract: A polarization-maintaining optical fiber which exhibits an excellent polarization-maintaining performance and significantly low splice loss when spliced with a polarization-maintaining optical fiber having a cladding 125 ?m in diameter even if the polarization-maintaining optical fiber has a small-diameter cladding of about 80 ?m. The polarization-maintaining optical fiber includes a core, a pair of stress-applying parts provided radially outwardly with respect to the core, and a cladding which surrounds the core and the stress-applying parts. With a diameter D of the stress-applying parts between 21 ?m and 32 ?m, a distance R between the stress-applying parts between 6 ?m and 17 ?m, and a relative refractive index difference ? between 0.3% to 0.5%, a sufficiently large mode field diameter (MFD) is obtained; thus splice loss can be reduced.

Abstract: A method for regulating the operating frequency of a closed loop fiber optic gyroscope. The demodulated output signal of a detector, as actual signal, is applied to the input of a main controller and, via a gating filter, to a VCO that determines the system clock of the FOG. An additional modulation signal, as analog signal is fed to separate phase correction electrodes that are formed together with the electrodes of a digital phase modulator in an integrated optical chip.

Abstract: Fiber optic gyroscopes having integrated power measurement capabilities and related methods and apparatus. More particularly, fiber optic gyroscopes having an integrated method for determining the optical power by applying an electronic stimulated rate internal to the closed loop digital electronics of the gyroscopes and monitoring the counts out per second (COPS) using each gyroscope's counts output signal. Knowing a COPS value, the optical power can be determined by dividing a constant K by the COPS value, i.e. Optical Power=K/COPS. The value of K is specific to each gyroscope, and can be calculated or measured.

Abstract: Fiber optic gyroscope architectures that incorporate both (i) a WDM-based wavelength control and (ii) a wavelength reference based on a narrowband fiber Bragg grating (FBG), with the latter component providing significant improvement in the stability of the wavelength reference by calibrating out wavelength errors associated with a WDM-based wavelength control scheme.

Abstract: An optical return loss detecting device is provided for measuring the optical return loss (ORL) of a device under test (DUT). The detecting device comprises a light source, an optical isolator connected to the light source for preventing reflected light by the DUT entering the light source, a first optical coupler connected to the isolator, a second optical coupler connected to the first coupler and the DUT respectively, and a module communicating with the second coupler for performing test and calculation functions thereof.

Abstract: The method according to the invention for preventing bias errors as a result of synchronous interference in fiber-optic gyroscopes (FOGs) provides for an additional signal ?E, which is periodical at the sampling clock rate and corresponds, for example, to a synchronous interference signal input to be added in the form of additional modulation to the modulation signal for a phase modulator within an MIOC. The demodulated detector signal from the FOG is preferably then correlated with the additional modulation, that is to say which is multiplied by the additional modulation and is added to it. The added-up signal, which is dependent on the error matching, controls a VCO (12) which readjusts the operating frequency of the FOG until the correlation tends to zero. The method can be used not only for phase ramp modulation but also for FOGs which operates using a random phase modulation method.

Abstract: A light source 10 is connected sequentially through a single mode optical fiber and a coupler to one end of a polarization maintaining optical fiber, the other end of which is connected to an optical waveguide of an optical integrated circuit having a branching optical waveguide which has a polarizing function with the polarization axis of the optical fiber being coincident with the direction of the TE mode in the optical waveguide. One end of each of polarization maintaining optical fibers are connected to two other ends of the optical waveguide with the polarization axis of the optical fibers being coincident with the direction of the TE mode in the optical waveguide. The other ends of the optical fibers are connected to one end of each of polarization maintaining optical fibers with their polarization axis displaced by an angle of 45° from each other. The other ends of the optical fibers are connected to the opposite ends of a single mode fiber optic coil.

Abstract: A photonic crystal interferometric optical gyroscope system including a light source for providing a primary beam of light, a photonic crystal sensing coil having a rotational axis, and a beam controlling device configured to split the primary beam into first and second counter-propagating beams in the photonic crystal sensing coil and configured to direct return of the counter-propagating beams wherein the power of the returning counter-propagating beams represents the phase shift between the counter-propagating beams and is indicative of the rate of rotation of the coil about the rotational axis.

Abstract: A spool (12), for supporting a fiber optic coil (14) and a shield (118) surrounding the spool and fiber optic coil, includes a centrally placed, bolt-receiving opening (29). The shield includes a lower shield portion (20), which supports the spool and the fiber optic coil, and an upper shield portion (118). The upper and lower shield portions are arranged to interfit with each other at an interface (121). The upper shield portion has a centrally placed fastener-receiving opening (124) which is alignable with the centrally placed, bolt-receiving opening of the spool. A bolt (156) has a head (156a), a shank (156b) and a threaded end (156c, 156d). The bolt head is engageable with the spool through intermediary structure (48). The shank is insertable through the centrally placed, bolt-receiving opening (29) and the lower shield opening (26), for radially centering the assembly and its components. The threaded end is disposed to engage a threaded opening (68) in a gyroscope assembly support (66).

Abstract: A method for increasing the long-term operational reliability of a fiber optic interferometer. Noise in a detector output signal is set to a desired value by correcting the detector light power. Detector light power is corrected by varying a light source current of a light source of the interferometer. A change in the light source power results. It is thereby possible to increase both the reliability and useful life of the interferometer.

Abstract: In an apparatus for inspecting and evaluating fiber material, for example a sliver or fleece, an opto-electronic system, is provided across the width of a textile machine and scans the moving fiber material and converts the measured values into electronic signals. The system is in communication with an image-evaluating device which evaluates the raw data of the system. In order to produce an apparatus that is space-saving and permits a lower overall height combined with at least the same image quality, three or more imaging devices are provided side by side and, in relation to the unit of width, the number of cameras increases as the distance between objective and fiber sliver decreases.

Abstract: The invention relates to the field of devices for measuring a nonreciprocal effect and especially to the field of fiber-optic gyrometers. Disclosed a device for measuring a nonreciprocal effect comprising a light source, a monomode spatial filter, a Sagnac ring having two branches, a light splitter, and a light detector. The splitter is a polarization splitter. The filter is nonpolarizing. The detector includes a system for analyzing the polarization state. The light splitter devides the light over branches of the ring. The invention can be applied to other devices for measuring a nonreciprocal effect, especially fiber-optic magnetometers.

Abstract: In a GPS-supported inertial attitude and heading reference system equipped with a Kalman correction filter and a multiple axis fiber optic gyroscope, the invention provides for only that scale factor error which is determined for the measurement axis (e.g. the vertical axis) with relatively fast motion dynamics to be used as the Kalman filter correction value for the scale factor error correction for all the measurement axes of the FOG to determine and compensate for the scale factor error caused by changes in the wavelength of a common light source. The scale factor error correction is used only with a long time constant.

Abstract: A fiber optic gyroscope includes a light source and a phase modulator coupled to an optical fiber coil. Light from the source is divided into a pair of first light signals that are directed into opposite ends of the coil to counter propagate through the coil and produce corresponding second light signals the relative phases of which are shifted by the modulator. In one embodiment, a waveform generator defines a modulation waveform so that a determined sequence of five or more phase shifts are set between the second light signals, including shifts of zero degrees, +90 degrees, ?90 degrees, +180 degrees and ?180 degrees. The second light signals interfere with one another to define a recombined light signal, and measurement signals corresponding to the intensity of the recombined light signal are obtained for each phase shift in the sequence. A rate of rotation of the coil is determined continuously in accordance with the measurement signals and a given interference function.

Abstract: The present invention relates to a reaction wheel assembly and fiber optic gyro device. The device includes a reaction wheel assembly having a reaction wheel assembly housing, a fiber optic gyro coil integrated with the reaction wheel assembly housing, and a fiber optic gyro electronics integrated with the reaction wheel assembly housing. The fiber optic gyro coil may be wound around the reaction wheel assembly housing. The gyro coil may also be located within the reaction wheel assembly housing.

Abstract: A system for detecting the eigen frequency of a sensing coil in a fiber optic gyro (FOG) that includes a fiber coupler connected to the light source, an integrated optics chip (IOC) capable of modulating light received from the light source via the fiber coupler, a sensing coil in communication with the IOC, a first modulation generator for imparting a first modulation signal to the light, and a photodetector for receiving light returning from the sensing coil that is representative of a rotation rate of the sensing coil. Along with the foregoing there is provided a second modulation generator for imparting a second, preferably sinusoidal, modulation signal to the light, a high-frequency demodulator in communication with a signal produced, at least indirectly, by the photodector, and a low-frequency demodulator in communication with the high-frequency demodulator.

Abstract: A microchip ring trap for cold atoms or neutral molecules consists of a particular multi-layer layout of wires on a microchip. These conductive wires may be produced by photolithography on a substrate (e.g. gold on sapphire). There are four wires crucial to the design, essentially a pair of “two-wire waveguides”. These wires are laid out on concentric circles with the inner and outer most wires on lower level of the chip, and the middle pair of wires on the top layer (the chip surface).

Abstract: The optical sensor contains an optical waveguide (1) with a substrate (104), waveguiding material (105), a cover medium (106) and a waveguide grating structure (101-103). By means of a light source (2), light can be emitted to the waveguide grating structure (101-103) from the substrate side and/or from the cover medium side. (101-103). With means of detection (11), at least two differing light proportions (7-10) radiated from the waveguide (1) can be detected. For carrying out a measurement, the waveguide can be immovably fixed relative to the light source (2) and the means of detection (11). The waveguide grating structure (101-103) itself consists of one or several waveguide grating structure units (101-103), which if so required can be equipped with (bio-)chemo-sensitive layers. The sensor permits the generation of absolute measuring signals.

Abstract: A magnetic shielding system for a fiber optic gyroscope is disclosed. The fiber optic gyroscope may have a sensing coil with a sensing axis. An exemplary magnetic shield may enclose the sensing coil and have a layer including a plurality of pieces connected at a seam. A portion of the seam may be substantially parallel to the sensing axis of the sensing coil. Also, the pieces may be connected together such that each piece has a portion of each of two sides and a wall of the magnetic shield. Additionally, multiple layers having orthogonal seams may be utilized with the magnetic shield.

Abstract: An optical waveguide device used as, for example, a variable optical attenuator or an optical switch includes: a substrate; a Mach-Zehnder interferometer that is provided on the substrate and that includes first and second waveguide sections interposed between a pair of branches; a heater that includes a conductive thin-film formed at a position corresponding to the first waveguide section and that, by emitting heat, heats the first waveguide section and thus causes a phase shift in the optical signal propagated in the first waveguide section; and a resistor connected, in series with the heater, to a power supply which supplies power to the heater. The resistor has a temperature coefficient of resistance that is lower than that of the heater. The waveguide device is preferably formed as a device having a silica glass waveguide structure.

Abstract: A glass base material, which is a base material of an optical fiber, comprising: a core; and a clad surrounding the core; wherein: a rate of change in a relative-refractive-index-difference between the core and the clad in a longitudinal direction of the glass base material is substantially 6% or less.

Abstract: A photonic crystal interferometric optical gyroscope system including a light source for providing a primary beam of light, a photonic crystal sensing coil having a rotational axis, and a beam controlling device configured to split the primary beam into first and second counter-propagating beams in the photonic crystal sensing coil and configured to direct return of the counter-propagating beams wherein the power of the returning counter-propagating beams represents the phase shift between the counter-propagating beams and is indicative of the rate of rotation of the coil about the rotational axis.

Abstract: The invention comprises a system and method for reducing a shot noise component of the Angle Random Walk Noise in a fiber optic sensor by providing a first optical amplifier prior to the photodetector of the sensor to increase the power seen at the detector. An optical amplifier and second detector may be provided to detect a source sample, which can be useful in reducing RIN noise. Optical isolators may be added at the optical amplifiers to prevent rear facet emissions from the optical amplifiers from affecting sensor signals. A coupler with an isolator, amplifier and detector may be provided to receive a sample of the facet emissions from the first optical amplifier, which may be subtracted from the sensor signal at the detector so as to eliminate the facet emissions from the sensor signals. Polarizers may be provided prior to each detector to further eliminate emissions.

Abstract: A method for increasing the long-term operational reliability of a fiber optic interferometer. Noise in a detector output signal is set to a desired value by correcting the detector light power. Detector light power is corrected by varying a light source current of a light source of the interferometer. A change in the light source power results. It is thereby possible to increase both the reliability and useful life of the interferometer.

Abstract: A fiber optic ring interferometer, such as an interferometric fiber optic gyro (IFOG), with a sensing loop doubler. The IFOG device includes a light source, a circulator in optical communication with the light source and a photo diode, an integrated optical chip (IOC) capable of splitting light emitted from the circulator into two paths each of which is capable of being modulated, the IOC further being capable of combining light from each of the two paths when light travels in a direction towards the circulator, a fiber coil, and a polarization maintaining (PM) combiner/splitter disposed in between the IOC and the fiber coil. The PM combiner/splitter operates to send light through the fiber coil a first time in a first polarization state and to subsequently send the same light a second time through the fiber coil in a second orthogonal polarization state, whereby light travels twice the distance compared to a single loop IFOG device and, as such, effectively doubles the LD product.

Abstract: A fiber optic gyroscope (FOG) including a depolarizer having substantially equal first and second fiber segments of polarization maintaining (PM) fiber coupled to a single mode (SM) fiber loop. The first PM fiber segment includes sections of fiber connected together via a splice having an angle from about 35° to 55° between major axes of polarization of the sections which it connects. Similarly, the second PM fiber segment includes sections of fiber connected together via a splice having an angle from about 35° to 55° between major axes of polarization of the sections which it connects. The length of each fiber section is chosen to maintain the thermal and mechanical symmetry of the SM fiber loop.