Abstract: Systems and methods for improving efficiency of a data converter. An example method generates a noise signal, alters the spectrum of the noise signal based on operation of an associated data converter, and supplies the altered spectrum noise signal to the associated data converter. The data converter is a digital-to-analog converter or an analog-to-digital converter. The altered spectrum noise signal is notched at frequencies of interest. The spectrum is altered by sending a signal generated by a random number generator to a delay device and adding the output of the delay device from the output of the random number generator. Also, the spectrum is altered by seeding first and second identical random number generators, delaying the operation of the first random number generator, and adding the output of the delayed first random number generator from the second random number generator.

Abstract: Apparatus is provided for a fiber optic gyro. The fiber optic gyro includes a ring resonator having first and second counter-propagating directions. The ring resonator includes a coil having an axis and an optical fiber having a hollow core. The ring resonator is configured to produce a first resonance frequency when a first light beam circulates through the hollow core in the first counter-propagating direction and produce a second resonance frequency when a second light beam circulates through the hollow core in the second counter-propagating direction. A difference between the resonance frequencies indicates a rotation rate of the fiber optic gyro about the axis.

Abstract: Methods and apparatus are provided for stabilizing laser light sources of a resonator gyro. A resonator gyro comprises a first light source configured to produce a first input light, a second light source configured to produce a second input light, a resonator coupled to the first and second light sources, a resonance detection circuit coupled to the resonator, and a controller coupled to the resonance detection circuit and the first and second light sources. The resonance detection circuit detects a resonance frequency for each of the counter-propagating directions of the resonator. The controller tunes the first input light to a clockwise resonance frequency, and tunes the second input light to a counter-clockwise resonance frequency. A difference between the resonance frequencies is proportional to a rotational rate of the resonator gyro.

Abstract: Methods and apparatus are provided for a low cost optical gyro with a free space closed optical path. A ring resonator comprises a substrate and reflectors formed or placed on the substrate. The reflectors comprise a closed optical path and are configured to direct each of first and second light beams in a different counter-propagating direction in the closed optical path. Each of the first and second light beams frequencies are tuned to the resonance frequency of the resonator in the direction of propagation for which the light beam is circulating in the closed optical path.

Abstract: Methods and apparatus are provided for attenuating rotation rate errors in a resonator gyro. The gyro includes a ring resonator having a hollow core optical fiber coil and optical elements that are selected and/or oriented to reduce stray light that may be present in input light beams introduced to the ring resonator. The resonator has a predetermined mode. One of the optical elements partially transmits a portion of the input light beam to a first end of the fiber coil while partially transmitting a portion of the input light beam to a filter. Light having the predetermined mode is accepted into the first end of the fiber coil, and the filter accepts light of the input light beam having a corresponding mode. Transmission components of the circulating light beams indicates resonance peaks of the counter-propagating directions of the ring resonator.

Abstract: Methods and apparatus are provided for sensing a rotation rate of a ring resonator in a transmission mode. A ring resonator for circulating light beams in counter-propagating directions comprises an optical fiber coil having a hollow core and first and second ends. A first optical element is configured to receive an input light beam and direct a portion of the input light beam in a counter-propagating direction of the ring resonator. A second optical element is configured to direct with the first optical element a majority of a circulating light beam in the counter-propagating direction of the ring resonator and derive a transmission mode component of the circulating light beam at one of the ends. The portion of the input light beam enters one of the first and second ends. The circulating light beam is based on the input light beam. The transmission mode component indicates a resonance peak of the counter-propagating direction of the ring resonator.

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 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 method is provided for sensing an environmental effect upon a sensing element and includes exposing the sensing element into the environmental effect, producing a light signal in the sensing element, modulating the light signal with a modulation signal, and determining a path length of the light signal as a function of the modulation signal. A fiber optic sensor is provided that includes a light source producing a light, a sensing element optically coupled to the light source such that the light propagates through the sensing element, a detector optically coupled to the sensing element. The detector detects light intensity propagating in the sensing element. An electronics processor receives the detector output and produces a modulation signal for the light. The processor further produces an output signal indicative of the environmental effect as a function of the modulation signal.

Abstract: A system and method is provided which suppresses relative intensity noise in a fiber optic gyroscope by taking advantage of the frequency response of erbium fiber. In operation, the gain provided by the erbium fiber is added to the gain of the other components in the feedback loop to provide for stable loop performance up to about 250 kHz. The frequency response of the erbium fiber of about 3 kHz also provides a 6 db per octave roll-off, which, when used in a negative feedback control loop for controlling the current flowing to the gyroscope light source, allows for a relative intensity noise control loop with a bandwidth much greater than 3 kHz; this may be used in high performance gyroscope applications.

Abstract: A method is provided for sensing an environmental effect upon a sensing element and includes exposing the sensing element into the environmental effect, producing a light signal in the sensing element, modulating the light signal with a modulation signal, and determining a path length of the light signal as a function of the modulation signal. A fiber optic sensor is provided that includes a light source producing a light, a sensing element optically coupled to the light source such that the light propagates through the sensing element, a detector optically coupled to the sensing element. The detector detects light intensity propagating in the sensing element. An electronics processor receives the detector output and produces a modulation signal for the light. The processor further produces an output signal indicative of the environmental effect as a function of the modulation signal.

Abstract: A system and method is provided which suppresses relative intensity noise in a fiber optic gyroscope by taking advantage of the frequency response of erbium fiber. In operation, the gain provided by the erbium fiber is added to the gain of the other components in the feedback loop to provide for stable loop performance up to about 250 kHz. The frequency response of the erbium fiber of about 3 kHz also provides a 6 db per octave roll-off, which, when used in a negative feedback control loop for controlling the current flowing to the gyroscope light source, allows for a relative intensity noise control loop with a bandwidth much greater than 3 kHz; this may be used in high performance gyroscope applications.

Abstract: A system is disclosed which suppresses relative intensity noise in a fiber optic gyroscope. A high-speed intensity modulator is placed in the gyroscope light path between the fiber light source and a tap coupler which provides a sample of the modulated signal for use in a feedback loop. A photodetector receives the sampled signal and provides current-to-voltage conversion of the signal. A high-bandwidth voltage amplifier then adjusts the gain and phase of the converted signal and drives the intensity modulator in such a manner as to stabilize the control loop and provide suppression of relative intensity noise. The present system modulates the intensity of the light at a frequency which is sufficiently high to allow suppression of high frequency components of the relative intensity noise.

Abstract: A fiber optic gyroscope having polarization error-correcting modulation. Polarization errors originate from the interference of primary waves and secondary cross-coupled waves. Although these error signals are very difficult to remove modulation signals may be applied to the integrated optics chip that minimize the total error over a period of time. By providing distinct but inter-related modulation signals to opposing inputs of the sensing coil, the various polarization errors can be averaged to zero over the period of the modulation signals.

Abstract: A rectification error reducer for a fiber optic gyroscope, which is an intensity servo or compensator for reducing vibration effects in the optical signals caused by modulation at vibration frequencies induced by the gyroscope operating environment. The vibration effects may be detected in signals from the photodiode output in amplitude form which is used in a control system to null out optical intensity variations at the frequencies of vibration.

Abstract: A rectification error reducer for a fiber optic gyroscope, which is an intensity servo or compensator for reducing vibration effects in the optical signals caused by modulation at vibration frequencies induced by the gyroscope operating environment. The vibration effects may be detected in signals from the photodiode output in amplitude form which is used in a control system to null out optical intensity variations at the frequencies of vibration.

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.

Abstract: A device for eliminating coherent pickup error in a fiber optic gyroscope. The polarity of the drive signal to the phase modulator of the gyroscope is switched periodically. The scale factor consequently changes. The phase and amplitude of coherent pickup error generated in the gyroscope circuits do not change during the switching. Therefore, nearly all of the coherent pickup error is subtracted out of the gyroscope signal during the digital signal processing of the signal.

Abstract: A device for providing a bias modulation at a proper frequency to the counterpropagating light waves in the sensing coil of an interferometric fiber optic gyroscope. The photodetector detects the light which has exited the sensing loop, and converts it to an electrical signal that is demodulated by two phase sensitive detector. One phase sensitive detector demodulates the signal that is in phase with the bias modulation signal and the other phase sensitive detector demodulates the quadrature signal with respect to the modulation signal, and controls the frequency of the bias phase modulator driver so as to reduce the quadrature to a minimum and to keep the modulator frequency at the proper frequency of the sensing coil. Increased intensity modulation can be attained with a DC voltage applied to an electrode of the modulator to produce the quadrature signal.

Abstract: A method for damping an optical fiber on a bias optical phase modulator having two optical fiber leads comprises the steps of securing the bias phase modulator, applying a silicone or acrylate type of substance to an outward facing surface of the fiber wound on the bias phase modulator means, applying the silicone or acrylate type of substance on the two optical fiber leads for at least 0.5 inch (1.28 cm.) along each lead which is apart from the place where the optical fiber wound on the bias phase modulator, frequently brushing or smoothing out the applied silicone or acrylate type of substance until the substance beings to set, and drying the substance on the optical fiber until the substance is cured. The applied damping material significantly reduces an amplitude of a frequency caused by mechanical vibrations in a rotation sensor.