Optical Passive Ring-resonator Gyro Research Articles

谐振式空心光子带隙光纤陀螺中的光克尔效应

谐振式空心光子带隙光纤陀螺中的光克尔效应

Waveguide-type optical passive ring resonator gyro using phase modulation spectroscopy technique

We report the first demonstration of silica waveguide optical passive ring resonator gyro (OPRG) based on the phase modulation spectroscopy technique. The ring resonator is composed of a 6-cm-long silica waveguide. Observed from the resonance curve, the free spectral range (FSR) of the resonator, the full width at half maximum (FWHM) of the resonance curve, the finesse (F) of the resonator, and the resonance depth are 3.4 GHz, 62 MHz, 54.8, and 70%, respectively. The detection sensitivity of this OPRG will be 7.3×10–5 rad/s. In the experiments, there is an acoustic-optical modulator (AOM) in each light loop. We lock the lasing frequency at the resonance frequency of the silica waveguide ring resonator for counterclockwise (CCW) lightwave; the frequency difference between the driving frequencies of the two AOMs is equivalent to the Sagnac frequency difference caused by gyro rotation. Thus, the gyro output is observed.

Reduction of a polarization-fluctuation-induced error in an optical passive ring-resonator gyro by using a single-polarization optical fiber

The authors evaluate the effect of a single-polarization optical fiber or a fiber polarizer to reduce polarization-fluctuation-induced error in an optical passive ring-resonator gyro. It is clarified that a large output error induced when using an ordinary polarization-maintaining fiber can be suppressed, and a moderate performance gyro can be achieved by using practical parameters of the ring resonator.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Method to reduce the optical Kerr-effect induced bias in an optical passive ring-resonator gyro

The optical passive ring-resonator gyro (OPRG) utilizes a high-finesse fiber ring resonator. A novel method to reduce the optical Kerr-effect-induced bias is proposed. The bias is monitored by modulating the light-source intensity, and fed back into one lightwave intensity traveling in the resonator to make it zero. The experiment to verify the basic operation of this method is successfully carried out. >

Bias of an optical passive ring-resonator gyro caused by the misalignment of the polarization axis in the polarization-maintaining fiber resonator

An analysis is presented of the bias of an optical passive ring-resonator gyro caused by the misalignment of the polarization axis in the resonator formed by the polarization-maintaining fiber. A large bias takes place when the phase difference between the two polarization modes of the fiber is equal to the amount of 2 pi times an integer. It is clarified that the bias can be suppressed by setting the fiber polarizers at the lead portions of the resonator, which was a method proposed originally to reduce the bias in an ideal resonator without the misalignment.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Method to reduce the optical Kerr-effect-induced bias in an optical passive ring-resonator gyro

The optical passive ring-resonator gyro (OPRG) utilizes a high-finesse fiber ring resonator. A novel method to reduce the optical Kerr-effect-induced bias is proposed. The bias is monitored by modulating the light-source intensity, and fed back into one lightwave intensity traveling in the resonator to make it zero. The experiment to verify the basic operation of this method is successfully carried out. >

Partially digital-feedback scheme and evaluation of optical Kerr-effect induced bias in optical passive ring-resonator gyro

The authors propose a partially digital-feedback scheme to improve the zero-point stability in an optical passive fiber ring-resonator gyro, in which the frequency of a light source is controlled in a digital way. Using an experimental setup stabilized by this method, the optical Kerr-effect induced bias was successfully evaluated in this type of gyroscope.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Evaluation of the output error in an optical passive ring-resonator gyro with a 90 degrees polarization-axis rotation in the polarization-maintaining fiber resonator

A previously developed method is used to evaluate the error in the optical passive ring-resonator gyro. This scheme is shown to have sufficient accuracy to meet high-grade aircraft-navigation requirements with enough tolerance for such resonator parameters as splice misalignment, finesse, and temperature.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Adjustment-free method to eliminate the noise induced by the backscattering in an optical passive ring-resonator gyro

An adjustment-free method to eliminate the noise induced by the interference between the signal wave and the backscattering in an optical passive ring-resonator gyro is proposed and demonstrated. In this method, the lightwave incident into the ring resonator is modulated by binary shift keying to eliminate its carrier component. This can easily be performed by using an acoustooptic modulator and a double balanced mixer. In the experiment, the noise is successfully reduced without any adjustment of the modulation parameters.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Waveguide-type optical passive ring-resonator gyro using time-division detection scheme

An optical passive ring-resonator gyro is demonstrated using a waveguide ring-resonator and a conventional distributed feedback laser diode. A novel detection technique for the Sagnac effect based on a time-division switching scheme is also proposed.

Backscattering in an optical passive ring-resonator gyro: experiment

We report the experimental results of the resonance characteristics of the backscattering in an optical passive ring-resonator gyro (OPRG). This resonance has two peaks with a separation equal to the Sagnac phase shift when rotation is given. The experimental results are in good agreement with the theory that we have already presented. This phenomenon degrades the gyro linearity almost 10% in a high sensitivity OPRG with the frequency output. A method to eliminate this noise is proposed.

Eigenstate of polarization in a fiber ring resonator and its effect in an optical passive ring-resonator gyro

Resonance characteristics of an optical fiber ring resonator are derived taking the effect of birefringence into account. We introduce the concept of the eigenstate of polarization to discuss the resonance characteristics resulting from the polarization fluctuation. Using this concept, the polarization problem in an optical passive ring-resonator gyro (OPRG) is discussed to reveal that this causes gyro drift. A way to reduce the drift is to use not polarizers but two polarization controllers. The precision required for polarization control is estimated; it is found difficult to do in practice. We discuss another configuration to solve the polarization problem in an OPRG without polarization controllers.

Resonance characteristics of backscattering in optical passive ring-resonator gyro

Resonance characteristics of the backscattering in an optical passive ring-resonator gyro (OPRG) are observed. This resonance has two peaks with a separation equal to the Sagnac phase shift when rotation is induced. The experimental results are in good agreement with the theory that we have already presented. This phenomenon degrades the gyro linearity in a configuration to obtain the frequency output.

Kerr effect in an optical passive ring-resonator gyro

The Kerr effect in an optical passive ring-resonator gyro (OPRG) is analyzed considering the optical source coherence. This effect causes the drift to be much greater than the theoretical limit of rotation sensing given by the detector shot noise for an OPRG with high sensitivity. The drift depends not only on the fluctuation of the power splitting ratio between two counter-propagating beams in the resonator, but also on the frequency modulation indices used to set the operating point. Square-wave intensity modulation of the incident beam is also discussed as a way to eliminate the drift. It is found that the ratio of the signal-beam round-trip time in the resonator to the modulation period must be an integer to optimize the drift elimination. From the practical viewpoint, the requirement for the modulation parameters is analyzed numerically.

Effect of Rayleigh backscattering in an optical passive ring-resonator gyro

Resonance characteristics of Rayleigh backscattering in an optical passive ring-resonator gyro (OPRG) are theoretically formulated taking the temporal coherence of the optical source into account. This resonance has two peaks with separation equal to the Sagnac phase shift when rotation is induced. This phenomenon degrades the gyro’s linearity in a configuration to obtain the frequency output. Rayleigh backscattering also can induce an enhanced noise at specific input rotation rates. The methods of solving these problems are discussed. The theoretical limit of rotation sensing, given by the detector shot noise, is also computed taking into account the optical source coherence. A spectrum width narrower than several tens of kHz is required to realize the OPRG for navigation use.