Yinzhou Zhi

Transmissive resonator optic gyro based on silica waveguide ring resonator

A transmissive resonator optic gyro (TROG) based on silica waveguide ring resonator with improved long-term bias stability is reported in this paper. The modeling of a transmissive resonator used in optic gyro is carried out. The polarization dependence of resonator and the influences of phase modulators residual intensity modulation on the gyro output are analyzed. The resonator is simulated, designed, fabricated, tested and used to build up a TROG prototype. A bias stability of 0.22°/s over one hour test with an integration time of 10s is successfully demonstrated. No obvious drift has been found from the Allan variance analysis result of a 10000s test data, which means that the TROG prototype has an improved long-term drift characteristic.

Suppression of backreflection noise in a resonator integrated optic gyro by hybrid phase-modulation technology

A method to suppress backreflection noise due to facet reflection in a resonator integrated optic gyro (RIOG) is demonstrated using hybrid phase-modulation technology (HPMT). First, calculations are carried out to evaluate the effect of the backreflection. Although its amplitude has been remarkably decreased by angle polishing, residual backreflection noise is still a severe factor in RIOGs. Next, a hybrid phase-modulation method to eliminate the backreflection noise is constructed, and the frequency spectra of the photodetector outputs before and after adopting HPMT are analyzed. Theoretical analysis shows that the backreflection noise spectra will split from each other as a result of the hybrid phase modulation. In association with the pectinate-filter characteristics of digital correlation detection, the backreflection noise can be suppressed. Finally, the RIOG experimental setup is established and compared with opposite-slope triangle phase-modulation technology. HPMT has the advantage of suppressing backreflection noise, with the RIOG bias stability greatly improved from 2.34 to 0.22 deg/s (10 s integration time).

Current modulation technique used in resonator micro-optic gyro

Resonator micro-optic gyro (RMOG) is a promising candidate for the next generation inertial rotation sensor based on the Sagnac effect. A current modulation technique used in an external cavity laser diode is proposed to construct the gyroscope system for the first time. The resonance curves before and after eliminating accompanying amplitude modulation are theoretically analyzed, calculated, and simulated; the demodulation curves with different modulation currents are formulated theoretically; and the optimum modulation current corresponding to the maximum sensitivity is obtained. The experiment results from the established RMOG experimental setup demonstrate that a bias stability of 2.7 deg/s (10 s integrated time) over 600 s, and dynamic range of ±500 deg/s are demonstrated in an RMOG with a silica optical waveguide ring resonator having a ring length of 12.8 cm.

Experiments on resonator micro-optic gyro using external cavity laser diode

Abstract. Based on the Sagnac effect, a resonator micro-optic gyro (RMOG) is a novel optical sensor used for measuring rotation velocity. Due to the advantages of small volume, narrow linewidth, and tunable wavelength, an external cavity laser diode (ECLD) is adopted. By analyzing the working mechanism of the ECLD, a new scheme of constant temperature and driving current tuning control is determined. First, a theoretical resonance curve is calculated. Then the laser frequency is successfully tracked in the RMOG. Finally, a bias stability of 1.6  deg/s over 600 s is obtained in the RMOG with a silica waveguide resonator of 12.8 cm.

Effect of intensity variation of laser in resonator integrated optic gyro

The performance of the resonator integrated optic gyro (RIOG) is inevitably influenced by the intensity variation of the laser. In this work, the effect of intensity variation of the laser is mathematically formulized, analyzed, and experimentally validated, to our knowledge for the first time. First, the demodulated curves with different light intensities input of the integrated optical resonator (IOR) are simulated; the relationship between the slope of the demodulated curve near the resonant point and the light intensity input of the IOR is obtained. Second, the amplitudes of the output square waveforms with different zero biases are demonstrated, and it can be concluded that the effect of intensity variation has a high correlation with the nonzero bias between the clockwise and counterclockwise resonant frequency. Third, the experimental setup is constructed and the related measurements are performed, the test results are in good agreement with the analytical and numerical simulation, and in order to reach the limited ultimate sensitivity of the RIOG, it is necessary to restrict the nonreciprocal zero bias within 8.1 deg/s under an open-loop output scheme. Furthermore, to eliminate the noise induced by intensity variation of the laser and realize a high performance RIOG, a closed-loop operation is required.

Reduction of backreflection noise in resonator micro-optic gyro by integer period sampling

In resonator micro-optic gyros (RMOGs), the interference between the backreflection light beam of one pathway and the signal light beam of the other pathway deteriorates the gyro output waveforms, resulting in severe reduction in the gyros accuracy. In this paper, an integer period sampling (IPS) method is introduced to minimize the sampling error caused by backreflection in RMOG for the first time to our knowledge. The experimental results show that both the bias repeatability and the short-term bias stability become better when the IPS condition is satisfied. A bias stability of 0.41°/s over one hour with an integration time of 10 s has been realized in a RMOG that employs a silica waveguide ring resonator.

In-line polarizer used in all-0°-splice resonator fiber-optic gyro

A method to suppress the polarization-fluctuation-induced drift in a resonator fiber-optic gyro is proposed in this paper. By inserting one in-line polarizer whose polarization extinction ratio is 30 dB into a polarization-maintaining fiber resonator with 0° polarization-axis splices, the unwanted resonance is introduced to high loss and therefore the ratio of the resonance height of the desired eigen-states of polarization (ESOP) to the unwanted ESOP is 74 dB theoretically; thus the polarization-fluctuation-induced drift is adequately suppressed. The new scheme has excellent operability and high temperature stability simultaneously. Compared to the resonator with twin 90° polarization-axis rotated splices, this scheme does not need precise length difference control. This work is of great importance in the research on resonator integrated optic gyros.

Low-delay, high-bandwidth frequency-locking loop of resonator integrated optic gyro with triangular phase modulation

A frequency-locking loop affects the bandwidth and output of the resonator integrated optic gyro (RIOG). A low-delay, high-bandwidth frequency-locking loop is implemented on a single field-programmable gate array with triangular phase modulation. The signal processing delay is reduced to less than 1 μs. The loop model is set up, and the influences of loop parameters on the bandwidth and unit step response are analyzed; the bandwidth of 10 kHz is obtained with the optimized loop parameters. As a result, the accuracy of the frequency-locking loop is reduced to 1.37 Hz (10 s integrated time). It is equivalent to a rotation rate of 0.005  deg/s, which is close to the ultimate sensitivity of the RIOG. Moreover, the bias stability of the RIOG is improved to 0.45  deg/s (10 s integrated time) based on the frequency-locking loop.

Analysis of optimal frequency bias of frequency-lock in passive ring resonator optic gyro

The frequency-lock (FL) accuracy of a passive ring resonator optic gyro (PROG), which is closely related to the frequency bias, determines the ultimate measurement precision of the gyro system; therefore it is particularly important to choose a proper frequency bias for the PROG to achieve excellent performance. The best performance of the PROG comes from the optimal signal-noise ratio (SNR), rather than the highest sensitivity. The relations among the SNR affected by the photon shot noise of the photodetector, sensitivity and the frequency bias of the PROG are analyzed in detail for both transmission-type and reflection-type PROGs under Lorentz function approximation in this paper, and the optimal FL frequency bias ranges are discussed. This work provides explicit theoretical guidance for the systematic optimization of the PROG.

Temperature-dependent, polarization-induced bias errors in a resonator integrated optical gyroscope

The performance of a resonator integrated optical gyroscope (RIOG) is inevitably influenced by polarization noise. In this work, the effects of temperature-dependent polarization on the performances of an integrated optical resonator (IOR) and a RIOG are formulated mathematically and analyzed. Firstly, resonant curves with different polarization extinction ratios (PERs) and different temperature fluctuations are demonstrated. The main performances of the IOR, i.e. depth and full width at half maximum (FWHM), are not only influenced by the waveguide birefringence, but also by the intensity coupling coefficient of the couplers, both of which change with the variation of temperature. Secondly, the relationship between the variation of temperature and the variation of depth, as well as the FWHM, are obtained. Thirdly, in order to evaluate the zero bias error caused by the temperature-dependent polarization, resonant asymmetry ratio (RAR) is introduced, which is strongly dependent on the temperature fluctuatio...