Fiber Optic Gyroscope Research Articles

Sensitivity improvement of the closed-loop resonant fiber-optic gyroscope interrogated with a broadband source

The resonant fiber-optic gyroscope (RFOG), interrogated with a broadband light source, represents an intriguing optical gyroscope that has been proposed as an extension of the traditional RFOG, which is driven by a narrow linewidth laser source. The implementation of a closed-loop detection system enhances the linearity and dynamic range of the gyroscope output. This paper is devoted to improving the sensitivity of the closed-loop broadband source-driven RFOG. First, a model for analysis and optimization of the feedback loop gain of a closed-loop broadband source-driven resonant fiber-optic gyroscope (RFOG) is developed, and the feedback loop gain is optimized. The experimental results indicate that the influence of the feedback loop noise on the gyro performance can be neglected. Subsequently, the noise contributions, including the shot noise, detector noise, and relative intensity noise, in the broadband source-driven RFOG system are investigated. A theoretical derivation and experimental verification of an expression for the reduction of the relative intensity noise by a fiber-optic ring resonator are presented. Finally, a packaged broadband source-driven RFOG prototype using a 175 m long fiber coil with an average diameter of 5.7 cm was constructed and evaluated. The experimental results demonstrate that the prototype achieves navigation-grade precision with an angular random walk of 0.003∘/h1/2 and a bias instability of 0.005°/h.

Reduction in Temperature-Dependent Fiber-Optic Gyroscope Bias Drift by Using Multifunctional Integrated Optical Chip Fabricated on Pre-Annealed LiNbO3

The refractive index change obtained after annealed proton exchange (APE) in lithium niobate (LiNbO3) crystals depends on both the proton exchange process carried out in hot acid and the structure of the crystals. In devices produced by the APE method, dislocations and lattice defects within the crystal structure are considered to be primary contributors to refractive index discontinuities and waveguide instability. In this study, the effects of pre-annealing LiNbO3 crystals at 500 °C on multifunctional integrated optical chips (MIOCs) were investigated through interferometric fiber-optic gyroscope (IFOG) system-level tests. It was observed that the pre-annealing process resulted in an improvement in the optical throughput of MIOCs (from %34 to %51) and the temperature-dependent bias drift stability of the IFOG (from 0.031–0.038°/h to 0.012–0.019°/h). The angle random walk (ARW) was measured as 0.0056 deg/√h.

Development of a 6-degrees-of-freedom measurement system using a robotic total station for a free-running model test

The measurement of a model ship's six degrees of freedom (6-DOF) using sensors such as Marvelmind beacons and robotic total stations (RTS) has previously demonstrated substantial error margins. To address these limitations, this study introduces a refined approach for accurate and reliable 6-DOF measurement through free-running model tests (FRMT). The tests were meticulously designed, with three RTS strategically positioned to meet the specific requirements of the measurement scenario. Given the potential constraints in an FRMT environment, we proposed feasible installation ranges for the RTS and prisms, ensuring the stable measurement of the model ship's 6-DOF. To achieve high-precision motion measurement, even in complex environments, we employed the prism queue algorithm, which identifies and processes overlapping or untracked prisms monitored by the RTS. The proposed methodology was validated through simulations and FRMT conducted in the ocean engineering basin of the Korea Research Institute of Ships and Ocean Engineering and by developing an actual implementation program. Comparative analysis using high-precision navigation equipment, such as fiber optic gyros, demonstrated that the method provided unbiased and stable data. Consequently, the proposed method shows significant promise as a viable alternative for precision navigation in real-world applications.

A novel dual-core fiber-optic gyroscope with independent rotation rate measurements in different cores of a dual-core optical fiber

A novel dual-core fiber-optic gyroscope with independent rotation rate measurements in different cores of a dual-core optical fiber

Design of Silicon Nitride Based TE-Pass Polarizer at 850 nm for Integrated Fiber Optic Gyroscope

Design of Silicon Nitride Based TE-Pass Polarizer at 850 nm for Integrated Fiber Optic Gyroscope

Analysis of the Temperature Field Characteristics and Thermal-Induced Errors of Miniature Interferometric Fiber Optic Gyroscopes in a Vacuum Environment

This paper investigates the mechanism of thermal-induced errors in interferometric fiber optic gyroscopes (IFOGs) caused by temperature changes in a vacuum environment, proposing a method for calculating thermal-induced errors in small fiber coils. Firstly, based on the Shupe effect and the thermal stress caused by temperature changes around the fiber coil, a three-dimensional thermal-induced error model for small fiber coils is established. Secondly, a spatial fiber optic inertial measurement unit (IMU) model is designed using the Creo 3D modeling software (creo 7.0.0). The model is then imported into the Ansys finite element simulation software (ANSYS Workbench 15.0), where a temperature field is applied to the IMU based on actual temperature profiles to obtain the temperature distribution of the fiber coil at different times in a vacuum state. These data are then used in the three-dimensional thermal-induced error model to calculate the thermal-induced error of the FOG. Finally, a thermal vacuum experimental platform is set up to collect temperature variation data from the inertial measurement components. The experimental data are compared with the three-dimensional error model proposed in this paper as well as traditional error models. The root mean square error is approximately 33% lower than that of traditional error calculation methods, which also proves the theoretical accuracy.

The Zero-Velocity Correction Method for Pipe Jacking Automatic Guidance System Based on Fiber Optic Gyroscope.

The pipe jacking guidance system based on a fiber optic gyroscope (FOG) has gained extensive attention due to its high degree of safety and autonomy. However, all inertial guidance systems have accumulative errors over time. The zero-velocity update (ZUPT) algorithm is an effective error compensation method, but accurately distinguishing between moving and stationary states in slow pipe jacking operations is a major challenge. To address this challenge, a "MV + ARE + SHOE" three-conditional zero-velocity detection (TCZVD) algorithm for the fiber optic gyroscope inertial navigation system (FOG-INS) is designed. Firstly, a Kalman filter model based on ZUPT is established. Secondly, the TCZVD algorithm, which combines the moving variance of acceleration (MV), angular rate energy (ARE), and stance hypothesis optimal estimation (SHOE), is proposed. Finally, experiments are conducted, and the results indicate that the proposed algorithm achieves a zero-velocity detection accuracy of 99.18% and can reduce positioning error to less than 2% of the total distance. Furthermore, the applicability of the proposed algorithm in the practical working environment is confirmed through on-site experiments. The results demonstrate that this method can effectively suppress the accumulated error of the inertial guidance system and improve the positioning accuracy of pipe jacking. It provides a robust and reliable solution for practical engineering challenges. Therefore, this study will contribute to the development of pipe jacking automatic guidance technology.

Polarization non-reciprocity error suppression in dual-polarization fiber optic gyroscopes

The dual-polarization interferometric fiber optic gyroscope is distinguished by the fact that both orthogonal polarized light beams in the fiber coil are simultaneously sensitive to the rotation rate. The relative intensity noise can be effectively suppressed due to the strong correlation between the two polarized light beams. However, the system exhibits significant polarization non-reciprocity errors, which worsen the bias instability. In this paper, we demonstrate how modulation depth affects the angular random walk and the bias instability. Polarization non-reciprocity errors can be efficiently mitigated while the angular random walk approaches optimal value by adjusting the modulation depth to π/2rad rather than 2.7 rad. It is confirmed that the bias instability and angular random walk can be simultaneously improved by optimizing the modulation depth without increasing the complexity of the optical path. Experimental results indicate that for a 500-m-long fiber coil, the bias instability is improved from 0.025∘/h (2.7 rad) to 0.010∘/h (π/2rad) while the angular random walk remains at 0.001∘/h through modulation depth optimization, which advances its application in navigation.

Simulation and comparative analysis of Fiber Optic Gyroscope for near-zero rotation rate measurement

Simulation and comparative analysis of Fiber Optic Gyroscope for near-zero rotation rate measurement

A Comparative Study of Fiber Optic Gyroscopes

A Comparative Study of Fiber Optic Gyroscopes

Quadrature demodulation with synchronous difference for broadband source-driven resonant fiber-optic gyroscopes

Quadrature demodulation with synchronous difference for broadband source-driven resonant fiber-optic gyroscopes

Atom interferometry at arbitrary orientations and rotation rates

The exquisite precision of atom interferometers has sparked the interest of a large community for uses ranging from fundamental physics to geodesy and inertial navigation. However, their implementation for onboard applications is still limited, not least because rotation and acceleration are intertwined in a single phase shift, which makes the extraction of a useful signal more challenging. Moreover, the spatial separation of the wave packets due to rotations leads to a loss of signal. We present an atom interferometer operating over a large range of random angles, rotation rates and accelerations. A model of the expected phase shift allows us to untangle the rotation and acceleration signals. We also implement a real-time compensation system using fiber-optic gyroscopes and a rotating reference mirror to maintain the full contrast of the interferometer. We demonstrate a single-shot sensitivity to acceleration of 24 μg for rotation rates reaching 14° s−1.

A health assessment method with attribute importance modeling for complex systems using belief rule base

In the health assessment for complex systems, system attributes refer to the indicators or components having an impact on the health state of the system. When assessing the health state of complex systems, the relative importance of system attributes should be accurately modeled, otherwise incorrect results may occur. Especially for some complex systems with small samples, data-driven methods are prone to overfitting. In this article, a new method using belief rule base (BRB) is proposed to model the relative importance of system attributes while assessing the health state. As an interpretable modeling tool, BRB constructs nonlinear mapping relationships between system attributes and health state. A data-knowledge hybrid-driven ensemble feature selection (DKH-EFS) method is developed to calculate the relative importance of the system attributes, namely attribute importance (AM). A random sensitivity analysis (RSA) method of the model output to the input of BRB is proposed to calculate the feature importance (FI) of BRB. A new parameter optimization model considering the consistency between the AM and FI is introduced to improve the modeling ability of BRB for the AM. A case study on the health assessment of the fiber optic gyroscope (FOG) validates the proposed method.

Research on stochastic error suppression method of FOG based on quasi-proportional information

Abstract In order to improve the precision of fiber optic gyro (FOG), it is necessary to suppress the stochastic error effectively. Therefore, the stochastic error suppression of FOG is studied. Firstly, the data of FOG at room temperature and variable temperature are analyzed. Then, a general form of FOG random error model is derived, and an adaptive filtering method based on quasi-proportional information is proposed to estimate the process noise covariance effectively. At last, the room temperature experiment, the variable temperature experiment and the dynamic experiment are carried out. Compared with the recently proposed adaptive filter algorithm, the variance reduction of the proposed algorithm at the average time of 33 s, 54 s and 55 s is more than 70%, and the suppression effect of the algorithm on the random walk coefficient is improved by more than 2%, showing strong robustness.

Six-state modulation method for improving the accuracy of fiber optic gyroscopes by reducing electrical crosstalk

Reducing the influence of electrical crosstalk is crucial for the development of fiber optic gyroscopes. We present a six-state modulation method that takes advantage of highly flexible modulation voltages to eliminate the correlation between the modulation voltage with a fixed phase delay and the demodulation sequence. Theoretical analysis indicates that our approach can eliminate the impact of crosstalk with a fixed phase delay at any modulation depth. Experimental measurements demonstrate that compared to the conventional four-state modulation method, the zero bias is reduced by about 0.3319°/h at the modulation depth of π/2 when our method is applied. Additionally, at the depths of π/2, 2π/3, and 7π/8, the bias instability is reduced by approximately 30%, and the angular random walk (ARW) is reduced by over 60%. The results confirm its effectiveness in decreasing electrical crosstalk, which holds profound implications for enhancing the accuracy of fiber optic gyroscopes.

Low-Drift Fiber-Optic Gyroscope Interrogated With Multiple Broadened Semiconductor Lasers

Low-Drift Fiber-Optic Gyroscope Interrogated With Multiple Broadened Semiconductor Lasers

METHODS OF REDUCING THE INFLUENCE OF TEMPERATURE GRADIENTS ON THE SENSITIVITY OF FIBER-OPTIC GYROSCOPE

Thermally induced error is one of the main limitations of the sensitivity of fiber-optic gyroscopes (FOGs). The analysis of thermal sensitivity of FOG is based on the study of the Shupe effect and the elastic-optical effect in the fiber circuit. The main requirement in this case is to preserve the principle of reciprocity for rays propagating in opposite directions of the fiber circuit. It was determined that the thermally induced phase difference of these rays should not exceed ∆φ(t) ≈ 10-7 rad. To reduce the thermal sensitivity of FOG, various methods are used, including quadrupole methods of winding the fiber circuit, using frameless coils, as well as coils made of special materials. Considerable attention is paid to improving the properties of fiber and adhesive compounds to minimize the effect of temperature on the optical-physical characteristics of these components of the fiber circuit. The article examines the advantages and disadvantages of each of the methods of compensating the thermally induced error of FOG. Analytical relations characterizing the effect of temperature gradients on the sensitivity of measuring angular velocity and Sagnac phase when using FOG are given. Part of the methods for solving this problem are discussed in this article. However, the elemental base and FOG signal processing tools are constantly being improved, the transition to integrated optical technologies is being carried out, which opens up new ways to increase the sensitivity of the FOG with minimal costs. On the basis of the conducted research, practical recommendations are given to reduce the influence of temperature gradients on the sensitivity of FOG. The work can be useful for specialists working in the field of FOG design.

Highly birefringent anti-resonant hollow-core fiber with meniscoid nested structure

We propose a meniscoid nested anti-resonant hollow-core fiber (MAF), wherein the fourfold rotational symmetry structure enables high birefringence and low loss in dual-wavelength range. Numerical investigation and simulation for variations in wall thickness along orthogonal directions are conducted, through which a formulated optimization criterion revealing the relationship between minimum difference in wall thickness and birefringence of 10−5 is obtained. A parameter of beat length to loss ratio η is defined to evaluate MAF performance with respect to birefringence and confinement loss (CL). With optimized MAF structure, the birefringence and CL are improved to 3.62 × 10−5 and 8.5 dB/km at 1.06 µm, 9.83 × 10−5 and 204.1 dB/km at 1.55 µm, respectively. Meanwhile, the bandwidths extend to 172 nm at 1.06 µm and 216 nm at 1.55 µm, and the superior bending resistance characteristics are validated. Our work offers valuable guidance for designing and optimizing highly birefringent anti-resonant hollow-core fiber (ARF), and the proposed MAF has great potential in polarization-dependent transmission and interferometric fiber gyroscopes.

Resonant fiber optic gyroscope driven by a broadband light source based on an over-coupled state fiber ring resonator

The resonant fiber optic gyroscope (RFOG) driven by a broadband light source has advantages over conventional RFOGs in terms of structure, solution, etc., and provides new ideas for the commercialization of RFOGs. In this paper, the basic working principle of RFOG driven by a broadband light source is introduced. The optimal modulation coefficients are provided for sinusoidal wave modulation. The influence of the length of the fiber-optic ring resonator (FRR) and the coupling coefficient of the fiber coupler on the sensitivity is analyzed. The FRR is constructed in the over-coupled state to improve the utilization of optical power, and thus significantly increase the system sensitivity. In experiments, an RFOG prototype with a diameter of 13 cm, a height of 7 cm, and a fiber ring length of 210 m is produced. A bias instability (BI) of 0.06°/h and an angular random walk (ARW) of 0.01∘/h are obtained.

Influence of the average wavelength on the scale factor stability of interferometric fiber optic gyroscope

The introduction of closed-loop mechanisms has significantly enhanced the performance of interferometric fiber optic gyroscopes (IFOGs). However, the poor scale factor (SF) stability limits its further application due to the use of broadband light sources. This study first reviewed the impact of the average wavelength of a light source on SF stability in a closed-loop IFOG setup. A simulation model is developed according to modulation and demodulation principles, and the SF error is found to be proportional to the wavelength drift in a closed-loop IFOG. Additionally, employing a laser with a more stable average wavelength instead of a super fluorescent fiber source (SFS) for driving the IFOG enhanced the SF stability by an order of magnitude to 0.38 ppm in ambient-air experiments, which is one of the best SF performances achieved thus far. With the significant improvement in stability during the variable temperature tests, the IFOG measures rotation rates more accurately.