Fiber Optic Gyroscope Scale Research Articles

Study on FOG scale factor error calibration in start-up stage based on GWO-GRU

The fiber optic gyroscope (FOG) is the core component of the inertial system, which has been widely utilized in aviation, maritime, automotive, and other fields. The scale factor is one of the critical parameters to characterize the dynamic performance of the FOG. Due to the temperature sensitivity of the optoelectronic devices, the scale factor errors will be caused with the temperature change. The traditional compensation method usually compensates the output of the FOG in a stable working state. Without considering the difference between the characteristics of the FOG in the start-up stage and the stable working state, the compensation accuracy of the traditional method cannot meet the demand for quick start-up in application areas. According to the above analysis, a novel scale factor error compensation method based on the grey wolf optimization (GWO) and gated recurrent unit (GRU) neural network is proposed in this paper. Furthermore, a new experiment is designed to calibrate the scale factor error in the start-up stage, which can reduce the calibration time and ensure the calibration accuracy. The experimental results demonstrate the proposed method significantly improves the compensation accuracy compared with other methods, such as the multilayer perceptrons (MLPs) and the traditional GRU network.

Research on light source average wavelength and crystal oscillator frequency for reducing temperature error of the FOG scale factor

Based on the working principle of the digital closed-loop fiber optic gyroscope (FOG), a model for the influence of crystal oscillator frequency on scale factor (SF) temperature error is theoretically derived. Besides, the correlation between the two main light sources average wavelength and the SF temperature error is discussed. The experimental results show that both the crystal oscillator frequency and the light source average wavelength have a greater impact on the FOG SF temperature error. There is a cubic function relationship between crystal oscillator frequency and temperature, the temperature error of the SF is inversely proportional to the crystal oscillator frequency. Using a higher frequency temperature-compensated crystal oscillator, the frequency stability can be improved by two orders of magnitude, from 67.14 ppm to 0.22 ppm, the SF temperature error is also greatly reduced. The SF error is proportional to the relative change in wavelength, and the change caused by the temperature is of the same order of magnitude. Compared with the super luminescent diode (SLD) light source, the Erbium-doped fiber light source has higher average wavelength stability, the SF error caused by it is also smaller. The error can be reduced by 15 ppm and controlled at about 10 ppm after temperature compensation.

Investigation of heat source position and fiber coil size for decreasing the FOG scale factor temperature error

In this paper, based on the finite element analysis and the heat transfer theory, we analyze the influence of the positions of heat source on the fiber optic gyroscope (FOG) scale factor temperature error. Meanwhile, we explore the effect of fiber diameter and turns and layers of the fiber coil on the scale factor temperature error. The result shows that influence factors of the FOG scale factor error are the space position of heat source and the fiber diameter. When the heat source is set on the top surface of the fiber coil, the scale factor temperature error is less than that of the outside set heat source situation, and reduce this error by 20ppm through using the temperature compensation. No matter how the length of the fiber and the average radius of the fiber coil change, selecting a fiber with a small diameter and a thin coating layer can reduce the scale factor temperature error by 10ppm. However, the variation of turns and layers of the fiber coil affects the scale factor temperature error within 0.05ppm, which is negligible.

Research and Compensation of Frequency Response of LiNbO3 Phase Modulator for High-Performance Fiber-Optic Gyroscope

A lithium niobate (LN) phase modulator is widely spread because ofhigh electro-optic coefficients. Particularly, it is a highly required component for a closed-loop fiber-optic gyroscope (FOG) of navigation and tactical grade. However, low-frequency distortions of LN phase modulator frequency response can degrade the FOG performance. This paper deals with the research and compensation of frequency response of an LN phase modulator. It is a complex task to measure the response of the LN phase modulator in a FOG because of its Sagnac interferometer. Therefore, the special and novel modulation/demodulation algorithm is proposed. To the best of our knowledge and belief, the proposed method is the first published method that provides the measurement of the pulse response of a phase modulator as a part of a closed-loop FOG. The pulse response obtained in the proposed way allows getting appropriate high order transfer function of a phase modulator. For the first time to the best of our knowledge, the humidity dependence of the LN phase modulator frequency response is found. Influence of the phase modulator frequency response on FOG angular random walk, bias drift, and scale factor nonlinearity and instability is theoretically analyzed and mathematically simulated. The algorithmic method of the phase modulator response compensation is proposed and experimentally confirmed. The experimental results show that the proposed measurement technique of the phase modulator transfer function allows creating the compensating inverse filter that provides phase modulator response being close to flat. The application of the proposed method in the FOG operating mode allows reducing unwanted spikes to the noise level.

单模光纤弯曲半径对光纤陀螺标度因数稳定性的影响

单模光纤弯曲半径对光纤陀螺标度因数稳定性的影响

单模光纤弯曲半径对光纤陀螺标度因数稳定性的影响

单模光纤弯曲半径对光纤陀螺标度因数稳定性的影响

Modeling Coherent Backscattering Errors in Fiber Optic Gyroscopes for Sources of Arbitrary Line Width

We present a new model of the noise and drift induced by coherent backscattering in a fiber optic gyroscope (FOG) interrogated with a light source of arbitrary temporal coherence. This study is critical to understand whether a FOG driven with a laser instead of a broadband source can attain high sensitivity and stability, which would have the overwhelming benefit of improving the FOG scale factor stability by at least ten-fold and would enable the use of FOGs for inertial navigation of aircrafts. Analytical and numerical solutions bring to light two significant new predictions. First, coherent-backscattering noise can be made negligibly small by utilizing a laser with a very narrow linewidth (less than ~ 20 kHz), although in this regime the drift is high. Second, by using a laser with a broad linewidth (greater than ~ 10 MHz), both the noise and the drift are low enough for aircraft inertial navigation. The dependencies of the noise and drift on fiber loss, loop coupling coefficient, and backscattering coefficient are also presented to define the optimum mode of operation of this new class of FOGs.