With the rapid growth of the demand for various unmanned platforms, such as small Unmanned Aerial Vehicles (UAVs), small Autonomous Underwater Vehicles (AUVs), Unmanned Underwater Vehicles (UUVs), and driverless vehicles, the miniaturized, integrated, and large-scale production of interferometric Fiber Optic Gyroscopes (FOGs) and the fiber-optic inertial navigation have become an important research field. This paper first introduces the research status of integrated chip gyroscope, and then designs a miniaturized interferometric integrated optical gyroscope based on silicon lithium niobate thin waveguide, focusing on the structural design of silicon lithium niobate thin waveguide. The high efficiency microwave/light wave interaction problem of silicon lithium niobate thin waveguide electro-optical modulation is solved, the volume of optical modulator is significantly reduced, and the half wave voltage of optical modulator is reduced. Polarized waveguide is added to realize the function of traditional lithium niobate waveguide modulator. Finally, due to the stable chemical properties and high hardness of lithium niobate material, it is difficult to process it with conventional silicon waveguide etching process. This paper has conducted a preliminary study on its low loss processing technology. Although the silicon lithium niobate thin waveguide can significantly reduce the volume of the FOG and improve the integration of the FOG, due to the large gap between the size of the thin waveguide and the single-mode fiber core, if the direct alignment coupling is inevitable, a large coupling loss will be introduced. It is necessary to further study the low loss optical coupling technology of silicon lithium niobate to meet the requirements of miniaturized and integrated FOG.
In this paper, in view of mode field matching problem between the anti-resonant hollow-core optical fiber and the conventional optical fibers. We introduce an intermediate SMF fiber with thermal expanded core (TEC) at one end as a transition fiber; at the same time, when we fusion splicing, we use multiple heating methods to avoid the transitional collapse of optical fibers. The optical fiber rotation method is used to monitor the change of optical power and achieve high matching to the shaft to obtain a higher extinction ratio.
In this paper, the theoretical analysis of hollow-core microstructure fiber for improving the temperature stability of fiber optic gyroscope (FOG) is carried out. The analysis shows that the thermally induced Shupe error can be reduced by a factor of about 23 in theory in a hollow-core microstructure FOG. A FOG prototype is constructed by utilizing a 300mlong 7-cell bandgap-guided hollow-core microstructure fiber, and its temperature stability is compared with that of traditional FOG under the same specification conditions. The experimental results exhibit that the hollow-core microstructure fiber in use can promote the temperature stability of FOG by 2.5 times.
A novel fiber optic gyroscope with low coherence laser as driving light source is designed in this letter, the low coherence laser has higher average wavelength stability and lower relative intensity noise which is achieved by using Gaussian white noise phase modulation to broaden the linewidth of a DFB laser. The scale factor stability of FOG can be effectively improved when applied to FOG research.
As a mature product with high commercialization, the fiber optic gyroscope is susceptible to the influence of environmental factors in actual use, which affects the measurement accuracy. In order to improve the temperature adaptability of the fiber optic gyroscope and improve the efficiency of temperature compensation in the engineering process of the gyroscope, a temperature modeling and compensation method based on a multilayer perceptron is proposed. First, based on the working principle of the fiber optic gyroscope, the mechanism that causes the temperature error of the fiber optic gyroscope is analyzed. Then, based on the neural network model of the multilayer perceptron, the structure design of the temperature compensation model of the fiber optic gyroscope is carried out, and the existing data is used to train the model. Finally, the compensation model was verified by experiments. The results show that the bias stability of the gyro can be improved by 80% after compensation using this model. Although this method requires a lot of calculations in the early stage, after the model parameters are solidified, it has strong adaptability, is easy to implement in engineering, and can effectively improve engineering efficiency.
A compact all-photonic-crystal-fiber (all-PCF) polarizer based on fused-type mode-selective fiber coupler is proposed theoretically. Around the wavelength of 1550 nm, the injected unpolarized fundamental mode in the solid-core PCF was selectively coupled into one polarization-mode of polarization-maintained photonic crystal fiber (PMPCF) by welldefined fiber cladding reduction, pretapering and fusion. Numerical simulations indicate the polarization direction of the excited polarization-mode depends on the tapered diameters of solid-core PCF and PMPCF. Moreover, the operation bandwidth of the proposed polarizer is more than 400 nm, which can completely cover the bandwidth of the erbiumdoped solid-core PCF amplified spontaneous emission (ASE) light source. The all-PCF polarizer is anticipated to serve as the key element in the PCF optic gyroscope.
A full-parameter simulating software is developed for closed loop fiber optic gyroscopes (FOGs), which is a very powerful tool for designing and optimizing a FOG. It is visual for researchers to investigate the photoelectric signal processing at all stages in FOGs. All optical and electrical components in FOG, including light source, coupler, MIOC, PMF coil, photodetector ADC, DAC and digital circuit, are modeled numerically in the software. The analyses of the amplitude effect on the spectrum of the light source, the modulation and feedback signal and the half-wave voltage adjustment using the software verify the power of the software.
Interferometric fiber optic gyroscopes driven by lasers are new hotspots in recent years at home and abroad. Semiconductor lasers are considered to be an alternative to traditional broadband light sources due to their high commercial maturity, good average wavelength stability, and low intensity noise. However, the semiconductor laser is a highly coherent light source with a narrow linewidth. When it is used in an interferometric fiber optic gyroscope, it will reintroduce non-ideal characteristics such as Rayleigh scattering, Kerr effect, polarization cross-coupling and so on, which will affect the accuracy of the gyroscope. The linewidth of the semiconductor laser is widened before use. Based on the OptiSystem simulation platform, the article builds a semiconductor laser linewidth widening model, and analyzes and evaluates several different phase modulation broadening techniques and their effects. It has certain guiding significance for the experimental design and engineering application of semiconductor laser linewidth broadening.
According to the principle of optical coherence domain polarimetry (OCDP) technique, the use of a ghost-peak-free white light interferometer is introduced for performance controlling of fiber optic gyroscope (FOG) fiber coils, including raw polarization maintaining fiber (PMF) quality inspection, PMF coil winding process design, coil winding machine performance evaluation and PMF coil temperature induced stress measurement. One can see from measuring result, OCDP testing at all of these stages does provide a very powerful distributed tool for improving the performance of fiber coils.
In view of mode field matching problem between the polarization-maintaining photonic crystal fiber and the conventional optical fibers, the polarization and mode field distribution characteristics of photonic crystal fiber were analyzed and investigated by using a finite element method. The loss mainly comes from the mismatch of two kinds of optical fiber mode field diameter (MFD). The collapse of air hole in photonic crystal fiber can be accurately controlled by heating photonic crystal fiber with fusion splicer, and MFD of photonic crystal fiber can be increased. We presented changing the fusion parameters of fusion splicer to reduce the fusion splicing loss and improve the splicing quality between PCFs and PMF with arc discharge of fusion splicer. Finally, we get a loss of 0.8dB for the later from PCF to PMF, and 0.5dB from PMF to PCF. At the same time, tensile strength is better than 100kpsi.
We propose an optical gyrocompass using a three-axis Fiber Optic Gyroscope (FOG) that is the technological heart of the optical gyrocompass. The core of the optical gyrocompass is a compact strap-down Inertial Measurement Unit (IMU), which contains a three-axis FOG, three accelerometers, and a real-time computer that is responsible for computing all the necessary data for demanding navigation. Thermal design is performed to manage heat conduction and quickly balance inner temperature of the optical gyrocompass for suppressing the thermally induced error, and then the uniform temperature environment is obtained for three-axis FOG. The long-endurance sea trial experiment result proves that the dynamic accuracy of the optical gyrocompass is lower than ±0.25° secant latitude, and it is capable of navigating in high latitude region. The optical gyrocompass is also certified to meet the requirements of the International Maritime Organization (IMO) for gyrocompasses.
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