High-Precision Fiber Optic Gyroscope (HPFOG) is the core sensor of the long-endurance fiber optic inertial navigation system. The improvement of the positioning accuracy of the inertial navigation system depends on the improvement of the bias performance and the scale performance of the gyroscope. The broadband ASE light source can effectively suppress the noise such as Kerr effect and Rayleigh scattering in the optical path of the FOG. The flatness of the output spectrum of the ASE light source also affects the scale of the FOG. In this paper, the influence of broadband fiber light source on the bias performance and scaling performance of HPFOG is analyzed theoretically, and the design of a high-flatness C+L band broadband ASE light source is developed. By analyzing the conditions of the output spectrum of the ASE light source from the C-band to the L-band until the C+L band is formed, the pump light power and the length of the erbium-doped fiber are optimized, and the output spectral width, power and spectral flatness of the ASE light source are simultaneously improved. Performance, the developed C+L band broad-spectrum ASE light source has a spectral width of 80nm and a flatness of less than 1.5dB. Subsequently, this paper compares the performance of HPFOG using traditional Gaussian ASE light sources and high-flatness C+L band light sources. The experimental results show that although the spectral symmetry of the C+L band broad ASE light source is weaker than that of the Gaussian spectrum ASE light source, but the scale factor performance of HPFOG is similar, and there is no obvious impact. The key is that the use of high-flat C+L band broad ASE light source significantly improves the bias stability of HPFOG. The normalized index shows that the 100s bias stability is improved by 30%.
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.
Firstly, the requirements of ultra-high precision gyroscope for light source are analyzed. Ultra-high precision fiber optic gyroscope (FOG) is used in long-term inertial navigation system for naval vessels, which requires high precision, stability of scale factor and nonlinearity of scale factor. The stability of the average wavelength of the light source directly affects the stability of the scale factor of the FOG. The high power output of the light source combined with other noise reduction methods can improve the signal-to-noise ratio of the FOG, thereby improving the detection accuracy. The coherence of light source spectrum will affect the coherent noise of the FOG, the symmetry of spectrum will affect the nonlinearity of scale factor, and the spectral width will affect the noise level. Therefore, ultra-high precision FOG requires high power, high wavelength stability, large spectral width, hyperspectral symmetry and low coherence light source. Second, an ASE source for ultra-high precision FOG is proposed in this paper. In terms of optical path, the optical path structure of ASE light source and the means to improve the average wavelength stability of the light source are analyzed. Two-stage Erbium fiber structure is used to obtain high power output. Faraday rotating mirror is used to reduce the polarization-dependent gain in Erbium fibers. High stability of average wavelength is achieved by optimizing erbium fiber parameters and pump power. The non-subpeak Gauss spectrum of the coherence function is chosen as the spectral scheme. In the design of the filter, the orthogonal experiment and hardware-in-the-loop simulation are used to optimize the filter parameters and perform the whole spectrum shaping filtering. The output spectrum width is over 20 nm, which is much wider than 7-13 nm of traditional filtering method,and reduces the noise of gyro noise. In the drive circuit, the high stability temperature control of the pump is realized. By controlling the temperature characteristics of the feedback loop devices, the power stability of the light source is greatly improved by using the power feedback mode. The ASE light source designed above can provide power output of more than 30 mW. The wavelength stability is less than 5 ppm in the whole temperature range, and less than 1 ppm at the constant temperature. The power variation is less than 1%, and the spectrum width of output is more than 20 nm. It is an ideal light source for ultra-high precision fiber optic gyroscope..
As high-precision fiber optic gyroscopes, especially three-axis high-precision fiber optic gyroscopes, face harsh electromagnetic environments, Y-junctions have become a key component that affect the precision of fiber optic gyroscopes. A high extinction ratio Y-junction is fabricated to suppress the polarization mode coupling of the fiber optic gyroscope and reduce the noise of the fiber optic gyroscope. The experimental results show that the above methods effectively solve the effect of the deterioration of the precision of the fiber optic gyroscope caused by the Y-junction.
With the change of working time and environmental conditions, the performance of optical fiber coil has deteriorated, which seriously affects its long-term stability. In recent years, the performance of fiber optic gyroscope(FOG) has been continuously improved, and the requirements for adhesive of fiber optical coil have become higher and higher. It is required not only to meet the stability of coil potting, but also to resist high and low temperature environment for a long time during operation of FOG. In view of this, the study in the environmental stress effects of optical fiber coil adhesive was carried out. Based on optical fiber coil, this paper introduces the environmental stress and its influence mechanism of polymer materials aging, and focuses on the optical fiber coil adhesive aging behavior, as well as analyses the physical and chemical properties of adhesive. On basis of this, environmental stress tests were carried out, and the physical and chemical properties of adhesive were obtained. The experiment and analysis results showed that the glass transition temperature will significant transfer under excessive ultraviolet exposure or a long time high temperature of 85degree Celsius and low temperature of -45degree Celsius, and the adhesive viscosity significantly increased in high humidity environment. Under the comprehensive effect of various environmental stress, the adhesive properties will changed and further affect the stability of optical fiber coil.
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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