With the rapid development of the fiber optical gyroscope technology and its widely applies, the multi-axis Fiber Optical Gyroscope (FOG) such as the triaxial FOG and its system are popular more and more.[1-2] For the requirement of less weight and less size,[2] the multi-axis FOG needs higher electromagnetic structure design skills and more critical devices compared with uniaxial FOG. The Z axis of some triaxial FOGs occur the problem of the bias instability over tolerance, which is a real engineering case in our development process. In this paper experiments are carried out after the influence factors are analyzed. Results show that the modulation of the Z axis is interfered by the other two axes. There are three test steps in the experiment including the optical unit test, the modulator test and the modulator shield test with different materials. A simulation of the original shield structure is applied in order to find the structure defects. Two defects are found on the base of the analysis of the electromagnetic structure check. The main defect is that there is a hollow structure on the top of the Z axis in the system which causes extra electromagnetic circuit from the other two axes. The other defect is that each axis is exposed under complex circumstance with less modulator shield. The modulator with less shield has the merit of less thermal stress owing to the free contraction between the metal packaging and the modulator. In our triaxial FOG system, the modulator shield structure inherits from the uniaxial FOG with less shield, in order to decrease the thermal stress. As we know, in the uniaxal FOG the modulator will still robustly work under a clean electromagnetic circumstance, even there is no shield upon the modulator. However, in the multi-axis FOG there are obvious crosstalk interference between the different axes, when all axes are working together with a close frequency. Based on the experiments and the analysis, the following design principles are given. Firstly, the thermal factors, the vibration factors and the electromagnetic factors should be considered at the same time when the modulator shield is designed. Secondly, the Fe-Ni material has better shield effect than the common metal like Aluminum. Thirdly, there are two kinds of resins, the hard buffer and soft buffer, to connect the Y-junction fiber tail and the metal capsulation. This paper is of great use to the engineering of the multi-axis fiber optical gyroscopes and the fiber optical gyroscope system applications.
As a new generation of INS products, high-precision FOG has been widely used. High precision fiber coil is the sensitive core of high precision fiber optic gyro. Its performance and reliability index determine the performance and reliability of high precision fiber optic gyro. In this paper, the key process methods and parameters that affect the performance and reliability of optical fiber coil are studied. Firstly, the process flow chart of high-precision fiber optic gyroscope is drawn, and every process link of high-precision fiber optic coil manufacture is deepened. Through theoretical analysis, the key process and process parameters affecting the performance and reliability of high-precision fiber optic coil are identified. Then carry out the corresponding process validation test at the same time, through the analysis of the test results to verify the previous theoretical analysis. Then the optimization design and reliability growth research are carried out for the key process, and the control of the key process is strengthened to improve the performance and reliability index of the coil from the process link.
Different from the traditional mechanical gyroscope, fiber optic gyroscope (FOG) has the characteristics of fast start-up speed, high precision, small volume, and low cost, which has been widely used in the fields of sea, land, air and so on. With the wide application of FOG, the problem of its reliability has gradually emerged. Among all kinds of reliability problems, the problem of degradation of the input axis misalignment angle of high-precision FOG with the time is particularly prominent. If it cannot be solved as soon as possible, this problem will seriously affect the actual use of highprecision FOG In this paper, a fault tree is established, which takes the degradation of the input axis misalignment angle of high-precision FOG with time as the top event. The physical and chemical factors and manufactucoil process parameters that cause the degradation of the misalignment angle are analyzed. Through the study of the degradation mechanism, it is concluded that the change of the size stability of the fiber coil is one of the main factors that cause the degradation of the misalignment angle with time. Then we design and build a special testing system for the misalignment angle of highprecision FOG. The degradation mechanism of the misalignment angle of high-precision FOG is verified by experiments. The theoretical analysis and experimental results show that the stability of the size of fiber-optic coil changes with time, which will have a very bad impact on the reliability of the misalignment angle of FOG. Finally, through the design and process optimization, the reliability of the misalignment angle of gyro can be improved.
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.
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