A Study On Optical Polarization And Thermal Properties Of IFOG

FOG is one of the most important achievements in the field of fiber-optic sensor. Via the unceasing development, it has gained the"preferred"status in the area of inertial technology since last century. In the process of developing FOG, a key technology is the suppression of optical path polarization error, which closely relates to the birefringence of optical devices and becomes particularly more serious and complicated under the influence of environmental factors, e.g. temperature. Thus, there is no hesitation to study the polarization characteristics and temperature performance of FOG's optical path, and improve the design to suppress the polarization errors. The dissertation focuses on the polarization properties and birefringence effect of FOG and studies the fiber coil influenced by the ambient temperature. The main researches are as follows:1. The reciprocity detection principle of FOG's optical path is studied. Using the statistical properties of optical field, the dissertation analyzes the gyro output spectrum changes of the induced association, and concludes the interferometer strictly depends on the light source and the polarization state. It analyzes the relationship between the birefringence and the polarization coupling in optical path by using Poincare sphere method, and speculates the intensity-type and the tamplitude-type polarization error of gyro. It analyzes the polarization state changes and the dependence of optical path polarization induced by parasitic error effect, i.e. the Kerr effect, Faraday magneto-optical effects, back reflection and Rayleigh scattering effect.2. According to the matrix optics principle, a transmission model of FOG's optical path and interference output model are established. Based on the model, the dissertation analyzes exactly the polarization degree of light source and the impact of polarization errors influenced by polarization coupling in the coil. Via the low degree of polarization consumption thought, the paper proposes Lyot depolarize should be introduced in optical path to improve the optical structure of existing single-axis FOG SLD light source, and verifies the advanced nature of the new structure by experiment.3. The dissertation establishes the plane stress model of the Panda type polarization maintaining fiber based on the finite element method, simulates the deformation, stress and distribution of birefringence in the curing process of polarization maintaining optical fiber, analyzes the birefringence of the core affected by temperature, verifies the model is reliability by using the complex variable function method.4. The local cross-section of fiber coil model is established, and the influence of optical fiber coil impacted by of the solid plastic handle is studied by using finite element transient thermal method. The results show that there is a temperature region that is related to the adhesive parameter within the optical fiber coil handled by solid plastic, and the optical fiber coil's sensitivity to temperature changes is to the minimum in this region. The paper validates the correctness and validity of the model by experiments.5. The dissertation proposes that temperature performance of fiber coil should be tested through inspecting the filter characteristic's value explorer of polarization state, establishes the evaluation system of temperature performance in the optical fiber coil based on the temperature experiment, and formulates the detailed test target. It confirms the validity of the scheme through actual test.6. The whole cross section of fiber coil model is set up. It simulates the changes of optical fiber coil's temperature field and interference birefringence during small scales of temperature change by using the finite element method. It also proposes the insulation coil processing programs based on polyurethane foam and the coil heat treatment programs based on and LY12 aluminum alloy hardware. The experimental results show that the improved programs significantly enhance FOG's stability when it is disturbed by temperature.