Study On Fused Biconical Tapering Manufacturing Technology Of Fine Polarization Maintaining Fiber Coupler

Polarization-maintaining fiber(PMF) couplers composition of PMF are important passive components for achieving polarization light coupling, splitting, and multiplexing and are key components of fiber optic gyroscopes(FOG). The fine fiber in the manufacture of PMF coupler can not only be used to reduce its volume, which increases the integration of FOG, cuts down production costs and reduces temperature sensitivity, but also can improve its performance. It is an important tendency in the development of optical component manufacture by fine PMF, so the study on fine PMF coupler manufacturing is very necessary.With the diameter of fine fiber using tendency to several tens of micrometers, many features, such as easy bending and torsion, less strength, are not conductive to the fiber alignment and fused biconical tapering(FBT). Therefore, in this paper, four key technologies on the fine PMF coupler manufacture are studied. High precision of fiber alignment, analysis of FBT creep, drawing force control and heating technology are deeply investigated in detail. Based on it, a fine PMF coupler manufacturing platform is designed.In the aspect of high precision of PMF alignment, the mathematical model of panda PMF index is established, and then the side view method is simulated. By the simulation result, the variation of maximum light intensity in the fiber image near the focus can be choosed to detect polarization axis parameter of PMF. A method on coaxial adjustment between the fiber core and the center of rotation stage is designed. The equation of the straight line of the fiber center and its intercept are obtained by image processing and the least squares method, further the distance of the fiber center and the rotary stage is determined. The experimental alignment data is processed using the Fourier filtering method. By fitting the experimental data with the cubic spine method, the panda PMF polarization axis is detected.In the aspect of analysis of FBT process, FBT procedure is the process of fiber creep. Glass transition temperature and fiticive temperature of viscoelastic material, mechanical property and characteristics of thermorheological simplicity are analyzed. The fiber material transition temperature is obtained by drawing experiment. Generalized Maxwell model is adopted to describe the stress relaxation of fiber material. The creep relaxation curves of the optical fiber material are measured. Based on them, retardation weights and times are solved by conditional optimization search with constraints of retardation moments. The relationships between retardation modulus and relaxation modulus can be determined and then relaxation weights and relaxation time are obtained. The fiber creep model established by the convolution relationship between the relaxation modulus and creep compliance, is numerical solved at two temperatures. Finally, creep model and creep velocity model of the optical fiber are obtained.In the aspect of drawing force control, a control drawing device is designed, which mainly consists of computer, drawing mechanism, rotary position encoders and electromagnetic force control circuit. By detecting the rotation angle of the fiber clamp, the drawing force can be controlled in real-time through changing the coil current. A three dimensional model of a permanent magnet and a coil is constructed, and the relationship among the coil current, rotation angle of the clamp, and electromagnetic force is determined using finite element simulations. Electromagnetic force control can be realized by computer simulation. Control circuit of electromagnetic force is designed and the relationship between drawing force and electromagnetic force is established. The expression among the current of coin, the rotating angle of fiber clamp and drawing force are obtained by the experiments, by which the drawing force control can be realized.Finally, a fine PMF coupler manufacturing platform is presented. The closed-loop controls of the voltage and current are applied for the success of the arc ignition and the stability of arc discharge current. The temperature detection device in which the infrared camera is adopted to measure the heating region temperature is designed. By the analysis of experimental data, the relationships among the frequency, arc control voltage, arc current, heating distance and arc region temperature are determined. Temperature of arc center region and heating stability are obtained and the preheating time is computed by finite element method. The fiber gripping clamps are designed and the velocity control strategy in FBT is studied. Optical path of extinction ratio detection is designed. Finally, using this manufacturing platform, PMF couplers are produced.