Research On The Key Techniques Of Manufacturing Polarization Maintaining Fused Couplers

Polarization Maintaining Couplers, which can transmit orthogonal linearly polarized light steadily and can maintain a state of polarization over long length, are necessary for coherent optical communications systems, fiber-optic sensing systems in military and civil field, especially in the high performance optical fiber gyros and PM hydrophones. Until now, fused biconical taper process has been done manually, using highly skillful techniques. Consequently, the fabrication yield has been low, the consistency of PM Couplers performance has been bad, and has led to high prices for these devices. Taking the theory of manufacturing and the key techniques by FBT as the point of research, the coupling mechanisms of interface between light wave transmission and manufacturing are analyzed, and the rules between fused taper components function and their processing parameters are presented. The purpose of this work is to develop typical manufacturing techniques and equipments for PM Fused Couplers. The contents are presented as follows:1. Azimuthal Alignment for PM Fiber is researched.Using Beam Propagation Method, computer simulation of azimuthal alignment for PANDA Fibers is done, which based on polarization observation by lens-effect-tracing (POL) technique. Basing on simulation results and experiment results, the imaging mechanisms of POL Method are obtained. And the theory of Five Characteristic Points Method is analyzed. The conclusions can provide theoretical direction to azimuthal alignment for Polarization Maintaining Optical Fiber.2. The coupling model of PM Fused Coupler is given and the coupling process theory is analyzed.Basing on the theory of thermal-structural-electromagnetic multiphysics field interaction, the model of PM Fused coupler is given. Using finite element method analysis the effects of the propagation properties for PM Fused Couplers, including the shape of stress applying parts, the refractive index difference between the stress applying part and cladding, the angle disparity of the birefringent axes, and the degrees of fused taper. And the coupling model of PM Fused Coupler is given basing on the coupling mode theory of optical waveguide. A new formula for coupling coefficient of PM Fused Couplers has been derived, which is appropriate for any PM Fiber with core of both circular and nonaligned birefringent axes.3. A manufacturing system for PM Fused Couplers is proposed.The key techniques of FBT system for PM Fused Couplers are analyzed, then designing requirements and principles are present. A high-fine automatic manufacturing system for PM Fused Couplers is present, and it is low cost. The performance is good.4. The processing parameters of fused biconical taper for PM Fused Coupler is studied.The processing parameters of FBT for PM Fused Couplers are investigated. An experimental method that takes into account the drawing speed, hydrogen flux, oxygen flux, and heater height in the FBT process is proposed. By the orthogonal experiments, the influence to the coupling ratio, the extinction ratio and the length of PM Fused Coupler by those parameters is analyzed. The influences of the process parameters to coupler performance are deduced.