Evolution of technological stress fields in cylindrical stress applying rod for optical fiber Panda-type during annealing

Investigated evolution regularities of the technological stress fields in the rod for preform of fiber Panda type during annealing. It is shown that the main reason of reducing the levels of the stress state is the relaxation, due to viscous deformation of silica glass in the temperature range of the glass transition. Implemented mathematical model of technological stresses formation in stress applying rod, on the basis of linear thermoviscoelasticity relations in conditions of annealing. Numerical analysis performed using finite element method (FEM). Identified the quantitative characteristics of stress relaxation in different process conditions of annealing. Defined modes that provide the maximum possible reduction of hazardous tensile normal stress and intensity of the stress tensor. Found that for the rod with uniform doping, the annealing process is more efficient than for the rod doped with regularity close to parabolic.