Numerical Computation of Diameter Fluctuation in Optical Fiber Drawing from Silica Glass Preform by Perturbation Method

Abstract

One-dimensional numerical model of optical fiber drawing to predict diameter fluctuation caused by periodical fluctuation of heat transfer between silica glass preform and furnace gas, has been developed by using perturbation method based on steady solution. It is assumed that heat transfer coefficient is fluctuating in neck-down region and its frequency range is 0.001∼100 Hz. As a result, it is revealed that relationship between fluctuation of heat transfer coefficient and that of diameter can be divided into three modes by the order of diameter gradient and velocity gradient at heat transfer fluctuating point. The diameter fluctuation of first mode is large in low frequency range and that of third mode is so in high frequency range. As drawing velocity become higher, the fluctuation of third mode becomes larger, because velocity gradient becomes higher. And as heater becomes longer, the region of second mode becomes wider, because velocity gradient of heater region decreases.