Analysis of glass flow during extrusion of optical fiber preforms

Billet extrusion is a powerful technique for fabricating soft glass optical fiber preforms. This paper reports progress in the understanding of the relationships between extrusion process parameters and the die geometry. The friction for glass flow within the die is described by a die constant that can be either calculated using die feature dimensions or determined using processing parameters and a glass with known temperature-viscosity behavior. In complex dies in which the glass flows through an array of feed holes the friction can be calculated from the number, length and diameter of the individual channels within the die. The glass flow analysis allows improvement of the extrusion process and guidance of future die design. © 2012 Optical Society of America.