Two-die assembly for the extrusion of glasses with dissimilar thermal properties for fibre optic preforms

摘要

Extrusion of a preform based on core and cladding glasses with different thermal properties is demonstrated. The core glass (50BaO-8B{sub}2O{sub}3-42P{sub}2O{sub}5) exhibits refractive index of 1.604 and softening temperature of 607℃, while the cladding glass (70Ba(PO{sub}3){sub}2-30B{sub}2O{sub}3) exhibits refractive index of 1.594 and softening temperature of 650℃. Due to the softer nature of the core glass compared to the cladding glass, a novel two-die assembly method is employed for extrusion. The results show that the core glass flows through the cladding glass and be extruded first before stabilising to enable the extrusion of a cane of core and cladding glasses.