Extrusion method for making fiber optic preforms of special glasses

Abstract

Extrusion of glass rods, tubes and core/clad performs of melt-derived, special glasses is being investigated to satisfy demand for preforms from which optical fiber can be drawn. These glasses include: heavy metal oxide, chalcogenide, halide as well as mixed systems such as oxyhalide, chalcohalide, and oxychalcogenide. Extruder equipment has been commissioned and progress in extrusion of rods, core/clad preforms and multimode, and monomode, proportioned tubes is described extruding water soluble sodium borosilicate glasses, for convenience. The extrusion process has been shown to produce good quality glass rods of close to 5mm diameter and tubes of sodium borosilicate glasses with OD of the order 10mm and OD/ID equals 2.5, 4.1, 7.1 and 11.0. The latter ratio approaches that required for a monomode proportioned preform. Tolerances on OD were within +/- 0.32mm and on ID were within +/- 0.19mm over at least 160mm of tube. The tube orifice out-of-round was <EQ 0.13mm at a measured point along the tubes. Also reported is the successful extrusion of Ga-La-S glasses which have potential as host glasses for rare earth doped optical devices.