Glasses and methods for making them

摘要

A glass suitable for use in optical fibre cores has a refractive index of 1.540-1.610, Na2O and B2O3 in a molar ratio of 1.05-2:1, 2-12 mole percent BaO, 40-63 mole percent SiO2, and 1.5-15 mole percent ZrO2, the proportion of SiO2 and ZrO2 together not exceeding 65 mole percent. The glass can be prepared in a highly reduced state by the use of CO and a redox buffering agent. The glass is especially suitable for the production of high numerical aperture wide cored fibres.