Fluoride glasses and methods for making optical fibers from the glasses

摘要

An optical fiber having a core with a composition consisting essentially of 48 to 60 mole percent ZrF.sub.4, 15 to 25 mole percent BaF. sub.2, 1 to 5 mole percent LaF.sub.3, 1 to 5 mole percent AlF.sub.3, 15 to 22 mole percent NaF, and 1 to 8 mole percent ThF.sub.4 ; and a cladding having an index of refraction lower than that of the core. The glass of the core can be doped, for example, with rare earths. Built-in casting, rotational casting, casting around a rod, and rod-in-tube methods can be used to produce optical fibers having a composition in accordance with the present invention and having improved resistance to crystallization, as compared to ZBLAN glasses, even in the presence of rare earth dopants.