High bandwidth optical waveguides and method of fabrication

摘要

A method of forming a preform or blank for a high bandwidth gradient index optical filament, the preform itself and the resulting optical filament is disclosed. The preform which ultimately forms the optical filament includes a barrier layer between a tubular starting member which comprises the cladding and the core, the index of refraction of the barrier layer being equal to or less than the index of refraction of the tubular starting member; there being no step increase in the index of refraction of the barrier layer at the barrier layer-cladding interface nor of the core at the core-barrier layer interface of the optical filament. The barrier layer is formed from a base glass, a first dopant B2O3, and at least one other dopant which is maintained substantially constant in the barrier layer and then gradually varied during the formation of the core. The quantity of B2O3 is also maintained substantially constant in the barrier layer but then gradually decreased during the formation of the core.