An apparatus used for the fabrication of fiberoptic waveguides utilizing a novel melting and resolidifying apparatus and method while under microgravity conditions is disclosed. In one embodiment, the optical fiber core has a lower melting point than the cladding and the core is melted and resolidified under microgravity conditions. The molten lower melting point core is thus contained by the higher melting point cladding while under microgravity conditions.

A furnace assembly for manufacturing a hollow-core optical fiber from a hollow-core fiber preform includes a furnace having a body defining a body cavity extending along a longitudinal axis between a preform input port and a hollow-core fiber output port. The body cavity is configured to locate the hollow-core optical fiber preform and a process gas. At least one primary heating element is proximate a necking region of the hollow-core optical fiber preform and configured to maintain the necking region at a draw temperature, the draw temperature sufficient to soften the necking region. The process gas occupies a flow field surrounding a cladding outer surface. The flow field extends from the necking region to the preform input port and the process gas has a flow with an average Grashof number less than 1.610.sup.4 in the flow field.

A furnace assembly for manufacturing a hollow-core optical fiber from a hollow-core fiber preform includes a furnace having a body defining a body cavity extending along a longitudinal axis between a preform input port and a hollow-core fiber output port. The body cavity is configured to locate the hollow-core optical fiber preform and a process gas. At least one primary heating element is proximate a necking region of the hollow-core optical fiber preform and configured to maintain the necking region at a draw temperature, the draw temperature sufficient to soften the necking region. The process gas occupies a flow field surrounding a cladding outer surface. The flow field extends from the necking region to the preform input port and the process gas has a flow with an average Grashof number less than 1.610.sup.4 in the flow field.