Abstract: A vapor delivery system for the manufacture of an optical preform includes a deposition bubbler (60) and another bubbler (40) referred to as a supply bubbler which is interposed between a reservoir (24) of a liquid and the deposition bubbler. Heat energy is applied to the supply bubbler and to the deposition bubbler to vaporize liquid therein. A carrier gas is introduced into the liquid in the supply bubbler at a location below the free surface and into the deposition bubbler to cause vapor of the liquid to become entrained in the carrier gas and to flow from the supply bubbler into the deposition bubbler and from the deposition bubbler to a substrate tube from which an optical preform is made. Facilities are provided for maintaining sufficient liquid in the supply bubbler and suitable temperatures of the liquid in the supply and deposition bubblers to control the vapor flow into and out of the deposition bubbler to prevent unintended perturbations in the deposition bubbler.

Abstract: A hybrid extruder provides plastic insulation which is as uniformly and tightly disposed about a substrate as that produced in a conventional pressure extruder and accommodates irregular substrates. The hybrid extruder includes a core tube which is positioned in a die cavity to form a flow passage which includes a restriction to the flow at the end of the core tube to maximize the pressure in the plastic material. The leading end of the core tube is spaced a distance from the land of a die which is substantially less than in conventional pressure extruders to form another portion of the flow passage having a predetermined configuration. After flowing through the restriction, the plastic material expands. This avoids any backflow of the plastic material into the core tube in the event the core tube is to allow the passage of oversized spliced portions of the substrate.

Abstract: A coating material is applied to drawn lightguide fiber in a manner which substantially prevents the inclusion of bubbles and which causes the fiber to be disposed substantially concentrically within the coating layer. The lightguide fiber is advanced through a continuum of coating material, which extends from a free surface of a reservoir and through first and second dies that are arranged in tandem, at a velocity which causes air to be entrained in the coating material. A pressure gradient is established between portions of the first die adjacent to its exit orifice. The first die communicates with the reservoir and is spaced from the second die to provide a chamber which communicates with a pressurized supply of the coating material.