Apparatus and method for producing light conducting fibers having a core disposed in a loose fitting cladding tube

摘要

A method and apparatus for producing a light conducting fiber having a core disposed in a loose fitting cladding tube characterized by a double crucible arrangement having a first crucible for a melt of the material for the cladding tube and a second crucible for the melt of the material of the core. The second crucible has an orifice of a given diameter and the first crucible has a ring-shaped orifice with an inner diameter greater than the given diameter of the orifice of the second crucible with the center of the ring-shaped orifice being arranged substantially on a central axis of the orifice of the second crucible so that a core drawn from the orifice of the second crucible is substantially concentrically disposed within the tube of material drawn from the ring-shaped orifice. In each embodiment of the apparatus, the first crucible is an annular crucible having a ring-shaped cross section and the second crucible is either disposed above the first crucible so that the core drawn from the second crucible passes through a hollow passage or is disposed in the central space either with spacing from the walls of the first crucible or with the inner wall of the first crucible forming the wall of the second crucible. Preferably, an inert gas is injected between the core and the tube to prevent collapsing of the tube during the drawing of the fiber.