Heraeus Quarzglas Gmbh & Co Kg

Furukawa Electric North America, Inc.

Heraeus Tenevo Gmbh

Oliver Humbach

Oliver Ganz

Thomas Bogdahn

Harald Hain

Hartwig Schaper

Donald Jablonowski

Norbert Treber

Frank G&auml;nsicke

Uwe Haken

On the basis of a known process for the production of a preform for an optical fiber for optical data transmission technology, the productivity of the process for the production of complex refractive index profiles is to be improved by providing a quartz glass substrate tube which exhibits different doping in radial direction, introducing a core glass made of synthetic quartz glass into the substrate tube and covering the substrate tube with a jacket tube. A substrate tube suitable therefor is also being provided which tube requires less core glass material for the production of the preform, whether during the internal deposition or for the core glass rod in the rod-in-tube technique. Regarding the process it is proposed according to the invention that a substrate tube be used which was obtained by vitrification of a porous tube-shaped SiOblank, the substrate tube being provided with a core glass layer which is produced in that to the first radial portion of the SiOblank there is added before the vitrification a first dopant which increases the refractive index of quartz glass. The substrate tube according to the invention has in the radial direction regions of different doping whereby it incorporates a core glass layer which has a refractive index of at least 1.459.

Method of making a jacketed preform for optical fibers using OVD

In a known method for the manufacture of a tube made of a vitreous material, especially of quartz glass, a hollow cylindrical semifinished product made of a vitreous material is carried essentially vertically to a heating zone, wherein it is heated and drawn off downwards&mdash;without the use of tools&mdash;to the tube by forming a transitional area from semifinished product to tube, while diameter and wall thickness of the tube are continuously measured, and the tube's measured geometrical data being used to generate a control signal with the aid of which a pressure difference is regulated between pressure P in the interior space of the semifinished product, the transitional area and the tube, as well as pressure P in the heating chamber which is regulated in the heating zone at least in the transitional area from semifinished product to tube and its adjacent tube area. This method is to be developed further so as to enable the processing of a broader spectrum of hollow cylindrical semifinished products to tubes with the desired inside and outside dimensions. This task is solved according to the invention such that for the manufacture of tubes with the ratio of their outside diameter (D ) to their inside diameter (D ) being greater than the ratio of the outside diameter (D ) to the inside diameter (D ) of the semifinished product&mdash;pressure P in the inside space of the semifinished product, the transitional area and the tube being kept at a value which is smaller than the value of pressure P in the heating chamber, with pressure P being maintained by means of a suction (vacuum) pump.

Method for producing a tube made of quartz glass using low internal pressure and control of diameters

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Seligenstadt, Germany

Oliver Humbach