Method for producing a substrate tube of quartz glass

Abstract

A method for producing substrate tubes of quartz glass includes continuously supplying a hollow cylinder of quartz glass to a heating zone, softening the hollow cylinder zonewise in the heating zone, and drawing off a tubular strand from the softened portion. The hollow cylinder has an outer diameter Ca, an inner diameter Ci and an inner bore. The tubular strand has an outer diameter Ta and an inner diameter Ti. The following parameters are applicable to the hollow cylinder and the tubular strand: Ca>180 mm, Cr>3 with Cr=Ca/Ci, Tr<1.6 with Tr=Ta/Ti and Ci/Ti<2.5. The blow pressure in an inner bore is adjusted to a value in the range of 4 to 10 mbar. Substrate tubes, obtained by cutting the tubular strand to the desired length, serve as semi-finished products for the manufacture of preforms for optical fibers.

Dependencies are inferred from the claim text.