Patent ID: 7021083

Claim:
A method of fabricating a glass tube, comprising: providing a starting member having an axis and arranged for deposition of a soot at a given axial end of the member; applying a first soot on the end of the starting member in such a manner as to form an elongated cylindrical soot core having a first density and which is substantially axially aligned with the starting member; applying a second soot including SiO 2 on the circumference of the soot core in such a manner as to form a soot cladding that surrounds the soot core, and at least a portion of the soot cladding in the region of the periphery of the soot core has a second density greater than the first density of the soot core, thus obtaining a porous soot body of a desired axial length; heating the soot body at a temperature sufficient for sintering the soot core and the soot cladding into a core glass and a cladding glass, wherein the core glass collapses at a greater rate than the cladding glass and the core glass separates radially from the cladding glass; and removing the core glass from inside the cladding glass to yield a glass tube.