Abstract: In a known method for the production of a blank mold for optical fibers, a fluorine-doped SiO2 enveloping glass is produced on a core glass cylinder that rotates about its longitudinal axis, wherein a silicon-containing starting substance is fed to a plasma burner, said substance is then oxidized in a plasma flame assigned to the plasma burner to obtain SiO2 particles, the SiO2 particles are deposited by layers on the enveloping surface of the cylinder of the core glass cylinder in the presence of fluorine and sintered into the enveloping glass. The invention aims at providing an economical method, which builds upon the above-mentioned method, in order to produce a blank mold from which optical multi-mode fibers (52) can be obtained.

Abstract: A known method for producing a cylindrical body uses a precipitation assembly (5) consisting of several precipitators (4), to which a parent substance is fed via medium supply lines (9), whereby the precipitation assembly (5) completes a closed trajectory (6) according to a predetermined displacement course, said trajectory comprising at least one precipitation path (8) that runs along the longitudinal axis (2) of the support. The aim of the invention is to provide an economical, reproducible, failsafe method based on said known procedure, which enables in particular the production of soot layers (3) on a support (1) at a high precipitation rate and nevertheless a high degree of uniformity. To achieve this, the displacement course (6) comprises a first loop (7a, 8) and a second loop (7b, 8), whereby the completion of the first loop (7a, 8) causes a right-hand torsion in the medium supply lines (9) and the completion of the second loop (7b, 8) causes a left-hand torsion in said lines (9).

Abstract: A hollow cylinder is held in a vertical orientation and sent continuously through a heating zone for sintering. In a first phase of the sintering operation, the hollow cylinder stands on a support while the upper end (12) of the cylinder is being sintered. In a second phase the cylinder hangs from a hanging element while its lower end (10) is sintered. A vertical rod is fixed to the base on which the lower end is supported, and extends through the hollow cylinder. A retaining ring is fixed inside the upper end of the hollow cylinder. During the first phase, the upper end vitrifies and contracts so that the retaining ring engages the vertical rod. Longitudinal contraction causes the lower end to lift off the base so that the cylinder is suspended during the second phase.

Abstract: A hollow cylinder is held in a vertical orientation and sent continuously through a heating zone for sintering. In a first phase of the sintering operation, the hollow cylinder stands on a support while the upper end (12) of the cylinder is being sintered. In a second phase the cylinder hangs from a hanging element while its lower end (10) is sintered. A vertical rod is fixed to the base on which the lower end is supported, and extends through the hollow cylinder. A retaining ring is fixed inside the upper end of the hollow cylinder. During the first phase, the upper end vitrifies and contracts so that the retaining ring engages the vertical rod. Longitudinal contraction causes the lower end to lift off the base so that the cylinder is suspended during the second phase.