Patent ID: 7716952

Claim:
A method for producing a preform for optical fibers, said method comprising: providing a core glass cylinder having a longitudinal axis, producing a fluorine-doped SiO 2 cladding glass on the core glass cylinder rotating about the longitudinal axis thereof, said producing including feeding a plasma burner with a silicon-containing starter substance, said starter substance being oxidized in a plasma flame of the plasma burner so as to obtain SiO 2 particles, and depositing the SiO 2 particles in layers on a cylindrical outer surface of the core glass cylinder in the presence of fluorine and sintering said SiO 2 particles deposited into the cladding glass, wherein said plasma flame emits ultraviolet light in one or more wavelengths of about 214 nm at an intensity of at least 0.9 μW, determined on the basis of a plasma flame intensity measurement, during the forming and depositing of the SiO 2 particles on the core glass cylinder.