Abstract: The present invention relates to an apparatus for carrying out a plasma chemical vapor deposition process by which one or more layers of doped or undoped silica can be deposited on the interior of an elongated glass substrate tube. The present invention further relates to a method for manufacturing an optical fiber using such an apparatus.

Abstract: A method for determining the fundamental oscillation frequency in an optical fibre during the drawing thereof from an optical preform, the oscillation of the optical fibre being measured perpendicular to the longitudinal axis thereof for the formation of a frequency spectrum using Fast Fourier Transformation (FFT), from which the fundamental oscillation frequency is determined, the method including the following steps: i) the determination of the frequency spectrum, ii) the mathematical processing of a number of spectra as determined in step i) to obtain a composite spectrum, iii) the re-determination of the spectrum, iv) the removal of the oldest spectrum from the composite spectrum, v) the mathematical processing of the spectrum according to iv) and the spectrum obtained according to iii) to obtain the composite spectrum, vi) the determination of the fundamental oscillation spectrum from the composite spectrum, vii) the repetition of steps iii)-vi).