A method for manufacturing a preform for drawing optical fiber and an apparatus for manufacturing a preform

摘要

The present invention relates to a method for manufacturing a preform for drawing optical fiber. The method comprises the steps of (A) providing a tube having a longitudinal center axis and (B) arranging a bottom part to the vicinity of a first end of the tube. Then, (C) a first granular material is introduced via a first nozzle into a first predetermined space in said tube to form a first material layer surrounding said longitudinal center axis in said tube. This step is followed by (D) introducing a second granular material via a second nozzle into a second predetermined space in said tube to form a second granular material layer, which is coaxial with said first granular material layer in said tube. Finally, (E, F) the tube is heated to a melting temperature for melting the tube and contents of the tube into a preform.