ACCUMULATING METHOD FOR FINE GLASS GRAIN

摘要

PURPOSE:To secure the stability of an air stream in a period of the accumulation of the fine glass grains and to form a porous glass layer having the superior quality by rotating and transferring slowly a burner along a locus circle in a period of the formation of the porous glass layer. CONSTITUTION:A rodlike base material 21 is interposed between a burner 11 and an exhaust port 18 and rotated in the direction shown in an arrow R and transferred in the V direction. An injection end part of the burner 11 is directed toward a point P of the exhaust port 8 which is deviated from a rotating axial core O of the base material 21. The fine glass grains are injected on an outside periphery of the base material 21 from the burner 11 to form a porous glass layer 22. When a laser beam L circumscribed to the peripheral surface of the base material 21 is interrupted by the accumulated formation of the porous glass layer 22, the burner 11 and an irradiator 19 provided thereby are drawn in the direction shown in an arrow S with a guide rail 13 as the guidance. The angular laser beam is made incident on a detector 20 and the porous glass layer 22 is accumulated up to a prescribed thickness. Thereby the air stream of the burner is smoothly flowed to the exhaust port 18 along the peripheral surface of the porous glass layer 22.