PURPOSE: To produce a parent material for optical fiber having neither occurrence of foams nor deformation, by heating a glass tube in which a glass rod is set from the outside by a heat source moving relatively to the glass tube to contract the glass tube, and cooling the vicinity of the heat source.
CONSTITUTION: The glass rod 2 is set in the glass tube, heated from the outside of the glass tube 1 by the burner 3 moving relatively in the arrow direction while being synchronously rotated, the glass tube 1 is contracted, the glass tube 1 is successively fused to the glass rod 2 in the axial direction, and integrated. The unfused part of the glass tube 1 in the vicinity of the burner 3 on the side of the arrow progress direction of the burner 3 is sprayed with a N2 gas from the nozzle 4, and cooled. Consequently, the contraction of the glass tube 1 is prevented, the inner face of the glass tube 1 and the glass rod 2 are sufficiently heated and fused. Consequently, a parent material for optical fiber can be obtained stably while leaving foams on the interface, preventing deformation.
TONO RYUJI
KYODO TSUNEHISA
URANO AKIRA
