PURPOSE: To manufacture an optical fiber having low transmission loss, in a short time, by drawing a hollow glass tube under heating with a heat source moving along the lengthwise direction of the tube in the inner-deposition CVD process, thereby forming a solid preform.
CONSTITUTION: A hollow glass tube 1 used as the starting material is attached to the rotary supporting means 2, 2', and oxygen gas and a raw material gas 6 for forming the glass layer, e.g. SiCl4, POCl3, GeCl4, etc. are introduced into the rotating glass tube 1. A glass layer 4 for forming a light transmission path having a specific refractive index is deposited to the inner surface of the glass tube 1 by reciprocally moving the heating source 3 such as oxyhydrogen burner along the lengthwise direction of the tube. Thereafter, the heat of the source 3 is intensified to contract the cross-section of the glass tube 1, the temperature is controlled at about 1,800°C, and the rotary supporting member 2' is moved along the direction of the arrow 22 while traversing the heating source 3 along the lengthwise direction of the tube 1 to effect the drawing and solidification of the glass tube 1 and obtain the solid preform.
OKAMURA KOUJI
YUASA MITSUO
