Method of processing glass optical fiber and method of drawing optical fiber

A method of drawing an optical fiber in which a glass optical fiber is drawn while fusing by heating and pulling by a pulling mechanism one end of an optical fiber preform made of glass, the method comprising:

• drawing the glass optical fiber from the one end of the optical fiber preform while controlling a drawing speed to make an external diameter of the glass optical fiber larger than an external diameter of a product-to-be glass-optical fiber;
• adjusting an external diameter of the glass optical fiber to an external diameter passable through a die for forming a coating;
• and
• arranging the die around the glass optical fiber having the external diameter passable through the die, wherein
• the drawing includes:
• increasing the external diameter of the glass optical fiber to a target external diameter at a drawing speed slower than a target drawing speed;
• accelerating the drawing speed to the target drawing speed while maintaining the external diameter of the glass optical fiber at the target external diameter after the external diameter of the glass optical fiber has reached the target external diameter;
• and
• drawing the glass optical fiber by a predetermined amount while maintaining the target external diameter and the target drawing speed, and in the adjusting, the external diameter of the glass optical fiber is adjusted concurrently with decelerating of the drawing speed to a drawing speed at which the die is arranged.