A method of manufacturing an optical fiber

The present invention provides a method of producing an optical fiber having a low transmission loss, the optical fiber comprising a core containing an alkali metal element. Optical fiber preform including a core portion and the clad portion is drawn with a drawing apparatus to form an optical fiber, the core portion has an average concentration of the alkali metal element is less than 5 atomic ppm. During the drawing, the glass temperature was maintained at 110 minutes or less than or equal to 1500 ° C at a time. Draw speed suitably not less than 1200 m / min, more suitably 1500 m / min to 2300 m / min. Suitable fiber preform having a diameter of 70 to 170 mm, more desirably 90 to 150 mm.