PRODUCTION OF OPTICAL FIBER PREFORM

摘要

PURPOSE:To provide a production method of an optical fiber preform capable of producing an optical fiber preform so that the cross section may become nearly circular and making density distribution in the circumferential direction uniform. CONSTITUTION:An optical fiber preform 5 is continually pulled up in a cycle independent of the growing rate of the tip or continuously pulled up in independent rate. Beam 9 of light which crosses the tip of the optical fiber preform 5 measures length of time blocked at the tip of the optical fiber preform 5 or measures length of time which is not blocked with a pulse counter 15 and a core part raw material gas flow rate controller 19a and clad part raw material gas flow rate controller 19b are controlled by the outlet and flow rate of the raw material gas fed to a burner 3 for core and a burner 4 for clad is controlled.