Patent ID: 8607592

Claim:
An optical fiber manufacturing method using an optical fiber manufacturing apparatus including a heating furnace in which an optical fiber is formed by melt-drawing an optical fiber preform having a dummy portion provided at an end portion thereof while the optical fiber preform is moved in a longitudinal direction thereof, and a sealing mechanism which is provided on an opening portion located at an upstream of the heating furnace, includes three or more seal members contacting an outer peripheral surface of the optical fiber preform and dividing an internal space into three or more compartments along the longitudinal direction of the optical fiber preform, and seals the heating furnace with an inert gas by preventing external air from intruding into the heating furnace while the optical fiber preform is inserted through the heating furnace, the optical fiber manufacturing method comprising: preparing an optical fiber preform having a dummy portion with a contraction portion having an outer diameter reduced more than that of a body and a changing reduction width; supplying an inert gas to a lowermost compartment closest to the heating furnace among the compartments and into the heating furnace; controlling a total sum of flow rates of the supplied inert gases to be substantially constant; and moving the optical fiber preform so that the contraction portion does not simultaneously meet all compartments from an uppermost compartment farthest from the heating furnace among the compartments to the lowermost compartment, wherein a distance between adjacent seal members is set to be greater than a length of the contraction portion in the longitudinal direction of the optical fiber preform.