Patent ID: 8661856

Claim:
An optical fiber manufacturing method, comprising: melting and deforming an optical fiber preform; drawing a melted and deformed portion from the optical fiber preform as a bare optical fiber; forcibly cooling the bare optical fiber in a cooling device; forming a protective cover layer on the cooled bare optical fiber in a coating device; and curing the protective cover layer, the method further comprising: connecting the cooling device and the coating device in an airtight manner and by preventing a cooling gas, flowing inside the cooling device, from flowing into the coating device by a meniscus of resin inside of the coating device, discharging a flow of the cooling gas inside the cooling device to an outside of an upper end of the cooling device as an upward stream; allowing helium gas as the cooling gas to flow into a lower portion of the cooling device and allowing carbon dioxide gas as the cooling gas which is separated from the helium gas to flow into a side lower than a position where the helium gas flows in, during the forcible cooling; and individually controlling a flow rate of the helium gas and a flow rate of the carbon dioxide gas by using both a signal indicating a coating diameter of the optical fiber and a signal indicating a drawing velocity of the optical fiber.