An object of the present invention is to provide an optical fiber manufacturing method and an optical fiber in which an increase in the transmission loss is suppressed by preventing hydroxyl group from entering near the core portion. Feed gas stream is cooled and separated into a vapor stream and a condensed stream. The system utilizes a plurality of short stroke pistonscylinders and a unique pulley and cable arrangement permitting the operating mechanism to be located directly above the mud flaps wherein the length of the cables required is kept to a minimum thus reducing the overall space requirements of the system.