Method of and apparatus for manufacturing optical fibers in which a preform is heated in a furnace which is provided with a graphite heating element and a fiber is drawn from the heated preform. The fiber is subsequently cooled, provided with a coating, and, after drying of the coating, the fiber is wound onto a reel.During drawing of the fiber, the preform and fiber are flushed with a gas. According to the invention the gas with which the fiber is flushed is passed along a condensation element.