A method of manufacturing an optical fiber, whereby a fiber is drawn from a molten extremity of a preform and is subsequently subjected to a torque, thereby causing a portion of the fiber to be twisted about its longitudinal axis and to be endowed with a spin. The torque is applied by running the fiber between a pair of wheels which rotate in mutually opposite senses about two different rotational axes, each wheel having a peripheral curved surface, the wheels being thus arranged that the fiber runs substantially tangential to their curved surfaces and is pressed therebetween, the wheels being moved back and forth relative to one another in a direction substantially perpendicular to the fiber so as to cause the fiber to be rolled back and forth between their curved surfaces.