Abstract: A method and a system based on the method imparts to an optical fiber a predetermined rotation about its axis, wherein the fiber is rotated by way of a frictional force acting on the fiber while it is advanced in a predetermined direction. The rotation actually imparted to the optical fiber is measured on-line while the fiber is advancing in the direction and the frictional force is controlled responsively to the measured rotation so as to obtain the predetermined rotation. Spinning devices acting on the optical fiber by way of an externally controllable frictional force and particularly suitable to be used with the method are disclosed.