METHOD AND APPARATUS FOR TWISTING A COATED OPTICAL FIBER DURING DRAWING FROM A PREFORM

A method for manufacturing an optical fiber (100) having low PMD, comprises the steps of: a) heating at least one end portion (3a) of a preform (3); (b) drawing an optical fiber (100) from a free end of said heated end portion (3a) along a fiber drawing axis (I-I); c) coating said optical fiber (100) with a suitable coating material; d) applying to said coated optical fiber (100) a torque about said fiber drawing axis (I-I); e) winding said coated optical fiber (100) onto a collecting spool (9). According to the invention, step d) is carried out by means of a pulley (16) supported upstream of said collecting spool (9) and rotated about the fiber drawing axis (I-I), said optical fiber (100) being wound up onto said pulley (16) for an angle of at least about 360 DEG . Advantageously, such method also allows to notably increase the amount of optical fiber produced per unit of time with respect to the prior art. Disclosed is also an apparatus for carrying out the method and a device for applying torque to the fiber comprising a pulley.