FIELD: optic glass fibers. SUBSTANCE: invention largely aims at controlling stretching of fibers when being drawn out. This aim in mind, one measures lateral vibrations of fibers, analyzes multitude of frequencies constituting lateral vibrations, selects one with maximum amplitude, ascertains the base frequency to be that with maximum amplitude, and calculates value of current stretching of fiber from measured diameter and base frequency of lateral vibrations. When calculated value deviates from desired stretching value, stabilization of stretching is performed in accordance with found deviation. Another part of invention concerns fiber manufacturing process and consists in that glass stock is heated, fiber is drawn out, passed through coating application device, and lateral vibrations of fiber are measured at a point between glass stock and coating application device. In event calculated fiber stretching deviates from desired value, stabilization of stretching is performed by way of changing temperature of heating glass stock. EFFECT: improved process control. 6 cl, 8 dwg
