PRODUCTION OF OPTICAL FIBER

摘要

PURPOSE:To stably obtain high-strength optical fiber, by continuously detecting drawing tension of optical fiber between a drawing furnace and a polymer coater in a noncontact may with optical fiber and setting a drawing condition to maintain the drawing tension constant. CONSTITUTION:A detector 7 for vibration frequency of optical fiber to continuously detect a vibration frequency f in the direction perpendicular to the drawing direction of an optical fiber 3 in a noncontact way with optical fiber is set between a drawing furnace 2 which heats and softens an optical fiber preform 1 and a polymer coater 8 to apply a polymer to the outer periphery of the optical fiber 3 formed by drawing. Then vibration frequency f of the optical fiber is continuously detected and drawing tension T of the optical tension 3 is calculated by the formula (rho is lineal density of the optical fiber 3; l is distance between molten fiber of an optical fiber preform 1 and the polymer coater 8). Then a drawing condition is subjected to feedback to maintain the drawing tension at a desired fixed value.