METHOD OF MEASURING DRAWING MELT VISCOSITY OF OPTICAL FIBER BASE MATERIAL

摘要

PURPOSE:To measure the viscosity of the melt deformed part of an optical fiber base material with high reliability by determining the distribution of the viscosity by using specific equation in the case of drawing the end part of the optical fiber base material in the axial direction Z of the heated and melted optical fiber base material by a drawing tension F while heating and melting the optical fiber base material. CONSTITUTION:The optical fiber base material 15 is inserted into a heating apparatus 11 along the axial direction Z thereof and the end part of the base material 15 heated and melted in the apparatus 11 is drawn by the drawing tension F in the Z-axis direc tion. The balance of viscous force and tension is dominant in the quartz glass which is the representative material of the base material 15 in this case. The outside diameter (a) of the melt deformed part 17 is measured in the case of designating the outside diameter of the melt deformed part 17 of the base material 15 as (a) and the velocity in the Z-axis direction of the melt deformed part 17 as (v) and the measured outside diameter value is substd. for a<2>V=constant to determine the velocity (v). The deter mined velocity (v) is substd. for pia<2>/4X3eta(av/aZ)=F=constant, by which the distribution of the viscosity eta of the melt deformed part 17 is determined.