High-speed drawing of optical fibers with pressurized coating

To make progress in high-speed drawing of optical fibers, a pressurized coating method was developed on the basis of viscous flow behavior of the coating resin. In a pressurized die, when the shear rate at the fiber surface is minimized, the pressure which is affected by the resin viscosity reaches on optimum condition, resulting in the coating diameter being dependent only on fiber and die diameters. Coating tension is given as a function of pressure so that it is closely related to the optimum pressure through the viscosity. Based on these fundamentals, a 1200-m/min drawing speed was achieved, indicating a smooth and uniform coating with good concentricity. It is clarified that fiber transmission loss does not fundamentally change in relation to the speed.