Slip mechanism in optical fiber coating with open-cup applicators

The allowable maximum coating speed of optical fibers has been correlated to the flow properties of the coating material itself. The maximum smooth coating speed has been measured from the coating thickness fluctuation-coating speed curves using several types of silicone resins. Flow curves of the silicone resins also have been measured by two different viscometers, i.e., cone-plate and capillary viscometers. The maximum smooth coating speed, at which the coating thickness fluctuation begins to increase, has been found to correspond to the critical shear rate at which the flow curve deviates from a power law. This correspondence probably results from the fact that the slip occurs both at the fiber-coating material interface and at the viscometer (cone, plate, or capillary)-coating material interface. Accordingly, the maximum smooth coating speed can be predicted from the critical shear rate value without the actual fiber coating experiments.