Optical fiber cables constitute one the key elements supporting current information technology society. Recently, the price reduction is becoming competitive among optical fiber manufacturers. In order to meet such a need, the manufacturers are now trying to increase the operating process speed when they manufacture optical fiber cables. Under these circumstances, severe vibrations were observed on a fiber cable traveling at a high speed during coating process. This paper summarizes a case study concerning traveling optical fiber vibrations and the examination results on the mechanism of vibrations. First, we outline the characteristics of traveling cable vibrations, secondly, we explain the results of model cable vibration tests and finally, we describe the theory to clarify the mechanism of the traveling cable vibrations. In the analytical part, we start with the equation of motion of a traveling cable together with the effect of the fluid force due to the leakage flow induced in a coating dice. The effect of the leakage flow in a coating dice is formulated based on annular leakage flow theory developed by author's group where the effect of viscosity of the coating material on the instability is taken into account. Then, the equation of a traveling cable under the effect of the leakage flow at the supporting point is successfully formulated. Based on the linearized equation of motion for the traveling cable, eigenvalue analysis was performed which leads to instability criteria selecting dice configuration and the temperature of the coating material as parameters. Finally, calculated results were compared with test experimental results and discussion on the design parameters for the stable operation is made.