A Study of the Transport Processes and of the Generation of Defect Centers in Optical Fiber Drawing

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The project is directed at the optical fiber drawing process in an effort to improve the quality of the fiber, by reducing the defects and irregularities generated in the process, and to increase the draw speed, by enhancing the cooling rate. The thermal transport and material flow processes associated with the drawing of optical fiber play a very important role in determining the quality of the fiber obtained and the optimum draw speed. A detailed numerical and experimental study will be performed to investigate the effect of the transport phenomena on the quality of the fiber, particularly on defect generation, and the enhancement of the heat transfer rate to increase draw speeds and reduce distances needed for cooling the fiber to a desired temperature level. The temperature distribution in the material, the surface profile in the neck down region, heat transfer rates and material distribution in the process are to be determined numerically, using the finite volume approach for the axisymmetric problem under consideration and employing the experimental results for the validation of the model and of the numerical scheme. The detailed results obtained are expected to contribute to a better understanding of the basic transport processes involved and to provide a scientific basis for improving existing procedures, impacting on processes such as high speed drawing, low cost of fiber fabrication, draw induced defect generation, ultra low loss fiber development, thermally induced phase separation and crystallization during drawing of non-oxide glasses, residual stress generation, etc.