The present study investigates the mass and heat transfer in the optical fibre fabrication process where a specialty optical preform with a non-homogeneous cross-sectional structure is drawn into a fibre. A finite element method was used to model the steady state fibre drawing process. The model included free surface calculation of the neck-down shape of the preform coupled with a two-dimensional heat transfer equation. The enclosure model was used for the radiation heat transfer. In addition to the silica preform the model took into account the graphite-resistance furnace structure and the inert gas surrounding the preform. Fibre designs with axisymmetric cross-sections with radial variations in material properties were modeled, including air silica structures. The effect of internal air structures was found to have a significant impact on temperature distribution. The effects of drawing parameters such as draw speed, preform diameter, draw temperature and furnace structure were also studied.

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