Preform heating is one of the most important steps in the polymer fibre fabrication process due to the potential distortion that can be introduced when exposing the structure to high temperatures. Such heating is further complicated when internal air-structures are introduced into the preform, such as in microstructured polymer optical fibre (MPOF) preforms. The aim of this study was thus to investigate heat transfer in an MPOF preform. The effect of air-structure was studied using both numerical heat transfer simulations and preform heating experiments. A two-dimensional conductive heat transfer model with surface radiation was used in simulating the transient heat transfer in MPOF preforms with the results compared to those for a solid preform. It was found that relatively long beating times were required to reach a uniform temperature distribution within a preform, and that depending on the preform's air fraction its centre could heat up either faster or slower than a solid preform. Experimental tests, where both a solid and an air-structured preform were heated in a drawing furnace with internal temperatures measured across the preform, confirmed the findings from the numerical simulations.
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