Heat transfer within a microstructured polymer optical fibre preform Katja Lyytikäinen 1,2 , Joseph Zagari 1,3 , Geoff Barton 3 , John Canning 1 1 Australian Photonics Cooperative Research Centre, Optical Fibre Technology Centre, University of Sydney, 206 National Innovation Centre, Australian Technology Park, Eveleigh NSW 1430, Australia k.lyytikainen@oftc.usyd.edu.au, j.canning@oftc.usyd.edu.au 2 School of Physics, University of Sydney, Sydney, NSW 2006, Australia 3 Department of Chemical Engineering, University of Sydney, Sydney, NSW 2006, Australia j.zagari@oftc.usyd.edu.au, barton@chemeng.usyd.edu.au Short title: Heat transfer within a microstructured polymer optical fibre preform Classification numbers: 44, 02.60.-x, 81.05.Lg Abstract: 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 heating 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. 1 Introduction Photonic crystal fibres, also known as microstructured or ‘holey’ fibres, were first developed in 1974 [1]. During the past few years, considerable effort has been devoted to researching their fabrication, properties and applications [2-5]. Such fibres are usually made from a single material in which the light guidance is defined by the air-structure, consisting of a number of air capillaries running along the length of the fibre surrounding either a solid or an air core. By changing the air-structure a wide range of fibre properties - such as dispersion [6], birefringence [7] and nonlinearities [8] - can be tailored to the required application. Traditionally photonic crystal fibres have been manufactured from silica or other glasses . Due to advantages such as low manufacturing cost and increased material flexibility, polymer was soon recognized a potential material for photonic crystal fibres [9, 10]. A number of studies have since been conducted in the area [11-13] and a strong potential for the development of high bandwidth optical fibres for LAN applications has been identified.