Modelling and experimental investigation of Structured Optical Fibres: Optimisation of drawing conditions
Structured Optical Fibres (SOFs) are the new generation of optical fibres characterised by their air-hole patterns. SOFs are advantageous over conventional optical fibres for their great flexibility in structure design that offers many new features such as significantly extended single-mode regime. The design and fabrication of SOFs with desirable optical properties are essential for their applications in modern telecommunications and networking, smart sensing, and material processing. The main objective of this study is to rigorously investigate the impacts of drawing conditions and parameters on the structure of SOFs and to develop an appropriate and simple analytical model to predict the optimum drawing conditions for the SOF fabrication. In this study, a rigorous experimental investigation was first conducted to understand the structure formation dynamics of SOFs during the drawing process. The effects of drawing parameters including drawing temperature, drawing pressure, drawing speed and preform feeding rate on SOF structure were studied in order to reach the optimal drawing conditions and achieve the required design features. Far-field tests were also conducted to verify the single-mode operation of the SOFs fabricated and to evaluate their optical properties. In the second part of this study, a modified Fitt model was established for the analytical analysis of the structure formation dynamics of SOFs. The modified model takes into account the influence of the internal structure of SOF which is considerably different from the single capillary considered in the Fitt model. By taking the influence of surrounding air-holes into consideration, an effective pressure was introduced into the modified model in relation to the difference between the applied drawing pressure and the external pressure from the lattice holes. The experimental results were then compared with those predicted by the modified model, and they were found in good agreement. This demonstrates that the model can provide a simple way to reliably predict the optimum drawing conditions for the fabrication of structured optical fibres.
Simple modelling, Structured Optical Fibres, Drawing condition, Experimental investigation
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