Author

# C. J. Voyce

Bio: C. J. Voyce is an academic researcher from University of Southampton. The author has contributed to research in topics: Fluid mechanics. The author has an hindex of 2, co-authored 2 publications receiving 15 citations.

Topics: Fluid mechanics

##### Papers

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TL;DR: In this paper, the authors examined the fluid dynamics of capillary drawing using an extensional-flow asymptotic approach based on the small aspect ratio of the capillary, and made predictions concerning the effects of fiber rotation.

Abstract: Understanding and controlling the manufacturing process of producing (“drawing”) microstructured optical fibres (“holey fibres”) is of paramount importance in obtaining optimal control of the final fibre geometry and identifying industrially useful production regimes. The high cost of the manufacturing process and the challenge of ensuring reproducible final fibre geometries renders theoretical approaches invaluable. In this study the fluid dynamics of capillary drawing is examined using an extensional-flow asymptotic approach based on the small aspect ratio of the capillary. The key focus of the study is the additional effects that may be introduced by adding fibre rotation to the manufacturing process. Predictions are made concerning the effects of rotation, and a variety of asymptotic limits are examined in order to gain an understanding of the physics involved. Drawing regimes that are useful from a practical point of view are identified and the role of fibre rotation, both as a control measure (that may be used to influence the final geometry of a capillary) and as a means of reducing unwanted effects (such as fibre birefringence and polarisation model dispersion), is discussed.

13 citations

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01 Jan 2004TL;DR: In this paper, a fluid mechanics model was constructed in order to allow anunderstanding of the drawing of the microstructured optical fibres, or "holey fibres" to be gained, and further the ability to predict and control the final fibre geometry.

Abstract: We describe a fluid mechanics model that has been constructed in order to allow anunderstanding of the drawing of microstructured optical fibres, or ‘holey fibres’, to be gained, and furtherour ability to predict and control the final fibre geometry. The effects of fibre rotation are included in the model. Predictions are made by solving the final model numerically.

2 citations

##### Cited by

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Abstract: The efficient and accurate fabrication of Microstructured optical fibers (MOFs) requires a practical understanding of the ‘draw process’ beyond what is achievable by trial and error, which requires the ability to predict the experimental drawing parameters needed to produce the desired final geometry. Our results show that the Fitt et al. fluid-mechanics model for describing the draw process of a single axisymmetric capillary fiber provides practical insights when applied to more complex multi-hole symmetric and asymmetric MOF geometries. By establishing a method to relate the multi-hole MOF geometry to a capillary and understanding how material temperature varies with the draw tower temperature profile, it was found that analytical equations given by the Fitt model could be used to predict the parameters necessary for the chosen structure. We show how this model provides a practical framework that contributes to the efficient and accurate fabrication of the desired MOF geometries by predicting suitable fiber draw conditions.

44 citations

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TL;DR: A key result is to demonstrate how a so-called reduced time variable serves as a natural parameter in describing how an axial-stretching problem interacts with the evolution of a general surface-tension-driven transverse flow via a single important function of $\tau $, derived from the total rescaled cross-plane perimeter.

Abstract: A general mathematical framework is presented for modelling the pulling of optical glass fibres in a draw tower. The only modelling assumption is that the fibres are slender; cross-sections along the fibre can have general shape, including the possibility of multiple holes or channels. A key result is to demonstrate how a so-called reduced time variable serves as a natural parameter in describing how an axial-stretching problem interacts with the evolution of a general surface-tension-driven transverse flow via a single important function of , herein denoted by , derived from the total rescaled cross-plane perimeter. For any given preform geometry, this function may be used to calculate the tension required to produce a given fibre geometry, assuming only that the surface tension is known. Of principal practical interest in applications is the ‘inverse problem’ of determining the initial cross-sectional geometry, and experimental draw parameters, necessary to draw a desired final cross-section. Two case studies involving annular tubes are presented in detail: one involves a cross-section comprising an annular concatenation of sintering near-circular discs, the cross-section of the other is a concentric annulus. These two examples allow us to exemplify and explore two features of the general inverse problem. One is the question of the uniqueness of solutions for a given set of experimental parameters, the other concerns the inherent ill-posedness of the inverse problem. Based on these examples we also give an experimental validation of the general model and discuss some experimental matters, such as buckling and stability. The ramifications for modelling the drawing of fibres with more complicated geometries, and multiple channels, are discussed.

36 citations

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TL;DR: In this article, a method is proposed for modeling the self-pressurization of optical fibers that are sealed before drawing, and a numerical investigation is undertaken to optimize the choice of experimental parameters to minimize the transient effects of sealed preform drawing.

Abstract: A method is proposed for modeling the self-pressurization of optical fibers that are sealed before drawing. The model is solved numerically and the results compared with experimental results. An explanation of the mechanism is presented and a numerical investigation is undertaken to optimize the choice of experimental parameters to minimize the transient effects of sealed preform drawing.

26 citations

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TL;DR: In this paper, a method for modeling the fabrication of capillary tubes is developed that includes the effects of preform rotation, and is used to reduce or remove polarization mode dispersion and fiber birefringence.

Abstract: A method for modeling the fabrication of capillary tubes is developed that includes the effects of preform rotation, and is used to reduce or remove polarization mode dispersion and fiber birefringence. The model is solved numerically, making use of extensive experimental investigations into furnace temperature profiles and silica glass viscosities, without the use of fitting parameters. Accurate predictions of the geometry of spun capillary tubes are made and compared directly with experimental results, showing remarkable agreement and demonstrating that the mathematical modeling of fiber drawing promises to be an accurate predictive tool for experimenters. Finally, a discussion of how this model impacts on the rotation of more general microstructured optical fiber preforms is given.

20 citations

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TL;DR: In this article, a mathematical model is presented describing the deformation, under the combined effects of surface tension and draw tension, of an array of channels in the drawing of a broad class of slender viscous fibres.

Abstract: A mathematical model is presented describing the deformation, under the combined effects of surface tension and draw tension, of an array of channels in the drawing of a broad class of slender viscous fibres. The process is relevant to the fabrication of microstructured optical fibres, also known as MOFs or holey fibres, where the pattern of channels in the fibre plays a crucial role in guiding light along it. Our model makes use of two asymptotic approximations, that the fibre is slender and that the cross-section of the fibre is a circular disc with well-separated elliptical channels that are not too close to the outer boundary. The latter assumption allows us to make use of a suitably generalised ‘elliptical pore model (EPM)’ introduced previously by one of the authors (Crowdy, J. Fluid Mech., vol. 501, 2004, pp. 251–277) to quantify the axial variation of the geometry during a steady-state draw. The accuracy of the elliptical pore model as an approximation is tested by comparison with full numerical simulations. Our model provides a fast and accurate reduction of the full free-boundary problem to a coupled system of nonlinear ordinary differential equations. More significantly, it also allows a regularisation of an important ill-posed inverse problem in MOF fabrication: how to find the initial preform geometry and the experimental parameters required to draw MOFs with desired cross-plane geometries.

19 citations