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RESEARCH PAPERS: Processes Equipment and Devices

Numerical Simulation of Transport in Optical Fiber Drawing with Core–Cladding Structure

[+] Author and Article Information
Chunming Chen

Department of Mechanical and Aerospace Engineering, Rutgers, The State University of New Jersey, New Brunswick, NJ 08903

Yogesh Jaluria

Department of Mechanical and Aerospace Engineering, Rutgers, The State University of New Jersey, New Brunswick, NJ 08903jaluria@jove.rutgers.edu

J. Heat Transfer 129(4), 559-567 (Sep 24, 2006) (9 pages) doi:10.1115/1.2709968 History: Received March 28, 2006; Revised September 24, 2006

Optical fibers are typically drawn from silica preforms, which usually consist of two concentric cylinders called the core and the cladding, heated in a high-temperature furnace. For optical communication purposes, the core always has a higher refractive index than the cladding to obtain total internal reflection. In order to investigate the effect of this core–cladding structure on optical fiber drawing, a numerical model has been developed in this work. Axisymmetric flows of a double-layer glass and aiding purge gas in a concentric cylindrical furnace are considered. The thermal and momentum transport in both glass layers and gas are coupled at the interface boundaries. The neck-down profile is generated using an iterative numerical scheme. The zonal method is applied to model the radiation transfer in the glass preform. The gas is taken as nonparticipating. Coordinate transformations are used to convert the resulting complex domains into cylindrical regions. The stream function, vorticity, and energy equations for the core, the cladding, and the purge gas are solved by finite difference methods, using a false transient approach coupled with the alternating direction implicit method. A second-order differencing scheme is used for discretization. The numerical results are validated by comparing with results available in the literature. The effects of changes in the refractive index and absorption coefficient due to doping on fiber drawing are investigated. This problem has received very little attention in the literature, particularly with respect to modeling, and this paper presents an initial study of the underlying transport.

Copyright © 2007 by American Society of Mechanical Engineers
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Figures

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Figure 1

Schematic diagram of the process for double-layer optical fiber drawing

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Figure 2

Radiosities and irradiations at the interfaces

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Figure 3

Radiative heat flux for uniform temperature distribution in the preform

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Figure 4

Effect of change in the refractive index on radiative heat flux

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Figure 5

Validation of the numerical model by comparing the temperature distribution at the free surface with single-layer fiber drawing

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Figure 6

Validation of the numerical model by comparing the neck-down profile

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Figure 7

Effect of change in the refractive index on the temperature distribution at the centerline

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Figure 8

Effect of change in the refractive index on the radial temperature lag

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Figure 9

Influence of the refractive index on the neck-down profile

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Figure 10

Influence of the refractive index on normalized defect distribution at the free surface

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Figure 11

Influence of the refractive index on draw tension: (thick lines) n(1)=n(2)=1.42; and (thin lines) n(1)=1.42;n(2)=1.278

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Figure 12

Effect of change in the absorption coefficient on the temperature distribution at the centerline

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Figure 13

Effect of change in the absorption coefficient on temperature lag

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Figure 14

Effect of change in the absorption coefficient on the neck-down profile

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Figure 15

Influence of the absorption coefficient on normalized defect distribution at free surface

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Figure 16

Influence of the absorption coefficient on draw tension: (thick lines) a1(2)=400m−1, a2(2)=15,000m−1; (thin lines) a1(2)=800m−1,a2(2)=30,000m−1

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