A general method that predicts the thermal behavior of optical fibers during the cooling stage of the drawing process was developed. The method can be used for thin diameter D < 200 μm, medium (200 μm < D < 500 μm), and thick (0.5 mm < D < 2 mm) single as well as core-clad fibers. A two-dimensional analysis implementing a finite difference method combined with the Kármán–Pohlhausen technique was performed to obtain the temperature profiles in thick fibers. This method accounted for axial and radial heat conduction, and can also be applied to thin and medium fibers. The case of the core-clad fibers was investigated to obtain the temperature profiles both in the radial and the axial directions. All results are presented in graphical form and can be used for optimization of the drawing process.

A new general method for determining the local dimensionless heat convection coefficient (Nusselt number) and the temperature distribution in thin and thick optical fibers during the drawing process was developed. The axial heat transfer by conduction was included in the analysis as an addition to previously developed models. The developed model can serve as a general thermal solver for thin (<200μm in dia.) and thick (>200μm in dia.) fibers. The general method was compared with existing methods and it was found to be in agreement in the case of thin fiber analysis but not in the case of thick fiber analysis, where axial conduction effects are significant. Results of a parametric study to examine the effects of diameter of fiber and drawing speed on the temperature distribution are presented.

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