Abstract
Microstructured optical fibers (MOFs) achieve their desired performance via a pattern of
holes that run along the length of the fiber. Varying the hole pattern allows a variety of optical
effects to be produced. However, the original hole pattern within the preform may not be
accurately transferred to the finished fiber due to the combined impact of material properties and
the drawing conditions experienced during fabrication. In this two-part paper, the processes of
drawing MOFs having arbitrary cross-sectional hole structures will be analyzed for the case of
Newtonian materials. Part I presents a modeling formalism to describe the drawing processes,
followed by a scaling analysis on a representative case, i.e., the nonisothermal drawing of an
axisymmetric annular hollow fiber, to reveal the major factors influencing the drawing of both
silica and polymer MOFs. By treating the primary draw process (i.e., from preform to intermediate
cane) in fabricating polymer MOFs as a transient, isothermal problem, numerical simulations were
carried out for an illustrative five-hole structure. The results revealed the central importance
of any steep neck-down region on hole-shape deformation as well as the importance of forces
additional to those associated with surface tension effects. Both experimental observations and
numerical modeling show that a diversity of hole"activities"(both in a hole's relative size and
shape) can occur when drawing MOFs. Part II will extend both the analysis and numerical modeling
with a focus on the steady-state continuous draw process (i.e., from preform or cane to fiber). In
parallel with this analysis, we also present experimental results for the drawing of
polymethylmethacrylate (PMMA) MOFs.
© 2005 IEEE
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