y..,TC describe the differential mulfipole method, an extended multipole method used to calculate the modes of mlcroetructured optical fibers with uoncircular inclusions. Vole use a multipole expansion centered on each inclusion and a differential method to calculate the scattering properties of the individual inclusions. Reprosentative results for a flber with one ring of elliptical inclusions are presented. and a direct comparison is made with an existing method. The new method is also

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... to a microstructured optical fiber with seven rings of elliptical inclusions, which is found. in effect, to support a single polarization of the fundamental mode.