Evaluation of chromatic dispersion in W-type fibers

Evaluation of chromatic dispersion in W-type fibers, based on the assumption that waveguide and material dispersion are additive effects, is examined. Actual and approximate dispersion of the LP(01) mode are calculated and compared for three W fibers. For two fibers the errors introduced by the approximate method are substantial, even larger than the total dispersion at most wavelengths in the range 1.1 microm < lambda < 1.6 microm. For a third fiber, however, the agreement between the actual and approximate results is close. It is shown that the accuracy of the approximate method improves if the wavelength derivatives of the index differences become smaller.