We perform an accurate numerical modelling of both tapered and microstructured fibers using a finite element numerical
approach. We compute the propagation modes, i.e., distribution of the electric field over the cross section, effective
modal area and dispersion characteristics. The dependence of the dispersion properties on wavelength are calculated by
solving the eigenvalue equation for fiber modes and using Sellmeier equation. The optical properties of tapered fibers are
shown to be very sensitive to the core size. The zero dispersion wavelength can be shifted to the visible range and, in
some cases, two zero dispersion wavelengths are observed. The dependence of the dispersion properties and of the
effective mode area of a microstructured fiber with hexagonal symmetry on the air-hole diameter and the hole-to-hole
spacing is also investigated.