This paper presents models for inhomogeneous dielectric cylindrical structures, like optical fibers, with two different radial profiles: W-type and M-type. Graphs for modal characteristics are presented, considering both small and¨ery high¨alues of dielectric steps. Also, for the fundamental LP -mode with weak guidance, dispersion data and 01 power confinement are computed. The fundamental mode cutoff is detected, and a numerical criterion that establish its occurrence is defined and discussed.