2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/106555In this paper we evaluate the cut-off properties of holey fibers (HFs) with a triangular lattice of air holes and the core formed by the removal of a single (HF1) or more air holes (HF3 and HF7). With the aid of finite-element simulations we determine the single-mode and multi-mode phases and also find the air hole diameters limiting the endlessly single-mode regime. From calculations of V and W parameters we find that in general HF1 is less susceptible to longitudinal non-uniformities compared to the other designs for equivalent effective areas. As an example we illustrate this general property for the particular case of a macro-bending induced loss.7 pages including 4 figures. Accepted for Opt. ExpressOpticsEndlessly single-mode holey fibers: the influence of core designtext