  In 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.
