We tackle holey fibers in full vectorial terms. From Maxwell's equations, w
e derive the dispersion relations of the modes guided by an infinitely self
-similar air hole lattice. We focus in particular on the fundamental mode (
the so-called space filling mode), and show that previous numerical results
based on vector methods are accurate, but scalar ones are not. We also fin
d the field flow lines, intensity distribution in the cross section, and li
near polarization ratio vs, wavelegth.