<p>A holey fiber includes a core portion located at a center thereof and a cladding portion located around the core portion and having holes formed in layers around the core portion; the holes are arranged so as to form a triangular lattice; when a diameter of the holes is d in micrometers and a lattice constant of the triangular lattice is › in micrometers, d/› is within a range of 0.43 ± 0.10 and A is 10.5 micrometers to 15 micrometers; at a wavelength of 1550 nanometers, an effective core-area is equal to or greater than 130 µm 2 and a bending loss upon bending at a diameter of 20 millimeters is equal to or less than 200 dB/m; and the holey fiber demonstrates a single-mode operation.</p>
