Patent ID: 8437594

Claim:
A holey fiber comprising: a core portion located at a center of the holey fiber; and a cladding portion located around the core portion, the cladding portion having holes formed in layers around the core portion, wherein the holes are arranged so as to form a triangular lattice while d/Λ is within a range of 0.33 to 0.43, Λ is within a range of 10.5 micrometers to 15 micrometers when a hole diameter is d in micrometer and a lattice constant of the triangular lattice is A in micrometer, and in a wavelength of 1550 nanometer, an effective core-area is equal to or greater than 130 μm 2 , a bending loss in a case of bending the holey fiber at a bend diameter of 20 millimeters is equal to or less than 200 dB/m, and the holey fiber demonstrates a single-mode operation, and a microbending loss which is defined as a transmission loss difference between a transmission loss of the holey fiber being wounded around a bobbin around which a sandpaper is wrapped and a transmission loss of the holey fiber being wounded around the bobbin without any sandpaper being wrapped is equal to or less than 1.5 dB/km in the wavelength of 1550 nanometers.