Patent ID: 7593611

Claim:
A photonic band gap fiber comprising: silica portions; multiple air holes, provided in the silica portions, extending in a longitudinal direction of the photonic band gap fiber; and a cladding having an air hole periodic structure in an extended triangular lattice configuration in a cross section of the photonic band gap fiber, wherein: first rows each having a number of air holes at a first pitch, and second rows each having a plurality of air holes at a second pitch which is twice the first pitch, are arranged such that the air holes of the first rows are disposed alternately with the air holes of the second rows, and wherein the first rows and the second rows are arranged so as to form the extended triangular lattice configuration in the cross section of the photonic band gap fiber; and the photonic band gap fiber further comprises an air hole core which has a substantially circular shape in the cross section of the photonic band gap fiber, and a diameter D of the air hole core satisfies 0.7Λ≦D≦3.3Λ with respect to the first pitch Λ.