Provide low bending losses (L B) and high-performance HAHF compatible only cut-off wavelength (λ c). In the high refractive index than the clad part core portion (11), that a cladding portion 12 surrounding, the hole assists porous light-oil (holey fiber) made by a plurality of public and surrounding parts of the core installed in the cladding part , the public is provided in the outside two-layer, equals the number of the inner public of the layer and the outside public layer public, outside the public (17) is arranged on that inner public 16 is not disposed position as viewed from the core center, Additionally, Λ 1 Λ distance (Λ 1) and a distance (Λ 2) of the core part center to the outside public center to the inner public center in the public is the center have the same diameter, the core portion constituting each of the public layer 2, and the inner diameter of the public (d 1) and the outside public diameter (d 2) the organic light-hole d 1 ≤d 2 characterized in that the assist-type porous.
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