Patent ID: 8861915

Claim:
An optical fiber comprising: a core portion; and a cladding portion that is formed around an outer periphery of the core portion and has a refractive index lower than a maximum refractive index of the core portion, wherein as characteristics of the optical fiber at a wavelength of 1550 nm, an effective core area in a fundamental propagation mode is 120 μm 2 or larger, an effective core area in a first higher-order propagation mode is 150 μm 2 or larger, an effective core area in a second higher-order propagation mode is 180 μm 2 or larger, an effective refractive index in the second higher-order propagation mode is larger than the refractive index of the cladding portion by 0.0002 or more, and an effective refractive index in a third higher-order propagation mode is less than the refractive index of the cladding portion; wherein the core portion includes a center core portion having the maximum refractive index and an outer core portion that is formed around an outer periphery of the center core portion and has a refractive index lower than the refractive index of the cladding portion; wherein a relative refractive-index difference Δ 1 of the center core portion relative to the cladding portion is 0.36% or more, a relative refractive-index difference Δ 2 of the outer core portion relative to the cladding portion is −0.05% or less, a diameter of the center core portion is 14.90 μm to 17.30 μm, and a ratio of an outside diameter of the outer core portion to the diameter of the center core portion is 2.0 or more.