Patent ID: 8787720

Claim:
An optical fiber comprising: a core portion that confines light therein and guides the light therethrough; and a cladding portion that is made of a first silica glass that is formed around an outer circumference of the core portion, wherein the core portion includes a center core portion that is made of a second silica glass that has a refractive index greater than a refractive index of the first silica glass of the cladding portion and the core portion includes an outer core portion that is made of a third silica glass that has a refractive index less than the refractive index of the first silica glass of the cladding portion, the outer core portion being around an outer circumference of the center core portion, the cladding portion contains between 12 to 36 holes arranged in a circular shape, a center of the circular shape laying on the core portion, a diameter of each of the holes is between 2 μm to 10 μm, and a distance between a center of one of the holes that is closest to the core portion and the center of the core portion is equal to or greater than 25 μm, and the holes are arranged to not affect the effective core area of the optical fiber and to not affect the chromatic dispersion characteristic.