Patent ID: 7321711

Claim:
An optical fiber comprising a core and cladding, characterized by: a dispersion “D” of not less than 2 ps/nm/km and not more than 8 ps/nm/km (2≦D≦8) over a wavelength range of 1400 to 1700 nm and, at least one extreme value of dispersion within said wavelength range, the optical fiber further comprising: a plurality of glass layers inside of the cladding having a reference refractive index, wherein one of two adjacent layers differs in composition from the other, first, second, third and fourth layers from the center to outside have relative refractive index differences of Δ 1 , Δ 2 , Δ 3 and Δ 4 from said reference refractive index of said cladding (0), respectively, and satisfy the following condition, Δ 1 >Δ 3 >Δ 4 >0Δ 2 .