Patent ID: 7085464

Claim:
An optical fiber comprising: a first core located in a central portion of the optical fiber and having a first refractive index; a second core located in an outer periphery of the first core and having a second refractive index lower than the first refractive index; a third core located in an outer periphery of the second core and having a third refractive index lower than the first refractive index and higher than the second refractive index; and a cladding located in an outer periphery of the third core and having a fourth refractive index lower than the third refractive index and higher than the second refractive index, wherein an absolute value of dispersion at a wavelength of 1550 nm is equal to or less than 10 ps/nm/km, an effective area at the wavelength of 1550 nm is equal to or less than 15 μm 2 , and a nonlinear constant n 2 /Aeff at the wavelength of 1550 nm is equal to or more than 25×10 −10 /W.