Patent ID: 8315494

Claim:
An optical fiber comprising: a center core portion; an inner core layer that is formed around an outer circumference of the center core portion, a refractive index of the inner core layer being less than that of the center core portion; an outer core layer that is formed around an outer circumference of the inner core layer, a refractive index of the outer core layer being less than that of the inner core layer; and a cladding portion that is formed around an outer circumference of the outer core layer, wherein a refractive index of the cladding portion is substantially equal to that of the inner core layer, wherein an effective core area at a wavelength of 1550 nm is equal to or larger than 130μm 2 , a bending loss at a wavelength of 1550 nm is equal to or less than 100 dB/m when the optical fiber is bent with a diameter of 20 mm, and a cable cut-off wavelength is equal to or less than 1530 nm.