Patent ID: 8837891
Filing Date: 2014-09-16
Classification: G02B

Abstract:
1. An optical fiber comprising a first core at a center thereof, a second core that is adjacent to the first core and covers an outer circumference of the first core, a third core that is adjacent to the second core and covers an outer circumference of the second core, and a cladding that is adjacent to the third core and covers an outer circumference of the third core, wherein with a refractive index of the cladding as a reference, Δ1 is a maximum value of a relative refractive index difference of the first core, Δ2 is a relative refractive index difference of a flat portion the second core, Δ3 is a minimum value of a relative refractive index difference of the third core, a maximum value Δ2max of the relative refractive index of the second core is Δ2max=(Δ1)/2, a minimum value Δ2min of the relative refractive index of the second core is Δ2min=(Δ3)/2, “a” is a half-value radial width for the Δ1 of the first core, “b” is a radius of a boundary between the second core and the third core relative to the half-value radial width of Δ3 of the third core, and “c” is a radius of a boundary between the third core and the cladding, the expressions 0.30%≦Δ1≦0.45%, −0.05%≦Δ2≦0.05%, −0.35%≦Δ3≦−0.15%, 2.5≦b/a, 3.5 μm≦a≦4.2 μm, 9 μm≦b≦13 μm, and 4.5 μm≦c−b≦7.0 μm are satisfied, a zero-dispersion wavelength is no less than 1300 nm and no greater than 1324 nm, and transmission loss increase for a wavelength of 1550 nm when the optical fiber is wound around a mandrel with a diameter of 10 mm is no greater than 1 dB/turn.