Dispersion shifted optical fiber

A dispersion shifted optical fiber comprising:

• a core, the core further comprising:
• a first segment including a center axis of the core,
• a second segment that surrounds an outer circumferential surface of the first segment with no gap,
• a third segment that surrounds an outer circumferential surface of the second segment with no gap, and
• a fourth segment that surrounds an outer circumferential surface of the third segment with no gap,
• wherein the first segment further comprises a first center segment having the center axis,
• a radius r0 of the first center segment is 0.5 μm or more and 2.8 μm or less, a radius r1 of the first segment is 1.8 μm or more and 4.5 μm or less, a radius r2 of the second segment is 4.0 μm or more and 8.0 μm or less, a radius r3 of the third segment is 4.5 μm or more and 8.5 μm or less, a radius r4 of the fourth segment is 8.0 μm or more and 16.0 μm or less, and a relation r0≤r1<r2<r3<r4 is held,
• a relative refractive index difference Δ0 of the first center segment to a cladding surrounding the core is 0.4% or more and 0.9% or less, a relative refractive index difference Δ2 of the second segment to the cladding is 0.00% or more and 0.07% or less, a relative refractive index difference Δ3 of the third segment to the cladding is 0.285% or more and 0.5% or less, a relative refractive index difference Δ4 of the fourth segment to the cladding is 0.005% or more and 0.04% or less, and in the first segment, a relative refractive index difference to the cladding is reduced from an outer circumference of the first center segment to an inner circumference of the second segment, and
• wherein the dispersion shifted optical fiber has a dispersion value of a light beam at a wavelength in a range of 1,530 to 1,625 nm is 2.0 ps/nm/km or more and 13.5 ps/nm/km or less, a dispersion slope of a light beam at a wavelength of 1,550 nm is 0.092 ps/nm2/km or less, a cable cutoff wavelength is a wavelength of 1,450 nm or less, an effective area of a light beam at a wavelength of 1,550 nm is 65 μm2 or more and 90 μm2 or less, and a mode field diameter of a light beam at a wavelength of 1,550 nm is 9.2 μm or more and 10.5 μm or less.