| 摘要 |
PROBLEM TO BE SOLVED: To make an optical fiber so that its manufacturing is easy and a transmission loss is low and also the sensitibity with respect to bending is low and also so as to show a negative dispersion whose inclination is gentle in an erbium amplifier area. SOLUTION: The optical fiber having color dispersion being equal to or smaller than -0.8 ps/(nm-km) in all wavelengths in the wavelength area of 1,530 to 1,565 nm is constituted of a center core area 31, a first ring shaped area 32 formed at surroundings of the area 31, a second ring shaped area 33 formed at the surroundings of the area 32, a clad layer 34 formed at surroundings of the area 33 and the refractive index of the core area 31 is n1 and the refractive index of the first ring shaped area 32 is n3 and its width is 4.5±105μm, the refractive index of the second ring shaped area 33 is n4 and the refractive index of the clad layer 34 is n2 and these refractive indexes satisfy 0.45<(n1-n2)/n2<0.58 and -0.09<(n3-n2)/n2<-0.05 and 0.20<(n4-n2)/n2<0.28.
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