| 摘要 |
PURPOSE: To provide an optical fiber, which is capable of forming an optical transmission line for wavelength division multiplexing transmission of a wavelength 1.5 μm band, using a Raman amplifier. CONSTITUTION: The effective core sectional area, in at least part of the set wavelength band of the wavelength 1.5 μm band, is specified to 40 to 60 μm¬2; the dispersion value at a wavelength, of 1.55 μm to 4 to 10 ps/nm/km; the dispersion slope at the wavelength 1.55 μm band to a positive value smaller than 0.04 ps/nm¬2/km; the zero dispersion wavelength is set to < =1.4 μm; the cut-off wavelength is set at a length 2 m to < =1.5 μm and the bending loss at a diameter 20 mm in the wavelength 1.5 μm band to < =5 dB/m. The refractive index profile of the optical fiber is set with a specific refractive index difference Δ1 with respect to the reference layer 6 of the first glass layer 1 on, for example, the innermost layer and a specific refractive index difference Δ3 with respect to the reference layer 6 of the third glass layer 3 of the third place from the inner side being made positive, and a specific refractive index difference Δ2 with respect to the reference layer 6 of the second glass layer of the second place from the inner side is made negative.
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