An optical fiber characterized by a dispersion of not less than 2 ps/nm/km and
not more than 10 ps/nm/km at a wavelength of 1550 nm, an effective area of 65 m2
or more at a wavelength of 1550 nm, a positive dispersion slope at a wavelength
of 1550 nm, a zero dispersion wavelength outside the wavelength range of 1400 nm
to 1460 nm, an absolute value of dispersion of not less than 2 ps/nm/km and not
more than 10 ps/nm/km at a wavelength of 1400 nm, a cutoff wavelength of 1400 nm
or shorter, and a transmission loss of 0.40 dB/km or less at a wavelength of 1400
nm is provided. By using the optical fiber of the present invention, the WDM transmission
both in the 1.55 m wavelength band and in the wavelength range between 1400
nm to 1460 nm is realized.
