Abstract: An optical transmission line configured to control both a waveform distortion due to non-linearity and a waveform distortion due to dispersion. The optical transmission line is formed by connecting in series a first optical fiber to a second optical fiber. The first optical fiber has a dispersion value of 6 to 14 ps/nm/km, and the second optical fiber has a dispersion value of −14 to −6 ps/nm/km, both for a given wavelength band within a 1.5 &mgr;m wavelength band. Further, a dispersion slope of the first optical fiber has an opposite sign to a dispersion value of the second optical fiber. In addition, the first optical fiber is arranged to be closer to an optical signal that inputs the optical transmission line than the second optical fiber.