Optical fiber transmission line, optical cable, and optical transmission system

An optical transmission line, comprising:

• a first optical fiber comprising an entrance end for receiving signal light and an exit end for emitting said signal light, said first optical fiber having, as characteristics at a wavelength of 1550 nm, a first effective area Aeff1 and a first chromatic dispersion D1, and having a first length L1;
• a second optical fiber comprising an entrance end fusion-spliced to the exit end of said first optical fiber, and an exit end for emitting said signal light, said second optical fiber having, as characteristics at the wavelength of 1550 nm, a second effective area Aeff2 smaller than said first effective area Aeff1 and a second chromatic dispersion D2 different from said first chromatic dispersion D1, and having a second length L2 different from said first length L1;
• a third optical fiber comprising an entrance end fusion-spliced to the exit end of said second optical fiber, and an exit end for emitting said signal light, said third optical fiber having, as characteristics at the wavelength of 1550 nm, a third effective area Aeff3 greater than said second effective area Aeff2 and a third chromatic dispersion D3 different from said second chromatic dispersion D2, and having a third length L3 different from said second length L2;
• and
• an optical multiplexer optically coupled to the entrance end of said first optical fiber so as to supply Raman amplification pumping light to said first optical fiber together with said signal light, or optically coupled to the exit end of said third optical fiber so as to supply Raman amplification pumping light to said third optical fiber while transmitting therethrough the signal light emitted from said third optical fiber;
• wherein at least one of said first to third optical fibers has a core region substantially made of pure silica glass.