SUBMARINE LONG-DISTANCE TRANSMISSION SYSTEM AND FIBER

PROBLEM TO BE SOLVED: To provide an optical system and a fiber which are adapted specially to submarine long-distance optical transmission.SOLUTION: A submarine long-distance transmission system includes an optical fiber transmission span and modules for coherent detection and digital signal processing for dispersion compensation. The optical fiber transmission span includes a first fiber with plus dispersion and a second fiber with negative dispersion which are substantially equal in length, the first fiber and second fiber are configured to supply signal output over a transmission longer than 10,000 km, and combined dispersion accumulated over an operation band width never exceeds the dispersion compensation capability of the modules for coherent detection and digital signal processing. A fiber used by a submarine long-distance transmission span has a dispersion coefficient in a range of -16 to 25 ps/nm km at a transmission wavelength of 1,550 nm and a dispersion slope in a range of 0.04 to 0.02 ps/nmkm.