Forty WDM 2.5-Gbit/s transmission over 12000 km using widely gain-flattened low-noise 980-nm pumped EDFAs

Summary form only given. This paper shows the results of forty WDM 2.5 Gbit/s transmission over 12000 km for the first time, to our knowledge, by solving two constraints. First, to realize a widely gain-flattened transmission line over 10000 km, we used 980-nm pumped erbium-doped fiber amplifiers (EDFAs) with a simple single peak gain shape, which allows us to have precise gain flattening. Secondly we suppressed fiber nonlinearity.