Alcatel of Paris has announced that it has demonstrated unrepeatered optical transmission at 1.6 Tb/s over a 321-km submarine span. The Alcatel researchers employed cascaded Raman amplification and 160 wavelengths in the test.

Cascaded Raman amplification uses one low-power and two high-power Raman pumps, detuned to 100 nm and to 90 nm below the wavelength of the C-band pump sources. Channel spacing in the experiment was 25 GHz, or 0.2 nm.