Researchers of the "Bell Labs", research and developement institution of Lucent Technologies, were able to send data with the speed of 2.56TeraBytes PER SECOND over a 4000km (2500mile) line!

Previous record was 1.6TB over a 2000km (1250mile) line.
More info: Can be found here

To make sure there is no dataloss, Bell Labs used the forward error correction en Differental Phase Shift Keying (DPSK) technique.