Going 100m is easy, 50km at 10G has been around for a long time.

The really hard part is getting 10Gb and 40Gb to go further than ~100km.

10Gb pulses of light start to merge together after 100-200km because of dispersion (some components of the pulse travel faster than others).

Up till now you had to put in expensive optical delay compensation filters to correct the dispersion.

At 40Gb the problems get 4 times worse - i.e. the light gets mushed after 25-50km, or you had to go through power hogging electro-0ptics every so often (very un-green).

The Nortel approach cleverly gets round this using techniques similar to those formerly applied to radios and modems - (i.e. Quadrature transmission, dual polarization and line compensation), except scaled up many times to operate at Optical line rates.