Forward error correction techniques in long-haul optical transmission systems

The use of forward error correction (FEC) provides significant coding gain, which has been used to demonstrate error-free transmission under severely-errored operating conditions, with high spectral efficiency, over distances exceeding 10,000 km, and at high bit rates. Recent experiments using FEC have demonstrated aggregate transmission capacity exceeding 2 Tb/s. FEC-coded transmission can tolerate a lower optical SNR on the line, which in turn reduces impairments induced by nonlinearities, with the net effect being an increase in the Q/sup 2/-factor when signal power is reduced.