Multi-Gigabit Coherent Communications Using Low-Rate Fec To Approach The Shannon Capacity Limit

Combining a rate-1/4 forward error-correcting code, a coherent receiver, and an optical phase-locked loop yields near error-free performance with 2-dB photon-per-bit sensitivity, which is <3-dB from the Shannon limit for a rate-1/4, pre-amplified, coherent receiver.