Coherent Optics Converging To The Shannon Limit

Coherent optics is converging to the Shannon limit. The Shannon limit represents the upper bound on information transfer for an optical channel. The gap between Shannon and various modulation schemes is shrinking. Note that the higher the transfer rate, the lower the optical reach. A lower optical reach means more OEM or optical amplification and this is an outcome carriers wish to avoid. These sort of tradeoffs permeate optical transmission. No free lunch. 

Graph Depicting Modulation Schemes Converging To The Shannon Limit

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