Information theory establishes fundamental limits on the rate of reliable communication over noisy channels. This talk reviews basic information-theoretic concepts, particularly as they apply to coherent optical data transmission over nonlinear optical fibers.
We analyze the information-capacity limitations of the optical communication channel, as determined by noise accumulation from optical amplification and nonlinear wave-mixing. We review the concepts of signal-to-noise ratio and entropy for binary-coded and continuous communications, leading to a definition of ultimate capacity for the optically-amplified channel. A unified quantum model, describing both amplification and nonlinearity limitations, makes possible to determine the power transmission window within which the channel capacity can be maximized.