We develop information-theoretical description of nonlinear optical communication systems. We present a non-perturbative calculation of the information capacity for different modulation formats, and demonstrate that fiber nonlinearity leads to exponential suppression of the channel capacity.
For studying the accurate impacts of nonlinear fiber propagation on channel capacity conveniently, a numerical calculating method derived from signal power transmission property is presented, its dependences on input pulses peak power is obtained, and spontaneous emission noise intensity, nonlinear coefficients and group velocity dispersion of fiber are amplified. It can also conclude that the improvement of nonlinear channel capacity will not go with the improvement of input signal power especially for larger power input case, which can be used as a guideline to calculate nonlinear channel capacity theoretically and improve nonlinear channel capacity in technical application.
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.