On the Soliton Spectral Efficiency in Non-linear Optical Fibers

Optical fiber communications can be modeled using the non-linear Schrodinger equation, which is integrable. In this paper we show how integrability can be exploited to communicate using multisoliton pulses. Starting with a white Gaussian input signal, we use the known distributions of eigenvalues and scattering data to derive an analytical expression for a lower bound to the spectral efficiency, taking into account the effects of noise due to amplification explicitly. We show that in the low noise regime, the soliton channel shows two different behaviors, interpolated by a single scalar parameter that controls the nonlinearity of the system. In the linear regime the soliton channel approaches an additive white Gaussian noise channel, while for strongly nonlinear systems the bound declines. The bound reaches a maximum between the two regions.