Nonlinear signal multiplexing for communication beyond the Kerr nonlinearity limit

Current optical fibre transmission systems rely on modulation, coding and multiplexing techniques which were originally developed for linear communication channels. However, linear transmission techniques are not fully compatible with a transmission medium with nonlinear optical response such as silica. As a consequence, the Kerr nonlinearity imposes a limit on the achievable transmission performance and capacity of conventional optical fibre communication systems. Here we show that transmission performance beyond the Kerr nonlinearity limit can be achieved by encoding all available degrees of freedom and nonlinearly multiplexing signals in the space of the so-called nonlinear spectrum, the evolution of which is linear along the fibre link. This result strongly motivates a paradigm shift and the developments of novel nonlinear coding and signal processing techniques in optical fibre transmission technology