Nonlinear effects in optical signal transmission using a multimode fibre with weak coupling

We present the results of numerical simulation of nonlinear propagation of an optical signal in multimode gradient- and step-index fibres with weak coupling. It is found that when signals propagate in different modes, the system quality factor ( Q -factor) for a gradient-index fibre increases with the number of the modes involved. The quality degradation of the transmitted data with increasing the number of the involved modes is demonstrated for the case when the signals in different modes travel at the same velocity. It is shown that the use of a step-index fibre may significantly deteriorate the signal quality due to the presence of a mode with a small dispersion parameter. (fibre-optic communication)