Nonlinear distortions as nonlinear noise in coherent fibre-optic communication lines

A phenomenological model describing nonlinear distortions in coherent fibre-optic communication lines is investigated. This model makes it possible to extend the range of application of the nonlinear noise model as compared with the well-known GN model. A method for experimental determination of the main parameters of the proposed model is described, and the sources of possible errors are discussed. (paper)