APPLICATION OF NONLINEAR PHASE FILTERS IN HIGH-SPEED, FIBRE-OPTICAL TRANSMISSION SYSTEMS WITH THE SPECTRAL MULTIPLEX
The problems of the application of nonlinear phase filters for the electronic compensation of nonlinear signal interaction in high-speed, fibre-optical transmission systems are discussed in the article. The signal interaction in such systems is determined by the combined action of chromatic dispersion and self-phase modulation. If a transmission system is multichannel and it uses several optical carriers then besides the self-phase modulation, phase cross modulation has a considerable influence on signal transmission. Nonlinear phase filters are electronic equivalent of a generalized nonlinear Schrödinger equation, describing the process of signal propagation in optical fiber. An operator describing such a filter refers to the operator class with unitary nonlinearity for which there is an inverse filter complex conjugate with the initial one. Corresponding inverse filter realized by analogy in a digital form can be used for the restoration of signals, passing a transmission line with the aim of the decrease of the influence of specified dispersive and nonlinear effects both in single-channel and multichannel transmission systems. The results of modeling and the analysis of the noise immunity of signal reception with the application of the considered algorithm are presented. It is shown that this algorithm gives the considerable gain (several decibels) both in single-channel and multichannel transmission systems in comparison with the well-known linear method of dispersion compensation using optical fiber, compensating the dispersion.