The influence of nonlinear phase interference of self-phase modulation and phase cross-modulation arising in an optical fiber on multichannel, spectrally separated signals is considered. A simulation program has been created in the environment of the object-oriented programming language C#, which makes it possible to calculate the BER in the receiving part depending on the parameters of the optical path. The program has several degrees of freedom in the following parameters: transmission rate, used linear signal code, optical power level in individual channels, length and type of optical fiber. It is shown that in order to achieve the required BER, it is necessary to limit the optical power levels in the channel signals. The results of simulation of signal transmission over a distance of 100 km for the number of channels 40, 80 and 160 with channel rates of 10 Gbit/s and 40 Gbit/s in NRZ and RZ linear codes are presented.