Analysis of linear and non-linear effects in the frequency domain for a three-channel optical transmission system

This paper presents the analysis of a wavelength division multiplexer communication system in the frequency domain, with the objective of visualizing the incidence of the linear phenomena of attenuation and chromatic dispersion, together with the phenomenon of phase self-modulation, the Kerr electro-optical effect and fourth wave mixing. The analyzed system consists of a laser transmitter with a Mach-Zender modulator and a standard G.625b single-mode fiber link transmitting three optical signals of 10 mW, 25 mW and 50 mW at a fundamental wavelength of 1550 nm at a rate of 10 Gbps. This system is analyzed through a graphical user interface programmed by the authors in the Python environment, which calculates the parameters corresponding to each phenomenon and graphically represents the transmission results at distances of 50 km and 100 km. The analysis methodology consists of varying the spectral separation of the transmitted channels, initially considering a spectral separation of 2 nm and subsequently a spectral separation of 0.2 nm, observing as a result that the harmonics generated by the fourth wave mixing phenomenon considerably alter the spectral density of the transmitted signals, since the energy of the harmonics is equal to the power of the transmitted signals. On the other hand, with the spectral spacing of 0.2 nm, it is obtained that, although the harmonics alter the spectral density waveform, the bandwidth is not compromised by these additional signals.