The aim of the diploma thesis is to analyze the WDM and OTDM optical telecommunication networks and the possibility of conversion between these two multiplexing methods. In the first chapter were mentioned the basics of optical communication. The next chapter describes the optical fiber. Specifically, their types, linear and nonlinear optical characteristics whitch are limiting transmission e.g. attenuation, dispersion, refraction, FWM, SPM and XPM. Followed by a general description of the multiplexing systems used in optics and individual elements used in various multiplexing systems. The last chapter was devoted to the design of the OTDM - WDM conversion model.