The rapid expansion of the Internet, phone and high-definition digital TV broadcast services, and the demand for bandwidth on the user side of the network is gradually increasing. The transmission speed of the current passive optical networks is now sufficient but in the near future it will be necessary to introduce new technologies in order to easily satisfy the growing needs. Until recently, the optical communication systems primarily employed conventional on-off-keyed signals, but nowadays a number of advanced optical modulation formats have attracted increased attention.
The main objective of this thesis is to compare two in circulation high-speed transmission systems based on their transmission quality. These were simulated by using VPI Transmission Maker software and real measurements were made. The systems are based on polarisation multiplexing binary phase-shift keying and partial DPSK modulation format. By using the two modulations, the coherent detection is comparable to the direct.detection scheme.
The qualitative characteristics of the transmission are analyzed in a typical wavelength division multiplexed enviroment taken into consideration the effects of attenuations, dispersions and nonlinearities. During the simulations, I’ll present both the advantages and disadvantages of the systems. We will see if the use of polarisation multiplexing BPSK is more spectrally efficient than partial DPSK. At the end of the thesis, I summarize the results and give comparison of the different forms of modulations.