Performance Analysis of Coherent Optical Transmission Systems with Different Modulation Schemes

Abstract

The huge revolution in the communication era needs a high traffic data rate to connect the entire world to become as small village, in this growth it is necessary to have an optical transmission network capable of providing high data rate speed with a high quality and low cost. This thesis will analyzes and demonstrates the performance of coherent transmission technology, which considered as the next generation technology in optical communication, due to its design and software are dependent, it enhances the optical signal quality and efficiency that is required for long haul high data rate transmission system. The thesis is structured from the background for optical communication and considering the most affective items that serve this research in coherent communication, as well as merging this technology with other multiplexing technologies for getting high data rate. A special optical communication design software called OptiSystem was used to simulate all the proposed scenarios in many stages starting from a single channel optical transmission system with different modulation formats for different transmission distance from short range to long haul transmission distance. The designed system with n-PSK modulation shows better performance for transmission distance. On the other hand the system with m-QAM showing best performance with high data rate. And then merging this technology with multiplexing technology such as optical OFDM and DWDM. This combination increases the optical transmission data rate and transmission distance to around 1000 km, also at this combination we simulate and analyze special cases first one for different channel with different data rate a performance analysis is done with results show the ability of using this method but with considering the high data rate signal requirements in the system design. The second case is a practically full DWDM system 40 lambda with coherent technology and without it. The results show a high increasing in the transmitted data rate for coherent technology which reach around 4Tbps for the designed system with the longest path with acceptable OSNR in the range which is around 16dB with BER around 10-5 for coherent system.