Math Modeling And Simulation Research Of Coherent Optical Communication Systems

At present, the development of communications changes quickly, the technology which can be adopted in systematic construction of communication has lots of choices, at the same time, public's command to communications' function is becoming higher and higher, the design of communication systems is becoming more complicated, the cost of built systems is increasing constantly. To communication systems which is planning or the communication project which is designing, we can set up corresponding model and use computer to simulate the model, then change manifold models' parameter to forecast system's running parameter and economic benefits in future; we can select the best project by means of analyzing simulation's result. When we want to improve the running communication system, we also can simulate the improved state and find out the most satisfactory project. The simulation of communication systems can draw out the optimal parameter and save huge investment. Especially to such systems as coherent optical communication, optical soliton communication, DWDM, etc. Their structure is complicated, the difficulty of experiment is large, and the components is expensive , so we haven't effective means of analyzing systematic function and to simulate these systems by computer have more practical value.This thesis set up the mathematics model of coherent optical communication system on the basis of coherent optical communication principle, then we run the simulation and drew some simulated wave forms , such as the wave form of modulating information, DPSK information wave form and DPSK signal wave form , the input wave form of double linear filters, the output wave form by judgement,etc. Thus we verified the exactness of this model and its performance was suitable for the performance demand of coherent optical communication system basically.According to the model of coherent optical communication, we used Monte Carlo law to simulate coherent optical communication system by dataflow simulation. For this reason, we defined user's function and worked out the simulation program under different phase noise, we drew the curve between the intensity of noise and BER, the simulation result indicated that double linear filters can finish the demodulation of the primitive signal with the less mistake rate, proved coherent optical communication system has better character of resisting the noise at the same time, so it can prolong the transmitting distance greatly , achieve the simulation purpose .