FSO Communication With Extracting DC Technique And Adaptive Decision Threshold

Free-space optical(FSO) communication has received rapid development because of its advantages including high capacity, high transmission security, free spectrum license and lower deployment costs. However due to the inhomogeneity of temperature and pressure fluctuations, the intensity of an optical wave fluctuates when an optical signal propagates through the atmosphere. Such fluctuation is known as scintillation effects, which can deteriorate the FSO transmission performance severely. Therefore, it is very important to find some ways to decrease effects of atmospheric turbulence with lower deployment costs.Firstly, intensity attenuation when signal propagates through atmospheric channel is studied in this paper. Statistical properties of intensity fluctuations caused by atmospheric turbulence is mainly dicussed and atmospheric turbulence channel model is described. Then,optical attenuation characteristics caused by fog,haze,rain and snow is analyzed. Finally, a model of FSO communication system is established.Secondly, due to disadvantages of reference continuous wave light assisted detection technique, DC component in the signal is extracted as a reference wave light to reduce the impact of atmospheric turbulence. Then performance of FSO communication system with DC extraction technique is studied. Furthermore, adaptive decision threshold technique is proposed to improve shortcoming traditional decision threshold technique. Finally, performance of OOK system with adaptive decision threshold is given considering influences of atmospheric turbulence, fog and haze weather conditions.Finally, Monte Carlo simulations are performed to analyze BER performance of DC extraction technique and adaptive decision threshold technique with different atmospheric turbulence intensity. Then, considering atmospheric turbulence, BER performance and transmission distance based on adaptive decision threshold technique are simulated respectively in fog and haze weather conditions. Simulation results show that the DC extraction technology and adaptive decision threshold technique can effectively reduce the influence of atmospheric turbulence, consquently improve the performance of FSO communication system.