Study On Large Aperture And Multiple Aperture Receiving Antenan In Wireless Optical Communication

Free space optical communication(FSO) has attracted a lot of attention in the field of communication recent years. However, FSO takes the atmosphere as the transmission channel, so atmospheric turbulence which caused by the laser intensity raises the system BER. In this paper, the large aperture and multiple apertures receiving technology has been used to restrain the effect of light intensity fluctuations effectively, and this study has given a thorough research of the effect of large aperture and multiple apertures receiving technology on the system performance.This paper has firstly introduced the basic principle of the circular polarization modulation, and then compared the characters between OOK modulation and CPol SK modulation. By the emulation analysis of Optisystem software, it has been seen that the eye diagram which the CPol SK received is with larger opening intensity and better symmetry than the ones of OOK. In the same reason, it has been shown that the dual receiving system performs better than the single road.Then the optical loss of whole system and the mathematical model of beam spreading loss have briefly been presented respectively, and the related results show that the larger the aperture of the lens receives, the smaller the beam expands for the same spot diameter. Furthermore, the Optisystem software has operated simulation analysis under different climate circumstances, the results has shown that the eye diagram is clearer when it’s sunny than the one of snowy. Meanwhile it can be seen that the loss of strength varies with the turbulence intensity and the loss is smaller with large aperture receiving.Based on the above theoretical basis, this article has given a further study of the effect of large aperture and multiple apertures receiving on the performance of the whole FSO and then concluded the formula of error rate for the large aperture. Besides, with a fixed index, the paper has been analyzed the relationship between without the influence of turbulence detector of signal-to-noise ratio and the diameter of the aperture. For the multiple apertures, the effect of 1~3 aperture receiving on the performance of communication has been mainly analyzed and the simulated results have shown that multiple receiving aperture antenna receiving technology can reduce the fluctuation of lens surface light intensity and bit error rate of the whole communication system. And with the increase of the aperture number of the whole system, the error rate has been reduced gradually.In order to verify this theory, in this paper, the experiment has been proved that the large aperture receiving and multiple apertures receiving have a great effect on the BER of the system. Research also shows that, in the same parameters, both large aperture and multiple apertures receiving technology can effectively reduce the variance of intensity fluctuation and improve the communication performance of the system.