Analysis And Simulation Of Turbulence Effects Of Atmospheric Laser Communication

Atmospheric laser communication uses laser as the carrier of information transmission, which has many advantages such as good confidentiality, high channel capability and effective anti- interference. However, atmospheric turbulence is one of the most important constraints and influencing factors, so it is significant to research the influence of atmospheric turbulence on atmosp heric laser communication.In this paper, statistical characteristics and formation of atmospheric turbulence is described, analytical methods and the turbulence power spectrum models for optical wave propagation through random medium are also introduced. Based on transmission characteristics and the scintillation index model of Gaussian beam in horizontal transmission condition, the random phase screen distorted by kolmogonov turbulence and rain mixed media is simulated by power spectrum Fourier transform method. The intensity distribution, beam wanders and scintillation index are simulated by multi- layer phase screens method. The results are in agreement with theoretical values. According to the scintillation model of horizontal transmission paths and the turbulent atmosphere structure function varies with height, the scintillation model of slant path is calculated using modified Rytov theory. The scintillation index on earth-space vertical path is simulated by the multi- layer phase screens method, besides, the angle-of-arrival fluctuations, beam drift and the amplitude variances through non-Kolmogorov turbulence are numerically calculated. The influences of atmospheric turbulence on the BER of the wireless optical communication systems are discussed with on-off keying(OOK), subcarrier phase-shift keying(PSK) and subcarrier differential phase-shift keying(DPSK) modulations. The results show that the subcarrier PSK modulation is superior to the OOK and 2PSK modulations when taking into account the influenc e of scintillation effect in optical communication system applications. Therefore, the performance of optical communication systems in atmosphere optical channels can be improved by using a larger system receiving aperture or appropriate demodulation means. This research work can provide somewhat guidance for the studying and development of atmospheric laser communication.