A novel method is proposed to get the adaptively optimized detection threshold of strong atmospheric turbulence channel model with K distributions, by estimating high-order accumulation of the covariance of received signal. Then performance of this adaptive signal threshold estimation method is tested and verified by Monte Carlo simulation, which shows that the threshold can be adaptively changed with the atmospheric turbulence channel conditions. Finally, the effectiveness of this method is verified by the actual measurement data under light rain, moderate rain and heavy rain. It is shown that the method proposed in this paper can effectively suppress the atmospheric turbulence and improve the performance of Free Space Optical communication system.
Cassegrain antenna is commonly used in Free Space Optic communication system. The double reflection structure
determines the system has a shade problem. In this paper, the off-axis emission (semi-aperture lighting) method is
applied to solve the shade problem caused by the secondary mirror. This method is simple both in structure an implement.
ZEMAX software and Fourier optics are used to analyze the Cassegrain antenna theoretically. We can improve the
performance of Cassegrain antenna under the guidance of the analytical results. Some experiment has been carried out.
The results showed that the percentage of exit-pupil power effectively increased from 9% to 53%, the diameter of spot
was not exceeding 200mm at the distance of 600m.It is significant for engineering applications.