Atmospheric Effects On Coherent Optical Communication Detection Method

With the maturity of the laser and optoelectronic devices, free space optical communication(FSO) technology has been rapid development. Coherent optical communication with high communication performance had got the attention and development in FSO. Air space optical communication whose carrier is the laser beam is a wireless communication transmission in the atmosphere. Therefore the effects of atmospheric channel attenuation and atmospheric turbulence on laser beam propagation are problems which cannot be let off. While the degree of atmospheric effects on the performance of the optical communication system of different detecting ways are different. Systematic analysis about the optical communication performance of several coherent detection modes in the atmospheric environment has an important significance.Paper introduces the research background and significance of coherent optical communication, and describes the development history and the research status of coherent optical communications, and overview briefly the research status of the effect of atmospheric turbulence on the communication system performance. The basic principle of the direct detection and coherent detection is described in detail, and compare and analysis the pros and cons of the two detection methods. According to the principle of coherent detection, the expression of SNR, bit error rate and efficiency of coherent heterodyne detection communication system are given. The effect of spatial conditions and frequency conditions on the size of them is analyzed. The SNR of single-ended detection and balanced detection in the coherent communication system is compared and analyzed. Paper provides an overview of the optical statistical properties of the atmospheric turbulence and its impact mechanism on the transmission by beam. It focuses on the effects of atmospheric turbulence on laser transmission characteristics. It analyzes the light intensity flashing and phase perturbation effect. It gives the analytical expression of the coherent detection system SNR under the effect of atmospheric turbulence.Finally, by means of Optisystem communication simulation software and as the reference to the actual device parameters, communication system simulation models with different detection methods are designed and constructed. Paper main compares eye and Q value size of the direct detection and heterodyne detection optical communication system under the effect of atmospheric effects. The change trends of Q value of the balance detection system and single-ended detection system with transmission distance, weather and local oscillator optical power is emulated. According the eye and Q value from the BER tester, simulation results were compared, and draw the appropriate conclusions. It provides a theoretical basis for atmospheric coherent optical communication system design and construction.