| Compared with the space-to-ground wireless optical communication under the vacuum channel,the practical application of the space optical communication system under the atmospheric channel is particularly common.Space optical communication technology based on atmospheric channels is used in multiple application fields such as metropolitan area network data expansion,optical fiber data backup,emergency data communication,cellular backhaul communication network,military data security communication,quantum data communication,and "last mile" Has been widely used.Among them,modulation technology is the key technology to realize its communication stability,which directly determines the reliability and robustness of signal transmission.At present,orthogonal frequency division multiplexing technology has a strong ability to resist frequency selective fading and narrow-band noise,and can effectively suppress inter-symbol interference and random fading effects.It has always been a hot spot in optical communication research.However,the orthogonal frequency division multiplexing system is difficult to adapt to the harsh channel environment,and will cause crosstalk between sub-carriers due to laser phase noise.The filter bank multi-carrier modulation technology makes up for the shortcomings of orthogonal frequency division multiplexing.It not only ensures the independence of sub-channels,but also does not require strict synchronization between sub-carriers.It is more suitable for space optical communication.Circular polarization modulation technology has higher penetrating power and anti-attenuation ability,and has better polarization maintaining characteristics against atmospheric turbulence,so it is also one of the research hotspots of space optical communication.Combining the polarization modulation technology and re-introducing the filter bank multi-carrier modulation technology can effectively combine the technical advantages of the two and apply to the system against the harsh multi-channel interference environment,improving the reliability and work in the wireless optical communication system Robustness.This paper studies the multi-carrier polarization modulation technology of the filter bank based on the terrestrial point-to-point atmospheric channel to solve the problems of traditional modulation methods in the current stage of research such as poor anti-turbulence ability,serious sub-carrier crosstalk,and poor ability to resist complex weather environments.The main research content and work results of the thesis are as follows:(1)First of all,in order to solve the problems of low spectrum efficiency of sub-carrier orthogonal frequency division multiplexing modulation technology,strict requirement of sub-carrier synchronization,and serious sub-carrier crosstalk,this paper proposes a filter bank multi-carrier modulation technology(FBMC)instead of sub-carrier normal Scheme of cross-frequency division multiplexing technology.The simulation results prove that the multi-carrier modulation technology based on the filter bank is more effective than the orthogonal frequency division multiplexing modulation technology in solving the problems of sub-carrier crosstalk and low spectral efficiency of the spatial optical communication modulation system,and can also improve the system’s signal-tonoise ratio.(2)Secondly,in view of the poor anti-air interference ability of the existing polarization modulation technology,this paper firstly proposes a combination of orthogonal differential phase shift technology and circular polarization modulation that is extremely insensitive to environmental impacts,and then In order to verify the anti-air interference capability of the multi-carrier circular polarization modulation technology of the filter bank,it is compared with the polarization modulation technology simulation of quadrature differential phase shift modulation proposed in this paper.The simulation results show that,in the same way that circularly polarized light is modulated,the modulation technique proposed in this paper can effectively improve the anti-interference ability under normal weather than the quadrature differential phase shift modulation technique.(3)Finally,in order to solve the problem of poor performance of the polarization modulation system based on the filter bank multi-carrier in combating atmospheric interference in complex weather,this paper proposes a scheme to replace the original single-input single-output system with the multiple-input multiple-output technology.Through parameter comparison between communication simulations under normal weather and extreme weather conditions,the analysis of the results shows that the technology can effectively combat complex weather environments and improve system performance. |
