Research On Performance Of Orbital Angular Momentum Multiplexing Optical Communication System With Oceanic Turbulence Channel

In recent years,with the increasingly important resource value and strategic significance of the ocean,the demand for Marine information transmission is constantly increasing.Underwater wireless optical communication(UWOC)has become a research hotspot due to its great potential in transmission rate and channel capacity.Multiplication of a new degree of freedom,oriital Angular Momentum(OAM)carried by a vortex beam,can greatly improve the channel capacity and spectrum utilization of underwater wireless optical communication.However,the ocean turbulence in underwater environment will cause channel crosstalk,which will affect the performance of OAM multiplexed underwater optical communication system.In order to reduce channel crosstalk caused by oceanic turbulence,the performance of OAM multiplexing optical communication system under the influence of oceanic turbulence channel is studied in this paper.The main tasks of this paper are as follows:1.Based on turbulent channel simulation theory,we simulate the influence of time-varying oceanic turbulent channel on OAM carried beam,and a simulation model of oceanic turbulent time-varying channel was established.The verification results of the channel model show that the phase structure function curve of the ocean turbulence phase screen in the channel model is consistent with the theoretical curve,and the OAM detection probability distribution after the channel is in good agreement with the theoretical formula.The channel can not only be used to simulate the influence of ocean turbulence on the beam in numerical simulation,but also be applied to the spatial light modulator for the experimental research of underwater optical communication.2.Based on the ocean turbulence time-varying channel model,the effects of space-time block codes(STBC)and vertically layered space-time codes(V-BLAST)on the bit error rate of the OAM multiplexing UWOC communication system under different signal-to-noise ratio,transmission distance and number of receiving aperture are analyzed.The results show that the use of space-time coding technology can effectively reduce the BER under the influence of oceanic turbulence.3.The effects of various MIMO detection algorithms on OAM multiplexing UWOC system's BER was studied.The simulations are carried out under conditions including different antenna number,different turbulence intensity to analyze the performance of MIMO detection algorithms.The results showed that the relatively optimal BER performance of OAM multiplexing UWOC system is achived with successive interference cancellation detection algorithm base on minimum mean square error.In this paper,a time-varying oceanic turbulence channel simulation model is studied.Based on this channel model,the effects of space-time coding and MIMO detection algorithms on the performance of OAM multiplexed underwater optical communication system are studied.The results can provide a reference for the design of OAM multiplexed optical communication system with ocean turbulent channel.