Investigation On Potential Application Of DAML Phase Estimation In QAM/FSO Systems

With the rapid development of the Internet and big data services,more and higher to the requirement of the new communication technology in terms of bandwidth,rate and so on.FSO communication with its various advantages is increasingly subject to public attention.FSO can support higher information rate with lower power loss,and does not require spectrum certification.However the laser signal was easily affected by atmospheric turbulence and various weather conditions when it transmits through communication channel.Free space coherent optical communication system was less affected by the communication link compared with IM/DD communication system,and its modulation mode is flexible,the current research on the PAM,PSK,and DPSK modulation based on space coherent optical communication system has been quite mature.QAM modulation has been paid more attention by researchers because of its higher spectral efficiency.In addition,the effects of phase noise on the performance of communication system cannot be ignored.Firstly,based on the analysis of atmospheric turbulence and attenuation.FSO communication system model based on QAM modulation is established.The SNR and BER of the system are derived under different atmospheric channel models,and the performance of the system is simulated.The performance of FSO communication system based on QAM modulation and DPSK modulation is compared.Secondly,the mature DSP phase estimation algorithm is introduced into the FSO communication system based on QAM modulation,According to the varying characteristics of turbulent phase fluctuation and laser phase noise.The estimation performance of DAML signal based on error rate formula was derived.Finally,a series of Monte Carlo simulations are carried out to study the effect of the phase noise on the BER performance of the communication system.