A Pseudo-flexible DAML Phase Estimation In Coherent Optical Orthogonal Frequency Division Multiplexing

Coherent optical orthogonal frequency division multiplexing(CO-OFDM)been widely concerned in the field of optical fiber communication for its high spectral efficiency and high chromatic dispersion(CD)and polarization mode dispersion tolerance.However,it is so sensitive to laser phase noise due to the long OFDM symbol intervals and the use of coherent detection,which is extremely important to analyze the phase estimate of coherent optical OFDM system.Since Decision-aided maximum likelihood(DA-ML)phase estimation has been applied in single-carrier communication system due to its many advantages and further extended to OFDM system,We introduce a pseudo-flexible DAML in CO-OFDM system.Firstly,We introduce the basic theory of CO-OFDM and DAML algoritmm,incluing the development,basic structure and key technologies.Phase noise estimation algorithms in CO-OFDM followed by theoretical analysis and simulation verification.And we pointed out improve the previous DAML algorithm.Secondly,a pseudo-flexible DAML phase estimation algorithm is proposed,and the principle of pseudo-flexible DANL phase estimation algorithm is analyzed in detail,which considering the varying phase noise over a long symbol interval is not constant.And the BER of the pseudo-flexible DAML is deduced and the theoretical and simulation are compared.Finally,the performance of the pseudo-flexible DAML phase estimation algorithm is analyzed in MATLAB and VPI simulations in detail.Simulation results show that the pseudo-flexible DAML phase estimation algorithm has lower complexity than DA + DF and obtained tne similar BER performance of DA+PA4 compared to DA + PA.However,the pseudo-flexible DAML phase estimation algorithm does not have additional pilot subcarriers for assistance and zero overhead.Overall,pseudo-flexible DAML algorithm appears to be more advantageous compared to other phase estimation algorithms in CO-OFDM.