Research On Adjacent Carrier Crosstalk And Polarization Mode Dispersion Compensation Technology

Under the general trend of the increasing development of communication technology,more and more information technologies have been proposed to meet people’s ever-increasing information needs.As the main carrier of Internet data traffic,optical fiber communication technology has attracted widespread attention due to its advantages such as large transmission capacity,low loss,good confidentiality,long transmission distance,and various modulation formats.The coherent optical communication technology is the mainstream technology in the optical communication system,and the receiving end of the coherent optical communication system usually uses various DSP technologies to restore the signal.The ultra-dense multi-carrier coherent optical transmission system can realize the transmission with the spacing between adjacent sub-carriers smaller than the baud rate.However,when the sub-carrier spacing of the transmission system is compressed,some interference that affects the signal quality will inevitably occur.Therefore,the research on interference recovery in ultra-dense multi-carrier systems is of great significance and application value.Aiming at the problems of adjacent carrier crosstalk and polarization mode dispersion in ultra-dense multi-carrier coherent optical communication systems,this thesis proposes three equalization algorithms that can improve system spectral efficiency and received signal quality according to different modulation formats or pulse waveforms.Through the joint simulation technology of Optisystem and Matlab,some ultra-dense multi-carrier dual-polarization systems with different modulation formats and different pulse waveforms are realized,and the proposed algorithms are verified by simulation.The main research work of this thesis is as follows:(1)Aiming at the problem of adjacent carrier crosstalk and polarization mode dispersion in ultra-dense multi-carrier dual-polarization QPSK coherent optical communication system,4 × 4 Multiple Input Multiple Output-Constant Modulus Algorithm(4×4 MIMO-CMA)is proposed.The algorithm rotates the carrier crosstalk component,combines the polarization crosstalk component and the signal to be equalized through the adaptive filter,and updates the filter coefficients adaptively based on the CMA equalization principle to realize simultaneous compensation of adjacent carrier crosstalk and polarization mode dispersion.The simulation results show that the multi-carrier dual-polarization QPSK system based on 4 × 4 MIMO-CMA algorithm can achieve the spacing between adjacent carriers equal to 75%of the signal baud rate.And the Q factor of the recovered signal after 800Km optical fiber transmission is 1.3dB higher than that of the traditional algorithm.(2)Aiming at the problems of adjacent carrier crosstalk and polarization mode dispersion in higher-order ultra-dense multi-carrier dual-polarization quadrature amplitude modulation(QAM)coherent optical communication systems,Multiple Input Multiple Output-Adaptive Step-Decision Directed Least Mean Square(MIMO-AS-DDLMS)is proposed.The algorithm first passes the rotated carrier crosstalk component and the signal to be equalized through the adaptive filter,and updates the filter coefficients adaptively based on the AS-CMA equalization principle,then passes the polarization crosstalk component and the signal to be equalized through the adaptive filter,based on The AS-DDLMS equalization principle adaptively updates filter coefficients to realize compensation for adjacent carrier crosstalk and polarization mode dispersion.The simulation results show that the ultra-dense multi-carrier dual-polarization 16QAM transmission system based on MIMO-AS-DDLMS algorithm and adding dispersion compensating fiber can realize that the interval between adjacent carriers is equal to 50%of the signal baud rate.And the Q factor of the recovered signal after 600Km optical fiber transmission is 1dB higher than that of the traditional algorithm.(3)Aiming at the problem of adjacent carrier crosstalk in 16QAM Nyquist Dense Wavelength Division Multiplexing(DWDM)coherent optical communication system,Multi Carrier-Multiple Input Multiple Output-Multi Modulus Algorithm(MC-MIMO-MMJA)is proposed.The algorithm performs corresponding rotation processing on multiple adjacent carrier crosstalk,passes through the adaptive filter together with the signal to be equalized,and adaptively updates the filter coefficients based on the MMA equalization principle to realize compensation for adjacent carrier crosstalk.The simulation results show that the 16QAM Nyquist DWDM system based on the MC-MIMO-MMA algorithm can realize that the interval between adjacent carriers is equal to the baud rate of the Nyquist signal.And when the carrier spacing of the system is equal to the baud rate,the Q factor of the received signal can be increased by about 0.8dB after adding the MC-MIMO-MMA algorithm.