光正交频分复用系统中的光纤非线性效应制约着系统进一步的扩容.针对此问题,提出一种数字相干叠加的方法,用于提高相干光正交频分复用系统对光纤非线性的容忍性.仿真中,5通道的波分复用下偏振复用相干光正交频分复用系统的每个通道传输...光正交频分复用系统中的光纤非线性效应制约着系统进一步的扩容.针对此问题,提出一种数字相干叠加的方法,用于提高相干光正交频分复用系统对光纤非线性的容忍性.仿真中,5通道的波分复用下偏振复用相干光正交频分复用系统的每个通道传输四进制正交振幅调制映射的71.53 Gbit/s信号在光纤中传输400km.首先,通道间隔为25 GHz,与传统相干光正交频分复用系统相比,色散补偿前后,使用数字相干叠加的相干光正交频分复用系统的信噪比分别提升了6.02 d B和9.05 d B,最佳入纤光功率均增大了2 d B;其次,通道间隔为50 GHz,色散补偿前后,信噪比分别提升了4.9 d B和8.75 d B.通过理论推导及仿真,验证了所提方法能有效消除相干光正交频分复用系统的一阶非线性失真,进而提高系统对光纤非线性的容忍性.展开更多
We propose the modified Kalman filter(MKF) using the received signal for observation and constructing an inverse process of the conventional Kalman filter(CKF) for polarization de-multiplexing in coherent optical(CO) ...We propose the modified Kalman filter(MKF) using the received signal for observation and constructing an inverse process of the conventional Kalman filter(CKF) for polarization de-multiplexing in coherent optical(CO) orthogonal frequency-division multiplexing(OFDM) transmissions. The MKF can avoid the convergence error problem in CKF without matrix inverse operation and has a faster converging speed and a much larger tolerance to the process and measurement noise covariance, about two orders of magnitude more than those of CKF. We experimentally demonstrate the 12 Gbaud OFDM signal transmission over 480 km standard singlemode fiber. The performance of MKF and CKF outperforms pilot-aided polarization de-multiplexing with better accuracy and nonlinearity tolerance.展开更多
Kalman filtering(KF) has good potential in fast rotation of state of polarization(RSOP) tracking. Different measurement equations cause the diverse RSOP tracking performances. We compare the conventional KF(CKF) and t...Kalman filtering(KF) has good potential in fast rotation of state of polarization(RSOP) tracking. Different measurement equations cause the diverse RSOP tracking performances. We compare the conventional KF(CKF) and the modified KF(MKF), which have different measurement equations. Semi-theoretical analysis indicates the lower conditional variances of measurement residuals and process noise of MKF. Compared with CKF, the MKF has > 3 d B optical signal-to-noise ratio(OSNR) improvement at the 10 MHz scrambling rate in simulation. For MKF, more significant tracking speed improvement exists for lower OSNR. MKF can be smoothly combined with an adaptive algorithm, which outperforms adaptive CKF throughout the simulations.展开更多
Fiber nonlinearity limits the use of coherent optical orthogonal frequency division multiplexing （CO- OFDM） to upgrade wavelength-division multiplexing （WDM） systems using legacy non-return-to-zero-on- off-keying ...Fiber nonlinearity limits the use of coherent optical orthogonal frequency division multiplexing （CO- OFDM） to upgrade wavelength-division multiplexing （WDM） systems using legacy non-return-to-zero-on- off-keying （NRZ-OOK） channels. This letter proposes to compensate for the fiber nonlinearity of COOFDM with NRZ-OOK neighbors by combining digital signal processing （DSP）-based self-phase modulation （SPM） post-compensation with pilot-tone-based cross-phase modulation （XPM） compensation. The simulation results demonstrate that the optimum low-pass filter bandwidth for pilot-tone-based XPM compensation depends on the pilot-to-signal ratio value and launch optical power. Our method allows a 4-dB increase in the launch power for a 40-Gb/s single polarization CO-OFDM channel placed in the middle of six 10.7-Gb/s NRZ channels in a 50-GHz space and 1 200-km WDM system.展开更多
文摘光正交频分复用系统中的光纤非线性效应制约着系统进一步的扩容.针对此问题,提出一种数字相干叠加的方法,用于提高相干光正交频分复用系统对光纤非线性的容忍性.仿真中,5通道的波分复用下偏振复用相干光正交频分复用系统的每个通道传输四进制正交振幅调制映射的71.53 Gbit/s信号在光纤中传输400km.首先,通道间隔为25 GHz,与传统相干光正交频分复用系统相比,色散补偿前后,使用数字相干叠加的相干光正交频分复用系统的信噪比分别提升了6.02 d B和9.05 d B,最佳入纤光功率均增大了2 d B;其次,通道间隔为50 GHz,色散补偿前后,信噪比分别提升了4.9 d B和8.75 d B.通过理论推导及仿真,验证了所提方法能有效消除相干光正交频分复用系统的一阶非线性失真,进而提高系统对光纤非线性的容忍性.
基金supported by the National Natural Science Foundation of China(NSFC)(Nos.61420106011,61871408,and 61871082)
文摘We propose the modified Kalman filter(MKF) using the received signal for observation and constructing an inverse process of the conventional Kalman filter(CKF) for polarization de-multiplexing in coherent optical(CO) orthogonal frequency-division multiplexing(OFDM) transmissions. The MKF can avoid the convergence error problem in CKF without matrix inverse operation and has a faster converging speed and a much larger tolerance to the process and measurement noise covariance, about two orders of magnitude more than those of CKF. We experimentally demonstrate the 12 Gbaud OFDM signal transmission over 480 km standard singlemode fiber. The performance of MKF and CKF outperforms pilot-aided polarization de-multiplexing with better accuracy and nonlinearity tolerance.
基金This work was supported by the National Key Research and Development Program of China(No.2018YFB1801704)National Natural Science Foundation of China(NSFC)(Nos.61871082 and 61871408)+2 种基金State Key Laboratory of Advanced Optical Communication Systems and Networks,Shanghai Jiao Tong University(No.2020GZKF014)Fundamental Research Funds for the Central Universities(Nos.ZYGX2020ZB043 and ZYGX2019J008)Open Fund of IPOC(BUPT)(No.IPOC2020A011)。
文摘Kalman filtering(KF) has good potential in fast rotation of state of polarization(RSOP) tracking. Different measurement equations cause the diverse RSOP tracking performances. We compare the conventional KF(CKF) and the modified KF(MKF), which have different measurement equations. Semi-theoretical analysis indicates the lower conditional variances of measurement residuals and process noise of MKF. Compared with CKF, the MKF has > 3 d B optical signal-to-noise ratio(OSNR) improvement at the 10 MHz scrambling rate in simulation. For MKF, more significant tracking speed improvement exists for lower OSNR. MKF can be smoothly combined with an adaptive algorithm, which outperforms adaptive CKF throughout the simulations.
基金supported by the National Natural Sci-ence Foundation of China(Nos.61071097and61107060)the State Key Laboratory of Advanced Optical Com-munication Systems and Networks
文摘Fiber nonlinearity limits the use of coherent optical orthogonal frequency division multiplexing （CO- OFDM） to upgrade wavelength-division multiplexing （WDM） systems using legacy non-return-to-zero-on- off-keying （NRZ-OOK） channels. This letter proposes to compensate for the fiber nonlinearity of COOFDM with NRZ-OOK neighbors by combining digital signal processing （DSP）-based self-phase modulation （SPM） post-compensation with pilot-tone-based cross-phase modulation （XPM） compensation. The simulation results demonstrate that the optimum low-pass filter bandwidth for pilot-tone-based XPM compensation depends on the pilot-to-signal ratio value and launch optical power. Our method allows a 4-dB increase in the launch power for a 40-Gb/s single polarization CO-OFDM channel placed in the middle of six 10.7-Gb/s NRZ channels in a 50-GHz space and 1 200-km WDM system.
