A novel suppression method of the phase noise is proposed to reduce the negative impacts of phase noise in coherent optical orthogonal frequency division multiplexing(CO-OFDM)systems.The method integrates the sub-symb...A novel suppression method of the phase noise is proposed to reduce the negative impacts of phase noise in coherent optical orthogonal frequency division multiplexing(CO-OFDM)systems.The method integrates the sub-symbol second-order polynomial interpolation(SSPI)with cubature Kalman filter(CKF)to improve the precision and effectiveness of the data processing through using a three-stage processing approach of phase noise.First of all,the phase noise values in OFDM symbols are calculated by using pilot symbols.Then,second-order Newton interpolation(SNI)is used in second-order interpolation to acquire precise noise estimation.Afterwards,every OFDM symbol is partitioned into several sub-symbols,and second-order polynomial interpolation(SPI)is utilized in the time domain to enhance suppression accuracy and time resolution.Ultimately,CKF is employed to suppress the residual phase noise.The simulation results show that this method significantly suppresses the impact of the phase noise on the system,and the error floors can be decreased at the condition of 16 quadrature amplitude modulation(16QAM)and 32QAM.The proposed method can greatly improve the CO-OFDM system's ability to tolerate the wider laser linewidth.This method,compared to the linear interpolation sub-symbol common phase error compensation(LI-SCPEC)and Lagrange interpolation and extended Kalman filter(LRI-EKF)algorithms,has superior suppression effect.展开更多
In this paper, we describe successful joint experiments with Deutsche Telecom on long-haul transmission of 100G and beyond over standard single mode fiber （SSMF） and with in-line EDFA-only amplification. The transmi...In this paper, we describe successful joint experiments with Deutsche Telecom on long-haul transmission of 100G and beyond over standard single mode fiber （SSMF） and with in-line EDFA-only amplification. The transmission link consists of 8 nodes and 950 km installed SSMF in DT＇ s optical infrastructure. Laboratory SSMF was added for extended optical reach. The first field experiment involved transmission of 8 x 216.8 Gbit/s Nyquist-WDM signals over 1750 km with 21.6 dB average loss per span. Each channel, modulated by a 54.2 Gbaud PDM-CSRZ-QPSK signal, is on a 50 GHz grid, which produces a net spectral efficiency （SE） of 4 bit/s/Hz. We also describe mixed-data-rate transmission coexisting with 1T, 400G, and 100G channels. The 400G channel uses four independent subcarriers modulated by 28 Gbaud PDM-QPSK signals. This yields a net SE of 4 bit/s/Hz, and 13 optically generated subcarriers from a single optical source are used in the 1T channel with 25 Gbaud PDM-QPSK modulation. The 100G signal uses real-time coherent PDM-QPSK transponder with 15% overhead of soft-decision forward-error correction （SD-FEC）. The digital post filter and 1 -bit maximum-likelihood sequence estimation （MLSE） are introduced at the receiver DSP to suppress noise, linear crosstalk, and filtering effects. Our results show that future 400G and 1T channels that use Nyquist WDM can transmit over long-haul distances with higher SE and using the same QPSK format.展开更多
基金supported by the National Natural Science Foundation of China(Nos.U21A20447 and 61971079)。
文摘A novel suppression method of the phase noise is proposed to reduce the negative impacts of phase noise in coherent optical orthogonal frequency division multiplexing(CO-OFDM)systems.The method integrates the sub-symbol second-order polynomial interpolation(SSPI)with cubature Kalman filter(CKF)to improve the precision and effectiveness of the data processing through using a three-stage processing approach of phase noise.First of all,the phase noise values in OFDM symbols are calculated by using pilot symbols.Then,second-order Newton interpolation(SNI)is used in second-order interpolation to acquire precise noise estimation.Afterwards,every OFDM symbol is partitioned into several sub-symbols,and second-order polynomial interpolation(SPI)is utilized in the time domain to enhance suppression accuracy and time resolution.Ultimately,CKF is employed to suppress the residual phase noise.The simulation results show that this method significantly suppresses the impact of the phase noise on the system,and the error floors can be decreased at the condition of 16 quadrature amplitude modulation(16QAM)and 32QAM.The proposed method can greatly improve the CO-OFDM system's ability to tolerate the wider laser linewidth.This method,compared to the linear interpolation sub-symbol common phase error compensation(LI-SCPEC)and Lagrange interpolation and extended Kalman filter(LRI-EKF)algorithms,has superior suppression effect.
文摘In this paper, we describe successful joint experiments with Deutsche Telecom on long-haul transmission of 100G and beyond over standard single mode fiber （SSMF） and with in-line EDFA-only amplification. The transmission link consists of 8 nodes and 950 km installed SSMF in DT＇ s optical infrastructure. Laboratory SSMF was added for extended optical reach. The first field experiment involved transmission of 8 x 216.8 Gbit/s Nyquist-WDM signals over 1750 km with 21.6 dB average loss per span. Each channel, modulated by a 54.2 Gbaud PDM-CSRZ-QPSK signal, is on a 50 GHz grid, which produces a net spectral efficiency （SE） of 4 bit/s/Hz. We also describe mixed-data-rate transmission coexisting with 1T, 400G, and 100G channels. The 400G channel uses four independent subcarriers modulated by 28 Gbaud PDM-QPSK signals. This yields a net SE of 4 bit/s/Hz, and 13 optically generated subcarriers from a single optical source are used in the 1T channel with 25 Gbaud PDM-QPSK modulation. The 100G signal uses real-time coherent PDM-QPSK transponder with 15% overhead of soft-decision forward-error correction （SD-FEC）. The digital post filter and 1 -bit maximum-likelihood sequence estimation （MLSE） are introduced at the receiver DSP to suppress noise, linear crosstalk, and filtering effects. Our results show that future 400G and 1T channels that use Nyquist WDM can transmit over long-haul distances with higher SE and using the same QPSK format.
