相干光通信中的数字信号处理算法的仿真与研究
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摘要
随着光通信对更大带宽、更长传输距离和更高接收灵敏度的不断追求,数字相干光通信技术应运而生。数字相干光通信技术不仅可以提高接收灵敏度,同时能够得到全部的光场信息,从而使其拥有传统强度调制／直接检测(IM/DD)系统无法比拟的优势。数字相干光通信技术的迅速发展,得益于新型码型调制技术和数字信号处理器(DSP)的高速发展。新型码型调制技术通过灵活的信息加载方式提高了相干光通信系统的频谱利用率,而随着数字信号处理器的运算速度的提高,数字化的相干光通信系统已经成为了下一代光网络的有力竞争者之一。
论文研究相干接收机内的数字补偿算法,重点研究载波频率差估计算法和载波相位恢复算法。首先通过VPItransmisionMakerTM软件或者Matlab软件仿真受到噪声影响的信号,再利用Matlab软件实现离线的信号处理,部分算法还做了相应的实验验证。借助以上仿真平台和算法,实现了没有色散补偿光纤、无需锁相环的偏振分集接收。同时,提出采用加权的前馈相位恢复算法,其可以提高灵敏度代价0.2dB；以及基于QPSK分类和最大似然检测的前馈相位恢复算法,其复杂度为同类算法的一半以下。所提出的新型载波恢复算法可以有效提高系统性能或降低系统复杂度,为方便今后实时高速相干光通信系统的实现。最后研究分析系统性能,论文所搭建的仿真平台及数字信号处理算法可以完成误码率小于10-3的PDM-QPSK以及PDM-16QAM相干传输,其结果能够真实反应实验现象,为以后数字相干光通信的高速实时实现提供研究基础和理论指导。
In the field of optical communications, with constant pursuit for larger bandwidth, longer transmission distance and higher receiver sensitivity, coherent optical communications technology came into being. Coherent detection can not only improve the receiver sensitivity but also acquire all the light field information can be obtained, thus giving coherent optical communications unparallel advantages over traditional Intensity Modulation/Direct Detection (IM/DD) system. Thanks to high-speed development in advanced modulation format and digital signal processor (DSP), digital coherent optical communication technology is developing rapidly. Advanced modulation formats provide flexible methods of information encoding in coherent optical communication system and improve the spectrum efficiency. On the other hand, with the improved digital signal processor computation speed, digital coherent optical communication systems has become a promised candidate for next-generation optical networks.
Thesis investigated the digital compensation algorithms in coherent communication receivers with the focus on carrier frequency offset estimation and carrier phase estimation. Firstly we investigate various noise and distortion effects in the transmission via a systematic simulation using VPItransmissionMakerTM and Matlab. Then, the received signal is off-line processed and the performance is analyzed. Also, some of the algorithms have been tested experimentally. By using the simulation platform and digital compensation algorithms mentioned above, we have achieved polarization diversity detection system with no dispersion compensation fiber and phase-lock-loop. Meanwhile, we proposed a carrier phase recovery algorithm with weighting coefficients, which can improve the sensitivity penalty by 0.2dB; a feedforward carrier phase recovery algorithm based on QPSK partitioning and maximum likelihood detection, the complexity is less than half of reported algorithms in other literatures, The proposed new carrier recovery algorithm either improves system performance or reduces computation complexity, which will relief hardware burden in future high-speed real-time coherent optical communication systems. Finally, system performance is analyzed. The paper sets up a simulation platform incorporated with digital signal processing algorithms and achieved PDM-QPSK and PDM-16QAM coherent transmission system with bit error rate lower than 10-3, the results agrees with experimental outcomes and will provide back ground and theoretical guidance for future high-speed digital coherent optical communication systems.
论文研究相干接收机内的数字补偿算法,重点研究载波频率差估计算法和载波相位恢复算法。首先通过VPItransmisionMakerTM软件或者Matlab软件仿真受到噪声影响的信号,再利用Matlab软件实现离线的信号处理,部分算法还做了相应的实验验证。借助以上仿真平台和算法,实现了没有色散补偿光纤、无需锁相环的偏振分集接收。同时,提出采用加权的前馈相位恢复算法,其可以提高灵敏度代价0.2dB；以及基于QPSK分类和最大似然检测的前馈相位恢复算法,其复杂度为同类算法的一半以下。所提出的新型载波恢复算法可以有效提高系统性能或降低系统复杂度,为方便今后实时高速相干光通信系统的实现。最后研究分析系统性能,论文所搭建的仿真平台及数字信号处理算法可以完成误码率小于10-3的PDM-QPSK以及PDM-16QAM相干传输,其结果能够真实反应实验现象,为以后数字相干光通信的高速实时实现提供研究基础和理论指导。
In the field of optical communications, with constant pursuit for larger bandwidth, longer transmission distance and higher receiver sensitivity, coherent optical communications technology came into being. Coherent detection can not only improve the receiver sensitivity but also acquire all the light field information can be obtained, thus giving coherent optical communications unparallel advantages over traditional Intensity Modulation/Direct Detection (IM/DD) system. Thanks to high-speed development in advanced modulation format and digital signal processor (DSP), digital coherent optical communication technology is developing rapidly. Advanced modulation formats provide flexible methods of information encoding in coherent optical communication system and improve the spectrum efficiency. On the other hand, with the improved digital signal processor computation speed, digital coherent optical communication systems has become a promised candidate for next-generation optical networks.
Thesis investigated the digital compensation algorithms in coherent communication receivers with the focus on carrier frequency offset estimation and carrier phase estimation. Firstly we investigate various noise and distortion effects in the transmission via a systematic simulation using VPItransmissionMakerTM and Matlab. Then, the received signal is off-line processed and the performance is analyzed. Also, some of the algorithms have been tested experimentally. By using the simulation platform and digital compensation algorithms mentioned above, we have achieved polarization diversity detection system with no dispersion compensation fiber and phase-lock-loop. Meanwhile, we proposed a carrier phase recovery algorithm with weighting coefficients, which can improve the sensitivity penalty by 0.2dB; a feedforward carrier phase recovery algorithm based on QPSK partitioning and maximum likelihood detection, the complexity is less than half of reported algorithms in other literatures, The proposed new carrier recovery algorithm either improves system performance or reduces computation complexity, which will relief hardware burden in future high-speed real-time coherent optical communication systems. Finally, system performance is analyzed. The paper sets up a simulation platform incorporated with digital signal processing algorithms and achieved PDM-QPSK and PDM-16QAM coherent transmission system with bit error rate lower than 10-3, the results agrees with experimental outcomes and will provide back ground and theoretical guidance for future high-speed digital coherent optical communication systems.
引文
[1]M. G. Taylor, "Coherent detection method using DSP for demodulation of signal and subsequent equalization of propagation impairments" IEEE Photon. Technol. Lett.16,674-676 (2004).
[2]S. Tsukamoto, D.-S Ly-Gagnon, K. Katoh, and K. Kikuchi, "Coherent demodulation of 40-Gbit/s polarization-multiplexed QPSK signals with 16-GHz spacing after 200-km transmission," in Proceedings of Optical Fiber Communications Conference 2005, paper PDP-29
[3]C.R.S. Fludger, T.Duthel, T. Wuth, C. Schulien, "Uncompensated Transmission of 86Gbit/s Polarization Multiplexed RZ-QPSK over 100km of NDSF Employing Coherent Equalisation," in Proceedings of ECOC 2006, Cannes, France, paper, Th4.3.3
[4]G. Charlet, J. Renaudier, M. Salsi, H. Mardoyan, P. Tran, S. Bigo "Efficient Mitigation of Fiber Impairments in an Ultra-Long Haul Transmission of 40Gbit/s Polarization-Multiplexed Data, by Digital Processing in a Coherent Receiver," in Proceedings of Optical Fiber Communications Conference 2007, paper PDP17
[5]S.J. Savory, G. Gavioli, R.I. Killey and P. Bayvel, "Electronic compensation of chromatic dispersion using a digital coherent receiver," Opt. Express 15, 2120-2126 (2007).
[6]S.J. Savory, A.D. Stewart, S. Wood, G. Gavioli, M.G. Taylor, R.I. Killey, P. Bayvel, "Digital Equalisation of 40Gbit/s per Wavelength Transmission over 2480km of Standard Fibre without Optical Dispersion Compensation," in Proceedings of ECOC 2006, Cannes, France, paper Th2.5.5, Sep.2006.
[7]朱然,相干光通信系统中调制码型及自动偏振控制技术的研究[学位论文].北京：北京邮电大学图书馆,2009
[8]杜晓,相干光通信系统中相位同步及校正技术研究[学位论文],北京：北京邮电大学图书馆,2010
[9]于洋,相干光通信及其应用,物理通报,2001(9)
[10]E. Ip and J.M Kahn, "Digital Equalization of Chromatic Dispersion and Polarization Mode Dispersion" J. Lightwave Technol.25,2033-2043 (2007)
[11]C. Laperle, B. Villeneuve, Z. Zhang, D. McGhan, H. Sun, M. O'Sullivan, "Wavelength Division Multiplexing (WDM) and Polarization Mode Dispersion (PMD) Performance of a Coherent 40Gbit/s Dual-Polarization Quadrature Phase Shift Keying (DP-QPSK) Transceiver," in Proceedings of Optical Fiber Communications Conference 2007, paper PDP16
[12]C. R. S. Fludger, T. Duthel, D. van den Borne, C. Schulien, E-D. Schmidt, T. Wuth, E. de Man, G. D. Khoe, H. de Waardt, "10 x 111 Gbit/s,50 GHz Spaced, POLMUX-RZ-DQPSK Transmission over 2375 km Employing Coherent Equalisation," in Proceedings of Optical Fiber Communications Conference 2007, paper PDP22
[13]D. van den Borne, H. de Waardt, G.-D. Khoe, T. Duthel, C. R.S. Fludger, C. Schulien, E.-D. Schmidt, "Electrical PMD Compensation in 43-Gb/s POLMUX-NRZ-DQPSK enabled by Coherent Detection and Equalization," in (?)oceedings ECOC 2007, Berlin, Germany, invited paper 8.3.1
[14]Yinwen Cao, Song Yu, Ying Chen, Yuliang Gao, Wanyi Gu, Yuefeng Ji,"Modified Frequency and Phase Estimation for M-QAM Optical Coherent Detection, "in Proceedings of ECOC 2010, Torino, Italy, paper, We.7.A.1.
[15]A. Leven et al., "Frequency Estimation in Intradyne Reception," IEEE Photon. Technol. Lett., Vol.19, No.6, pp366-368, March,2007.
[16]A. J. Viterbi et al., "Nonlinear estimation of PSK-modulated carrier phase with (?)lication to burst digital transmission," IEEE Transactions on Information (?)ory, Vol. IT-29, No.4, pp543-551, July 1983.
[17]D. S. Ly-Gagnon, S. Tsukarnoto, K. Katoh, and K. Kikuchi, "Coherent detection of optical quadrature phase-shift keying signals with carrier phase estimation," J. Lightwave Technol.24,12-21 (2006).
[18]L. Li, Z. Tao, T. Hoshida and J. C. Rasmussen, Carrier synchronization in 43Gbit/s coherent QPSK receiver, OECC 2007, paper 12B1-3.
[19]L. Li, Z. Tao, S. Oda, T. Hoshida, and J. C. Rasmussen, "Wide-range, accurate and simple digital frequency offset compensator for optical coherent receivers," in Proc. Optical Fiber Communication Conf. and Exposition and The National Fiber Optic Engineers Conf., vol.2,2008 OSA Tech. Dig. Series (Optical Society of America,2008), Paper OWT4.
[20]Z. Tao, L. Li, A. Isomura, T. Hoshida, and J. C. Rasmussen, "Multiplier-free phase recovery for optical coherent receivers," in Proc. Optical Fiber Communication Conf. and Exposition and The National Fiber Optic Engineers Conf., vol.2,2008 OSA Technical Digest Series (Optical Society of America, 2008), Paper OWT2.
[21]S. Hoffmann, S. Bhandare, T. Pfau, O. Adamczyk, C. Wordehoff, R. Peveling, M. Porrmann, and R. Noe, "Frequency and phase estimation for coherent QPSK transmission with unlocked DFB lasers," IEEE Photon. Technol. Lett., vol.20, no. 18, pp.1569-1571, Sep.15,2008.
[22]T. Pfau et al., "Hardware-Efficient Coherent Digital Receiver Concept with Feedforward Carrier Recovery for M-QAM Constellations," IEEE J. Lightwave Technol., VOL.27, NO.8, APRIL 15,2009
[23]Matthias Seimetz, Laser Linewidth Limitations for Optical Systems with High-Order Modulation Employing Feed Forward Digital Carrier Phase Estimation, OFC 2008, San Diego, California, Feb.2008, paper OTuM2.
[24]X. Zhou, "An Improved Feed-Forward Carrier Recovery Algorithm for Coherent Receivers with M-QAM Modulation Format", IEEE Photonics Technology Letters, vol.22, no.14, pp.1051-1053,2010.
[25]I. Fatadin, D. Ives and S. J. Savory, "Laser Linewidth Tolerance for 16-QAM Coherent Optical Systems using QPSK Partitioning ", IEEE Photonics Technology Letters, vol.22, no.9, pp.631-633,2010.
[2]S. Tsukamoto, D.-S Ly-Gagnon, K. Katoh, and K. Kikuchi, "Coherent demodulation of 40-Gbit/s polarization-multiplexed QPSK signals with 16-GHz spacing after 200-km transmission," in Proceedings of Optical Fiber Communications Conference 2005, paper PDP-29
[3]C.R.S. Fludger, T.Duthel, T. Wuth, C. Schulien, "Uncompensated Transmission of 86Gbit/s Polarization Multiplexed RZ-QPSK over 100km of NDSF Employing Coherent Equalisation," in Proceedings of ECOC 2006, Cannes, France, paper, Th4.3.3
[4]G. Charlet, J. Renaudier, M. Salsi, H. Mardoyan, P. Tran, S. Bigo "Efficient Mitigation of Fiber Impairments in an Ultra-Long Haul Transmission of 40Gbit/s Polarization-Multiplexed Data, by Digital Processing in a Coherent Receiver," in Proceedings of Optical Fiber Communications Conference 2007, paper PDP17
[5]S.J. Savory, G. Gavioli, R.I. Killey and P. Bayvel, "Electronic compensation of chromatic dispersion using a digital coherent receiver," Opt. Express 15, 2120-2126 (2007).
[6]S.J. Savory, A.D. Stewart, S. Wood, G. Gavioli, M.G. Taylor, R.I. Killey, P. Bayvel, "Digital Equalisation of 40Gbit/s per Wavelength Transmission over 2480km of Standard Fibre without Optical Dispersion Compensation," in Proceedings of ECOC 2006, Cannes, France, paper Th2.5.5, Sep.2006.
[7]朱然,相干光通信系统中调制码型及自动偏振控制技术的研究[学位论文].北京：北京邮电大学图书馆,2009
[8]杜晓,相干光通信系统中相位同步及校正技术研究[学位论文],北京：北京邮电大学图书馆,2010
[9]于洋,相干光通信及其应用,物理通报,2001(9)
[10]E. Ip and J.M Kahn, "Digital Equalization of Chromatic Dispersion and Polarization Mode Dispersion" J. Lightwave Technol.25,2033-2043 (2007)
[11]C. Laperle, B. Villeneuve, Z. Zhang, D. McGhan, H. Sun, M. O'Sullivan, "Wavelength Division Multiplexing (WDM) and Polarization Mode Dispersion (PMD) Performance of a Coherent 40Gbit/s Dual-Polarization Quadrature Phase Shift Keying (DP-QPSK) Transceiver," in Proceedings of Optical Fiber Communications Conference 2007, paper PDP16
[12]C. R. S. Fludger, T. Duthel, D. van den Borne, C. Schulien, E-D. Schmidt, T. Wuth, E. de Man, G. D. Khoe, H. de Waardt, "10 x 111 Gbit/s,50 GHz Spaced, POLMUX-RZ-DQPSK Transmission over 2375 km Employing Coherent Equalisation," in Proceedings of Optical Fiber Communications Conference 2007, paper PDP22
[13]D. van den Borne, H. de Waardt, G.-D. Khoe, T. Duthel, C. R.S. Fludger, C. Schulien, E.-D. Schmidt, "Electrical PMD Compensation in 43-Gb/s POLMUX-NRZ-DQPSK enabled by Coherent Detection and Equalization," in (?)oceedings ECOC 2007, Berlin, Germany, invited paper 8.3.1
[14]Yinwen Cao, Song Yu, Ying Chen, Yuliang Gao, Wanyi Gu, Yuefeng Ji,"Modified Frequency and Phase Estimation for M-QAM Optical Coherent Detection, "in Proceedings of ECOC 2010, Torino, Italy, paper, We.7.A.1.
[15]A. Leven et al., "Frequency Estimation in Intradyne Reception," IEEE Photon. Technol. Lett., Vol.19, No.6, pp366-368, March,2007.
[16]A. J. Viterbi et al., "Nonlinear estimation of PSK-modulated carrier phase with (?)lication to burst digital transmission," IEEE Transactions on Information (?)ory, Vol. IT-29, No.4, pp543-551, July 1983.
[17]D. S. Ly-Gagnon, S. Tsukarnoto, K. Katoh, and K. Kikuchi, "Coherent detection of optical quadrature phase-shift keying signals with carrier phase estimation," J. Lightwave Technol.24,12-21 (2006).
[18]L. Li, Z. Tao, T. Hoshida and J. C. Rasmussen, Carrier synchronization in 43Gbit/s coherent QPSK receiver, OECC 2007, paper 12B1-3.
[19]L. Li, Z. Tao, S. Oda, T. Hoshida, and J. C. Rasmussen, "Wide-range, accurate and simple digital frequency offset compensator for optical coherent receivers," in Proc. Optical Fiber Communication Conf. and Exposition and The National Fiber Optic Engineers Conf., vol.2,2008 OSA Tech. Dig. Series (Optical Society of America,2008), Paper OWT4.
[20]Z. Tao, L. Li, A. Isomura, T. Hoshida, and J. C. Rasmussen, "Multiplier-free phase recovery for optical coherent receivers," in Proc. Optical Fiber Communication Conf. and Exposition and The National Fiber Optic Engineers Conf., vol.2,2008 OSA Technical Digest Series (Optical Society of America, 2008), Paper OWT2.
[21]S. Hoffmann, S. Bhandare, T. Pfau, O. Adamczyk, C. Wordehoff, R. Peveling, M. Porrmann, and R. Noe, "Frequency and phase estimation for coherent QPSK transmission with unlocked DFB lasers," IEEE Photon. Technol. Lett., vol.20, no. 18, pp.1569-1571, Sep.15,2008.
[22]T. Pfau et al., "Hardware-Efficient Coherent Digital Receiver Concept with Feedforward Carrier Recovery for M-QAM Constellations," IEEE J. Lightwave Technol., VOL.27, NO.8, APRIL 15,2009
[23]Matthias Seimetz, Laser Linewidth Limitations for Optical Systems with High-Order Modulation Employing Feed Forward Digital Carrier Phase Estimation, OFC 2008, San Diego, California, Feb.2008, paper OTuM2.
[24]X. Zhou, "An Improved Feed-Forward Carrier Recovery Algorithm for Coherent Receivers with M-QAM Modulation Format", IEEE Photonics Technology Letters, vol.22, no.14, pp.1051-1053,2010.
[25]I. Fatadin, D. Ives and S. J. Savory, "Laser Linewidth Tolerance for 16-QAM Coherent Optical Systems using QPSK Partitioning ", IEEE Photonics Technology Letters, vol.22, no.9, pp.631-633,2010.