Carrier recovery for high speed coherent optical communication systems based on digital signal processing

CARRIER PHASE RECOVERY FOR HIGH SPEED COHERENT OPTICAL COMMUNICATION SYSTEMS BASED ON DIGITAL SIGNAL PROCESSING XU ZHUORAN (B.Eng.), National University of Singapore, Singapore A THESIS SUBMITTED FOR THE DEGREE OF DOCTOR OF PHILOSOPHY DEPARTMENT OF ELECTRICAL AND COMPUTER ENGINEERING NATIONAL UNIVERSITY OF SINGAPORE 2014 ii DECLARATION I hereby declare that this thesis is my original work and it has been written by me in its entirety. I have duly acknowledged all the sources of information which have been used in the thesis. This thesis has also not been submitted for any degree in any university previously. XU ZHUORAN January 28, 2015 iii iv Acknowledgement First of all, I would like to express my deepest gratitude and most sincere appreciation to my supervisors Dr. Changyuan Yu and Prof. Pooi-Yuen Kam for their valuable guidance and kind support throughout my Ph.D study. They enlightened me by sharing their knowledge and experience in research. This thesis would not been possible without their help and encouragement. I very appreciate for my thesis committee’s effort and time to review my thesis. Besides, I wish to thank my seniors Dr. Zhang Shaoliang, Dr. Zhang Banghong and Dr. Shao Xuguang with whom I gain a lot of knowledge in research. My thanks also go to my colleagues in NUS for providing friendly environment and exchanging insightful ideas. Last but not least, I would like to thank my parents and relatives who are always there to support me. I am indebted for their love. v ACKNOWLEDGEMENT vi Contents Acknowledgement v Summary xi List of Tables xv List of Figures xxi List of Abbreviations xxv Introduction 1.1 Review of Coherent Optical Communication . . . . . . . . . . . 1.2 Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.3 Contribution of the Thesis . . . . . . . . . . . . . . . . . . . . 1.4 Outline of the Thesis . . . . . . . . . . . . . . . . . . . . . . . 11 Background 2.1 15 Advanced Modulation Formats . . . . . . . . . . . . . . . . . . 16 2.1.1 Signal Model . . . . . . . . . . . . . . . . . . . . . . . 16 2.1.2 Generation Methods . . . . . . . . . . . . . . . . . . . 17 vii CONTENTS 2.2 2.3 2.4 2.2.1 Linear Channel Impairments . . . . . . . . . . . . . . . 21 2.2.2 Fiber Nonlinearity . . . . . . . . . . . . . . . . . . . . 24 Coherent Receiver . . . . . . . . . . . . . . . . . . . . . . . . . 27 2.3.1 Coherent Detection . . . . . . . . . . . . . . . . . . . . 27 2.3.2 Signal-to-Noise Ratio 2.3.3 Laser Phase Noise . . . . . . . . . . . . . . . . . . . . 32 2.3.4 DSP Algorithms in Coherent Receivers . . . . . . . . . 34 . . . . . . . . . . . . . . . . . . 30 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 Trellis-Based Maximum Likelihood Sequence Detection 3.1 3.2 Transmission Links . . . . . . . . . . . . . . . . . . . . . . . . 21 41 The Principle of Maximum Likelihood Sequence Detection . . . 42 3.1.1 Signal Model . . . . . . . . . . . . . . . . . . . . . . . 43 3.1.2 Conditional PDF of Carrier Phase . . . . . . . . . . . . 45 3.1.3 Decision Metric of Viterbi Algorithm . . . . . . . . . . 47 The Performance of MLSD in M PSK and M -QAM . . . . . . . 51 3.2.1 Performance of MLSD in Linear Phase Noise Channel . 51 3.2.2 Performance of MLSD in Long Haul Transmission System 64 3.3 Analysis of Phase Estimation Error . . . . . . . . . . . . . . . . 70 3.4 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75 Adaptive MLSD Algorithm 77 4.1 The Principle of Adaptive MLSD . . . . . . . . . . . . . . . . . 78 4.2 Simulation Performance of Adaptive MLSD . . . . . . . . . . . 83 4.2.1 Performance of Adaptive MLSD in Linear Phase Noise Channel . . . . . . . . . . . . . . . . . . . . . . . . . . 83 viii CONTENTS 4.2.2 4.3 4.4 Performance of Adaptive MLSD in Long Haul System . 88 Experiment . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92 4.3.1 Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . 92 4.3.2 Experimental results . . . . . . . . . . . . . . . . . . . 95 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100 Pilot Assissted MLSD Algorithm 103 5.1 The Principle of PA MLSD . . . . . . . . . . . . . . . . . . . . 104 5.2 Simulation Study of PA MLSD . . . . . . . . . . . . . . . . . . 107 5.3 Experiment . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112 5.4 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116 Conclusion and Future Work 119 6.1 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119 6.2 Future work . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121 6.2.1 Joint Estimation . . . . . . . . . . . . . . . . . . . . . 121 6.2.2 Sequence Detection in OFDM . . . . . . . . . . . . . . 122 6.2.3 Multi-channel System . . . . . . . . . . . . . . . . . . 122 References 139 Publication List 141 ix CONTENTS x REFERENCES [20] D.-S, Ly-Gaynon, S.Tsukamoto, K.Katoh, and K.Kikuchi, “Coherent detection of optical quadrature phase-shift keying signals with carrier phase estimation,” J. Lightw. Technol., vol. 24, no. 1, pp. 12–21, 2006. [21] M. G. Taylor, “Coherent detection method using DSP for demodulation of signal and subsequent equalization of propagation impairments,” Photonics Technology Letters, vol. 16, no. 2, pp. 674–676, 2004. [22] P. J. Winzer, “Beyond 100G Ethernet,” IEEE Commun. Mag., vol. 48, no. 7, pp. 26–30, 2010. [23] X. Liu, S. Chandrasekhar, and P. J. Winzer, “Digital Signal Processing Techniques Enabling Multi-Tb/s Superchannel Transmission,” IEEE Signal Processing Magazine, vol. 14. [24] S. Chandrasekhar, X. Liu, B. Zhu, and D. W. Peckham, “Transmission of a 1.2-Tb/s 24-carrier no-guard-interval coherent OFDM superchannel over 7200-km of ultra-large-area fiber,” in Prodeedings of European Conf. Optical Communication (ECOC), 2009. [25] Y.-K. Huang, E. Ip, Z. Wang, M.-F. Huang, Y. Shao, and T. Wang, “Transmission of spectral efficient super-channels using all-optical OFDM and digital coherent receiver technologies,” J. Lightwave Technol., vol. 29, no. 24, pp. 3838–3844, 2011. [26] Y. Ma, Q. Yang, Y. Tang, S. Chen, and W. Shieh, “1-Tb/s single-channel coherent optical OFDM transmission over 600-km SSMF fiber with subwavelength bandwidth access,” Opt.Express, vol. 17, no. 11, pp. 9421– 9427, 2009. 128 REFERENCES [27] G. Bosco, V. Curri, A. Carena, P. Poggiolini, and F. Forghieri, “On the performance of Nyquist-WDM terabit superchannels based on PMBPSK, PM-QPSK, PM-8QAM or PM-16QAM subcarriers,” J. Lightwave Technol., vol. 29, no. 1, pp. 53–61, 2011. [28] A. http://http://www3.alcatel-lucent.com/400g pse/, “[online].” [29] X. Liu, S. Chandrasekhar, P. J. Winzer, T. Lotz, J. Carlson, J. Yang, G. Cheren, and S. Zederbaum, “1.5-Tb/s guard-banded superchannel transmission over 56x 100-km (5600-km) ULAF using 30-Gbaud pilotfree OFDM-16QAM signals with 5.75-b/s/Hz net spectral efficiency,” in Prodeedings of European Conf. Optical Communication (ECOC), 2012. [30] B. Zhu, T. Taunay, M. Fishteyn, X. Liu, S. Chandrasekhar, M. F. Yan, J. M. Fini, E. M. Monberg, and F. V. Dimarcello, “112-Tb/s space-division multiplexed DWDM transmission with 14-b/s/Hz aggregate spectral efficiency over a 76.8-km seven-core fiber,” Opt. Express, vol. 19, no. 17, pp. 16 665–16 671, 2011. [31] B. Puttnam, W. Klaus, Y. Awaji, N. Wada, A. Kanno, T. Kawanishi, K. Imamura, H. Inaba, K. Mukasa, R. Sugizaki, T. Kobayashi, and M. Watanabe, “19-core fiber transmission of 19×00×72-Gb/s SDMWDM-PDM-QPSK signals at 305Tb/s,” in Proceedings of Optical Fiber Communication Conference and Exposition and the National Fiber Optic Engineers Conference (OFC/NFOEC), 2012. [32] I. B. Djordjevic, H. G. Batshon, L. Xu, and T. Wang, “Coded polarizationmultiplexed iterative polar modulation (PM-IPM) for beyond 400 129 REFERENCES Gb/s serial optical transmission,” in Proceedings of Optical Fiber Communication Conference and Exposition and the National Fiber Optic Engineers Conference (OFC/NFOEC), 2010. [33] E. Agrell and M. Karlsson, “Power-Efficient Modulation Formats in Coherent Transmission Systems,” J. Lightw. Technol., vol. 27, no. 22, pp. 5115–5126, 2009. [34] H. Zhang, H. G. Batshon, D. Foursa, M. Mazurczyk, J. Cai, C. Davidson, A. Pilipetskii, G. Mohs, and N. Bergano, “30.58 Tb/s transmission over 7,230 km using PDM half 4D-16QAM coded modulation with 6.1 b/s/Hz spectral efficiency,” in Proceedings of Optical Fiber Communication Conference and Exposition and the National Fiber Optic Engineers Conference (OFC/NFOEC), 2013. [35] A. J. Viterbi and A. N. Viterbi, “Nonlinear estimation of PSK-modulated carrier phase with application to burst digital transmission,” IEEE Trans. Inf. Theory, vol. IT-29, no. 4, pp. 543–551, 1983. [36] Y. Cao, S. Yu, Y. Chen, Y. Gao, W. Gu, and Y. Ji, “Modified frequency and phase estimation for M-QAM optical coherent detection,” in Prodeedings of European Conf. Optical Communication (ECOC), 2010. [37] I. Fatadin, D. Ives, and S. J. Savory, “Laser linewidth tolerance for 16-QAM coherent optical systems using QPSK partitioning,” Photonics Technology Letters, vol. 22, no. 9, pp. 631–633, 2010. 130 REFERENCES [38] M. Seimetz, “Laser linewidth limitations for optical systems with highorder modulation employing feed-forward digital carrier phase estimation,” in Proc. OFC/NFOEC, 2008. [39] S. Zhang, P. Y. Kam, C. Yu, and J. Chen, “Laser linewidth tolerance of decisionaided maximum likelihood phase estimation in coherent opticalMary PSK and QAM systems,” Photonics Technology Letters, vol. 21, no. 15, pp. 1075–1077, 2009. [40] H. Louchet, K. Kuzmin, and A.Richter, “Improved DSP algorithms for coherent 16-QAM transmission,” in Prodeedings of European Conf. Optical Communication (ECOC), 2008. [41] T. Pfau, S. Hoffmann, and R. No´ e, “Hardware-efficient coherent digital receiver concept with feed-forward carrier recovery for M-QAM constellations,” J. Lightw. Technol., vol. 27, no. 8, pp. 989–999, 2009. [42] S. Zhang, X. Li, P. Y. Kam, C. Yu, and J. Chen, “Pilot-assisted decisionaided maximum-likelihood phase estimation in coherent optical phasemodulated systems with nonlienar phase noise,” Photonics Technology Letters, vol. 22, no. 6, pp. 380–382, 2010. [43] S. Zhang, P. Y. Kam, J. Chen, and C. Yu, “Decisionaided maximum likelihood detection in coherent optical phase-shift-keying system,,” Opt. Express, vol. 17, no. 2, pp. 703–715, 2009. [44] L. M. Pessoa, H. M. Salgado, and I. Darwazeh, “Joint mitigation of optical impairments and phase estimation in coherent optical systems,” in Prodeedings of IEEE LEOS Summer Topical Meetings, 2008. 131 REFERENCES [45] S. Zhang, P. Y. Kam, C. Yu, and J. Chen, “Decision-aided carrier phase estimation for coherent optical communications,” J. Lightw. Technol., vol. 28, no. 11, pp. 1597–1607, 2010. [46] X. Zhou, “An improved feed-forward carrier recovery algorithm for coherent receiver with M-QAM modulation format,” Photonics Technology Letters, vol. 22, no. 14, pp. 1051–1053, 2010. [47] X. Zhou, L. E. Nelson, P. Magill, R. Isaac, B. Zhu, D. W. Peckham, P. Borel, and K. Carlson, “High spectral efficiency 400 Gb/s transmission using PDM time-domain hybrid 32-64QAM and training-asssisted carrier recovery,” J. Lightw. Technol., vol. 31, no. 7, pp. 999–1005, 2013. [48] J.G.Proakis, Digital Communications. McGraw-Hill. [49] P. Y. Kam, “Maximum-likelihood digital data sequence estimation over the Gaussian channel with unknown carrier phase,” IEEE Transactions on Communications, vol. 35, no. 7, pp. 764–767, 1987. [50] Y. Li, P. Y. Kam, and C. C. Chui, “Adaptive sequence detection for MPSK/MQAM with unknown carrier phase characteristics,” in Proceedings of WCNC, 2009. [51] A. Barbieri, G. Colavolpe, T. Foggi, E. Forestieri, and G. Prati, “OFDM versus Single-Carrier Transmission for 100 Gbps Optical Communication,” J. Lightw. Technol., vol. 28, no. 17, pp. 2537–2551, 2010. [52] I. P. Kaminow, T. Li, and E. A. E. Willner, Optical Fiber Telecommunications. Academic Press, vol. B. 132 REFERENCES [53] S.Walklin and J.Conradi, “Multilevel signaling for increasing the reach of 10Gb/s lightwave systems,” J. Lightw. Technol., vol. 17, no. 11, pp. 2235–2248, 1999. [54] K.-P.Ho, Phase-Modulated Optical Communication Systems. Springer. [55] F.Koyama and K.Oga, “Frequency chirping in extermal modulators,” J. Lightw. Technol., vol. 6, no. 1, pp. 79–91, 2007. [56] C. Weber, J. K. Fischer, C.-A. Bunge, and K. Petermann, “Electronic precompensation of intrachannel nonlinearities at 40 Gb/s,” Photonics Technology Letters, vol. 18, no. 16. [57] Y.Mori, C. Zhang, K. Igarashi, K. Katoh, and K. Kikuchi, “Unrepeated 200-km transmission of 40-Gbit/s 16-QAMsignals using digital coherent receiver,” Opt.Express, vol. 17, no. 3, pp. 1435–1441, 2009. [58] P. Winzer, A. Gnauck, C. Doerr, M. Magarini, and L. Buhl, “Spectrally efficient long-haul optical networking using 112-Gb/s polarization multiplexed 16-QAM,” J. Lightw. Technol., vol. 28, no. 4, pp. 547–556, 2010. [59] P. J. Winzer, D. Stahl, and H. Kim, “Impact of pulse carver chirp on RZDPSK receiver performance,” in Proc. ECOC, 2003. [60] M. I. Hayee and A. E. Willner, “NRZ versus RZ in 10 - 40Gb/s dispersionmanaged WDM transmission systems,” Photonics Technology Letters, vol. 11, no. 8, pp. 991–993, 1999. 133 REFERENCES [61] P. J. Winzer and R.-J. Essiambre, “Advanced modulation formats for highcapacity optical transport networks,” J. Lightw. Technol., vol. 24, no. 12, pp. 4711–4728, 2006. [62] G.P.Agrawal, Nonlinear Fiber Optics. Academic Press. [63] T. Miya, Y. Terunuma, T. Hosaka, and T. Miyashita, “Ultimate low-loss singlemode fibre at 1.55 m,” Electron. Lett, vol. 15, no. 4, pp. 106–108, 1979. [64] A. Bjarklev, Optical Fiber Amplifiers: Design and System Applications. Artech House. [65] L. Gr¨uner-Nielsen, M. Wandel, P. Kristensen, C. Jørgensen, L. V. Jørgensen, B. Edvold, B. P´alsd´ttir, and D. Jakobsen, “Dispersioncompensating fibers,” J. Lightw. Technol., vol. 23, no. 11, pp. 3566–3579, 2005. [66] E. Ip and J. M. Kahn, “Digital equalization of chromatic dispersion and polarization mode dispersion,” J. Lightw. Technol., vol. 25, no. 8, pp. 2033–2043, 2007. [67] C.Yu, Polarization mode dispersion (PMD) monitoring. Academic Press. [68] C. D. Poole, “Statistical treatment of polarization dispersion in singlemode fiber,” Opt. Lett., vol. 13, no. 8, pp. 687–689, 1988. [69] E. Ip, A. P. T. Lau, D. J. F. Barros, and J. M. Kahn, “Coherent detection in optical fiber systems,” Opt. Express, vol. 16, no. 2, pp. 753–791, 2008. 134 REFERENCES [70] S. J. Savory, “Digital filters for coherent optical receivers,” Opt. Express, vol. 16, no. 2, pp. 804–817, 2008. [71] J. P. Gordon and L. F. Mollenauer, “Phase noise in photonic communications systems using linear amplifiers,” Opt.Lett., vol. 15, no. 5, pp. 1351–1353, 1990. [72] K.-P. Ho and J. M. Kahn, “Electronic compensation technique to mitigate nonlinear phase noise,” J. Lightw. Technol., vol. 22, no. 3, pp. 779–783, 2004. [73] E. Ip and J. M. Kahn, “Compensation of dispersion and nonlinear impairments using digital backpropagation,” J. Lightwave Technol, vol. 26, no. 20, pp. 3416–3425, 2008. [74] M. Seimetz and C.-M. Weinert, “Options, feasibility, and availability of × 90◦ hybrids for coherent optical systems,” J. Lightw. Technol., vol. 24, no. 3, pp. 1317–1322, 2006. [75] R.-J. Essiambre, G. Kramer, P. J. Winzer, G. J. Foschini, and B. Goebel, “Capacity limits of optical fiber networks,,” J. Lightw. Technol., vol. 28, no. 4, pp. 662–701, 2010. [76] G. Nicholson, “Probability of error for optical heterodyne DPSK system with quantum phase noise,” Electron. Lett., vol. 20, no. 24, pp. 1005– 1007, 1984. [77] F. M. Gardner, “A BPSK/QPSK timing-error detector for sampled receivers,” IEEE Trans. Commun., vol. COM-34, no. 5, pp. 423–429, 1986. 135 REFERENCES [78] I. Fatadin, S. J. Savory, and D. Ives, “Compensation of quadrature imbalance in an optical QPSK coherent receiver,” Photonics Technology Letters, vol. 20, no. 20, pp. 1733–1735, 2008. [79] S. Tsukamoto, K. Katoh, and K. Kikuchi, “Unrepeated transmission of 20-Gb/s optical quadrature phase-shift-keying signal over 200-km standard singlemode fiber based on digital processing of homodyne-detected signal for groupvelocity dispersion compensation,” Photonics Technology Letters, vol. 18, no. 9, pp. 1016–1018, 2006. [80] Y. Han and G. Li, “Coherent optical communication using polarizationmultipleinput-multiple-output,” Opt. Express, vol. 13, no. 19, pp. 7527–7534, 2005. [81] D. I. I. Fatadin and S. J. Savory, “Blind equalizatoin and carrier phase recovery in a 16-QAM optical coherent system,” J. Lightw. Technol., vol. 27, no. 15, pp. 3042–3049, 2009. [82] Y.Wang, E. Serpedin, and P. Ciblat, “Non-data aided feedforward estimation of psk-modulated carrier frequency offset,” in Proc. ICC, 2002. [83] M. R. F. Rice and B. Cowley, “A new algorithm for 16QAM carrier phase estimation using QPSK partitioning,” Digital Signal Processing, vol. 12, no. 1, pp. 77–86, 2002. [84] Y.Mori, C. Zhang, K. Igarashi, K. Katoh, and K. Kikuchi, “Unrepeated 200-km transmission of 40-Gbit/s 16-QAM signals using digital coherent receiver,” Opt. Express, vol. 17, no. 3, pp. 1435–1441, 2007. 136 REFERENCES [85] G. Ferrari, G. Colavolpe, and R. Raheli, “A unified framework for finite memory detection,” IEEE J. Sel. Areas Commen., vol. 23, pp. 1697–1706, 2005. [86] P. Y. Kam, “Maximum likelihood carrier phase recovery for linear suppressed-carrier digital data modulations,” IEEE Trans. Commun., vol. COM-34, pp. 522–527, 1986. [87] H. L. V. Trees, Detection, Estimation, and Modulation Theory: Part II. Wiley. [88] H. L. Van. Trees, Detection, Estimation, and Modulation Theory: Part I. Wiley. [89] W. J. Weber, “Differential encoding for multiple amplitude and phase shift keying systems,,” IEEE Trans. Commun., vol. 26, no. 3, pp. 385– 391, 1978. [90] Z. Xu, P. Y. Kam, and C. Yu, “Adaptive Maximum Likelihood Sequence Detection for QPSK Coherent Optical Communication System,” Photonics Technology Letters, vol. 26, no. 6, pp. 583–586, 2014. [91] P. Y. Kam, K. H. Chua, and X. Yu, “Adaptive symbol-by-symbol reception of MPSK on the Gaussian channel with unknown carrier phase characteristics,” IEEE Transactions on Communications, vol. 46. [92] K. Kikuchi, “Electronic Post-compensation for Nonlinear Phase Fluctuations in a 1000-km 20-Gbit/s Optical Quadrature Phase-shift Keying 137 REFERENCES Transmission System Using the Digital Coherent Receiver,” Opt. Express, vol. 16, no. 2, pp. 889–896, 2008. [93] Y. Gao, A. P. T. Lau, C. Lu, Y. Dai, and X. Xu, “Blind cycle-slip detection and correction for coherent communication systems,” in Prodeedings of European Conf. Opt. Commun (ECOC), 2013. [94] D. V. Souto, B.-E. Olsson, C. Larsson, and D. A. A. Mello, “JointPolarization and Joint-Subchannel Carrier Phase Estimation for 16-QAM Optical Systems,” J. Lightw. Technol., vol. 30, no. 20, pp. 3185–3191, 2012. [95] T.-H. Cheng and D. Huang, “Adaptive joint-polarization carrier phase recovery for optical coherent communication,” in Prodeeding of 2013 8th International ICST Conference, 2013. [96] Y. Gao, A. P. T. Lau, S. Yan, , and C. Lu, “Low-complexity and phase noise tolerant carrier phase estimation for dual-polarization 16-QAM systems,” Opt. Express, vol. 19, no. 22, pp. 21 717–21 729, 2011. [97] T. F. Portela, B.-E. Olsson, C. Larsson, and D. Mello, “Experimental demonstration of joint-polarization phase recovery algorithms for dual-polarization 16QAM transmission,” in Proceedings of Optical Fiber Communication Conference and Exposition and the National Fiber Optic Engineers Conference (OFC/NFOEC), 2012. [98] J. H. Ke, K. P. Zhong, Y. Gao, A. Bakhshali, and J. C. Cartledge, “LowComplexity Joint Frequency Offset and Carrier Phase Estimation Based 138 REFERENCES on QPSK Partitioning for DP 16-QAM,” in Proceedings of Optical Fiber Communication Conference and Exposition and the National Fiber Optic Engineers Conference (OFC/NFOEC), 2013. [99] A. Meiyappan, P.-Y. Kam, and H. Kim, “On Decision Aided Carrier Phase and Frequency Offset Estimation in Coherent Optical Receivers,” J. Lightw. Technol., vol. 31, no. 13, pp. 2055–2069, 2013. [100] S. Cao, P. Y. Kam, and C. Yu, “Decision-aided phase estimation in single carrier and OFDM coherent optical communication systems,” Photonics Technology Letters, vol. 24, no. 22, pp. 2067–2069, 2012. [101] X. Zhou, L. Nelson, P. Magill, R. Isaac, B. Zhu, D. Peckham, P. Borel, and K. Carlson, “8 × 450-Gb/s, 50-GHz-spaced, PDM-32QAM transmission over 400km and one 50GHz-grid ROADM,” in Proceedings of Optical Fiber Communication Conference and Exposition and the National Fiber Optic Engineers Conference (OFC/NFOEC), 2012. [102] M. F. Huang, A. Tanaka, E. Ip, Y. K. Huang, D. Qian, Y. Zhang, S. Zhang, P. N. Ji, T. W. I. Djordjevic, Y. Aono, S. Murakami, T. Tajima, T. J. Xia, and G. Wellbrock, “Terabit/s Nyquist superchannels in high capacity fiber field trials using DP-16QAM and DP-8QAM modulation for regional and long-haul applications,” J. Lightw. Technol., vol. 32, no. 4, pp. 776–782, 2014. 139 PUBLICATION LIST 140 Publication List Journal Papers 1. Z. Xu, P. Y. Kam, and C. Yu, Adaptive Maximum Likelihood Sequence Detection for QPSK Coherent Optical Communication System, IEEE Photon. Technol. Lett., vol. 26, no. 6, pp. 583-586, 2014. 2. Z. Xu, C. Yu, and P. Y. Kam, Trellis-Based Maximum Likelihood Sequence Detection in Coherent Optical Communication Systems, J. Lightw. Technol.,submitted. Conference Papers 1. Z. Xu, H. Zheng, C. Yu, and P.Y. Kam, Performance of pilot-assisted maximum-likelihood sequence detection in a rotated-8QAM coherent optical system, OptoElectronics and Communications Conference (OECC) 2014, Paper TH10E-1, pp. 1-3, Melbourne, Australia, July 6-10, 2014. 2. Z. Xu, P. Y. Kam and C. Yu, Performance of Pilot-Assisted Maximum Likelihood Sequence Detection for QAM Signals, Proc. Signal Process- 141 PUBLICATION LIST ing in Photonic Communications (SPPCom), Paper SW1C.2, pp. 1-3, San Diego, CA, USA, July 13-17, 2014. 3. C. Yu, P. Y. Kam, and Z. Xu, Carrier recovery in coherent receiver of optical fiber communication system with laser phase noise, International Photonics and OptoElectronics Meetings (POEM), Paper OTh3B.1, pp. 1-3, Wuhan, China, June 18-21, 2014. 4. Z. Xu, B. Zhang, C. Yu, and P. Y. Kam, Adaptive Maximum Likelihood Sequence Detection in 100-Gb/s Coherent Optical Communication Systems, Conference on Optical Fiber Communication (OFC) 2013, Paper JTh2A.46, pp. 1-3, Anaheim, CA, USA, March 17-21, 2013. 5. Z. Xu, C. Yu, and P. Y. Kam, Performance of Adaptive Maximum Likelihood Sequence Detection with Nonlinear Phase Noise, OptoElectronics and Communications Conference (OECC) 2013, Paper TuPR-16, pp. 1-2, Kyoto, Japan, June 30-July 4, 2013. 6. Z. Xu, S. Zhang, P. Y. Kam, and C. Yu, On the performance of decisionaided maximum likelihood and its adaptive phase estimation with nonlinear phase noise, OptoElectronics and Communications Conference (OECC) 2011, Paper 6B3-3, pp. 1-2, Kaohsiung, Taiwan, July 4-8, 2011. 7. X. Li, Z. Xu, W. D. Zhong, A. Alphones, and C. Yu, Independent component analysis based modified constant modulus algorithm in coherent optical receiver, OptoElectronics and Communications Conference (OECC) 2014, Paper TH10E-3, pp. 1-3, Melbourne, Australia, July 6-10, 2014. 142 PUBLICATION LIST 8. Y. Yu, C. F. Loh, Z. Xu, and C. Yu, OSNR monitoring for PDM RZDQPSK system by low bandwidth sampling technique, Asia-Pacific Conference on Communications (APCC) 2013, Paper V-2.1, pp. 1-2, Bali Dynasty Resort, Bali, Indonesia, August 29-31, 2013. 143 [...]... lightwave systems that employ optical fibers for information transmission The carrier frequencies for optical communication systems are in the range of 100 THz which is the visible or near-infrared region of the electromagnetic spectrum [1] Thus the available bandwidth for information transmission is much higher than in microwave systems To meet the demand of fast increasing data traffic, fiber-optic communication. .. of coherent optical communication is given, followed by the motivation and outline of this thesis 1.1 Review of Coherent Optical Communication The coherent optical communication systems draw considerable attention and were intensively investigated in 1980s The LO in the receiver dramatically im- 2 1.1 Review of Coherent Optical Communication proves the receiver sensitivity and transmission distance... communication systems can be divided into two categories based on their detection method One is referred to as intensity modulation with direct detection (IM/DD) The information is modulated on the intensity of an optical carrier After transmission through fiber link, the incident signal is converted 1 INTRODUCTION directly to electrical domain using photo detectors The capability of the direct detection system... high- speed analog-todigital converters (ADCs) have revived the coherent detection systems The full information of the electromagnetic field can be preserved at the receiver by sampling the received signal into digital waveforms Thus the amplitude, phase and polarization information of the signal can be modulated simultaneously to increase the transmission capacity Advanced modulation formats such as M ary... communication systems have been widely deployed since 1980 for metropolitan and trans-ocean communications Especially in the past two decades, the amount of data traffic on the backbone networks has been growing exponentially at about 30 to 60% per year [2] The rapid development of cloud computing also requires high speed data communication within data-centers and high performance computers [3] The optical communication. .. be utilized in the receiver to perform all-electronic chromatic dispersion (CD) and polarization-mode dispersion (PMD) compensation, frequency offset and phase noise mitigation, polarization de-multiplexing and so on [17–21] Therefore, the bulky optical components are replaced by compact and cheap DSP circuits in the receiver Single carrier 100-Gbit/s coherent optical systems are commercially available... single -carrier- modulated signals that are seamlessly multiplexed under the coherent optical orthogonal frequencydivision multiplexing (OFDM) conditions [25, 26] Later the concept of superchannel is generalized to the optical signals that are modulated and multiplexed together with high spectral efficiency at a common originating site, transmitted through common optical link and received at a common destination... this method heavily depends on nonlinear operations such as rectangular to polar/polar to rectangular transformations, M th power operation and phase unwrapping [20] In addition, the M th power scheme is first proposed for M -PSK signals, thus extra modifications are required for non-constant-amplitude modulation formats [36, 37] To extend the M th-power scheme to M -ary QAM signals, we can use a subgroup... the coherent receiver is reduced from O(L · M ) to O(M ), where L is the window size for MLSD Simulations for back-to-back and transmission systems are conducted to compare the performance for adaptive and non-adaptive MLSD algorithms It is observed that the adaptive version achieves optimal performance as MLSD with optimum window size For QAM signals, the adaptive MLSD experiences constellation penalty... promising solution to increase the data rate without increasing required bandwidth However, one of the challenges in coherent optical systems is to recover the carrier phase, which is perturbed by laser phase noise and nonlinear phase noise In this thesis, we will study carrier recovery algorithms to compensate for phase noise impairments for coherent optical systems Firstly, a trellis -based maximum . CARRIER PHASE RECOVERY FOR HIGH SPEED COHERENT OPTICAL COMMUNICATION SYSTEMS BASED ON DIGITAL SIGNAL PROCESSING XU ZHUORAN (B.Eng.), National University of Singapore,. factor and is continuously updated based on received symbols. It is shown that the adaptive MLSD outperforms the non-adaptive version especially for MPSK signals. For QAM modulation format, although. of high- speed analog-to -digital converters (ADCs), full information of electric field can be preserved, such as amplitude, phase and polarization. Advanced modulation formats together with coherent detection