Feed-forward carrier phase recovery for offset-QAM Nyquist WDM transmission.

Due to the half symbol delay between in-phase and quadrature components for offset quadrature amplitude modulation (OQAM) signal, phase noise cannot only lead to constellation rotation but also introduce additional crosstalk. Therefore, OQAM signal has very poor tolerance to the laser linewidth. Here, we carry out a semi-analytical investigation of phase noise induced crosstalk during OQAM Nyquist WDM transmission, and find that the carrier phase recovery (CPR) has to be implemented prior to the inter-symbol-interference (ISI) equalization. Then, after a function separation of polarization de-multiplexing and ISI equalization, we propose a new DSP flow with a linewidth-tolerant blind feed-forward CPR scheme for OQAM signal. Its effectiveness is verified under the scenario of 5-channel 28-Gbaud polarization multiplexing (PM) OQAM Nyquist WDM systems. A tolerance of linewidth and symbol duration products of 6.5×10(-4) and 1.1×10(-4) is secured for 4-OQAM and 16-OQAM, respectively, given 1-dB required-OSNR penalty at BER = 10(-3).

[1]  Shuping Peng,et al.  European Conference on Optical Communications (ECOC) , 2014 .

[2]  André Bourdoux,et al.  Dual-polarization OFDM-OQAM for communications over optical fibers with coherent detection. , 2013, Optics express.

[3]  K. Kikuchi,et al.  Coherent detection of optical quadrature phase-shift keying signals with carrier phase estimation , 2006, Journal of Lightwave Technology.

[4]  H. Louchet,et al.  Improved DSP algorithms for coherent 16-QAM transmission , 2008, 2008 34th European Conference on Optical Communication.

[5]  Gabriella Bosco,et al.  Performance Limits of Nyquist-WDM and CO-OFDM in High-Speed PM-QPSK Systems , 2010, IEEE Photonics Technology Letters.

[6]  P. Poggiolini,et al.  On the Performance of Nyquist-WDM Terabit Superchannels Based on PM-BPSK, PM-QPSK, PM-8QAM or PM-16QAM Subcarriers , 2011, Journal of Lightwave Technology.

[7]  Ming Tang,et al.  Nyquist WDM superchannel using offset-16QAM and receiver-side digital spectral shaping. , 2014, Optics express.

[8]  Jianqiang Li,et al.  Approaching Nyquist Limit in WDM Systems by Low-Complexity Receiver-Side Duobinary Shaping , 2012, Journal of Lightwave Technology.

[9]  S. Chandrasekhar,et al.  Study of multicarrier Offset-QAM for spectrally efficient coherent optical communications , 2011, 2011 37th European Conference and Exhibition on Optical Communication.

[10]  Chongjin Xie,et al.  The accuracy assessment of different polarization mode dispersion models , 2006 .

[11]  S. Chandrasekhar,et al.  Generation of 224-Gb/s multicarrier offset-QAM using a real-time transmitter , 2012, OFC/NFOEC.

[12]  J. Zhao,et al.  Offset-QAM based coherent WDM for spectral efficiency enhancement. , 2011, Optics express.

[13]  F. Buchali,et al.  1-Tbit/s dual-carrier DP 64QAM transmission at 64Gbaud with 40% overhead soft-FEC over 320km SSMF , 2013, 2013 Optical Fiber Communication Conference and Exposition and the National Fiber Optic Engineers Conference (OFC/NFOEC).

[14]  R Schmogrow,et al.  Real-time Nyquist pulse generation beyond 100 Gbit/s and its relation to OFDM. , 2012, Optics express.

[15]  J. Fickers,et al.  Multicarrier offset-QAM modulations for coherent optical communication systems , 2014, OFC 2014.

[16]  Ting Wang,et al.  64-Tb/s, 8 b/s/Hz, PDM-36QAM Transmission Over 320 km Using Both Pre- and Post-Transmission Digital Signal Processing , 2011, Journal of Lightwave Technology.

[17]  Chao Li,et al.  Experimental demonstration of 110-Gb/s unsynchronized band-multiplexed superchannel coherent optical OFDM/OQAM system. , 2013, Optics express.

[18]  Xiang Zhou,et al.  An Improved Feed-Forward Carrier Recovery Algorithm for Coherent Receivers With $M$ -QAM Modulation Format , 2010, IEEE Photonics Technology Letters.

[19]  A. Ellis,et al.  Spectral density enhancement using coherent WDM , 2005, IEEE Photonics Technology Letters.

[20]  Jessica Fickers,et al.  Multicarrier Offset-QAM for Long-Haul Coherent Optical Communications , 2014, Journal of Lightwave Technology.

[21]  R. Noe,et al.  Hardware-Efficient Coherent Digital Receiver Concept With Feedforward Carrier Recovery for $M$ -QAM Constellations , 2009, Journal of Lightwave Technology.

[22]  Z. Pan,et al.  Generation of spectrally efficient Nyquist-WDM QPSK signals using DSP techniques at transmitter , 2012, OFC/NFOEC.

[23]  M. S. Moreolo,et al.  Optical Fiber Communication Conference , 2014 .

[24]  Benyuan Zhu,et al.  PDM-Nyquist-32QAM for 450-Gb/s Per-Channel WDM Transmission on the 50 GHz ITU-T Grid , 2012, Journal of Lightwave Technology.

[25]  T Pfau,et al.  Phase-Noise-Tolerant Two-Stage Carrier Recovery Concept for Higher Order QAM Formats , 2010, IEEE Journal of Selected Topics in Quantum Electronics.

[26]  W. Freude,et al.  Real-time digital Nyquist-WDM and OFDM signal generation: Spectral efficiency versus DSP complexity , 2012, 2012 38th European Conference and Exhibition on Optical Communications.