Digital backpropagation for spectrally efficient WDM 112 Gbit / s PM mary QAM transmission

We report the performance of coherently-detected nine-channel WDM transmission over high dispersion fibers, using polarization multiplexed m-ary quadrature amplitude modulation (m = 4, 16, 64, 256) at 112 Gbit/s. Compensation of fiber nonlinearities via digital backpropagation enables up to 10 dB improvement in maximum transmittable power and ~8 dB Qeff improvement which translates to a nine-fold enhancement in transmission reach for PM-256QAM, where the largest improvements are associated with higher-order modulation formats. We further demonstrate that even under strong nonlinear distortion the transmission reach only reduces by a factor of ~2.5 for a 2 unit increase in capacity (log2m) when full band DBP is employed, in proportion to the required back-to-back OSNR. ©2011 Optical Society of America OCIS codes: (060.2320) Fiber optics communications; (060.1660) Coherent communications; (060.4370) Nonlinear optics, fibers. References and links 1. A. D. Ellis, J. Zhao, and D. Cotter, “Approaching the Non-Linear Shannon Limit,” J. Lightwave Technol. 28(4), 423–433 (2010). 2. R.-J. Essiambre, G. Kramer, P. J. Winzer, G. J. Foschini, and B. Goebel, “Capacity Limits of Optical Fiber Networks,” J. Lightwave Technol. 28(4), 662–701 (2010). 3. S. Makovejsm, D. S. Millar, V. Mikhailov, G. Gavioli, R. I. Killey, S. J. Savory, and P. Bayvel, “Experimental Investigation of PDMQAM16 Transmission at 112 Gbit/s over 2400 km,” Optical Fiber Communication Conference, OFC 2010, OMJ6, (2010). 4. J. Yu, X. Zhou, Y. Huang, S. Gupta, M. Huang, T. Wang, and P. Magill, “112.8-Gb/s PM-RZ 64QAM Optical Signal Generation and Transmission on a 12.5GHz WDM Grid,” Optical Fiber Communication Conference, OFC 2010, OThM1, (2010). 5. M. Nakazawa, S. Okamoto, T. Omiya, K. Kasai, and M. Yoshida, “256 QAM (64 Gbit/s) Coherent Optical Transmission over 160 km with an Optical Bandwidth of 5.4 GHz,” Optical Fiber Communication Conference, OFC 2010, OThD5, (2010). 6. S. J. Savory, “Compensation of fiber impairments in digital coherent systems,” Optical Communication, 2008. ECOC 2008. 34th European Conference on, Mo.3.D.1, (2008). 7. E. Ip, “Nonlinear Compensation Using Backpropagation for Polarization-Multiplexed Transmission,” J. Lightwave Technol. 28(6), 939–951 (2010). 8. E. Mateo, L. Zhu, and G. Li, “Impact of XPM and FWM on the digital implementation of impairment compensation for WDM transmission using backward propagation,” Opt. Express 16(20), 16124–16137 (2008). 9. D. Rafique, J. Zhao, and A.D. Ellis, “Impact of Dispersion Map Management on the Performance of BackPropagation for Nonlinear WDM Transmissions,” OECC, 00107, (2010). 10. S. Oda, T. Tanimura, T. Hoshida, C. Ohshima, H. Nakashima, Z. Tao, and J. C. Rasmussen, “112 Gb/s DPQPSK transmission using a novel nonlinear compensator in digital coherent receiver,” Optical Fiber Communication Conference, OFC 2009, OThR6, (2009). 11. D. Rafique, and A. D. Ellis, “Impact of signal-ASE four-wave mixing on the effectiveness of digital backpropagation in 112 Gb/s PM-QPSK systems,” Opt. Express (accepted for publication). 12. L. B. Du, and A. J. Lowery, “Improved single channel backpropagation for intra-channel fiber nonlinearity compensation in long-haul optical communication systems,” Opt. Express 18(16), 17075–17088 (2010). 13. D. Rafique, J. Zhao, and A. D. Ellis, “Performance Improvement by Fiber Nonlinearity Compensation in 112 Gb/s PM M-ary QAM,” OFC (accepted for publication). #139547 $15.00 USD Received 13 Dec 2010; revised 12 Jan 2011; accepted 15 Jan 2011; published 4 Mar 2011 (C) 2011 OSA 14 March 2011 / Vol. 19, No. 6 / OPTICS EXPRESS 5219