Weighted finite impulse response filter for chromatic dispersion equalization in coherent optical fiber communication systems

Time-domain chromatic dispersion (CD) equalization using finite impulse response (FIR) filter is now a common approach for coherent optical fiber communication systems. The complex weights of FIR filter taps are calculated from a truncated impulse response of the CD transfer function, and the modulus of the complex weights is constant. In our work, we take the limited bandwidth of a single channel signal into account and propose weighted FIR filters to improve the performance of CD equalization. A raised cosine FIR filter and a Gaussian FIR filter are investigated in our work. The optimization of raised cosine FIR filter and Gaussian FIR filter are made in terms of the EVM of QPSK, 16QAM and 32QAM coherent detection signal. The results demonstrate that the optimized parameters of the weighted filters are independent of the modulation format, symbol rate and the length of transmission fiber. With the optimized weighted FIR filters, the EVM of CD equalization signal is decreased significantly. The principle of weighted FIR filter can also be extended to other symmetric functions as weighted functions. OCIS codes: (060.4510) Optical communications; (230.3670) optical fiber;(040.5160) chromatic dispersion. References and Links 1. P. Henry, "Lightwave primer," Quantum Electronics 21(12), 1862–1879 (1985). 2. M. G. Taylor, "Coherent detection method using DSP for demodulation of signal and subsequent equalization of propagation impairments," Photonics Technology Letters 16(2), 674–676 (2004). 3. E. Ip and J. M. Kahn, "Digital Equalization of Chromatic Dispersion and Polarization Mode Dispersion," J. Lightwave Technol. 25(8), 2033-2043 (2007). 4. S. J. Savory, "Compensation of fibre impairments in digital coherent systems," in 34th European Conference on Optical Communication (IEEE, 2008), pp. 1–4. 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(5), 2120–2126 (2007). 6. B. Spinnler, F. N. Hauske, and M. Kuschnerov, "Adaptive equalizer complexity in coherent optical receivers," in European Conference on Optical Communication (IEEE, 2008), pp. 1–2. 7. H. Bülow, F. Buchali, and A. Klekamp, "Electronic Dispersion Compensation," J. Lightwave Technol. 26(1), 158–167 (2008). 8. M. Malekiha, I. Tselniker, and D. Plant, "Chromatic dispersion mitigation in long-haul fiber-optic communication networks by sub-band partitioning," Opt. Express 23(25), 32654–32663 (2015). 9. Y. Wang, "Adaptive Channel Estimator Based on Least Mean Square Error for Wireless LAN," in 2008 Fourth International Conference on Natural Computation (IEEE 2008), pp. 64–66. 10. W. Liu, P. P. Pokharel and J. C. Principe, "The Kernel Least-Mean-Square Algorithm," IEEE Transactions on Signal Processing 56(2), 543–554 (2008). 11. X. Zhou, K. Zhong, J. Huo, L. Gao, Y. Wang, L. Wang, Y. Yang, J. Yuan, K. Long, L. Zeng, A. Lau, and C. Lu, "112 Gb/s transmission over 80 km SSMF using PDM-PAM4 and coherent detection without optical amplifier," Opt. Express 24(15), 17359–17371 (2016). 12. S. Tsukamoto, K. Katoh and K. Kikuchi, "Unrepeated transmission of 20-Gb/s optical quadrature phase-shiftkeying signal over 200-km standard single-mode fiber based on digital processing of homodyne-detected signal for Group-velocity dispersion compensation," IEEE Photonics Technology Letters18(9), 1016–1018 (2006). 13. S. Tsukamoto, K. Katoh, and K. Kikuchi, "Unrepeated 20-Gbit/s QPSK Transmission over 200-km Standard Single-Mode Fiber Using Homodyne Detection and Digital Signal Processing for Dispersion Compensation," in Optical Fiber Communication Conference and Exposition and The National Fiber Optic Engineers Conference, Technical Digest (CD) (Optical Society of America, 2006), paper OWB4. 14. S. J. Savory, "Digital filters for coherent optical receivers," Opt. Express 16(2), 804–817 (2008). 15. T. Xu, G. Jacobsen, S. Popov, J. Li, E. Vanin, K. Wang, A. T. Friberg, and Y. Zhang, "Chromatic dispersion compensation in coherent transmission system using digital filters," Opt. Express 18(15), 16243–16257 (2010). 16. R. Schmogrow et al., "Error Vector Magnitude as a Performance Measure for Advanced Modulation Formats,” Photonics Technology Letters 24(1), 61–63 (2012). 17. H. A. Mahmoud and H. Arslan, "Error vector magnitude to SNR conversion for non-data-aided receivers," IEEE Transactions on Wireless Communications 8(5), 2694–2704 (2009).