Mitigation of Linear and Nonlinear Impairments in High-Speed Optical Networks by using LDPC-Coded Turbo Equalization

Ivan B. Djordjevic, Lyubomir L. Minkov, Hussam G. Batshon

Research output: Contribution to journalArticlepeer-review

63 Scopus citations


We study a turbo equalization scheme based on low-density parity-check (LDPC) coded turbo equalization (TE). This scheme is suitable for simultaneous: (i) suppression of intrachannel nonlinearities, (ii) chromatic dispersion compensation, and (iii) polarization-mode dispersion (PMD) compensation. LDPC coding is based on large girth (g > 8) block-circulant codes, and maximum a posteriori probability (MAP) equalizer is based on Bahl-Cocke-Jelinek-Raviv (BJCR) algorithm. The ultimate channel capacity limits, assuming an independent identically distributed (i.i.d.) source are reported as well. In the presence of intrachannel nonlinearities the LDPC-coded TE provides almost 12 dB improvement over BCJR equalizer at BER of 10-8. For an NRZ system operating at 10 Gb/s with residual dispersion of 11200 ps/nm and for differential group delay of 50 ps, the LDPC-coded TE is only 1 dB away from the i.i.d channel capacity. The efficiency of LDPC-coded TE in PMD compensation is demonstrated experimentally, with decoding performed off line.

Original languageEnglish (US)
Pages (from-to)73-83
Number of pages11
JournalIEEE Journal on Selected Areas in Communications
Issue number6
StatePublished - Aug 2008


  • Fiber-optics communications
  • chromatic dispersion
  • intra-channel nonlinearities
  • low-density parity-check (LDPC) codes
  • polarization-mode dispersion (PMD)
  • turbo equalization

ASJC Scopus subject areas

  • Computer Networks and Communications
  • Electrical and Electronic Engineering


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