Low-density parity-check codes for 40-gb/s optical transmission systems

Abstract-The FEC limit paradigm is the prevalent practice for designing optical communication systems to attain a certain bit-error rate (BER) without forward error correction (FEC). This practice assumes that there is an FEC code that will reduce the BER after decoding to the desired level. In this paper, we challenge this practice and show that the concept of a channel-independent FEC limit is invalid for soft-decision bitwise decoding. It is shown that for low code rates and high order modulation formats, the use of the soft FEC limit paradigm can underestimate the spectral efficiencies by up to 20%. A better predictor for the BER after decoding is the generalized mutual information, which is shown to give consistent post-FEC BER predictions across different channel conditions and modulation formats. Extensive optical full-field simulations and experiments are carried out in both the linear and nonlinear transmission regimes to confirm the theoretical analysis.

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“…. , n and p ∈ {x, y}, soft information on the code bits C 5 , also known as logarithmic likelihood ratios, as…”

Section: A Channel and System Modelmentioning

confidence: 99%

Replacing the Soft-Decision FEC Limit Paradigm in the Design of Optical Communication Systems

Alvarado

Agrell

Lavery

et al. 2016

J. Lightwave Technol.

106

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“…This approach is based on bit-interleaved coded modulation [18], and low-density parity-check (LDPC) codes [19]- [21]. It was recently introduced by author in [10], [11].…”

Section: Beyond 100-gb/s Optical Transmission Using Bit-interleaved Lmentioning

confidence: 99%

“…For completeness of presentation we briefly describe the LDPC codes employed in simulations. For more details on LDPC codes suitable for use in optical communications an interested reader is referred to [19]- [21], and references therein.…”

Section: H I T R K S T B H T K S T B H Tmentioning

confidence: 99%

LDPC-coded modulation for beyond 100-Gb/s optical transmission

Djordjević

2007

SPIE Proceedings

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The future Internet traffic growth will require deployment of optical transmission systems with bit rates higher than rate of currently available 40-Gb/s systems, such as 100-Gb/s and above. However, at data rates beyond 100-Gb/s the signal quality is significantly degraded mainly due to impact of polarization mode dispersion (PMD), and intra-channel nonlinear effects. All electrically time-division multiplexed (ETDM) multiplexers and de-multiplexers operating at ~100-Gb/s are becoming commercially available. However, the modulators operating ~100-Gb/s are not widely available so that alternative approaches to enable 100-Gb/s transmission and beyond using commercially available components operating at 40-Gb/s are of high practical importance. In this invited paper, several joint coded-modulation and multiplexing schemes enabling beyond 100-Gb/s transmission using commercially available components operating at 40-Gb/s are presented. Using this approach, modulation, coding and multiplexing are performed in a unified fashion so that, effectively, the transmission, signal processing, detection and decoding are done at much lower symbol rates, where dealing with the nonlinear effects and PMD is more manageable, while the aggregate data rate is maintained above 100-Gb/s. The main elements of our approach include: (i) bit-interleaved LDPC-coded modulation, (ii) multilevel coding (MLC) with LPDC component codes, and (iii) LDPC-coded orthogonal frequency division multiplexing (OFDM). The modulation formats of interest in this paper are M-ary quadrature-amplitude modulation (QAM) and Mary phase-shift keying (PSK), where M=2,…,16, both combined with either Gray or natural mapping rule. It will be shown that coherent detection schemes significantly outperform direct detection ones and provide an additional margin that can be used either for longer transmission distances or for application in an all-optical networks.

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“…Finally, after the A/D conversion and cyclic extension removal, the signal is demodulated by using the FFT algorithm. The soft outputs of the FFT demodulator are used to estimate the bit reliabilities that are fed to identical LDPC iterative decoders implemented based on the sum-product algorithm [12].…”

Section: Rf Input Of a Mach-zehnder Modulator (Mzm)mentioning

confidence: 99%

“…Three classes of FEC based on girth-8 LDPC codes are introduced in this section (girth refers to the shortest cycle length in corresponding bipartite graph of an LDPC code [12]). The first code-class is the class of girth-8 regular LDPC codes designed based on the concept of mutually-orthogonal Latin rectangles (MOLS) [20].…”

Section: Selection Of Ldpc Codesmentioning

confidence: 99%

LDPC-Coded OFDM for Optical Communication Systems with Direct Detection

Djordjević

Vasić

Neifeld

2007

IEEE J. Select. Topics Quantum Electron.

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Abstract-Low-density parity-check (LDPC) coded orthogonal frequency division multiplexing (OFDM) is proposed as an efficient coded modulation technique suitable for optical communication systems. We show that in long-haul fiber optics communications, LDPC-coded OFDM increases spectral efficiency, and reduces the influence of residual chromatic dispersion and the influence of fiber nonlinearities. LDPC-coded OFDM is as also a promising polarization-mode dispersion (PMD) compensation technique. In free space optical communications, LDPC-coded OFDM improves the immunity to the atmospheric turbulence; while in multimode fiber links, it reduces the influence of intermodal dispersion. In plastic optical fiber links it reduces the influence of dispersion and helps to overcome the bandwidth limitations. Several power efficient OFDM schemes and LDPC codes suitable for use in LDPCcoded OFDM optical communication systems are introduced.Index Terms-Fiber optics communications, free space optical communications, graded-index plastic optical fiber links, lowdensity parity-check (LDPC) codes, optical communications, orthogonal frequency division multiplexing (OFDM).

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Low-density parity-check codes for 40-gb/s optical transmission systems

Cited by 71 publications

References 32 publications

Replacing the Soft-Decision FEC Limit Paradigm in the Design of Optical Communication Systems

Replacing the Soft-Decision FEC Limit Paradigm in the Design of Optical Communication Systems

LDPC-coded modulation for beyond 100-Gb/s optical transmission

LDPC-Coded OFDM for Optical Communication Systems with Direct Detection

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