Suppression of intrachannel nonlinear effects using pseudoternary constrained codes

Djordjević, Ivan B.; Chilappagari, Shashi Kiran; Vasić, Bane

doi:10.1109/jlt.2005.862448

Cited by 24 publications

(9 citation statements)

References 13 publications

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“…They can be classified into two broad categories. The constrained coding based mitigation techniques are described in [13], [14], while the LDPC-coded turbo equalization is described in [12], [15]. The role of constrained coding is to avoid those waveforms in the transmitted signal that are most likely to be received incorrectly.…”

Section: Resultsmentioning

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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Section: Resultsmentioning

confidence: 99%

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

Djordjević

2007

SPIE Proceedings

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“…The Raman coefficient T R is set to a typical value 3.0 × 10 −15 [38]. As demonstrated in our recent publications [21], [22], the simulator used to estimate the probability density functions for mark-and state-bits, described above, gives an excellent agreement with commercially available VPI transmissionMaker WDM version 5.5. For example, in Fig.…”

Section: A Simulator Description and Verificationmentioning

confidence: 88%

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

Djordjević

Sankaranarayanan

Chilappagari

et al. 2006

IEEE J. Select. Topics Quantum Electron.

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Abstract-In this paper, we compare performance of three classes of forward error correction schemes for 40-Gb/s optical transmission systems. The first class is based on the concatenation of Reed-Solomon codes and this is employed in the state-of-theart fiber-optics communication systems. The second class is the turbo product codes with Bose-Chaudhuri-Hocquenghen component codes. The application of these codes in optical communication systems was extensively studied by Sab and Lemarie, and Mizuochi et al. The third class is the low-density parity-check (LDPC) codes that have attracted much attention over the past decade. We present enhanced decoding algorithms for Turbo product codes and LDPC codes that use probability density function of output sequences instead of calculating initial likelihood ratios assuming (inaccurate) Gaussian or chi-square approximation. The analysis in this paper shows that the LDPC codes perform better than the other codes in the waterfall region at bit error rates as low as 10 −9 . We also presented error floors results obtained by analyzing decoding failures of hard-decision iterative decoders.

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“…It was shown in [5,6] that proper choice of initial phases may result in suppression of IFWM. The IFWM will be suppressed in any sub-sequence of length L, c i c i+1 …c i+L-1 , if the following ghost-pulse constraint is satisfied: for all integers k, l, m∈{i,i+L-1} such that c k = c l = c m =1 (k and l not necessarily distinct), choose the initial phases θ k , θ l and θ m such that their contribution cancel each other at resonant position k+l-m, i.e.…”

Section: Description Of An Ifwm Cancellation Schemementioning

confidence: 99%

“…Previous methods used to overcome this phenomenon are basically summarized in: (i) finding a proper modulation format [ 2], [ 3,4], (ii) using constrained (line or modulation) coding [5][6][7][8], and (iii) using the equalization techniques [9][10][11][12]. As the creation of ghost pulses is a phase sensitive effect, the aim for the first approach is to remove short-term phase coherence.…”

Section: Introductionmentioning

confidence: 99%

“…The pseudo-ternary constrained code proposed in [6] is successful in suppression of IFWM, however it reduces the code rate down to 0.9. In this paper we present an efficient method for suppression of intrachannel four-wave mixing by choosing the initial pulse phases in a way to disturb the zero-bit position in "resonance" instead of canceling the effect of different ghost-pulse contributors, without reducing the code rate.…”

Section: Introductionmentioning

confidence: 99%

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An efficient modulation technique for suppressing intrachannel FWM in 40Gb/s optical transmission systems

2006

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In high bit-rate return-to-zero (RZ) on-off keying (OOK) systems operating at 40Gb/s and beyond ghost pulses induced by intrachannel four-wave mixing (IFWM), and intrachannel cross-phase modulation (IXPM) are dominant factors affecting the performance of a high-speed optical transmission system. As the creation of ghost pulses is a phase sensitive effect, the common approach to deal with IFWM is to remove short-term phase coherence by employing a proper modulation format. Another approach, known as constrained or line coding, is to identify the most troublesome sequences and to forbid them during encoding process. This paper presents an efficient method for testing the efficiency of a modulation techniques for countering the effects of IFWM by calculating the sum of all the contributors at a given resonance position. For a modulation technique to counter these effects the initial pulses phases must be chosen properly so that different contributors to the ghost pulse creation cancel each other in bit being in "resonance". In addition to this method, we are proposing a modulation technique that shows a significant Q-factor improvement of up to 7.5dB (depending on the number of spans and the phase sequence implemented) over the uncoded RZ-OOK as will be demonstrated. Finally, implementation of this phase modulation technique is very efficient in extending the non-linearity tolerance and enhancing the performance of a high-speed optical transmission system.

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Suppression of intrachannel nonlinear effects using pseudoternary constrained codes

Abstract: To suppress detrimental effects of intrachannel nonlinearities in 40Gb/s systems and beyond, the usage of modulation codes is proposed. Significant Q-factor improvement is demonstrated, ranging from 4.5 dB to 14 dB depending on modulation format, modulation code and number of spans.

Cited by 24 publications

References 13 publications

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

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

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

An efficient modulation technique for suppressing intrachannel FWM in 40Gb/s optical transmission systems

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