Search

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-the-art 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 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 [ABSTRACT FROM PUBLISHER]

In this paper, a novel approach for suppressing the intrachannel nonlinear effects using pseudoternary constrained codes is proposed. A significant Q-factor improvement of up to 9.75 dB is obtained. The eye opening penalty (EOP) is also significantly improved by more than 10.24 dB. [ABSTRACT FROM PUBLISHER]

A bandwidth- and power-efficient modulation scheme using M-ary differential phase-shift keying (DPSK)/differential quadrature amplitude modulation (DQAM) and low-density parity-check (LDPC) codes as component codes in a multilevel coding (MLC) is proposed for optical transmission systems with direct detection. An MLC scheme with 2 b/s/Hz spectral efficiency based on block-circulant component codes provides the coding gain of 12.3 dB when compared to uncoded 8-DPSK, and 8.3 dB when compared to uncoded 4-DPSK (QDPSK). [ABSTRACT FROM PUBLISHER]

A problem of suppression of intrachannel nonlinearities through the use of constrained coding is considered. Three different techniques are proposed and compared with respect to their efficiency, namely 1) constrained coding; 2) combined constrained and error control coding; and 3) deliberate error insertion. Significant Q-factor improvement up to 16 dB depending on code rate and number of spans is demonstrated. A combined constrained-iterative forward error correction (FEC) scheme can operate in the presence of strong intrachannel nonlinearities when even advanced FEC schemes would be overwhelmed with errors. It provides a coding gain of 12.1 dB at a bit error rate (BER) of 10-9. Deliberate error insertion is an efficient approach to balance the encoder complexity and the achievable coding gain. [ABSTRACT FROM PUBLISHER]

In an earlier paper, we reported that the low-density parity-check (LDPC) codes from finite planes outperform any other known forward error-correction (FEC) scheme for optical communications. However, the number of different LDPC codes of code rate above 0.8 is rather small. As a natural extension of the prior work, in this paper, we consider LDPC codes on m flats derived from projective and affine geometries, which outperform codes from finite planes. The codes on m flats also provide a greater selection of structured LDPC codes of rate 0.8 or higher. The performance of the codes in a long-haul optical-communication system was assessed using an advanced simulator able to capture all important transmission impairments. Specifically, they achieve a coding gain of 10 dB at a bit error rate (BER) of 10-9, outperforming, therefore, the best turbo product codes proposed for optical communications. In addition, the simulator implements a fixed-point (FP) iterative decoder that allows control of the precision of the soft information used in the decoder. Such quantization is required to facilitate hardware implementations of the iterative decoder, and the high-speed operations for long-haul optical transmission systems. The loss in performance due to reduced precision of the soft information can be as low as 0.2 dB. [ABSTRACT FROM PUBLISHER]

There have been numerous attempts to determine the channel capacity of a nonlinear fiber-optic communication channel. The main approach was to consider amplified spontaneous emission (ASE) noise as a predominant effect and to observe the fiber nonlinearities as the perturbation of a linear case or as the multiplicative noise. In this paper, the achievable information rates for high-speed optical transmission (40 Gb/s and above) are calculated using the finite-state-machine approach. In calculations, the combined effect of ASE noise, Kerr nonlinearity [self-phase modulation (SPM), intrachannel four-wave mixing (IFWM), intrachannel cross-phase modulation (IXPM)], stimulated Raman scattering (SRS), chromatic dispersion, and (optical/electrical) filtering is taken into account. [ABSTRACT FROM PUBLISHER]

This paper is concerned with investigating the performance of regular and irregular, randomlike and structured generalized low-density parity-check (GLDPC) codes for long-haul transmission. The proposed GLDPC codes outperform currently known turbo and low-density parity-check (LDPC) coding schemes with comparable parameters utilized in optical communication systems. For a GLDPC coding scheme with 23.6% redundancy, the largest so far reported coding gain of at least 11dB (at 40 Gb/s) is demonstrated. [ABSTRACT FROM PUBLISHER]

Low-density parity-check (LDPC) codes are excellent candidates for optical network applications due to their inherent low complexity of both encoders and decoders. A cyclic or quasi-cyclic form of finite geometry LDPC codes simplifies the encoding procedure. In addition, the complexity of an iterative decoder for such codes, namely the min-sum algorithm, is lower than the complexity of a turbo or Reed-Solomon decoder. In fact, simple hard-decoding algorithms such as the bit-flipping algorithm perform very well on codes from projective planes. In this paper, the authors consider LDPC codes from affine planes, projective planes, oval designs, and unitals. The bit-error-rate (BER) performance of these codes is significantly better than that of any other known foward-error correction techniques for optical communications. A coding gain of 9-10 dB at a BER of 10-9, depending on the code rate, demonstrated here is the best result reported so far. In order to assess the performance of the proposed coding schemes, a very realistic simulation model is used that takes into account in a natural way all major impairments in long-haul optical transmission such as amplified spontaneous emission noise, pulse distortion due to fiber nonlinearities, chromatic dispersion, crosstalk effects, and intersymbol interference. This approach gives a much better estimate of the code's performance than the commonly used additive white Gaussian noise channel model. [ABSTRACT FROM PUBLISHER]

A forward-error correction (FEC) scheme based on low-density parity check (LDPC) codes and iterative decoding using belief propagation in code graphs is presented in this paper. We show that LDPC codes provide a significant system performance improvement with respect to the state-of-the-art FEC schemes employed in optical communications systems. We present a class of structured codes based on mutually orthogonal Latin rectangles. Such codes have high rates and can lend themselves to very low-complexity encoder/decoder implementations. The system performance is further improved by a code design that eliminates short cycles in a graph employed in iterative decoding. [ABSTRACT FROM PUBLISHER]

Using the nonlinear second-order phase-locked loop (PLL) model the performance of the heterodyne coherent optical phase shift keying (PSK) systems with Costas loop in multichannel environment is considered in this paper for the first time. The shot noise of the corresponding photodiodes and adjacent channel interferences are described through the signal-to-noise ratio (SNR) in the loop bandwidth, while the laser phase noise is described through the normalized frequency fluctuations instead of the phase ones. The theory and results presented in this paper can be applied when analyzing and optimizing the performance in the region where the linear PLL model is not enough good [ABSTRACT FROM PUBLISHER]

We propose a three-dimensional (3-D) low-density parity check (LDPC)-coded modulation scheme that enables optical transmission beyond 320 Gb/s in aggregate rate using currently available commercial components operating at 40 giga-symbols/s. The proposed scheme introduces significant performance improvement of up to 4.1 dB at a bit-error ratio of 10-9 over the corresponding two-dimensional scheme. In addition, by using LDPC-coded 1024-3D-constellation it is possible, at least in theory, to achieve beyond a total of 1-Tb/s transmission using transmission equipment operating at 100 giga-symbols/s, once it reaches the maturity of 40-Gb/s systems. [ABSTRACT FROM PUBLISHER]

Polarization-mode dispersion (PMD) compensation by low-density parity-check (LDPC) coded turbo equalization is experimentally demonstrated for a nonreturn-to-zero (NRZ) system operating at 10 Gb/s. This technique provides significant improvement of bit-error rate compared to the optimum threshold receiver. The channel capacity loss due to PMD and quantization is studied as well. It was found that the proposed PMD turbo equalizer is about 1.5 dB away from the theoretical limit. [ABSTRACT FROM PUBLISHER]

A turbo equalization scheme suitable for electronic polarization-mode dispersion compensation based on low-density parity-check coding and the Bahl-Cocke-Jelinek-Raviv (BCJR) equalizer is proposed. For reasonable BCJR equalizer complexity, the differential group delay of up to three bit-periods can be compensated. [ABSTRACT FROM PUBLISHER]

An iterative bandwidth-efficient coded modulation scheme based on bit-interleaving low-density parity-check (LDPC) codes, and M-ary differential phase-shift keying is proposed. A bit-interleaved LDPC-coded scheme, carrying 3 bits/symbol, provides the coding gain of 8.3 dB at a bit-error rate (BER) of 10-7. The expected coding gain at BER of 10-12 is 12.8 dB. Possible applications include 100G Ethernet, and high-speed (>100 Gb/s) long-haul transmission [ABSTRACT FROM PUBLISHER]

The possibility of 10-Gb/s transmission over graded-index plastic optical fiber (GI-POF) using the orthogonal frequency-division multiplexing (OFDM) and iteratively decodable codes is demonstrated by simulations. Several classes of low-density parity-check (LDPC) codes suitable for use in LDPC-coded OFDM transmission over GI-POF are presented as well. Several power efficient OFDM schemes are introduced [ABSTRACT FROM PUBLISHER]

The possibility of 100-Gb/s transmission over 25-GHz bandwidth using orthogonal frequency-division multiplexing (OFDM) is demonstrated. It is shown that 100-Gb/s transmission over 3840 km can be achieved using single-sideband quadrature-phase-shift keying OFDM transmission and low-density parity-check codes [ABSTRACT FROM PUBLISHER]

An iterative equalization scheme for suppressing intrachannel nonlinearities in high-speed optical transmission systems operating at 40 Gb/s is presented. The proposed method employs a noise-predictive filter to mitigate the colored noise due to amplified spontaneous emission noise and optical filtering. The maximum a posteriori probability symbol detection implemented as the Bahl-Cocke-Jelinek-Raviv (BCJR) algorithm is employed to suppress the intrachannel nonlinear effects. Soft decision outputs provided by the noise-predictive BCJR equalizer are processed by an iterative low-density parity-check decoder [ABSTRACT FROM PUBLISHER]

We propose a class of moderate-length nonbinary low-density parity-check (LDPC) codes for long-haul high-speed optical transmission systems. In particular, we present an LDPC code with 12.59% redundancy that achieves a 9.9-dB coding gain at a bit-error rate of 10-10. A similar coding gain is obtained for a long nonbinary LDPC code with a redundancy of only 6.7%. [ABSTRACT FROM PUBLISHER]

A novel family of low-density parity-check codes is proposed based on MacNeish-Mann theorem for construction of mutually orthogonal Latin squares. Codes from this family have high code rate, girth at least six, large minimum distance, and significantly outperform conventional forward error correction schemes based on Reed-Solomon (RS) and turbo codes. [ABSTRACT FROM PUBLISHER]

Forward error correction (FEC) scheme based on low density parity check codes (LDPC) codes is presented in this paper. We show that LDPC codes provide a significant system performance enhancement with respect to the state-of-the-art FEC schemes employed in optical communication systems. [ABSTRACT FROM PUBLISHER]