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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]

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]

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]

We propose an efficient coded modulation scheme for multiple input/multiple output free-space optical systems with Q-ary pulse-position modulation. It is based on multilevel coding and low-density parity-check codes as component codes. The proposed scheme provides excellent coding gain in the regime of strong atmospheric turbulence. [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]