Concatenated FEC experiment over 5000 km long straight line WDM test bed

271

183

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.

Section: Bw Receiversmentioning

confidence: 99%

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

Alvarado

Agrell

Lavery

et al. 2015

271

183

“…Thus, the SSC-induced BER of the received uncoded data sequence can be estimated by BER erfc (12) For an FEC code with code rate , the signaling rate for a fixed data rate increases to , so that the maximum number of collisions for each soliton increases to . Thus, the SSC-induced BER of the received FEC encoded data sequence becomes BER erfc (13) and the ratio of BER BER increases very rapidly with increased redundancy because yields BER BER . Even though the error correction capability of the FEC code increases with redundancy, the price to be paid in this case is increased SSC-induced BER of the received data sequence.…”

Section: A Rs Codes For Ssc-induced Errors Without Line Codingmentioning

confidence: 99%

“…The concatenated RS-convolutional code is a strong concatenated FEC coding scheme that has been proposed for long-haul submarine optical fiber communications [13], where ASE noise is dominant. We show that this concatenated FEC coding scheme, however, is not as effective as our proposed concatenated RS-SWC code for correcting SSC-induced errors.…”

Section: B Concatenated Rs-swc Coding Schemementioning

confidence: 99%

Sliding window criterion codes and concatenation scheme for mitigating timing-jitter-induced errors in WDM fiber transmissions

Cai

Menyuk

Morris

2002

We propose a concatenated coding scheme, which effectively reduces bit errors induced by soliton-soliton collisions (SSC) in wavelength division multiplexing (WDM) soliton transmission systems. A block line coding scheme, the sliding window criterion (SWC) code, is developed based on the nature of SSC-induced timing jitter in soliton communications. We show, by simplified collision model simulations, that the SWC code alone can decrease the SSC-induced timing jitter and, by concatenation to a Reed-Solomon (RS) code, improve both the bit rate and the channel spacing capacity in WDM systems. We compare the performance of our scheme both analytically and by simulations with those of various RS codes and concatenated RS-convolutional code used in optical fiber transmission systems, and show that high redundancy (overhead) does not always give better code performance. Finally, by using full simulations, we show that the SWC code is an effective and promising technique for dispersion-managed fiber WDM systems.

“…ASE noise has an asymmetric statistical nature, and the chi-square distribution model is currently a commonly used model of the ASE noise statistics in the receiver after passing through a square law photodetector and a narrow-band filter [6], [7]. For simplicity, the chi-square distributions are often approximated with Gaussian distributions in characterizing optical-fiber channels [2]- [5]. Moreover, most existing FEC codes are developed and evaluated with the additive white Gaussian noise (AWGN) assumption.…”

Section: Introductionmentioning

confidence: 99%

On turbo code decoder performance in optical-fiber communication systems with dominating ASE noise

Cai

Morris

Adalı

et al. 2003

In this paper, we study the effects of different ASE noise models on the performance of turbo code (TC) decoders. A soft-decoding algorithm, the Bahl, Cocke, Jelinek, and Raviv (BCJR) decoding algorithm [1], is generally used in the TC decoders. The BCJR algorithm is a maximum a posteriori probability (MAP) algorithm, and is very sensitive to the noise statistics. The Gaussian approximation of the ASE noise is widely used in the study of optical-fiber communication systems [2]-[8], and there exist standard TCs for additive white Gaussian noise (AWGN) channels. We show that using a MAP decoding algorithm based on the Gaussian noise assumptions, however, may significantly degrade the TC decoder performance in an optical-fiber channel with non-Gaussian ASE noise. To take full advantage of TC, the accurate noise statistics in optical-fiber transmissions should be used in the MAP decoding algorithm.