| 1. |
- Alvarado, Alex, 1982, et al.
(författare)
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LDPC codes for optical channels: Is the "FEC limit" a good predictor of post-FEC BER?
- 2015
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Ingår i: 2015 Optical Fiber Communications Conference and Exhibition, (OFC) 2015, Los Angeles, United States, 22-26 March 2015. - Washington, D.C. : OSA. - 9781557529374 ; , s. 7121706-
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Konferensbidrag (refereegranskat)abstract
- We answer the question in the title negatively. More precisely, the FEC limit is invalid for soft decision decoding and low to medium code rates. A better predictor is the generalized mutual information.
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| 2. |
- Alvarado, A., et al.
(författare)
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Replacing the Soft-Decision FEC Limit Paradigm in the Design of Optical Communication Systems
- 2016
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Ingår i: Journal of Lightwave Technology. - : Institute of Electrical and Electronics Engineers (IEEE). - 0733-8724 .- 1558-2213. ; 34:2, s. 707-721
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Tidskriftsartikel (refereegranskat)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 bit-wise decoding. It is shown that for low code rates and high-order modulation formats, the use of the soft-decision 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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| 3. |
- Czegledi, Cristian Bogdan, 1988, et al.
(författare)
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Digital backpropagation accounting for polarization-mode dispersion
- 2017
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Ingår i: Optics Express. - 1094-4087 .- 1094-4087. ; 25:3, s. 1903-1915
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Tidskriftsartikel (refereegranskat)abstract
- Digital backpropagation (DBP) is a promising digital-domain technique to mitigate Kerr-induced nonlinear interference. While it successfully removes deterministic signal-signal interactions, the performance of ideal DBP is limited by stochastic effects, such as polarizationmode dispersion (PMD). In this paper, we consider an ideal full-field DBP implementation and modify it to additionally account for PMD; reversing the PMD effects in the backward propagation by passing the reverse propagated signal also through PMD sections, which concatenated equal the inverse of the PMD in the forward propagation. These PMD sections are calculated analytically at the receiver based on the total accumulated PMD of the link estimated from channel equalizers. Numerical simulations show that, accounting for nonlinear polarization-related interactions in the modified DBP algorithm, additional signal-to-noise ratio gains of 1.1 dB are obtained for transmission over 1000 km.
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| 4. |
- Czegledi, Cristian Bogdan, 1988, et al.
(författare)
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Modified Digital Backpropagation Accounting for Polarization-Mode Dispersion
- 2017
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Ingår i: Optical Fiber Communication Conference. - 9781943580231
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Konferensbidrag (refereegranskat)abstract
- We propose a modified DBP algorithm accounting for PMD. The accumulated PMD at the receiver is factorized into several PMD sections, and inserted into the DBP routine to distributively compensate for PMD, outperforming the conventional approach by 1.1 dB in SNR.
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| 5. |
- Czegledi, Cristian Bogdan, 1988, et al.
(författare)
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Polarization-Mode Dispersion Aware Digital Backpropagation
- 2016
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Ingår i: 42nd European Conference on Optical Communication, ECOC 2016; Dusseldorf; Germany; 18 September 2016 through 22 September 2016. - 9783800742745 ; , s. 1091-1093
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Konferensbidrag (refereegranskat)abstract
- We study a modified DBP algorithm that accounts for PMD. Based on the accumulated PMD at the receiver, the algorithm distributively compensates for PMD in the reverse propagation and outperforms the conventional approach by up to 2.1 dB.
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| 6. |
- Galdino, Lidia, et al.
(författare)
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On the limits of digital back-propagation in the presence of transceiver noise
- 2017
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Ingår i: Optics Express. - 1094-4087 .- 1094-4087. ; 25:4, s. 4564-4578
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Tidskriftsartikel (refereegranskat)abstract
- © 2017, OSA - The Optical Society. All rights reserved. This paper investigates the impact of transceiver noise on the performance of digital back-propagation (DBP). A generalized expression to estimate the signal-to-noise ratio (SNR) obtained using DBP in the presence of transceiver noise is described. This new expression correctly accounts for the nonlinear beating between the transceiver noise and the signal in the optical fiber transmission link. The transceiver noise-signal nonlinear beating has been identified as the main reason for the discrepancy between predicted and practical performance of DBP; which has not been previously suggested. This nonlinear beating has been included in the GN model, allowing DBP gains in practical systems to be predicted analytically. Experiments and split-step simulations with and without polarization-mode dispersion (PMD) in the transmission link have been performed. The results show that the impact of transceiver noise greatly outweighs that of PMD, and the analytical expressions are confirmed by the numerical simulations.
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