| 1. |
- Agrell, Erik, 1965, et al.
(författare)
-
Implications of information theory in optical fibre communications
- 2016
-
Ingår i: Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences. - : The Royal Society. - 1364-503X .- 1471-2962. ; 374:2062
-
Forskningsöversikt (refereegranskat)abstract
- Recent decades have witnessed steady improvements in our ability to harness the information-carrying capability of optical fibres. Will this process continue, or will progress eventually stall? Information theory predicts that all channels have a limited capacity depending on the available transmission resources, and thus it is inevitable that the pace of improvements will slow. However, information theory also provides insights into how transmission resources should, in principle, best be exploited, and thus may serve as a guide for where to look for better ways to squeeze more out of a precious resource. This tutorial paper reviews the basic concepts of information theory and their application in fibre-optic communications.
|
|
| 2. |
- Agrell, Erik, 1965, et al.
(författare)
-
Performance Prediction Recipes for Optical Links
- 2021
-
Ingår i: IEEE Photonics Technology Letters. - 1041-1135 .- 1941-0174. ; 33:18, s. 1034-1037
-
Tidskriftsartikel (refereegranskat)abstract
- Although forward error-correction (FEC) coding is an essential part of modern fiber-optic communication systems, it is impractical to implement and evaluate FEC in transmission experiments and simulations. Therefore, it is desirable to accurately predict the end-to-end link performance including FEC from transmission data recorded without FEC. In this tutorial, we provide ready-to-implement “recipes” for such prediction techniques, which apply to arbitrary channels and require no knowledge of information or coding theory. The appropriate choice of recipe depends on properties of the FEC encoder and decoder. The covered metrics include bit error rate, symbol error rate, achievable information rate, and asymptotic information, in all cases computed using a mismatched receiver. Supplementary software implementations are available.
|
|
| 3. |
- Agrell, Erik, 1965, et al.
(författare)
-
Roadmap on optical communications
- 2024
-
Ingår i: Journal of Optics. - 2040-8978 .- 2040-8986. ; 26:9
-
Forskningsöversikt (refereegranskat)abstract
- The Covid-19 pandemic showed forcefully the fundamental importance broadband data communication and the internet has in our society. Optical communications forms the undisputable backbone of this critical infrastructure, and it is supported by an interdisciplinary research community striving to improve and develop it further. Since the first ‘Roadmap of optical communications’ was published in 2016, the field has seen significant progress in all areas, and time is ripe for an update of the research status. The optical communications area has become increasingly diverse, covering research in fundamental physics and materials science, high-speed electronics and photonics, signal processing and coding, and communication systems and networks. This roadmap describes state-of-the-art and future outlooks in the optical communications field. The article is divided into 20 sections on selected areas, each written by a leading expert in that area. The sections are thematically grouped into four parts with 4-6 sections each, covering, respectively, hardware, algorithms, networks and systems. Each section describes the current status, the future challenges, and development needed to meet said challenges in their area. As a whole, this roadmap provides a comprehensive and unprecedented overview of the contemporary optical communications research, and should be essential reading for researchers at any level active in this field.
|
|
| 4. |
- Alvarado, A., et al.
(författare)
-
A Simple Approximation for the Bit-Interleaved Coded Modulation Capacity
- 2014
-
Ingår i: IEEE Communications Letters. - : Institute of Electrical and Electronics Engineers (IEEE). - 1558-2558 .- 1089-7798. ; 18:3, s. 495-498
-
Tidskriftsartikel (refereegranskat)abstract
- The generalized mutual information (GMI) is an achievable rate for bit-interleaved coded modulation (BICM) and is highly dependent on the binary labeling of the constellation. The BICM-GMI, sometimes called the BICM capacity, can be evaluated numerically. This approach, however, becomes impractical when the number of constellation points and/or the constellation dimensionality grows, or when many different labelings are considered. A simple approximation for the BICM-GMI based on the area theorem of the demapper's extrinsic information transfer (EXIT) function is proposed. Numerical results show the proposed approximation gives good estimates of the BICM-GMI for labelings with close to linear EXIT functions, which includes labelings of common interest, such as the natural binary code, binary reflected Gray code, etc. This approximation is used to optimize the binary labeling of the 32-APSK constellation defined in the DVB-S2 standard. Gains of approximately 0.15 dB are obtained.
|
|
| 5. |
- Alvarado, A., et al.
(författare)
-
Achievable rates for four-dimensional coded modulation with a bit-wise receiver
- 2014
-
Ingår i: Optics InfoBase Conference Papers. - Washington, D.C. : OSA. - 2162-2701.
-
Konferensbidrag (refereegranskat)abstract
- We study achievable rates for four-dimensional (4D) constellations for spectrally efficient optical systems based on a (suboptimal) bit-wise receiver. We show that PM-QPSK outperforms the best 4D constellation designed for uncoded transmission by approximately 1 dB. Numerical results using LDPC codes validate the analysis.
|
|
| 6. |
|
|
| 7. |
- Alvarado, A., et al.
(författare)
-
High-SNR Asymptotics of Mutual Information for Discrete Constellations With Applications to BICM
- 2014
-
Ingår i: IEEE Transactions on Information Theory. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9448 .- 1557-9654. ; 60:2, s. 1061-1076
-
Tidskriftsartikel (refereegranskat)abstract
- Asymptotic expressions of the mutual information between any discrete input and the corresponding output of the scalar additive white Gaussian noise channel are presented in the limit as the signal-to-noise ratio (SNR) tends to infinity. Asymptotic expressions of the symbol-error probability (SEP) and the minimum mean-square error (MMSE) achieved by estimating the channel input given the channel output are also developed. It is shown that for any input distribution, the conditional entropy of the channel input given the output, MMSE, and SEP have an asymptotic behavior proportional to the Gaussian Q-function. The argument of the Q-function depends only on the minimum Euclidean distance (MED) of the constellation and the SNR, and the proportionality constants are functions of the MED and the probabilities of the pairs of constellation points at MED. The developed expressions are then generalized to study the high-SNR behavior of the generalized mutual information (GMI) for bit-interleaved coded modulation (BICM). By means of these asymptotic expressions, the long-standing conjecture that Gray codes are the binary labelings that maximize the BICM-GMI at high SNR is proven. It is further shown that for any equally spaced constellation whose size is a power of two, there always exists an anti-Gray code giving the lowest BICM-GMI at high SNR.
|
|
| 8. |
- Alvarado, A., et al.
(författare)
-
Replacing the Soft-Decision FEC Limit Paradigm in the Design of Optical Communication Systems
- 2016
-
Ingår i: Journal of Lightwave Technology. - : Institute of Electrical and Electronics Engineers (IEEE). - 0733-8724 .- 1558-2213. ; 34:2, s. 707-721
-
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.
|
|
| 9. |
- Alvarado, A., et al.
(författare)
-
Replacing the Soft-Decision FEC Limit Paradigm in the Design of Optical Communication Systems
- 2015
-
Ingår i: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 33:20, s. 4338-4352
-
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.
|
|
| 10. |
- Oliari, Vinícius, et al.
(författare)
-
Frequency Logarithmic Perturbation on the Group-Velocity Dispersion Parameter with Applications to Passive Optical Networks
- 2021
-
Ingår i: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 39:16, s. 5287-5299
-
Tidskriftsartikel (refereegranskat)abstract
- Signal propagation in an optical fiber can be described by the nonlinear Schrdinger equation (NLSE). The NLSE has no known closed-form solution when both dispersion and nonlinearities are considered simultaneously. In this paper, we present a novel integral-form approximate model for the nonlinear optical channel, with applications to passive optical networks. The proposed model is derived using logarithmic perturbation in the frequency domain on the group-velocity dispersion (GVD) parameter of the NLSE. The model can be seen as an improvement of the recently proposed regular perturbation (RP) on the GVD parameter. RP and logarithmic perturbation (LP) on the nonlinear coefficient have already been studied in the literature, and are hereby compared with RP on the GVD parameter and the proposed LP model. As an application of the model, we focus on passive optical networks. For a 20 km PON at 10 Gbaud, the proposed model improves the normalized square deviation by 1.5 dB with respect to LP on the nonlinear coefficient. For the same system, histogram-based detectors are developed using the received symbols from the models. The detector obtained from the proposed LP model reduces the uncoded bit-error-rate by up to 5.4 times at the same input power or reduces the input power by 0.4 dB at the same information rate compared to the detector obtained from LP on the nonlinear coefficient.
|
|
