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Journal ArticleDOI

Rate Adaptation and Reach Increase by Probabilistically Shaped 64-QAM: An Experimental Demonstration

01 Apr 2016-Journal of Lightwave Technology (IEEE)-Vol. 34, Iss: 7, pp 1599-1609

TL;DR: A transmission system with adjustable data rate for single-carrier coherent optical transmission is proposed, which enables high-speed transmission close to the Shannon limit, and it is experimentally demonstrated that the optical transmission of probabilistically shaped 64-QAM signals outperforms the transmission reach of regular 16- QAM and regular 64-ZAM signals.
Abstract: A transmission system with adjustable data rate for single-carrier coherent optical transmission is proposed, which enables high-speed transmission close to the Shannon limit. The proposed system is based on probabilistically shaped 64-QAM modulation formats. Adjustable shaping is combined with a fixed-QAM modulation and a fixed forward-error correction code to realize a system with adjustable net data rate that can operate over a large reach range. At the transmitter, an adjustable distribution matcher performs the shaping. At the receiver, an inverse distribution matcher is used. Probabilistic shaping is implemented into a coherent optical transmission system for 64-QAM at 32 Gbaud to realize adjustable operation modes for net data rates ranging from 200 to 300 Gb/s. It is experimentally demonstrated that the optical transmission of probabilistically shaped 64-QAM signals outperforms the transmission reach of regular 16-QAM and regular 64-QAM signals by more than 40% in the transmission reach.
Citations
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Journal ArticleDOI
Bo Liu1, Ying Zhang2, Kaihui Wang, Miao Kong  +4 moreInstitutions (2)
TL;DR: The star-shaped 16-ary quadrature amplitude modulation scheme shows superiority over the PS-Square-16QAM in terms of the BER improvement.
Abstract: We investigate and compare the performance of star-shaped 16-ary quadrature amplitude modulation (Star-16QAM) and square-shaped 16QAM (Square-16QAM) in the probabilistic shaping (PS) and uniform schemes with coherent detection. With the help of PS technology, the bit error ratio (BER) improvement achieved in the PS-Star-16QAM scheme is greater than that of the PS-Square-16QAM when compared with the uniform schemes in our numerical simulation and experiment. Therefore, the PS-Star-16QAM shows superiority over the PS-Square-16QAM in terms of the BER improvement.

307 citations


Cites methods from "Rate Adaptation and Reach Increase ..."

  • ...The application of PS in optical communication is able to operate the systems more approach to the Shannon limit thus outperforming conventional modulation formats [2]–[4], [11]....

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Journal ArticleDOI
03 Sep 2018-Optics Express
TL;DR: Focusing on the optical transport and switching layer, aspects of large-scale spatial multiplexing, massive opto-electronic arrays and holistic optics-electronics-DSP integration, as well as optical node architectures for switching and multiplexed of spatial and spectral superchannels are covered.
Abstract: Celebrating the 20th anniversary of Optics Express, this paper reviews the evolution of optical fiber communication systems, and through a look at the previous 20 years attempts to extrapolate fiber-optic technology needs and potential solution paths over the coming 20 years. Well aware that 20-year extrapolations are inherently associated with great uncertainties, we still hope that taking a significantly longer-term view than most texts in this field will provide the reader with a broader perspective and will encourage the much needed out-of-the-box thinking to solve the very significant technology scaling problems ahead of us. Focusing on the optical transport and switching layer, we cover aspects of large-scale spatial multiplexing, massive opto-electronic arrays and holistic optics-electronics-DSP integration, as well as optical node architectures for switching and multiplexing of spatial and spectral superchannels.

270 citations


Journal ArticleDOI
Abstract: Different aspects of probabilistic shaping for a multispan optical communication system are studied. First, a numerical analysis of the additive white Gaussian noise (AWGN) channel investigates the effect of using a small number of input probability mass functions (PMFs) for a range of signal-to-noise ratios (SNRs), instead of optimizing the constellation shaping for each SNR. It is shown that if a small penalty of at most 0.1 dB SNR to the full shaping gain is acceptable, just two shaped PMFs are required per quadrature amplitude modulation (QAM) over a large SNR range. For a multispan wavelength division multiplexing optical fiber system with 64QAM input, it is shown that just one PMF is required to achieve large gains over uniform input for distances from 1400 to 3000 km. Using recently developed theoretical models that extend the Gaussian noise (GN) model and full-field split-step simulations, we illustrate the ramifications of probabilistic shaping on the effective SNR after fiber propagation. Our results show that, for a fixed average optical launch power, a shaping gain is obtained for the noise contributions from fiber amplifiers and modulation-independent nonlinear interference (NLI), whereas shaping simultaneously causes a penalty as it leads to an increased NLI. However, this nonlinear shaping loss is found to have a relatively minor impact, and optimizing the shaped PMF with a modulation-dependent GN model confirms that the PMF found for AWGN is also a good choice for a multi-span fiber system.

245 citations


Journal ArticleDOI
TL;DR: The most recent advanced concepts and methods employed in the cutting-edge spectrally efficient coherent fiber-optic transoceanic transmission systems, such as probabilistic shaping, adaptive digital nonlinear compensation, rate-adaptive spatially coupled low-density parity check codes, and dual-band C+L-band transmission are reviewed.
Abstract: We review the most recent advanced concepts and methods employed in the cutting-edge spectrally efficient coherent fiber-optic transoceanic transmission systems, such as probabilistic shaping, adaptive digital nonlinear compensation, rate-adaptive spatially coupled low-density parity check codes, and dual-band C+L-band transmission. Building upon all these concepts and methods, we demonstrate transmission of 179 channels carrying a record net data rate of 65 Tb/s over 6600 km, achieving a spectral efficiency of 7.3 b/s/Hz, and a record average per-channel net bit rate of 363.1 Gb/s. We provide numerical and experimental results, which serve us to comment on the pertinence of the physicist's intuitive measure of performance, the signal-to-noise ratio, versus the information theorist's more accurate measure, the generalized mutual information, for the systems under study.

108 citations


Cites background from "Rate Adaptation and Reach Increase ..."

  • ...The implication of this flexibility for optical networks is discussed in [28], [29]....

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Proceedings ArticleDOI
01 Sep 2017-
TL;DR: It is shown that the normalized generalized mutual information represents an excellent forward error correction (FEC) threshold for uniform as well as for probabilistically shaped QAM and hence allows to accurately predict post-FEC performance from measured pre-Fec data.
Abstract: We show that the normalized generalized mutual information represents an excellent forward error correction (FEC) threshold for uniform as well as for probabilistically shaped QAM and hence allows to accurately predict post-FEC performance from measured pre-FEC data.

108 citations


Cites background from "Rate Adaptation and Reach Increase ..."

  • ...Equations (3) and (4) indicate that given a code rate and entropy = log of the underlying uniform -QAM constellation, we can adjust the information rate of coded PS- -QAM by controlling the rate parameter ≥ 0 ....

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References
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Robert G. Gallager1Institutions (1)
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"Rate Adaptation and Reach Increase ..." refers background in this paper

  • ...In particular, [19] estimates lower bounds on the capacity, while [20] derives an upper...

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716 citations


Journal ArticleDOI
TL;DR: The fundamental mechanism that explains why “convolutional-like” or “spatially coupled” codes perform so well is described, and it is conjecture that for a large range of graphical systems a similar saturation of the “dynamical” threshold occurs once individual components are coupled sufficiently strongly.
Abstract: Convolutional low-density parity-check (LDPC) ensembles, introduced by Felstrom and Zigangirov, have excellent thresholds and these thresholds are rapidly increasing functions of the average degree. Several variations on the basic theme have been proposed to date, all of which share the good performance characteristics of convolutional LDPC ensembles. We describe the fundamental mechanism that explains why “convolutional-like” or “spatially coupled” codes perform so well. In essence, the spatial coupling of individual codes increases the belief-propagation (BP) threshold of the new ensemble to its maximum possible value, namely the maximum a posteriori (MAP) threshold of the underlying ensemble. For this reason, we call this phenomenon “threshold saturation.” This gives an entirely new way of approaching capacity. One significant advantage of this construction is that one can create capacity-approaching ensembles with an error correcting radius that is increasing in the blocklength. Although we prove the “threshold saturation” only for a specific ensemble and for the binary erasure channel (BEC), empirically the phenomenon occurs for a wide class of ensembles and channels. More generally, we conjecture that for a large range of graphical systems a similar saturation of the “dynamical” threshold occurs once individual components are coupled sufficiently strongly. This might give rise to improved algorithms and new techniques for analysis.

703 citations


Journal ArticleDOI
TL;DR: The information rate of finite-state source/channel models can be accurately estimated by sampling both a long channel input sequence and the corresponding channel output sequence, followed by a forward sum-product recursion on the joint source/ channel trellis.
Abstract: The information rate of finite-state source/channel models can be accurately estimated by sampling both a long channel input sequence and the corresponding channel output sequence, followed by a forward sum-product recursion on the joint source/channel trellis. This method is extended to compute upper and lower bounds on the information rate of very general channels with memory by means of finite-state approximations. Further upper and lower bounds can be computed by reduced-state methods

552 citations


"Rate Adaptation and Reach Increase ..." refers background in this paper

  • ...The concept of mismatched decoding [22], [23] is a powerful tool that allows to derive achievable rates and decoding rules in situations when the exact channel law is not known [24]–[26]....

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Performance
Metrics
No. of citations received by the Paper in previous years
YearCitations
20221
202167
2020126
2019108
201869
201748