| 21. |
- Keykhosravi, Kamran, 1990, et al.
(author)
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Data preprocessing for machine-learning-based adaptive data center transmission
- 2022
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In: ICT Express. - : Elsevier BV. - 2405-9595. ; 8:1, s. 37-43
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Journal article (peer-reviewed)abstract
- To enable optical interconnect fluidity in next-generation data centers, we propose adaptive transmission based on machine learning in a wavelength-routing network. We consider programmable transmitters that can apply N possible code rates to connections based on predicted bit error rate (BER) values. To classify the BER, we employ a preprocessing algorithm to feed the traffic data to a neural network classifier. We demonstrate the significance of our proposed preprocessing algorithm and the classifier performance for different values of N and switch port count.
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| 22. |
- Keykhosravi, Kamran, 1990, et al.
(author)
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When to Use Optical Amplification in Noncoherent Transmission: An Information-Theoretic Approach
- 2020
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In: IEEE Transactions on Communications. - 0090-6778 .- 1558-0857. ; 68:4, s. 2438-2445
-
Journal article (peer-reviewed)abstract
- The standard solution for short-haul fiber-optic communications is to deploy noncoherent systems, i.e., to modulate and detect only the light intensity. In such systems, the signal is corrupted with optical noise from amplifiers and with thermal (electrical) noise. The capacity of noncoherent optical links has been studied extensively in the presence of either optical noise or thermal noise. In this paper, for the first time, we characterize the capacity under an average power constraint with both noise sources by establishing upper and lower bounds. In the two extreme cases of zero optical noise or zero thermal noise, we assess our bounds against some well-known results in the literature; improvements in both cases are observed. Next, for amplified fiber-optic systems, we study the trade-off between boosting signal energy (mitigating the effects of thermal noise) and adding optical noise. For a wide spectrum of system parameters and received power levels, we determine the optimal amplification gain. While mostly either no amplification or high-gain amplification is optimal, the best performance is for some parameter intervals achieved at finite gains.
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| 23. |
- Li, Shen, 1994, et al.
(author)
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Antialiased transmitter-side digital backpropagation
- 2020
-
In: IEEE Photonics Technology Letters. - 1041-1135 .- 1941-0174. ; 32:18, s. 1211-1214
-
Journal article (peer-reviewed)abstract
- Digital backpropagation (DBP) is an electronic scheme for compensating nonlinear distortions in fiber transmission systems. Due to the nonlinearity-induced spectral broadening, the data must be oversampled to avoid aliasing, which increases the complexity and power consumption of the scheme. In this work, we show that aliasing can alternatively be prevented by distributed antialiasing filters, at a lower complexity. We proposed a new modified split-step Fourier method (SSFM) with easy-To-implement low-pass filters (LPFs) in the linear steps to avoid aliasing due to spectral broadening. Both the forward fiber propagation and a transmitter-side DBP are simulated using the modified SSFM. High-order modulation formats such as 256-Ary quadrature-Amplitude-modulation (256-QAM) and 1024-QAM transmissions at 28 Gbaud and 64 Gbaud over 1000 km fiber are considered, and our results show that the complexity of the DBP can be reduced by up to 50%. The optimal bandwidth of the LPFs is studied for both forward propagation and the DBP.
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| 24. |
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| 25. |
- Li, Shen, 1994, et al.
(author)
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Designing Voronoi Constellations to Minimize Bit Error Rate
- 2021
-
In: IEEE International Symposium on Information Theory - Proceedings. - 2157-8095. ; 2021-July, s. 1017-1022
-
Conference paper (peer-reviewed)abstract
- In a classical 1983 paper, Conway and Sloane presented fast encoding and decoding algorithms for a special case of Voronoi constellations (VCs), for which the shaping lattice is a scaled copy of the coding lattice. Feng generalized their encoding and decoding methods to arbitrary VCs. Less general algorithms were also proposed by Kurkoski and Ferdinand, respectively, for VCs with some constraints on their coding and shaping lattices. In this work, we design VCs with a cubic coding lattice based on Kurkoski's encoding and decoding algorithms. The designed VCs achieve up to 1.03 dB shaping gains with a lower complexity than Conway and Sloane's scaled VCs. To minimize the bit error rate (BER), pseudo-Gray labeling of constellation points is applied. In uncoded systems, the designed VCs reduce the required SNR by up to 1.1 dB at the same BER, compared with the same VCs using Feng's and Ferdinand's algorithms. In coded systems, the designed VCs are able to achieve lower BER than the scaled VCs at the same SNR. In addition, a Gray penalty estimation method for such VCs of very large size is introduced.
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| 26. |
- Li, Shen, 1994, et al.
(author)
-
Improved Simulation Accuracy of the Split-Step Fourier Method
- 2020
-
In: Optical Fiber Communication Conference. - 9781943580712
-
Conference paper (peer-reviewed)abstract
- We investigate a modified split-step Fourier method (SSFM) by including low-pass filters in the linear steps. This method can simultaneously achieve a higher simulation accuracy and a slightly reduced complexity.
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| 27. |
- Li, Shen, 1994, et al.
(author)
-
Low-Complexity Voronoi Shaping for the Gaussian Channel
- 2022
-
In: IEEE Transactions on Communications. - 0090-6778 .- 1558-0857. ; 70:2, s. 865-873
-
Journal article (peer-reviewed)abstract
- Voronoi constellations (VCs) are finite sets of vectors of a coding lattice enclosed by the translated Voronoi region of a shaping lattice, which is a sublattice of the coding lattice. In conventional VCs, the shaping lattice is a scaled-up version of the coding lattice. In this paper, we design low-complexity VCs with a cubic coding lattice of up to 32 dimensions, in which pseudo-Gray labeling is applied to minimize the bit error rate. The designed VCs have considerable shaping gains of up to 1.03 dB and finer choices of spectral efficiencies in practice compared with conventional VCs. A mutual information estimation method and a log-likelihood approximation method based on importance sampling for very large constellations are proposed and applied to the designed VCs. With error-control coding, the proposed VCs can have higher information rates than the conventional scaled VCs because of their inherently good pseudo-Gray labeling feature, with a lower decoding complexity.
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| 28. |
- Li, Shen, 1994, et al.
(author)
-
Power-Efficient Voronoi Constellations for Fiber-Optic Communication Systems
- 2023
-
In: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 41:5, s. 1298-1308
-
Journal article (peer-reviewed)abstract
- Voronoi constellations (VCs) are considered as an effective geometric shaping method due to their high power efficiencies and low complexity. In this paper, the performance of 16- and 32-dimensional VCs with a variety of spectral efficiencies transmitted in the nonlinear fiber channel are investigated. Both single-channel and wavelength-division multiplexing systems are considered for the transmission of the VCs, as well as different signal processing schemes, including chromatic dispersion compensation and digital backpropagation. Multiple performance metrics including the uncoded bit error rate, mutual information (MI), and generalized mutual information (GMI) of VCs are evaluated. Compared with quadrature amplitude modulation (QAM) formats, the VCs provide 1.0--2.4 dB launch power gains, up to 0.50 bits/symbol/dimension-pair MI gains, up to around 30% potential reach increase at the same MI, and up to 0.30 bits/symbol/dimension-pair GMI gains in a limited launch power range. The observed performance gains over QAM are found higher than in the back-to-back case. Moreover, a general GMI estimation method for very large constellations using importance sampling is proposed for the first time.
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| 29. |
- Mirani, Ali, 1992, et al.
(author)
-
Comparison of Physical Realizations of Multidimensional Voronoi Constellations in Single Mode Fibers
- 2022
-
In: European Conference on Optical Communication, ECOC.
-
Conference paper (peer-reviewed)abstract
- We investigate experimentally and numerically the impact of using different fiber dimensions to spread out the 32-dimensional Voronoi constellations. We find similar performance in experiments and less than 5.4% reach improvements in long-haul transmission simulations by spreading the constellation dimensions over time slots compared to wavelengths
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| 30. |
- Mirani, Ali, 1992, et al.
(author)
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Experimental Demonstration of 8-Dimensional Voronoi Constellations with 65,536 and 16,777,216 Symbols
- 2021
-
In: 2021 European Conference on Optical Communication, ECOC 2021. - 9781665438681
-
Conference paper (peer-reviewed)abstract
- We experimentally demonstrate high-cardinality, low-complexity Voronoi constellations based on the E8 lattice over multiple time slots with OSNR and launch power gains of up to 1.7 and 2.4 dB for back-to-back and 80 km fiber transmission, respectively, compared to QAM formats.
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