| 21. |
- Bao, Husileng, 1991, et al.
(författare)
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Wideband mm-wave 6 × 2 Distributed MIMO Transmitter using Sigma-Delta-over-Fiber
- 2024
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Ingår i: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 42:9, s. 3107-3117
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Tidskriftsartikel (refereegranskat)abstract
- This paper investigates a millimeter-wave sigma-delta-over-fiber distributed multiple-input-multiple-output (D-MIMO) solution, in which a central unit connects two remote radio heads (RRH) with two standardized QSFP28 fiber connections. The four subchannels of the QSFP28 carry three individually controlled intermediate frequency (IF) sigma-delta modulated bitstreams and one local oscillation signal to each RRH. At each RRH, the upconversion to mm-wave frequency is performed while maintaining full phase coherence between all channels and distributed RRHs. This solution offers an effective and scalable way to feed multiple radio heads with coherent signals proper for high performance millimeter-wave D-MIMO systems. Wireless performance of the transmitter is experimentally verified by multiple-input-single-output (MISO) and multiple-user MIMO cases in a 1.4 m × 1.6 m area with 748 MHz wideband signals. The comparison with other publications shows that the proposed system is the first millimeter-wave sigma-delta-over-fiber D-MIMO solution that serves multiple users and reaches the largest bandwidth.
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| 22. |
- Beygi, Lotfollah, 1977, et al.
(författare)
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Rate-Adaptive Coded Modulation for Fiber-Optic Communications
- 2014
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Ingår i: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 32:2, s. 333-343
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Tidskriftsartikel (refereegranskat)abstract
- Rate-adaptive optical transceivers can play an important role in exploiting the available resources in dynamic optical networks, in which different links yield different signal qualities. We study rate-adaptive joint coding and modulation, often called coded modulation (CM), addressing non-dispersion-managed (non-DM) links, exploiting recent advances in channel modeling of these links.We introduce a four-dimensional CM scheme, which shows a better tradeoff between digital signal processing complexity and transparent reach than existing methods. We construct a rate-adaptive CM scheme combining a single low-density parity-check code with a family of three signal constellations and using probabilistic signal shaping. We evaluate the performance of the proposed CM scheme for single-channel transmission through long-haul non-DM fiber-optic systems with electronic chromatic-dispersion compensation. The numerical results demonstrate improvement of spectralefficiency over a wide range of transparent reaches, an improvement over 1 dB compared to existing methods.
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| 23. |
- Beygi, Lotfollah, 1977, et al.
(författare)
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Signal Statistics in Fiber-Optical Channels with Polarization Multiplexing and Self-Phase Modulation
- 2011
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Ingår i: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 29:16, s. 2379 - 2386
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, the statistics of received signals in a single-channel dispersion-managed dual-polarization fiber-optical channel are derived in the limit of low dispersion. The joint probability density function (pdf) of the received amplitudes and phases of such a system is derived for both lumped and distributed amplification. The new pdf expressions are used to numerically evaluate the performance of modulation formats over channels with nonlinear phase noise. For example, a sensitivity gain of up to 2 dB is calculated for a specific system using polarization-multiplexed 8-ary phase shift keying compared with a similar single-polarization system at the same spectral efficiency and a symbol error rate of 5*10^(-4). Moreover, the accuracy of the derived pdf is evaluated for some single-channel dispersion-managed fiber-optical links with different dispersion-maps using the split-step Fourier transform method.
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| 24. |
- Bjork, G., et al.
(författare)
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Proposed Implementation of "Non-Physical" Four-Dimensional Polarization Rotations
- 2016
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Ingår i: Journal of Lightwave Technology. - : Institute of Electrical and Electronics Engineers (IEEE). - 0733-8724 .- 1558-2213. ; 34:14, s. 3317-3322
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Tidskriftsartikel (refereegranskat)abstract
- Recently one of us proposed a new formalism for modeling electromagnetic wave transformations for coherent communication using a real, four-vector description instead of the conventionally used Jones calculus or the Mueller matrices. The four-vector can then handle all superpositions of two orthogonal polarization basis and two orthogonal time bases (e.g., the in-phase and quadrature phase). In developing this formulation it was found that to provide a general but minimal framework for such rotations, it is natural to divide the six generators of four-dimensional (4d) rotations into two groups of three generators, the right-and the left-isoclinic matrices. Of the six transformations these generators define, it was furthermore found that four of them are readily implemented by linear optical components, while two of then were impossible to implement by such means. In this paper, we detail the reason these two "unphysical" rotations cannot be implemented with linear optics. We also suggest how they can be implemented, but at a cost in the signal-to-noise ratio, and give this minimum cost.
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| 25. |
- Björk, Gunnar, et al.
(författare)
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Proposed Implementation of "Non-Physical" Four-Dimensional Polarization Rotations
- 2016
-
Ingår i: Journal of Lightwave Technology. - : IEEE. - 0733-8724 .- 1558-2213. ; 34:14, s. 3317-3322
-
Tidskriftsartikel (refereegranskat)abstract
- Recently one of us proposed a new formalism for modeling electromagnetic wave transformations for coherent communication using a real, four-vector description instead of the conventionally used Jones calculus or the Mueller matrices. The four-vector can then handle all superpositions of two orthogonal polarization basis and two orthogonal time bases (e.g., the in-phase and quadrature phase). In developing this formulation it was found that to provide a general but minimal framework for such rotations, it is natural to divide the six generators of four-dimensional (4d) rotations into two groups of three generators, the right-and the left-isoclinic matrices. Of the six transformations these generators define, it was furthermore found that four of them are readily implemented by linear optical components, while two of then were impossible to implement by such means. In this paper, we detail the reason these two "unphysical" rotations cannot be implemented with linear optics. We also suggest how they can be implemented, but at a cost in the signal-to-noise ratio, and give this minimum cost.
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| 26. |
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| 27. |
- Buchberger, Andreas, 1990, et al.
(författare)
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Probabilistic Eigenvalue Shaping for Nonlinear Fourier Transform Transmission
- 2018
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Ingår i: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 36:20, s. 4799-4807
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Tidskriftsartikel (refereegranskat)abstract
- We consider a nonlinear Fourier transform (NFT)-based transmission scheme, where data is embedded into the imaginary part of the nonlinear discrete spectrum. Inspired by probabilistic amplitude shaping, we propose a probabilistic eigenvalue shaping (PES) scheme as a means to increase the data rate of the system. We exploit the fact that for an NFT-based transmission scheme the pulses in the time domain are of unequal duration by transmitting them with a dynamic symbol interval and find a capacity-achieving distribution. The PES scheme shapes the information symbols according to the capacity-achieving distribution and transmits them together with the parity symbols at the output of a low-density parity-check encoder, suitably modulated, via time-sharing. We furthermore derive an achievable rate for the proposed PES scheme. We verify our results with simulations of the discrete-time model as well as with split-step Fourier simulations.
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| 28. |
- Butler, Rick M., et al.
(författare)
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Model-Based Machine Learning for Joint Digital Backpropagation and PMD Compensation
- 2021
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Ingår i: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 39:4, s. 949-959
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Tidskriftsartikel (refereegranskat)abstract
- In this article, we propose a model-based machine-learning approach for dual-polarization systems by parameterizing the split-step Fourier method for the Manakov-PMD equation. The resulting method combines hardware-friendly time-domain nonlinearity mitigation via the recently proposed learned digital backpropagation (LDBP) with distributed compensation of polarization-mode dispersion (PMD). We refer to the resulting approach as LDBP-PMD. We train LDBP-PMD on multiple PMD realizations and show that it converges within 1% of its peak dB performance after 428 training iterations on average, yielding a peak effective signal-to-noise ratio of only 0.30 dB below the PMD-free case. Similar to state-of-the-art lumped PMD compensation algorithms in practical systems, our approach does not assume any knowledge about the particular PMD realization along the link, nor any knowledge about the total accumulated PMD. This is a significant improvement compared to prior work on distributed PMD compensation, where knowledge about the accumulated PMD is typically assumed. We also compare different parameterization choices in terms of performance, complexity, and convergence behavior. Lastly, we demonstrate that the learned models can be successfully retrained after an abrupt change of the PMD realization along the fiber.
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| 29. |
- Börjeson, Erik, 1984, et al.
(författare)
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Energy-Efficient Implementation of Carrier Phase Recovery for Higher-Order Modulation Formats
- 2021
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Ingår i: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 39:2, s. 505-510
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Tidskriftsartikel (refereegranskat)abstract
- We introduce circuit implementations of one- and two-stage carrier phase recovery (CPR) for 256QAM coherent optical receivers. We describe in detail the optimizations of algorithms, such as modified Viterbi-Viterbi (mVV), blind phase search (BPS), and principal component-based phase estimation (PCPE), that are required to develop energy-efficient CPR circuits and show how design parameter settings and limited fixed-point resolution affect the SNR penalty. 30-GBaud CPR circuit netlists synthesized in a 22-nm CMOS process technology allow us to study trade-offs between energy per bit and SNR penalty. We show that it is possible to reach an energy dissipation of around 1 pJ/bit at an SNR penalty of 0.6 dB for two-stage PCPE+BPS and mVV+BPS implementations, and that PCPE+BPS is the preferred choice thanks to its smaller area.
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| 30. |
- Börjeson, Erik, 1984, et al.
(författare)
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Fiber-on-Chip: Digital Emulation of Channel Impairments for Real-Time DSP Evaluation
- 2023
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Ingår i: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 41:3, s. 888-896
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Tidskriftsartikel (refereegranskat)abstract
- We describe the Fiber-on-Chip (FoC) approach to verification of digital signal processing (DSP) circuits, where digital models of a fiber-optic communication system are implemented in the same hardware as the DSP under test. The approach can enable cost-effective long-term DSP evaluations without the need for complex optical-electronic testbeds with high-speed interfaces, shortening verification time and enabling deep bit-error rate evaluations. Our FoC system currently contains a digital model of a transmitter generating a pseudo-random bitstream and a digital model of a channel with additive white Gaussian noise, phase noise and polarization-mode dispersion. In addition, the FoC system contains digital features for real-time control of channel parameters, using low-speed communication interfaces, and for autonomous real-time analysis, which enable us to batch multiple unsupervised emulations on the same hardware. The FoC system can target both field-programmable gate arrays, for fast evaluation of fixed-point logic, and application-specific integrated circuits, for accurate power dissipation measurements.
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