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199 results on '"Buchali, Fred"'

1. Improving the Bootstrap of Blind Equalizers with Variational Autoencoders

Author

Lauinger, Vincent, Buchali, Fred, and Schmalen, Laurent

Subjects
Electrical Engineering and Systems Science - Signal Processing, Computer Science - Information Theory, Computer Science - Machine Learning
Abstract

We evaluate the start-up of blind equalizers at critical working points, analyze the advantages and obstacles of commonly-used algorithms, and demonstrate how the recently-proposed variational autoencoder (VAE) based equalizers can improve bootstrapping., Comment: Accepted and to be presented at the Optical Fiber Communication Conference (OFC) 2023

Published
2023

2. Blind Equalization and Channel Estimation in Coherent Optical Communications Using Variational Autoencoders

Author

Lauinger, Vincent, Buchali, Fred, and Schmalen, Laurent

Subjects
Electrical Engineering and Systems Science - Signal Processing, Computer Science - Information Theory, Computer Science - Machine Learning
Abstract

We investigate the potential of adaptive blind equalizers based on variational inference for carrier recovery in optical communications. These equalizers are based on a low-complexity approximation of maximum likelihood channel estimation. We generalize the concept of variational autoencoder (VAE) equalizers to higher order modulation formats encompassing probabilistic constellation shaping (PCS), ubiquitous in optical communications, oversampling at the receiver, and dual-polarization transmission. Besides black-box equalizers based on convolutional neural networks, we propose a model-based equalizer based on a linear butterfly filter and train the filter coefficients using the variational inference paradigm. As a byproduct, the VAE also provides a reliable channel estimation. We analyze the VAE in terms of performance and flexibility over a classical additive white Gaussian noise (AWGN) channel with inter-symbol interference (ISI) and over a dispersive linear optical dual-polarization channel. We show that it can extend the application range of blind adaptive equalizers by outperforming the state-of-the-art constant-modulus algorithm (CMA) for PCS for both fixed but also time-varying channels. The evaluation is accompanied with a hyperparameter analysis., Comment: Published (Open Access) in IEEE Journal on Selected Areas in Communications, Sep 2022

Published
2022
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3. Distributed Transmission and Spatially Coupled Forward Error Correction in Regenerative Multipoint-to-Point Networks

Author

Schmalen, Laurent, Eriksson, Tobias A., Buchali, Fred, Dischler, Roman, and Gebhard, Ulrich

Subjects
Computer Science - Information Theory
Abstract

We investigate the performance of coded modulation for multi-hop regenerative optical networks. We analyze options for computing decoder input LLRs, show reach increases by optimized regenerator placement and experimentally compare strategies and guidelines for distributed FEC., Comment: published at European Conference on Optical Communication (ECOC) 2017

Published
2022
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4. On the Comparison of Single-Carrier vs. Digital Multi-Carrier Signaling for Long-Haul Transmission of Probabilistically Shaped Constellation Formats

Author

Benyahya, Kaoutar, Ghazisaeidi, Amirhossein, Aref, Vahid, Chagnon, Mathieu, Arnould, Aymeric, Ranzini, Stenio, Mardoyan, Haik, Buchali, Fred, and Renaudier, Jeremie

Subjects
Electrical Engineering and Systems Science - Signal Processing, Computer Science - Information Theory
Abstract

We report on theoretical and experimental investigations of the nonlinear tolerance of single carrier and digital multicarrier approaches with probabilistically shaped constellations. Experimental transmission of PCS16QAM is assessed at 120 GBd over an ultra-long-haul distance., Comment: presented in Optical Fiber Communication (OFC) Conference 2021, June 2021; Paper M3H.6

Published
2021

5. Exploring and Experimenting with Shaping Designs for Next-Generation Optical Communications

Author

Jardel, Fanny, Eriksson, Tobias A., Méasson, Cyril, Ghazisaeidi, Amirhossein, Buchali, Fred, Idler, Wilfried, and Boutros, Joseph J.

Subjects
Computer Science - Information Theory
Abstract

A class of circular 64-QAM that combines 'geometric' and 'probabilistic' shaping aspects is presented. It is compared to square 64-QAM in back-to-back, single-channel, and WDM transmission experiments. First, for the linear AWGN channel model, it permits to operate close to the Shannon limits for a wide range of signal-to-noise ratios. Second, WDM simulations over several hundreds of kilometers show that the obtained signal-to-noise ratios are equivalent to - or slightly exceed - those of probabilistic shaped 64-QAM. Third, for real-life validation purpose, an experimental comparison with unshaped 64-QAM is performed where 28% distance gains are recorded when using 19 channels at 54.2 GBd. This again is in line - or slightly exceeds - the gains generally obtained with probabilistic shaping. Depending upon implementation requirements (core forward-error correcting scheme for example), the investigated modulation schemes may be key alternatives for next-generation optical systems., Comment: 11 pages, 9 figures

Published
2018
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6. Experimental Demonstration of Capacity Increase and Rate-Adaptation by Probabilistically Shaped 64-QAM

Author

Buchali, Fred, Böcherer, Georg, Idler, Wilfried, Schmalen, Laurent, Schulte, Patrick, and Steiner, Fabian

Subjects
Computer Science - Information Theory
Abstract

We implemented a flexible transmission system operating at adjustable data rate and fixed bandwidth, baudrate, constellation and overhead using probabilistic shaping. We demonstrated in a transmission experiment up to 15% capacity and 43% reach increase versus 200 Gbit/s 16-QAM., Comment: Accepted for presentation as postdeadline paper at ECOC 2015

Published
2015

8. Higher-Order Modulation Formats – Concepts and Enabling Devices

Author

Idler, Wilfried, Buchali, Fred, Rhodes, William T., Editor-in-Chief, Adibi, Ali, Series Editor, Asakura, Toshimitsu, Series Editor, Krausz, Ferenc, Series Editor, Masters, Barry R., Series Editor, Midorikawa, Katsumi, Series Editor, Venghaus, Herbert, Series Editor, Weber, Horst, Series Editor, Weinfurter, Harald, Series Editor, and Grote, Norbert, editor

Published
2017
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11. Deep Neural Network-Based Digital Pre-distortion for High Baudrate Optical Coherent Transmission

Author

Bajaj, V. (author), Buchali, Fred (author), Chagnon, Mathieu (author), Wahls, S. (author), Aref, Vahid (author), Bajaj, V. (author), Buchali, Fred (author), Chagnon, Mathieu (author), Wahls, S. (author), and Aref, Vahid (author)

Abstract

High-symbol-rate coherent optical transceivers suffer more from the critical responses of transceiver components at high frequency, especially when applying a higher order modulation format. Recently, we proposed in [20] a neural network (NN)-based digital pre-distortion (DPD) technique trained to mitigate the transceiver response of a 128~GBaud optical coherent transmission system. In this paper, we further detail this work and assess the NN-based DPD by training it using either a direct learning architecture (DLA) or an indirect learning architecture (ILA), and compare performance against a Volterra series-based DPD and a linear DPD. Furthermore, we willfully increase the transmitter nonlinearity and compare the performance of the three DPDs considered. The proposed NN-based DPD trained using DLA performs the best among the three contenders, providing more than 1~dB signal-to-noise ratio (SNR) gains for uniform 64-quadrature amplitude modulation (QAM) and PCS-256-QAM signals at the output of a conventional coherent receiver DSP. Finally, the NN-based DPD enables achieving a record 1.61~Tb/s net rate transmission on a single channel after 80~km of standard single mode fiber (SSMF)., Accepted Author Manuscript, Team Sander Wahls

Published
2022
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12. Ultrahigh-Net-Bitrate 363 Gbit/s PAM-8 and 279 Gbit/s Polybinary Optical Transmission Using Plasmonic Mach-Zehnder Modulator

Author

Hu, Qian, primary, Borkowski, Robert, additional, Lefevre, Yannick, additional, Cho, Junho, additional, Buchali, Fred, additional, Bonk, Rene, additional, Schuh, Karsten, additional, De Leo, Eva, additional, Habegger, Patrick, additional, Destraz, Marcel, additional, Del Medico, Nino, additional, Duran, Hamit, additional, Tedaldi, Valentino, additional, Funck, Christian, additional, Fedoryshyn, Yuriy, additional, Leuthold, Juerg, additional, Heni, Wolfgang, additional, Baeuerle, Benedikt, additional, and Hoessbacher, Claudia, additional

Published
2022
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15. 128 GSa/s SiGe Analog Multiplexer Enabling PDM-DSCM-PCS-256QAM Transmission over 80 km SSMF

Author

Hu, Qian, primary, Schuh, Karsten, additional, Aref, Vahid, additional, Buchali, Fred, additional, Tannert, Tobias, additional, Grözing, Markus, additional, Berroth, Manfred, additional, Schmidt, Christian, additional, Schostak, Jonathan, additional, Caspar, Christoph, additional, Choi, Jung Han, additional, Jungnickel, Volker, additional, and Freund, Ronald, additional

Published
2022
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17. Neural Networks-based Nonlinear Digital Pre-Distortion of High-Speed Coherent Optical Transmitter

Author

Bajaj, Vinod, Buchali, Fred, Chagnon, Mathieu, Wahls, Sander, and Aref, Vahid

Subjects
ComputingMethodologies_IMAGEPROCESSINGANDCOMPUTERVISION, Data_CODINGANDINFORMATIONTHEORY, Digital pre-distortion, Computer Science::Information Theory
Abstract

A neural network-based digital pre-distortion technique is presented which compensates for the nonlinearity of an optical coherent transmitter.

Published
2021
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18. High-speed IM/DD transmission with analog (de-)multiplexers

Author

Schuh, Karsten, primary, Hu, Qian, additional, Dischler, Roman, additional, Aref, Vahid, additional, Buchali, Fred, additional, Le, Son Thai, additional, Collisi, Michael, additional, Moller, Michael, additional, Hettrich, Horst, additional, Schmid, Rolf, additional, Du, Xuan-Quang, additional, Grozing, Markus, additional, and Berroth, Manfred, additional

Published
2021
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19. Plasmonic-MZM-based Short-Reach Transmission up to 10 km Supporting >304 GBd Polybinary or 432 Gbit/s PAM-8 Signaling

Author

Hu, Qian, primary, Borkowski, Robert, additional, Lefevre, Yannick, additional, Buchali, Fred, additional, Bonk, Rene, additional, Schuh, Karsten, additional, Leo, Eva De, additional, Habegger, Patrick, additional, Destraz, Marcel, additional, Medico, Nino Del, additional, Duran, Hamit, additional, Tedaldi, Valentino, additional, Funck, Christian, additional, Fedoryshyn, Yuriy, additional, Leuthold, Juerg, additional, Heni, Wolfgang, additional, Baeuerle, Benedikt, additional, and Hoessbacher, Claudia, additional

Published
2021
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21. Mitigation of fiber nonlinear impairements in polarization division multiplexed OFDM transmission

Author

Liu, Xiang, Buchali, Fred, Tkach, Robert W., and Chandrasekhar, Sethumadhavan

Subjects
Fiber optic networks -- Methods, Fiber transmission equipment, Company business management, Science and technology, Telecommunications industry
Abstract

A joint self-phase modulation compensation scheme for single-channel transmission and a orthogonal frequency division multiplexed frame design and a dispersion management scheme for reducing the cross-phase-modulation for wavelength division multiplexed transmission are discussed. These techniques mitigate fiber nonlinear impairments.

Published
2010

22. Optical OFDM: a promising high-speed optical transport technology

Author

Buchali, Fred, Dischler, Roman, and Liu, Xiang

Subjects
Optical communications -- Technology application, Technology application, Science and technology, Telecommunications industry
Abstract

Orthogonal frequency division multiplexing (OFDM) is a promising enabling technology in light of the emerging demand for a 100+ gigabytes per second data rate in future optical transport systems. OFDM's architecture is reviewed and its performance under various system conditions is discussed.

Published
2009

23. Neural-Network-Based Nonlinearity Equalizer for 128 GBaud Coherent Transcievers

Author

Neskorniuk, Vladislav, Buchali, Fred, Bajaj, Vinod, Turitsyn, Sergei K., Prilepsky, Jaroslaw E., Aref, Vahid, Neskorniuk, Vladislav, Buchali, Fred, Bajaj, Vinod, Turitsyn, Sergei K., Prilepsky, Jaroslaw E., and Aref, Vahid

Abstract

We propose an efficient neural-network-based equalization jointly compensating fiber and transceiver nonlinearities for high-symbol-rate coherent short-reach links. Providing about 0.9 dB extra SNR gain, it allows achieving experimentally the record single-channel 1.48 Tbps net rate over 240 km G.652 fiber.

Published
2021

24. 54.5 Tb/s WDM Transmission over Field Deployed Fiber Enabled by Neural Network-Based Digital Pre-Distortion

Author

Bajaj, V. (author), Buchali, Fred (author), Chagnon, Mathieu (author), Wahls, S. (author), Aref, Vahid (author), Bajaj, V. (author), Buchali, Fred (author), Chagnon, Mathieu (author), Wahls, S. (author), and Aref, Vahid (author)

Abstract

We demonstrate a record 54.5 Tb/s WDM transmission at 11.35 bit/s/Hz over 48 km of field-deployed SMF connecting business and academic parks enabled by a novel joint I-Q Neural Network-based transmitter digital pre-distortion technique., Accepted Author Manuscript, Team Sander Wahls

Published
2021

34. SiGe HBTs and BiCMOS Technology for Present and Future Millimeter-Wave Systems

Author

Zimmer, Thomas, primary, Bock, Josef, additional, Buchali, Fred, additional, Chevalier, Pascal, additional, Collisi, Michael, additional, Debaillie, Bjorn, additional, Deng, Marina, additional, Ferrari, Philippe, additional, Fregonese, Sebastien, additional, Gaquiere, Christophe, additional, Ghanem, Haitham, additional, Hettrich, Horst, additional, Karakuzulu, Alper, additional, Maiwald, Tim, additional, Margalef-Rovira, Marc, additional, Maye, Caroline, additional, Moller, Michael, additional, Mukherjee, Anindya, additional, Rucker, Holger, additional, Sakalas, Paulius, additional, Schmid, Rolf, additional, Schneider, Karina, additional, Schuh, Karsten, additional, Templ, Wolfgang, additional, Visweswaran, Akshay, additional, and Zwick, Thomas, additional

Published
2021
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41. Single-channel 1.61 Tb/s optical coherent transmission enabled by neural network-based digital pre-distortion

Author

Bajaj, V. (author), Buchali, Fred (author), Chagnon, Mathieu (author), Wahls, S. (author), Aref, Vahid (author), Bajaj, V. (author), Buchali, Fred (author), Chagnon, Mathieu (author), Wahls, S. (author), and Aref, Vahid (author)

Abstract

We propose a novel digital pre-distortion (DPD) based on neural networks for high-baudrate optical coherent transmitters. We demonstrate experimentally that it outperforms an optimized linear DPD giving a 1.2 dB SNR gain in a 128GBaud PCS-256QAM single-channel transmission over 80km of standard single-mode fiber resulting in a record 1.61 Tb/s net data rate., Accepted Author Manuscript, Team Sander Wahls

Published
2020
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42. Drastic reduction of gate leakage in InAlAs/InGaAs HEMT's using a pseudomorphic InAlAs hole barrier layer

Author

Heedt, Christian, Buchali, Fred, Prost, Werner, Brockerhoff, Wolfgang, Fritzsche, Dieter, Nickel, Heinrich, Losch, Rainer, Schlapp, Winfried, and Tegude, Franz-Josef

Subjects
High-electron-mobility transistors -- Research, Gallium arsenide semiconductors -- Research, Business, Electronics, Electronics and electrical industries
Abstract

Insertion of a thin pseudomorphic InAlAg hole barrier layer having high Al content into the spacer of an InAlAs/InGaAs HEMT increases the valence band discontinuity and decreases the excess gate leakage current. Photocurrent and DC measurements help determine the efficiency of the hole barrier while Hall and RF measurements help determine the influence of hole barrier on transport characteristics. Experimental results show that impact ionization in the InGaAs channel is responsible for the excess gate leakage current.

Published
1994

48. 49.2-Tbit/s WDM Transmission Over 2x93-km Field-Deployed Fiber

Author

Schuh, Karsten, primary, Buchali, Fred, additional, Dischler, Roman, additional, Chagnon, Mathieu, additional, Aref, Vahid, additional, Buelow, Henning, additional, Hu, Qian, additional, Pulka, Florian, additional, Frascolla, Massimo, additional, Alhammadi, Esmaeel, additional, Samhan, Adel, additional, Younis, Islam, additional, El-Zonkoli, Mohamed, additional, and Winzer, Peter, additional

Published
2020
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