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  • 1.
    Deriushkina, Ekaterina
    et al.
    Chalmers University of Technology, Sweden.
    Rebolledo-Salgado, Israel
    RISE Research Institutes of Sweden, Safety and Transport, Measurement Technology. Chalmers University of Technology, Sweden.
    Mazur, Mikael
    Nokia Bell Labs, USA.
    Torres-Company, Victor
    Chalmers University of Technology, Sweden.
    Andrekson, Peter
    Chalmers University of Technology, Sweden.
    Schroder, Jochen
    Chalmers University of Technology, Sweden.
    Karlsson, Magnus
    Chalmers University of Technology, Sweden.
    Dual-Comb Swept-Wavelength Interferometry: Theory and Experiment2022In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 40, no 19, p. 6508-6516Article in journal (Refereed)
    Abstract [en]

    Much efforts have been put to elaborate and improve different high precision measurement schemes for characterization of advanced photonic devices and optical fibers with increasing bandwidth requirements. In light of this, swept-wavelength interferometry and dual-comb spectroscopy have been extensively applied in characterization procedures. In this paper we present in detail an experimental scheme that combines these two techniques and overcomes their limitations by using a tunable laser source in order to sweep over the frequency comb spacing and capture all intermediate frequencies. We demonstrate full-field broadband measurements over 1.25 THz comb bandwidth with increased frequency resolution, which can be performed in only 5 ms sweep. We also show that the nonlinearity of the laser sweep can be removed without an auxiliary interferometer in the setup. 

  • 2.
    Djupsjöbacka, Anders
    RISE, Swedish ICT, Acreo.
    On Differential Group-Delay Statistics for Polarization-Mode Dispersion Emulators2001In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 19, no 2, p. 285-Article in journal (Refereed)
  • 3. Djupsjöbacka, Anders
    et al.
    Sahlen, O.
    Dispersion compensation by differential time delay1994In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 12, no 10, p. 1849-1853Article in journal (Refereed)
    Abstract [en]

    A technique for optical pre- or postdistortion in order to compensate for fiber dispersion is discussed theoretically, The dispersion compensation device is based on differential time delay for the upper and the lower sideband of the modulated signal. The proposed scheme is primarily intended for high bit rate (>10 Gbit/s) time division multiplexed transmission, and in an ideal case the transmitting distance could be enhanced by a factor of 4 in a dispersive limited system. With more realistic demands on the dispersion compensation device, the gained distance is in the order of 2.5.

  • 4.
    Estarán, Jose
    et al.
    Nokia Bell Labs, France.
    Mardoyan, Haik
    Nokia Bell Labs, France.
    Jorge, Filipe
    Nokia Bell Labs, France.
    Ozolins, Oskars
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo.
    Udalcovs, Aleksejs
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo.
    Konczykowska, Agnieszka
    Nokia Bell Labs, France.
    Riet, Muriel
    Nokia Bell Labs, France.
    Duval, Bernadette
    Nokia Bell Labs, France.
    Nodjiadjim, Virginie
    Nokia Bell Labs, France.
    Dupuy, Jean Yves
    Nokia Bell Labs, France.
    Pang, Xiaodan
    KTH Royal Institute of Technology, Sweden.
    Westergren, Urban
    KTH Royal Institute of Technology, Sweden.
    Chen, Jiajia
    KTH Royal Institute of Technology, Sweden.
    Popov, Sergei
    KTH Royal Institute of Technology, Sweden.
    Bigo, Sebastien
    Nokia Bell Labs, France.
    140/180/204-Gbaud OOK Transceiver for Inter- and Intra-Data Center Connectivity2019In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 37, no 1, p. 178-187, article id 8500133Article in journal (Refereed)
    Abstract [en]

    We report on an on-off keying intensity-modulation and direct-detection C-band optical transceiver capable of addressing all datacenter interconnect environments at well-beyond 100Gbaud. For this, the transmitter makes use of two key InP technologies: a 2:1 double heterojunction bipolar transistor selector multiplexer and a monolithically integrated distributed-feedback laser traveling-wave electro-absorption modulator, both exceeding 100-GHz of 3-dB analog bandwidth. A pre-amplified 110-GHz PIN photodiode prior to a 100-GHz analog-to-digital converter complete the ultra-high bandwidth transceiver module; the device under study. In the experimental work, which discriminates between intra- and inter-data center scenarios (dispersion unmanaged 120, 560, 960m; and dispersion-managed 10, and 80km of standard singlemode fiber), we evaluate the bit-error rate evolution against the received optical power at 140, 180, and 204Gbaud on-off keying for different equalization configurations (adaptive linear filter with and without the help of short-memory sequence estimation) and forward error correction schemes (hard-decision codes with 7% and 20% overhead); drawing conclusions from the observed system-level limitations of the respective environments at this ultra-high baudrate, as well as from the operation margins and sensitivity metrics. From the demonstration, we highlight three results: successful operation with >6-dB sensitivity margin below the 7% error-correction at 140Gbaud over the entire 100m-80km range with only linear feed-forward equalization. Then the transmission of a 180Gbaud on-off-keying carrier over 80km considering 20% error-correction overhead. And finally, 10-km communication at 204Gbaud on-off keying with up to 6dB sensitivity margin, and regular 7%-overhead error-correction.

  • 5.
    Garcia-Ruiz, Andres
    et al.
    University of Alcala, Spain.
    Martins, Hugo
    University of Alcala, Spain.
    Magalhães, Regina
    University of Alcala, Spain.
    Pereira, Joao
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo.
    Tarasenko, Oleksandr
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo.
    Norin, Lars
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo.
    Margulis, Walter
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo.
    Martin-Lopez, Sonia
    University of Alcala, Spain.
    Gonzalez-Herraez, Miguel
    University of Alcala, Spain.
    Hermetic carbon coatings for electro-thermal all-fiber phase modulators2019In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 37, no 18, p. 4567-4572Article in journal (Refereed)
    Abstract [en]

    Joule effect and thermal response of several carbon coated fibers are modelled and analysed. An electro thermally driven all-fiber phase modulator based on these principles is proposed and a proof of concept of it is characterized. This kind of fibers could be the basis for developing all fiber components aimed to operate in environments where the strength increase and impermeability to hydrogen diffusion guaranteed by the carbon coating is crucial.

  • 6.
    Han, Mengyao
    et al.
    KTH Royal Institute of Technology, Sweden; Beijing Jiaotong University, China.
    Joharifar, Mahdieh
    KTH Royal Institute of Technology, Sweden.
    Wang, Muguang
    Beijing Jiaotong University, China.
    Schatz, Richard
    KTH Royal Institute of Technology, Sweden.
    Puerta, Rafael
    Ericsson, Sweden; KTH Royal Institute of Technology, Sweden.
    Sun, Yan-Ting
    KTH Royal Institute of Technology, Sweden.
    Fan, Yuchuan
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems. KTH Royal Institute of Technology, Sweden.
    Maisons, Gregory
    mirSense, France.
    Abautret, Johan
    mirSense, France.
    Roland, Roland
    mirSense, France.
    Zhang, Lu
    Zhejiang University, China.
    Spolitis, Sandis
    Riga Technical University, Latvia.
    Bobrovs, Vjaceslavs
    Riga Technical University, Latvia.
    Lourdudoss, Sebastian
    KTH Royal Institute of Technology, Sweden.
    Yu, Xianbin
    Zhejiang University, China.
    Popov, Sergei
    KTH Royal Institute of Technology, Sweden.
    Ozolins, Oskars
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems. KTH Royal Institute of Technology, Sweden.
    Pang, Xiaodan
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems. KTH Royal Institute of Technology, Sweden; Riga Technical University, Latvia.
    High Spectral Efficiency Long-wave Infrared Free-Space Optical Transmission with Multilevel Signals2023In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 41, no 20, p. 6514-Article in journal (Refereed)
    Abstract [en]

    This study explores the potential of long-wave infrared free-space optical (FSO) transmission that leverages multilevel signals to attain high spectral efficiency. The FSO transmission system consists of a directly modulated-quantum cascade laser (DM-QCL) operating at 9.15 μm and a mercury cadmium telluride (MCT) detector. To fully understand the system, we conduct measurements on the DM-QCL chip and MCT detector and assess the overall amplitude response of the DM-QCL, MCT detector, and all electrical components. We apply various signals, including on-off keying (OOK), 4-level pulse amplitude modulation (PAM4), 6-level PAM (PAM6), and 8-level PAM (PAM8) to maximize the bit rate and spectral efficiency of the FSO transmission. Through a two-dimensional sweeping of the laser bias current and MCT detector photovoltage, we optimize the transmission performance. At the optimal operation point, the FSO system achieved impressive results which are up to 6 Gbaud OOK, 3.5 Gbaud PAM4, 3 Gbaud PAM6, and 2.7 Gbaud PAM8 signal transmissions, with a bit error rate performance below 6.25% overhead hard decision-forward error correction limit when the DM-QCL operates at 10 °C. We also evaluate the eye diagrams and stability of the system to showcase its remarkable transmission performance. Our findings suggest that the DMQCL and MCT detector-based FSO transceivers offer a highly competitive solution for the next generation of optical wireless communication systems

  • 7.
    Irukulapati, Maga
    et al.
    Ericsson AB, Sweden.
    Secondini, Marco
    TeCIP Institute, Italy.
    Agrell, Erik
    Chalmers University of Technology, Sweden.
    Johannisson, Pontus
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Wymeersch, Henk
    Chalmers University of Technology, Sweden.
    Improved Lower Bounds on Mutual Information Accounting for Nonlinear Signal--Noise Interaction2018In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 36, no 22, p. 5152-5159Article in journal (Refereed)
    Abstract [en]

    In fiber-optic communications, evaluation of mutual information (MI) is still an open issue due to the unavailability of an exact and mathematically tractable channel model. Traditionally, lower bounds on MI are computed by approximating the (original) channel with an auxiliary forward channel. In this paper, lower bounds are computed using an auxiliary backward channel, which has not been previously considered in the context of fiber-optic communications. Distributions obtained through two variations of the stochastic digital backpropagation (SDBP) algorithm are used as auxiliary backward channels and these bounds are compared with bounds obtained through the conventional digital backpropagation (DBP). Through simulations, higher information rates were achieved with SDBP, which can be explained by the ability of SDBP to account for nonlinear signal--noise interactions

  • 8.
    Jia, Shi
    et al.
    Zhejiang University, China.
    Pang, Xiaodan
    KTH Royal Institute of Technology, Sweden.
    Ozolins, Oskars
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo.
    Yu, Xiobin
    Zhejiang University, China.
    Hu, Hao
    DTU Technical University of Denmark, Denmark.
    Yu, Jinlong
    Tianjin University, China.
    Guan, Pengyu
    DTU Technical University of Denmark, Denmark.
    Da Ros, Francesco
    DTU Technical University of Denmark, Denmark.
    Popov, Sergei
    KTH Royal Institute of Technology, Sweden.
    Jacobsen, Gunnar
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo.
    Galili, Michael
    DTU Technical University of Denmark, Denmark.
    Morioka, Toshio
    DTU Technical University of Denmark, Denmark.
    Zibar, Darko
    DTU Technical University of Denmark, Denmark.
    Oxenloewe, Leif K.
    DTU Technical University of Denmark, Denmark.
    0.4 THz Photonic-Wireless Link with 106 Gbit/s Single Channel Bitrate2018In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 36, no 2, p. 610-616Article in journal (Refereed)
    Abstract [en]

    To accommodate the demand of exponentially increased global wireless data traffic, the prospective data rates for wireless communication in the market place will soon reach 100 Gbit/s and beyond. In the lab environment, wireless transmission throughput has been elevated to the level of over 100 Gbit/s attributed to the development of photonic-assisted millimeter wave (MMW) and THz technologies. However, most of recent demonstrations with over 100 Gbit/s data rates are based on spatial or frequency division multiplexing techniques, resulting in increased system's complexity and energy consumption. Here, we experimentally demonstrate a single channel 0.4 THz photonic-wireless link achieving a net data rate of beyond 100 Gbit/s by using a single pair of THz emitter and receiver, without employing any spatial/frequency division multiplexing techniques. The high throughput up to 106 Gbit/s within a single THz channel is enabled by combining spectrally efficient modulation format, ultra-broadband THz transceiver and advanced digital signal processing (DSP) routine. Besides that, our demonstration from system-wide implementation viewpoint also features high transmission stability, and hence shows its great potential to not only decrease the system's complexity, but also meet the requirements of prospective data rates for bandwidth-hungry short-range wireless applications.

  • 9.
    Joharifar, Mahdieh
    et al.
    KTH Royal Institute of Technology, Sweden.
    Dely, Hamza
    Sorbonne University, France.
    Pang, Xiaodan
    KTH Royal Institute of Technology, Sweden.
    Schatz, Richard
    KTH Royal Institute of Technology, Sweden.
    Gacemi, Djamal
    Sorbonne University, France.
    Salgals, Toms
    Riga Technical University, Latvia.
    Udalcovs, Aleksejs
    RISE Research Institutes of Sweden, Digital Systems.
    Sun, Yan-Ting
    KTH Royal Institute of Technology, Sweden.
    Fan, Yuchuan
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems. KTH Royal Institute of Technology, Sweden.
    Zhang, Lu
    Zhejiang University, China.
    Rodriguez, Etienne
    Sorbonne University, France.
    Spolitis, Sandis
    Riga Technical University, Latvia.
    Bobrovs, Vjaceslavs
    Riga Technical University, Latvia.
    Yu, Xianbin
    Zhejiang University, China.
    Lourdudoss, Sebastian
    KTH Royal Institute of Technology, Sweden.
    Popov, Sergei
    KTH Royal Institute of Technology, Sweden.
    Vasanelli, Angela
    Sorbonne University, France.
    Ozolins, Oskars
    KTH Royal Institute of Technology, Sweden.
    Sirtori, Carlo
    Sorbonne University, France.
    High-Speed 9.6-μm Long-Wave Infrared Free- Space Transmission with a Directly-Modulated QCL and a Fully-Passive QCD2023In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 41, no 4, p. 1087-Article in journal (Refereed)
    Abstract [en]

    Free-space optics (FSO) in the mid-infrared (mid- IR) contains rich spectral resources for future ultrahigh-speed wireless communications yet is currently under-exploited. Two atmospheric transmission windows at the mid-IR, namely, the mid-wave IR (MWIR, 3-5 µm) and the long-wave IR (LWIR, 8-12 µm), show great potential in supporting free-space communications for both terrestrial and space application scenarios. Particularly, the LWIR signal with a longer wavelength has high intrinsic robustness against aerosols' scattering and turbulence-induced scintillation and beam broadening effects, which are the main concerns hindering the wide deployment of practical FSO systems. In this context, high-bandwidth semiconductor-based mid-IR FSO transceivers will be desirable to meet the requirements of low energy consumption and small footprints for large-volume development and deployment. Quantum cascade devices, including quantum cascade lasers (QCLs) and quantum cascade detectors (QCDs), appear promising candidates to fulfill this role. In this work, we report a high-speed LWIR FSO transmission demonstration with a 9.6-µm directly-modulated (DM)-QCL and a fully passive QCD without any active cooling or bias voltage. Up to 8 Gb/s, 10 Gb/s, and 11 Gb/s signal transmissions are achieved when operating the DM- QCL at 10°C, 5°C, and 0°C, respectively. These results indicate a significant step towards an envisioned fully-connected mid-IR FSO solution empowered by the quantum cascade semiconductor devices.

  • 10.
    Kerrebrouck, Joris Van
    et al.
    Ghent University, Belgium.
    Pang, Xiaodan
    KTH Royal Institute of Technology, Sweden.
    Ozolins, Oskars
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo.
    Lin, Rui
    Huazhong University of Science and Technology, China.
    Udalcovs, Aleksejs
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo.
    Zhang, Lu
    Shanghai Jiao Tong University, China.
    Li, Haolin
    Ghent University, Belgium.
    Spiga, Silvia
    Technical University of Munich, Germany.
    Amann, MC
    Technical University of Munich, Germany.
    Gan, Ling
    Huazhong University of Science and Technology, China.
    Tang, Ming
    Huazhong University of Science and Technology, China.
    Fu, Soignian
    Huazhong University of Science and Technology, China.
    Schatz, Rickhard
    KTH Royal Institute of Technology, Sweden.
    Jacobsen, Gunnar
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo.
    Popov, Sergei
    KTH Royal Institute of Technology, Sweden.
    Liu, Deming
    Huazhong University of Science and Technology, China.
    Tong, Weijun
    YOFC Yangtze Optical Fibre and Cable, China.
    Torfs, Guy
    Ghent University, Belgium.
    Bauwelinck, Johan
    Ghent University, Belgium.
    Chen, Jiajia
    KTH Royal Institute of Technology, Sweden.
    Yin, Xin
    Ghent University, Belgium.
    High-speed PAM4-based Optical SDM Interconnects with Directly Modulated Long-wavelength VCSEL2019In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 37, no 2, p. 356-362Article in journal (Refereed)
    Abstract [en]

    This paper reports the demonstration of high-speed PAM-4 transmission using a 1.5-μm single-mode vertical cavity surface emitting laser (SM-VCSEL) over multicore fiber with 7 cores over different distances. We have successfully generated up to 70 Gbaud 4-level pulse amplitude modulation (PAM-4) signals with a VCSEL in optical back-to-back, and transmitted 50 Gbaud PAM-4 signals over both 1-km dispersion-uncompensated and 10-km dispersion-compensated in each core, enabling a total data throughput of 700 Gbps over the 7-core fiber. Moreover, 56 Gbaud PAM-4 over 1-km has also been shown, whereby unfortunately not all cores provide the required 3.8 × 10<formula><tex>$^-3$</tex></formula>bit error rate (BER) for the 7% overhead-hard decision forward error correction (7% OH HDFEC). The limited bandwidth of the VCSEL and the adverse chromatic dispersion of the fiber are suppressed with pre-equalization based on accurate end-to-end channel characterizations. With a digital post-equalization, BER performance below the 7% OH-HDFEC limit is achieved over all cores. The demonstrated results show a great potential to realize high-capacity and compact short-reach optical interconnects for data centers.

  • 11.
    Li, Lianyi
    et al.
    Zhejiang University, China.
    Zhang, Lu
    Zhejiang University, China.
    Zhang, H
    Zhejiang University, China.
    Lyu, Z
    Zhejiang University, China.
    Yang, Z
    Zhejiang University, China.
    Pang, Xiaodan
    KTH Royal Institute of Technology, Sweden; Riga Technical University, Latvia.
    Bobrovs, Vjaceslavs
    Riga Technical University, Latvia.
    Ozolins, Oskars
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems. KTH Royal Institute of Technology, Sweden; Riga Technical University, Latvia.
    Zhao, H
    China Mobile (Hangzhou) Information Technology Co Ltd, China.
    Li, F
    China Mobile (Hangzhou) Information Technology Co Ltd, China.
    Zhang, C
    Zhejiang Lab, China.
    Yu, X
    Zhejiang Lab, China.
    THz-over-fiber System with Orthogonal Chirp Division Multiplexing for Integrated Sensing and Communication2024In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 42, no 1, p. 176-Article in journal (Refereed)
    Abstract [en]

    To achieve integrated sensing and communication (ISAC) applications with high data rates and high resolution, the terahertz-over-fiber (ToF) system has been recognized as a promising solution. However, the frequency-selective fading would deteriorate the performance of the ToF-based ISAC systems. In this work, we propose the orthogonal chirp division multiplexing (OCDM) waveform-based ToF system for high-performance ISAC applications. The system encodes data with the phase of the sub-chirps and obtains radar images by processing echoes with the zero-padded matched filtering algorithm. We experimentally demonstrate a proof-of-concept OCDM-ToF system, which simultaneously achieves a 32 Gbit/s data rate and 1.875 cm range resolution after transmission over a 10 km optical fiber and a 3.14 m wireless link at the THz band, for the first time. The experimental results indicate that the OCDM-ToF system can enhance robustness against the frequency-selective fading issue, as a benefit improving communication performance with high data rates while preserving the high sensing resolution of OFDM in the THz ISAC applications.

  • 12.
    Lyu, Z.
    et al.
    Zhejiang University, China.
    Zhang, L.
    Zhejiang University, China.
    Zhang, H.
    Zhejiang University, China.
    Yang, Z.
    Zhejiang University, China.
    Yang, H.
    Zhejiang University, China.
    Li, L.
    Zhejiang University, China.
    Zhang, C.
    Zhejiang Laboratory, China.
    Bobrovs, V.
    Riga Technical University, Latvia.
    Ozolins, Oskars
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems. Riga Technical University, Latvia; KTH Royal Institute of Technology, Sweden.
    Pang, Xiaodan
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems. KTH Royal Institute of Technology, Sweden.
    Yu, X.
    Zhejiang University, China; Zhejiang Laboratory, China.
    Preamble-Free Synchronization Based on Dual-chirp Waveforms for Photonic THz-ISAC2024In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 42, no 8, p. 2657-Article in journal (Refereed)
    Abstract [en]

    The integrated sensing and communication (ISAC) systems based on the linear frequency modulation (LFM) waveforms have attracted substantial attention. However, existing routines suffer from additional synchronization preamble overhead, which limits both communication and sensing performance. This work, using the dual-chirp with opposite slopes, exploits a preamble-free synchronization scheme for the LFM-based ISAC. We first theoretically analyze the quasi-orthogonal property of the proposed dual-chirp LFM waveform and derive its achievable communication rate and range ambiguity function. A photonics-assisted proof-of-concept ISAC experiment is conducted in the 300 GHz frequency band, achieving a 20 Gbps data rate with a distinguished peak sidelobe ratio (PSLR) of up to 29.2 dB and 1.5 cm range resolution. More importantly, less than 0.5% synchronous power overhead is needed in our scheme. In addition, the performance trade-off induced by the data rate and amplitude ratio is validated in the experiment, which is in line with our theoretical analysis. Therefore, the proposed scheme provides a promising solution for synchronizing LFM-based future ISAC systems.

  • 13.
    Navarro, Jaime Rodrigo
    et al.
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo.
    Kakkar, Aditya
    KTH Royal Institute of Technology, Sweden.
    Pang, Xiaodan
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo.
    Ozolins, Oskars
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo.
    Schatz, Richard
    KTH Royal Institute of Technology, Sweden.
    Olmedo, Miguel Iglesias
    KTH Royal Institute of Technology, Sweden.
    Jacobsen, Gunnar
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo.
    Popov, Sergei
    KTH Royal Institute of Technology, Sweden.
    Carrier Phase Recovery Algorithms for Coherent Optical Circular mQAM Systems2016In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 34, no 11, p. 2717-2723Article in journal (Refereed)
    Abstract [en]

    The phase noise tolerance of circular multilevel quadrature amplitude modulation (C-mQAM) constellations employing different carrier phase recovery (CPR) algorithms is studied. A differential decoding scheme and a bit mapping for this type of constellations are proposed. A novel CPR scheme for C-mQAM constellations is also presented. The particular distribution of the constellation points in a C-mQAM signal is exploited to reduce the required Nth power for the removal of the modulation component by a factor of two. Hence, the computational complexity of the proposed algorithm is drastically reduced. The combined linewidth symbol duration product (??Ts) tolerance of different CPR algorithms for C-mQAM constellations is studied and compared with the proposed CPR scheme. The results are analyzed at 3.8e-3 and 1e-2 bit error rate forward error correction limits. The proposed CPR scheme achieves similar ??Ts tolerance compared to single stage BPS algorithm while its computational complexity is reduced by group factors of 27.2 | 32.3, and 30.5 | 32.6 (in the form of multipliers | adders) for C-16QAM and C-64QAM, respectively.

  • 14.
    Ostrovskis, A.
    et al.
    Riga Technical University, Latvia.
    Salgals, T.
    Riga Technical University, Latvia.
    Krüger, B.
    Keysight Technologies GmbH, Germany.
    Pittalà, F.
    Keysight Technologies GmbH, Germany.
    Joharifar, M.
    KTH Royal Institute of Technology, Sweden.
    Schatz, Richard
    KTH Royal Institute of Technology, Sweden.
    Koenigsmann, M.
    Keysight Technologies GmbH, Germany.
    Fan, Yuchuan
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems.
    Chacinski, M.
    Coherent, Sweden.
    Westergren, U.
    KTH Royal Institute of Technology, Sweden.
    Zhang, L.
    Zhejiang University, China; Zhejiang Lab, China.
    Mardoyan, H.
    Nokia Bell Labs, France.
    Spolitis, S.
    Riga Technical University, Latvia.
    Popov, S.
    KTH Royal Institute of Technology, Sweden.
    Yu, X.
    Zhejiang University, China; Zhejiang Lab, China.
    Gruen, M.
    Keysight Technologies GmbH, Germany.
    Bobrovs, V.
    Riga Technical University, Latvia; .
    Louchet, H.
    Keysight Technologies GmbH, Germany.
    Pang, Xiaodan
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems. Riga Technical University, Latvia; KTH Royal Institute of Technology, Sweden.
    Ozolins, Oskars
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems.
    106.25 Gbaud On-Off Keying and Pulse Amplitude Modulation Links Supporting Next Generation Ethernet on Single Lambda2024In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 42, no 4, p. 1272-Article in journal (Refereed)
    Abstract [en]

    Development of Data Center based computing technology require energy efficient high-speed transmission links. This leads to optical amplification-free intensity modulation and direct detection (IM/DD) systems with low complexity equalization compliant with IEEE standardized electrical interfaces. Switching from on-off keying to multi-level pulse amplitude modulation would allow to reduce lane count for next generation Ethernet interfaces. We characterize 106.25 Gbaud on-off keying, 4-level and 6-level pulse amplitude modulation links using two integrated transmitters: O-band directly modulated laser and C-band externally modulated laser. Simple feed forward or decision feedback equalizer is used. We demonstrate 106.25 Gbaud on-off keying links operating without forward error correction for both transmitters. We also show 106.25 Gbaud 4-level and 6-level pulse amplitude modulation links with performance below 6.25% overhead hard-decision forward error threshold of 4.5×10-3. Furthermore, for EML-based transmitter we achieve 106.25 Gbaud 4-level pulse amplitude modulation performance below KP-FEC threshold of 2.2×10-4. That shows that we can use optics to support (2x)100 Gbps Ethernet on single lambda at expense of simple forward error correction.

  • 15.
    Ozolins, Oskars
    et al.
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems.
    Joharifar, Mahdieh
    KTH Royal Institute of Technology, Sweden.
    Salgals, Toms
    Riga Technical University, Latvia.
    Louchet, Hadrien
    Keysight Technologies GmbH, Germany.
    Schatz, Richard
    KTH Royal Institute of Technology, Sweden.
    Gruen, Markus
    Keysight Technologies GmbH, Germany.
    Dippon, Thomas
    Keysight Technologies GmbH, Germany.
    Kruger, Benjamin
    Keysight Technologies GmbH, Germany.
    Pittala, Fabio
    Keysight Technologies GmbH, Germany.
    Che, Di
    Nokia Bell Labs, USA.
    Matsui, Yasuhiro
    II-VI Incorporated, USA.
    Fan, Yuchuan
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems. KTH Royal Institute of Technology, Sweden.
    Udalcovs, Aleksejs
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems.
    Westergren, Urban
    KTH Royal Institute of Technology, Sweden.
    Zhang, Lu
    Zhejiang Universitsy, China.
    Yu, Xianbin
    Zhejiang Universitsy, China.
    Spolitis, Sandis
    Riga Technical University, Latvia.
    Bobrovs, Vjaceslavs
    Riga Technical University, Latvia.
    Popov, Sergei
    KTH Royal Institute of Technology, Sweden.
    Pang, Xiaodan
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems. KTH Royal Institute of Technology, Sweden.
    Optical Amplification-Free High Baudrate Links for Intra-Data Center Communications2023In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213Article in journal (Refereed)
    Abstract [en]

    The enormous traffic growth sets a stringent requirement to upgrade short-reach optical links to 1.6 TbE capacity in an economically viable way. The power consumption and latency in these links should be as low as possible, especially for high-speed computing. This is possible to achieve using high baudrate on-off keying links thanks to a better noise tolerance and a relaxed requirement on linearity for electronics and photonics. In this regard, we demonstrate a 200 Gbaud on-off keying link without any optical amplification using an externally modulated laser with 3.3 dBm of modulated output power operating at 1541.25 nm wavelength. We achieve transmission over 200 meters of single-mode fiber with performance below 6.25% overhead hard-decision forward error correction threshold for each baudrate and all selection of modulation formats. We also show 108 Gbaud on-off keying link with superior performance without decision feedback equalizer up to 400 meters of single-mode fiber. In addition, we benchmark the short-reach optical link with 112 Gbaud four-level pulse amplitude modulation and 100 Gbaud six-level pulse amplitude modulation. For 108 Gbaud on-off keying and 112 Gbaud four-level pulse amplitude modulation, we can achieve an even lower bit error rate.

  • 16.
    Ozolins, Oskars
    et al.
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo.
    Pang, Xiaodan
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo.
    Olmedo, Miguel Iglesias
    KTH Royal Institute of Technology, Sweden.
    Kakkar, Aditya
    KTH Royal Institute of Technology, Sweden.
    Udalcovs, Aleksejs
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo.
    Gaiarin, Simone
    KTH Royal Institute of Technology, Sweden.
    Navarro, Javier Rodrigo
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo.
    Engenhardt, Klaus M.
    Tektronix GmbH, Germany.
    Asyngier, Tadeusz
    Tektronix GmbH, Germany.
    Schatz, Richard
    KTH Royal Institute of Technology, Sweden.
    Li, Jie
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo.
    Nordwall, Fredrik
    Tektronix AB, Sweden.
    Westergren, Urban
    KTH Royal Institute of Technology, Sweden.
    Zibar, Darko
    DTU Technical University of Denmark, Denmark.
    Popov, Sergei
    KTH Royal Institute of Technology, Sweden.
    Jacobsen, Gunnar
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo.
    100 GHz Externally Modulated Laser for Optical Interconnects2017In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 35, no 6, p. 1174-1179, article id 7814142Article in journal (Refereed)
    Abstract [en]

    We report on a 116 Gb/s on-off keying (OOK), four pulse amplitude modulation (PAM) and 105-Gb/s 8-PAM optical transmitter using an InP-based integrated and packaged externally modulated laser for high-speed optical interconnects with up to 30 dB static extinction ratio and over 100-GHz 3-dB bandwidth with 2 dB ripple. In addition, we study the tradeoff between power penalty and equalizer length to foresee transmission distances with standard single mode fiber.

  • 17.
    Pang, Xiaodan
    et al.
    RISE, Swedish ICT, Acreo. DTU Technical University of Denmark, Denmark.
    Lebedev, Alexander
    DTU Technical University of Denmark, Denmark.
    Olmos, J. J. Vegas
    DTU Technical University of Denmark, Denmark.
    Monroy, Idelfonso Tafur
    DTU Technical University of Denmark, Denmark.
    Multigigabit W-Band (75-110 GHz) Bidirectional Hybrid Fiber-Wireless Systems in Access Networks2014In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 32, no 23, p. 3983-3990Article in journal (Refereed)
    Abstract [en]

    We experimentally demonstrate multigigabit capacity bidirectional hybrid fiber-wireless systems with RF carrier frequencies at the W-band (75-110 GHz) that enables the seamless convergence between wireless and fiber-optic data transmission systems in access networks. In this study, we evaluate the transmission performances in two scenarios: a fiber-wireless access link that directly provide high-speed connections to wireless end users, and a fiber-wireless-fiber signal relay where a high capacity wireless link can be used to bridge two access fiber spans over physical obstacles. In both scenarios, we compare the transmission performances in terms of achievable wireless distances with and without using a high-frequency electrical power amplifier at the wireless transmitter. A downlink 16-Gbit/s QPSK signal and an uplink 1.25-Gbit/s ASK signal transmission over the two implementations are experimentally evaluated in terms of bit-error-rate (BER) performance. Results show that the use of the power amplifier can extend the wireless distance from similar to 1 m to over 15 m in an indoor environment with BER performance within the7% FEC threshold.

  • 18.
    Pang, Xiaodan
    et al.
    KTH Royal Institute of Technology, Sweden.
    Ozolins, Oskars
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems.
    Jia, Shi
    DTU Technical University of Denmark, Denmark.
    Zhang, Lu
    Zhejiang University, China.
    Schatz, Richard
    KTH Royal Institute of Technology, Sweden.
    Udalcovs, Aleksejs
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems.
    Bobrovs, Vjaceslavs
    Riga Technical University, Latvia.
    Hu, H.
    DTU Technical University of Denmark, Denmark.
    Morioka, T.
    DTU Technical University of Denmark, Denmark.
    Sun, Y.
    KTH Royal Institute of Technology, Sweden.
    Chen, Jiajia
    Chalmers University of Technology, Sweden.
    Lourdudoss, S.
    KTH Royal Institute of Technology, Sweden.
    Oxenloewe, L. K.
    DTU Technical University of Denmark, Denmark.
    Popov, Sergei
    KTH Royal Institute of Technology, Sweden.
    Yu, X.
    Zhejiang University, China.
    Bridging the Terahertz Gap: Photonics-assisted Free-Space Communications from the Submillimeter-Wave to the Mid-Infrared2022In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 40, no 10, p. 3149-3162Article in journal (Refereed)
    Abstract [en]

    Since about one and half centuries ago, at the dawn of modern communications, the radio and the optics have been two separate electromagnetic spectrum regions to carry data. Differentiated by their generation/detection methods and propagation properties, the two paths have evolved almost independently until today. The optical technologies dominate the long-distance and high-speed terrestrial wireline communications through fiber-optic telecom systems, whereas the radio technologies have mainly dominated the short- to medium-range wireless scenarios. Now, these two separate counterparts are both facing a sign of saturation in their respective roadmap horizons, particularly in the segment of free-space communications. The optical technologies are extending into the mid-wave and long-wave infrared (MWIR and LWIR) regimes to achieve better propagation performance through the dynamic atmospheric channels. Radio technologies strive for higher frequencies like the millimeter-wave (MMW) and sub-terahertz (sub-THz) to gain broader bandwidth. The boundary between the two is becoming blurred and intercrossed. During the past few years, we witnessed technological breakthroughs in free-space transmission supporting very high data rates, many achieved with the assistance of photonics. This paper focuses on such photonics-assisted free-space communication technologies in both the lower and upper sides of the THz gap and provides a detailed review of recent research and development activities on some of the key enabling technologies. Our recent experimental demonstrations of high-speed free-space transmissions in both frequency regions are also presented as examples to show the system requirements for device characteristics and digital signal processing (DSP) performance.

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  • 19.
    Pang, Xiaodan
    et al.
    KTH Royal Institute of Technology, Sweden.
    Ozolins, Oskars
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems.
    Lin, Rui
    Chalmers University of Technology, Sweden.
    Zhang, L.
    Shanghai Jiao Tong University, China.
    Udalcovs, Aleksejs
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems.
    Xue, L.
    Chalmers University of Technology, Sweden.
    Schatz, R.
    KTH Royal Institute of Technology, Sweden.
    Westergren, U.
    KTH Royal Institute of Technology, Sweden.
    Xiao, S.
    Shanghai Jiao Tong University, China.
    Hu, W.
    Shanghai Jiao Tong University, China.
    Jacobsen, Gunnar
    RISE Research Institutes of Sweden.
    Popov, S.
    KTH Royal Institute of Technology, Sweden.
    Chen, J.
    Chalmers University of Technology, Sweden.
    200 Gbps/lane IM/DD Technologies for Short Reach Optical Interconnects2020In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 38, no 2Article in journal (Refereed)
    Abstract [en]

    Client-side optics are facing an ever-increasing upgrading pace, driven by upcoming 5G related services and datacenter applications. The demand for a single lane data rate is soon approaching 200 Gbps. To meet such high-speed requirements, all segments of traditional intensity modulation direct detection (IM/DD) technologies are being challenged. The characteristics of electrical and optoelectronic components, and the performance of modulation, coding and digital signal processing (DSP) techniques are being stretched to their limits. In this context, we witnessed technological breakthroughs in several aspects, including development of broadband devices, novel modulation formats and coding, and high-performance DSP algorithms for the past few years. A great momentum has been accumulated to overcome the aforementioned challenges. In this paper, we focus on IM/DD transmissions, and provide an overview of recent research and development efforts on key enabling technologies for 200 Gbps per lane and beyond. Our recent demonstrations of 200 Gbps short-reach transmissions with 4-level pulse amplitude modulation (PAM) and discrete multitone signals are also presented as examples to show the system requirements in terms of device characteristics and DSP performance. Apart from digital coherent technologies and advanced direct detection systems, such as Stokes-vector and Kramers-Kronig schemes, we expect high-speed IM/DD systems will remain advantageous in terms of system cost, power consumption and footprint for short reach applications in the short- to mid- term perspective.

  • 20.
    Pang, Xiaodan
    et al.
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems. KTH Royal Institute of Technology, Sweden.
    Salgals, Toms
    Riga Technical University, Latvia.
    Louchet, Hadrien
    Keysight Technologies GmbH, Germany.
    Che, Di
    Nokia Bell Labs, USA.
    Gruen, Markus
    Keysight Technologies GmbH, Germany.
    Matsui, Yasuhiro
    Nokia Bell Labs, USA.
    Dippon, Thomas
    Keysight Technologies GmbH, Germany.
    Schatz, Richard
    KTH Royal Institute of Technology, Sweden.
    Joharifar, Mahdieh
    KTH Royal Institute of Technology, Sweden.
    Kruger, Benjamin
    Keysight Technologies GmbH, Germany.
    Pittala, Fabio
    Keysight Technologies GmbH, Germany.
    Fan, Yuchuan
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems.
    Udalcovs, Aleksejs
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems.
    Zhang, Lu
    Zhejiang University, China; Zhejiang Lab, China.
    Yu, Xianbin
    Zhejiang University, China; Zhejiang Lab, China.
    Spolitis, Sandis
    Riga Technical University, Latvia.
    Bobrovs, Vjaceslavs
    Riga Technical University, Latvia.
    Popov, Sergei
    KTH Royal Institute of Technology, Sweden.
    Ozolins, Oskars
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems. KTH Royal Institute of Technology, Sweden.
    200 Gb/s Optical-Amplifier-Free IM/DD Transmissions using a Directly Modulated O-band DFB+R Laser targeting LR Applications2023In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 41, no 11, p. 3635-Article in journal (Refereed)
    Abstract [en]

    We experimentally demonstrate an O-band single-lane 200 Gb/s intensity modulation direct detection (IM/DD) transmission system using a low-chirp, broadband, and high-power directly modulated laser (DML). The employed laser is an isolator-free packaged module with over 65-GHz modulation bandwidth enabled by a distributed feedback plus passive waveguide reflection (DFB+R) design. We transmit high baud rate signals over 20-km standard single-mode fiber (SSMF) without using any optical amplifiers and demodulate them with reasonably low-complexity digital equalizers. We generate and detect up to 170 Gbaud non-return-to-zero on-off-keying (NRZ-OOK), 112 Gbaud 4-level pulse amplitude modulation (PAM4), and 100 Gbaud PAM6 in the optical back-to-back configuration. After transmission over the 20-km optical-amplifier-free SSMF link, up to 150 Gbaud NRZ-OOK, 106 Gbaud PAM4, and 80 Gbaud PAM6 signals are successfully received and demodulated, achieving bit error rate (BER) performance below the 6.25%-overhead hard-decision (HD) forward-error-correction code (FEC) limit. The demonstrated results show the possibility of meeting the strict requirements towards the development of 200Gb/s/lane IM/DD technologies, targeting 800Gb/s and 1.6Tb/s LR applications.

  • 21.
    Pang, Xiaodan
    et al.
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems. KTH Royal Institute of Technology, Sweden.
    Schatz, Richard
    KTH Royal Institute of Technology, Sweden.
    Joharifar, Mahdieh
    KTH Royal Institute of Technology, Sweden.
    Udalcovs, Aleksejs
    RISE Research Institutes of Sweden, Digital Systems.
    Bobrovs, Vjaceslavs
    Riga Technical University, Latvia.
    Zhang, Lu
    Zhejiang University, China.
    Yu, Xianbin
    Zhejiang Lab, China; MirSense, France.
    Sun, Yan-Ting
    KTH Royal Institute of Technology, Sweden.
    Maisons, Gregory
    MirSense, France.
    Carras, Mathieu
    MirSense, France.
    Popov, Sergei
    KTH Royal Institute of Technology, Sweden.
    Lourdudoss, Sebastian
    KTH Royal Institute of Technology, Sweden.
    Ozolins, Oskars
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems. KTH Royal Institute of Technology, Sweden; Riga Technical University, Latvia.
    Direct Modulation and Free-Space Transmissions of up to 6 Gbps Multilevel Signals With a 4.65-μQuantum Cascade Laser at Room Temperature2022In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 40, no 8, p. 2370-2377Article in journal (Refereed)
    Abstract [en]

    A roadmap for future wireless communications is expected to exploit all transmission-suitable spectrum bands, from the microwave to the optical frequencies, to support orders of magnitude faster data transfer with much lower latency than the deployed solutions nowadays. The currently under-exploited mid-infrared (mid-IR) spectrum is an essential building block for such an envisioned all-spectra wireless communication paradigm. Free-space optical (FSO) communications in the mid-IR region have recently attracted great interest due to their intrinsic merits of low propagation loss and high tolerance of atmospheric perturbations. Future development of viable mid-IR FSO transceivers requires a semiconductor source to fulfill the high bandwidth, low energy consumption, and small footprint requirements. In this context, quantum cascade laser (QCL) appears as a promisingtechnological choice. In this work, we present an experimental demonstration of a mid-IR FSO link enabled by a 4.65-μm directly modulated (DM) QCL operating at room temperature. We achieve a transmission data rate of up to 6 Gbps over a 0.5-m link distance. This achievement is enabled by system-level characterization and optimization of transmitter and receiver power level and frequency response and assisted with advanced modulation and digital signal processing (DSP) techniques. This work pushes the QCL-based FSO technology one step closer to practical terrestrial applications, such as the fixed wireless access and the wireless mobile backhaul. Such a QCL-based solution offers a promising way towards the futuristic all-spectra wireless communication paradigm by potentially supporting the whole spectrum from the MIR to the terahertz (THz). 

  • 22.
    Quintana, Crisanto
    et al.
    Airbus, UK.
    Wang, Qin
    RISE Research Institutes of Sweden, Digital Systems, Smart Hardware.
    Jakonis, Darius
    RISE Research Institutes of Sweden, Digital Systems, Smart Hardware.
    Öberg, Olof
    RISE Research Institutes of Sweden, Digital Systems, Smart Hardware.
    Erry, Gavin
    Airbus, UK.
    Platt, Duncan
    RISE Research Institutes of Sweden, Digital Systems, Smart Hardware.
    Thueux, Yoann
    Airbus, UK.
    Faulkner, Graham
    University of Oxford, UK.
    Chun, Hyunchae
    Incheon National University, Korea.
    Gomez, Ariel
    Microsoft Research Cambridge, UK.
    Salter, Michael
    RISE Research Institutes of Sweden, Digital Systems, Smart Hardware.
    O'Brien, Dominic
    University of Oxford, UK.
    A high speed retroreflective free space optics links with UAV2021In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 39, no 18, p. 5699-5705Article in journal (Refereed)
    Abstract [en]

    In this work we report the design and implementation of a very high speed retroreflective free space communication system between a ground station and a commercial unmanned aerial vehicle (UAV). The system uses a pixelated electro-absorption modulator (EAM) modulating retroreflector (MRR) to establish a data link operating at 500 Mbps at a range of 560 m and a bit error rate (BER) of 7.610-4. The MRR provides an effective aperture of 11mm and full field of view (FFOV) of 6.4. To the best of our knowledge, this is the fastest demonstration of an outdoor link of this type. In this paper the design and implementation of the system is described, as well as results from experimental trials.

  • 23. Thylen, L.
    et al.
    Djupsjöbacka, Anders
    Ericsson, Sweden.
    Bandpass response traveling-wave modulator with a transit time difference compensation scheme1985In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 3, no 1, p. 47-51Article in journal (Refereed)
    Abstract [en]

    We propose and analyze a new traveling-wave modulator, where the bandwidth limiting effects of walk off between the microwave and the optical wave is compensated by a drive signal polarity reversal scheme thus significantly enhancing the achievable bandwidth, at the expense of baseband response.

  • 24.
    Udalcovs, Aleksejs
    et al.
    KTH Royal Institute of Technology, Sweden.
    Schatz, Richard
    RISE - Research Institutes of Sweden, ICT, Acreo. KTH Royal Institute of Technology, Sweden.
    Wosinska, Lena
    KTH Royal Institute of Technology, Sweden.
    Monti, Paolo
    KTH Royal Institute of Technology, Sweden.
    Analysis of Spectral and Energy Efficiency Tradeoff in Single-Line Rate WDM Links2017In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 35, no 10, p. 1847-1857, article id 7812686Article in journal (Refereed)
    Abstract [en]

    This paper investigates, through simulations, the tradeoff between energy efficiency (EE) and the overall spectral efficiency (SE) of fiber optic links for a given capacity and a link length. The comparison is made for various modulation formats, span lengths, and with/without using forward error correction (FEC). The power consumption of the different system components is estimated from the data sheets of the state-of-the-art equipment. Results show that the use of long single-mode fiber spans (i.e., more than 40 km) improves EE when coherent modulation formats are used. However, with noncoherent formats, the span length must be selected depending on SE, aggregated traffic amount needs to be transmitted, and link length. For almost all modulation formats, FEC reduces the overall energy consumption despite being one of the main power consumers in fiber optic communication systems. The power consumption of 3Rs becomes particularly important when the linear crosstalk limits the system reach. In all other cases, the power consumption of transponders and optical line amplifiers is dominating, but their contribution changes depending on the aggregated traffic amount and system reach.

  • 25.
    Verplaetse, Michiel
    et al.
    Ghent University, Belgium.
    Lin, Rui
    KTH Royal Institute of Technology, Sweden.
    Van Kerrebrouck, Joris
    Ghent University, Belgium.
    Ozolins, Oskars
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo.
    De Keulenaer, Timothy
    Ghent University, Belgium.
    Pang, Xiaodan
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo.
    Pierco, Ramses
    Ghent University, Belgium.
    Vaernewyck, Renato
    Ghent University, Belgium.
    Vyncke, Arno
    Ghent University, Belgium.
    Schatz, Richard
    KTH Royal Institute of Technology, Sweden.
    Westergren, Urban
    KTH Royal Institute of Technology, Sweden.
    Jacobsen, Gunnar
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo.
    Popov, Sergei
    KTH Royal Institute of Technology, Sweden.
    Chen, Jiajia
    KTH Royal Institute of Technology, Sweden.
    Torfs, Guy
    Ghent University, Belgium.
    Bauwelinck, Johan
    Ghent University, Belgium.
    Yin, Xin
    Ghent University, Belgium.
    Real-Time 100 Gb/s Transmission Using Three-Level Electrical Duobinary Modulation for Short-Reach Optical Interconnects2017In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 35, no 7, p. 1313-1319, article id 7795163Article in journal (Refereed)
    Abstract [en]

    Electrical duobinary modulation is considered as a promising way to realize high capacity because of the low bandwidth requirement on the optical/electrical components and high tolerance toward chromatic dispersion. In this paper, we demonstrate a 100 Gb/s electrical duobinary transmission over 2 km standard single-mode fiber reaching a bit error rate under 7% HD-FEC threshold with the use of PRBS7. This link is tested in real-time without any form of digital signal processing. In-house developed SiGe BiCMOS transmitter and receiver ICs are used to drive an electroabsorption modulated laser and decode the received signal from a PIN-photodiode. The performance of 50 and 70 Gb/s nonreturn-to-zero and electrical duobinary transmission are investigated for comparison.

  • 26.
    Zhang, Lu
    et al.
    Shanghai Jiao Tong University, China.
    Kerrebrouck, Joris Van
    Universiteit Gent, Belgium.
    Lin, Rui
    Huazhong University of Science and Technology, China.
    Pang, Xiaodan
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo.
    Udalcovs, Aleksejs
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo.
    Ozolins, Oskars
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo.
    Spiga, Silvia
    Technical University of Munich, Germany.
    Amann, M. C.
    Technical University of Munich, Germany.
    Steenberge, Geert Van
    Ghent University, Belgium.
    Gan, Lin
    Huazhong University of Science and Technology, China.
    Tang, Ming
    Huazhong University of Science and Technology, China.
    Fu, Songnian
    Huazhong University of Science and Technology, China.
    Schatz, Richard
    KTH Royal Institute of Technology, Sweden.
    Popov, Sergei
    KTH Royal Institute of Technology, Sweden.
    Liu, Deming
    Huazhong University of Science and Technology, China.
    Tong, Weijun
    YOFC Yangtze Optical Fibre and Cable, China.
    Xiao, Shilin
    Shanghai Jiao Tong University, China.
    Torfs, Guy
    Ghent University, Belgium.
    Chen, Jiajia
    KTH Royal Institute of Technology, Sweden.
    Bauwelinck, Johan
    Ghent University, Belgium.
    Yin, Xin
    Ghent University, Belgium.
    Nonlinearity Tolerant High-speed DMT Transmission with 1.5-μm Single-mode VCSEL and Multi-core Fibers for Optical Interconnects2019In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 37, no 2, p. 380-388Article in journal (Refereed)
    Abstract [en]

    We experimentally demonstrate the generation of 107-Gbit/s net-rate optical discrete multitone (DMT) signal using a 1.5-&amp;#x03BC;m single-mode vertical cavity surface emitting laser (VCSEL) with modulation bandwidth of 22-GHz. Utilizing a nonlinearity-tolerant channel equalization algorithm for digital signal processing (DSP), total net-rates of 726.6-Gbit/s over 2.5-km dispersion-uncompensated 7-core fiber and 533.1-Gbit/s over 10-km dispersion-compensated 7-core fiber below 7% overhead hard-decision forward error correction (HD-FEC) limit have been experimentally achieved with a 1.5-&amp;#x03BC;m VCSEL based intensity-modulation direct-detection (IM/DD) system. The features of the 1.5-&amp;#x03BC;m single-mode VCSEL, 2.5-km/10km multi-core fibers and fan-in/fan-out modules are presented. Besides, the Volterra series based nonlinearity-tolerant channel equalization algorithm, which improves the signal-to-noise ratio (SNR) with more than 5-dB, is mathematically described and experimentally validated. The results have demonstrated that 1.5-&amp;#x03BC;m single-mode VCSEL and multi-core fiber based transmission can be a promising candidate to solve the capacity challenges in short-reach optical interconnects.

  • 27.
    Öhlén, Peter
    et al.
    Ericsson Research, Sweden.
    Skubic, Björn
    Ericsson Research, Sweden.
    Rostami, Ahmad
    Ericsson Research, Sweden.
    Fiorani, Matteo
    RISE, Swedish ICT, Acreo, Broadband Technology. KTH Royal Institute of Technology, Sweden.
    Monti, Paolo
    RISE, Swedish ICT, Acreo, Broadband Technology. KTH Royal Institute of Technology, Sweden.
    Ghebretensaé, Zere
    Ericsson Research, Sweden.
    Mårtensson, Jonas
    RISE, Swedish ICT, Acreo.
    Wang, Kun
    RISE, Swedish ICT, Acreo.
    Wosinska, Lena
    RISE, Swedish ICT, Acreo, Broadband Technology. KTH Royal Institute of Technology, Sweden.
    Data Plane and Control Architectures for 5G Transport Networks2016In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 34, no 6, p. 1501-1508Article in journal (Refereed)
    Abstract [en]

    Next generation 5G mobile system will support the vision of connecting all devices that benefit from a connection, and support a wide range of services. Consequently, 5G transport networks need to provide the required capacity, latency, and flexibility in order to integrate the different technology domains of radio, transport, and cloud. This paper outlines the main challenges, which the 5G transport networks are facing and discusses in more detail data plane, control architectures, and the tradeoff between different network abstraction models.

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