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  • 1.
    Al-Awis, Suhail Najm
    et al.
    University of Technology, Iraq.
    Schatz, Richard
    KTH Royal Institute of Technology, Sweden.
    Pang, Xiaodan
    RISE, Swedish ICT, Acreo.
    Ozolins, Oskars
    RISE, Swedish ICT, Acreo.
    Jacobsen, Gunnar
    RISE, Swedish ICT, Acreo. KTH Royal Institute of Technology, Sweden.
    Popov, Sergei
    KTH Royal Institute of Technology, Sweden.
    Fattah, Ali Y.
    University of Technology, Iraq.
    Chen, Jiajia
    KTH Royal Institute of Technology, Sweden.
    Phenomenological Formula for Modelling of Physical Layer Impairments in Elastic Optical Networks2015In: Asia Communications and Photonics Conference 2015, 2015, article id ASu2A.75Conference paper (Refereed)
    Abstract [en]

    An empirical modelling technique is introduced to estimate impact of physical layer impairments in elastic optical networks, which can be used to evaluate transmission quality. The model has been verified experimentally with accuracy beyond (97.3%).

  • 2.
    Brunnström, Kjell
    et al.
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems. Mid Sweden University, Sweden.
    Djupsjöbacka, Anders
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems.
    Billingham, Johsan
    FIFA Fédération Internationale de Football Association, Switzerland.
    Wistel, Katharina
    FIFA Fédération Internationale de Football Association, Switzerland.
    Andrén, Börje
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems.
    Ozolins, Oskars
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems.
    Evans, Nicolas
    FIFA Fédération Internationale de Football Association, Switzerland.
    Video expert assessment of high quality video for Video Assistant Referee (VAR): A comparative study2023In: Multimedia tools and applications, ISSN 1380-7501, E-ISSN 1573-7721Article in journal (Refereed)
    Abstract [en]

    The International Football Association Board decided to introduce Video Assistant Referee (VAR) in 2018. This led to the need to develop methods for quality control of the VAR-systems. This article focuses on the important aspect to evaluate the video quality. Video Quality assessment has matured in the sense that there are standardized, commercial products and established open-source solutions to measure it with objective methods. Previous research has primarily focused on the end-user quality assessment. How to assess the video in the contribution phase of the chain is less studied. The novelties of this study are two-fold: 1) The user study is specifically targeting video experts i.e., to assess the perceived quality of video professionals working with video production. 2) Six video quality models have been independently benchmarked against the user data and evaluated to show which of the models could provide the best predictions of perceived quality. The independent evaluation is important to get unbiased results as shown by the Video Quality Experts Group. An experiment was performed involving 25 video experts in which they rated the perceived quality. The video formats tested were High-Definition TV both progressive and interlaced as well as a quarters size format that was scaled down half the size in both width and height. The videos were encoded with both H.264 and Motion JPEG for the full size but only H.264 for the quarter size. Bitrates ranged from 80 Mbit/s down to 10 Mbit/s. We could see that for H.264 that the quality was overall very good but dropped somewhat for 10 Mbit/s. For Motion JPEG the quality dropped over the whole range. For the interlaced format the degradation that was based on a simple deinterlacing method did receive overall low ratings. For the quarter size three different scaling algorithms were evaluated. Lanczos performed the best and Bilinear the worst. The performance of six different video quality models were evaluated for 1080p and 1080i. The Video Quality Metric for Variable Frame Delay had the best performance for both formats, followed by Video Multimethod Assessment Fusion method and the Video Quality Metric General model. 

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  • 3.
    Brunnström, Kjell
    et al.
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems. Mid Sweden University, Sweden.
    Djupsjöbacka, Anders
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems.
    Billingham, Johsan
    FIFA Fédération Internationale de Football Association, Switzerland.
    Wistel, Katharina
    FIFA Fédération Internationale de Football Association, Switzerland.
    Andrén, Börje
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems.
    Ozolins, Oskars
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems. KTH Royal Institute of Technology, Sweden.
    Evans, Nicolas
    FIFA Fédération Internationale de Football Association, Switzerland.
    Video quality of video professionals for Video Assisted Referee (VAR)2023In: IS and T International Symposium on Electronic Imaging Science and Technology, ISSN 2470-1173, Vol. 35, no 10, article id 259Article in journal (Refereed)
    Abstract [en]

    Changes in the footballing world’s approach to technology and innovation contributed to the decision by the International Football Association Board to introduce Video Assistant Referees (VAR). The change meant that under strict protocols referees could use video replays to review decisions in the event of a "clear and obvious error" or a "serious missed incident". This led to the need by Fédération Internationale de Football Association (FIFA) to develop methods for quality control of the VAR-systems, which was done in collaboration with RISE Research Institutes of Sweden AB. One of the important aspects is the video quality. The novelty of this study is that it has performed a user study specifically targeting video experts i.e., to measure the perceived quality of video professionals working with video production as their main occupation. An experiment was performed involving 25 video experts. In addition, six video quality models have been benchmarked against the user data and evaluated to show which of the models could provide the best predictions of perceived quality for this application. Video Quality Metric for variable frame delay (VQM_VFD) had the best performance for both formats, followed by Video Multimethod Assessment Fusion (VMAF) and VQM General model.

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  • 4.
    Brunnström, Kjell
    et al.
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems. Mid Sweden University, Sweden.
    Djupsjöbacka, Anders
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems.
    Ozolins, Oskars
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems. KTH Royal Institute of Technology, Sweden.
    Billingham, Johsan
    FIFA Fédération Internationale de Football Association, Switzerland.
    Wistel, Katarina
    FIFA Fédération Internationale de Football Association, Switzerland.
    Evans, Nicolas
    FIFA Fédération Internationale de Football Association, Switzerland.
    Quality measurement methods for video assisting refereeing systems2023In: Sports Engineering, ISSN 1369-7072, E-ISSN 1460-2687, Vol. 26, no 1, article id 17Article in journal (Refereed)
    Abstract [en]

    Changes in the footballing world’s approach to technology and innovation, along with major advancements in broadcasting contributed to the decision by the International Football Association Board to introduce Video Assistant Referees in 2018. The change meant that under strict protocols referees could use video replays to review decisions in the event of a “clear and obvious error” or a “serious missed incident”. At the time of writing 48-Member Associations have introduced the Video Assistant Referees protocol in at least one of their tournaments and there are many technology providers who work with organisers to implement the Video Assistant Referees systems. To ensure that the use of Video Assistant Referees has a positive effect on the game, Fédération Internationale de Football Association collaborated with the RISE Research Institutes of Sweden to develop objective test methods that could be used to ensure that a system can provide an adequate solution. Each provider must be able to pass requirements that ensure that they can deal with the challenges of processing, coding, decoding, synchronising, and re-formatting of the broadcast feeds. This article will describe the development of the test methods and illustrate some initial results from a test event on Video Assistant Referees system candidates. The methods have shown to be robust and appropriate for their intended purpose and will be developed over the years to ensure the quality of Video Assistant Referees. The developed measurement methods are general and can be applied to other broadcast and video systems as well as to other sports. © 2023, The Author(s).

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  • 5.
    Chen, XÍ
    et al.
    Huazhong University of Science and Technology, China.
    Lin, Rui
    Huazhong University of Science and Technology, China.
    Cui, Jingxian
    Huazhong University of Science and Technology, China.
    Gan, Li
    Huazhong University of Science and Technology, China.
    Pang, Xiaodan
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems. KTH Royal Institute of Technology, Sweden.
    Ozolins, Oskars
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo.
    Udalcovs, Aleksejs
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo.
    Jiang, Tao
    Huazhong University of Science and Technology, China.
    Schatz, Richard
    KTH Royal Institute of Technology, Sweden.
    Popov, Sergei
    KTH Royal Institute of Technology, Sweden.
    Chena, Jiajia
    KTH Royal Institute of Technology, Sweden.
    Tang, Ming
    Huazhong University of Science and Technology, China.
    Fu, Songnian
    Huazhong University of Science and Technology, China.
    Liu, Deming
    Huazhong University of Science and Technology, China.
    TDHQ Enabling Fine-granularity Adaptive Loading for SSB-DMT Systems2018In: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 30, no 19, p. 1687-1690Article in journal (Refereed)
    Abstract [en]

    In this letter, we introduce time domain hybrid quadrature amplitude modulation (TDHQ) for the single sideband (SSB) discrete multi-tone (DMT) systems. Experimental results reveal that with a single precoding set and the proposed adaptive loading algorithm, the TDHQ scheme can achieve finer granularity and therefore smoother continuous growth of data rate than that with the conventional quadrature amplitude modulation (QAM). Besides, thanks to the frame construction and the tailored mapping rule, the scheme with TDHQ has an obviously better peak to average power ratio (PAPR).

  • 6.
    Cristofori, Valentina
    et al.
    DTU Technical University of Denmark, Denmark.
    Da Ros, Francesco
    DTU Technical University of Denmark, Denmark.
    Ozolins, Oskars
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo.
    Chaibi, Mohamed Essghair
    University of Rennes 1, France.
    Bramerie, Laurent
    University of Rennes 1, France.
    Ding, Yunhong
    DTU Technical University of Denmark, Denmark.
    Pang, Xiaodan
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo.
    Shen, Alexandre
    III-V Lab, France.
    Gallet, Antonin
    III-V Lab, France.
    Duan, Guanghua
    III-V Lab, France.
    Hassan, Karim
    CEA, France.
    Olivier, Segolene Gol Ne
    CEA, France.
    Popov, Sergei Yu
    KTH Royal Institute of Technology, Sweden.
    Jacobsen, Gunnar
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo.
    Oxenlöwe, Leif Katsuo
    DTU Technical University of Denmark, Denmark.
    Peucheret, Christophe
    University of Rennes 1, France.
    25-Gb/s transmission over 2.5-km SSMF by silicon MRR enhanced 1.55-μm III-V/SOI DML2017In: 30th Annual Conference of the IEEE Photonics Society, IPC 2017, Institute of Electrical and Electronics Engineers Inc. , 2017, p. 357-360Conference paper (Refereed)
    Abstract [en]

    The use of a micro-ring resonator (MRR) to enhance the modulation extinction ratio and dispersion tolerance of a directly modulated laser (DML) is experimentally investigated with a bit rate of 25 Gb/s as proposed for the next generation data center communications. The investigated system combines a 11-GHz 1.55-m directly modulated hybrid III-V/SOI DFB laser realized by bonding III-V materials (InGaAlAs) on a silicon-on-insulator (SOI) wafer and a silicon MRR also fabricated on SOI. Such a transmitter enables error-free transmission (BER< 10 -9 )at 25 Gb/s data rate over 2.5-km SSMF without dispersion compensation nor forward error correction (FEC). As both laser and MRR are fabricated on the SOI platform, they could be combined into a single device with enhanced performance, thus providing a cost-effective transmitter for short reach applications.

  • 7.
    Cristofori, Valentina
    et al.
    DTU Technical University of Denmark, Denmark.
    Da Ros, Francescos
    DTU Technical University of Denmark, Denmark.
    Ozolins, Oskars
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo.
    Chaibi, Mohamed E.
    FOTON Laboratory, France.
    Bramerie, Laurent
    FOTON Laboratory, France.
    Ding, Yunhong
    DTU Technical University of Denmark, Denmark.
    Pang, Xiaodan
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo.
    Shen, Alexandre
    Thales, France.
    Gallet, Antonin
    Thales, France.
    Duan, Guang-Hua
    Thales, France.
    Hassan, Karem
    III-V Lab, France.
    Olivier, Segolene
    III-V Lab, France.
    Popov, Sergei
    KTH Royal Institute of Technology, Sweden.
    Jacobsen, Gunnar
    Oxenløwe, Leif K.
    DTU Technical University of Denmark, Denmark.
    Peucheret, Christophe
    FOTON Laboratory, France.
    25-Gb/s transmission over 2.5-km SSMF by silicon MRR enhanced 1.55-μm III-V/SOI DML2017In: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 29, no 12, p. 960-963, article id 7917280Article in journal (Refereed)
    Abstract [en]

    The use of a micro-ring resonator (MRR) to enhance the modulation extinction ratio and dispersion tolerance of a directly modulated laser is experimentally investigated with a bit rate of 25 Gb/s as proposed for the next generation data center communications. The investigated system combines a 11-GHz 1.55-μm directly modulated hybrid III-V/SOI DFB laser realized by bonding III-V materials (InGaAlAs) on a silicon-on-insulator (SOI) wafer and a silicon MRR also fabricated on SOI. Such a transmitter enables error-free transmission (BER < 10-9) at 25 Gb/s data rate over 2.5-km standard single mode fiber without dispersion compensation nor forward error correction. As both laser and MRR are fabricated on the SOI platform, they could be combined into a single device with enhanced performance, thus providing a cost-effective transmitter for short reach applications.

  • 8.
    Da Ros, Francesco
    et al.
    DTU Technical University of Denmark, Denmark.
    Cristofori, Valentina
    DTU Technical University of Denmark, Denmark.
    Ozolins, Oskars
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo.
    Chaibi, Mohamed E.
    University of Rennes, France.
    Pang, Xiaodan
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo.
    Jacobsen, Gunnar
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo.
    Popov, Sergei
    KTH Royal Institute of Technology, Sweden.
    Galili, Michael
    DTU Technical University of Denmark, Denmark.
    Oxenløwe, Leif K.
    DTU Technical University of Denmark, Denmark.
    Peucheret, Christophe
    University of Rennes, France.
    4-PAM dispersion-uncompensated transmission with micro-ring resonator enhanced 1.55-μm DML2017In: Optics InfoBase Conference Papers, 2017, article id STu1M.5.Conference paper (Refereed)
    Abstract [en]

    Real-time transmission of 14-GBd 4-PAM signal is demonstrated by combining a commercial 1.55-μm DML with a silicon MRR. BER below the HD-FEC threshold is measured after 26-km SSMF transmission without offline digital signal processing.

  • 9.
    Dely, H.
    et al.
    CNRS, France.
    Joharifar, M.
    KTH Royal Institute of Technology, Sweden.
    Pang, Xiaodan
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems. KTH Royal Institute of Technology, Sweden.
    Gacemi, D.
    CNRS, France.
    Salgals, T.
    Riga Technical University, Latvia.
    Schatz, R.
    KTH Royal Institute of Technology, Sweden.
    Sun, Y. -T
    KTH Royal Institute of Technology, Sweden.
    Bonazzi, T.
    CNRS, France.
    Rodriguez, E.
    CNRS, France.
    Todorov, Y.
    CNRS, France.
    Vasanelli, A.
    CNRS, France.
    Udalcovs, Aleksejs
    RISE Research Institutes of Sweden.
    Spolitis, S.
    Riga Technical University, Latvia.
    Bobrovs, V.
    Riga Technical University, Latvia.
    Ozolins, Oskars
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems.
    Popov, Sergei
    KTH Royal Institute of Technology, Sweden.
    Sirtori, C.
    CNRS, France.
    High bitrate data transmission in the 8-14 µm atmospheric window using an external Stark-effect modulator with digital equalization2023In: Optics Express, E-ISSN 1094-4087, Vol. 31, no 5, p. 7259-7264Article in journal (Refereed)
    Abstract [en]

    High bitrate mid-infrared links using simple (NRZ) and multi-level (PAM-4) data coding schemes have been realized in the 8 µm to 14 µm atmospheric transparency window. The free space optics system is composed of unipolar quantum optoelectronic devices, namely a continuous wave quantum cascade laser, an external Stark-effect modulator and a quantum cascade detector, all operating at room-temperature. Pre- and post-processing are implemented to get enhanced bitrates, especially for PAM-4 where inter-symbol interference and noise are particularly detrimental to symbol demodulation. By exploiting these equalization procedures, our system, with a full frequency cutoff of 2 GHz, has reached transmission bitrates of 12 Gbit/s NRZ and 11 Gbit/s PAM-4 fulfilling the 6.25 % overhead hard-decision forward error correction threshold, limited only by the low signal-to-noise ratio of our detector. 

  • 10.
    Deng, Qiuzhuo
    et al.
    Zhejiang University, China.
    Zhang, Lu
    Zhejiang University, China.
    Zhang, Hongqi
    Zhejiang University, China.
    Yang, Zuomin
    Zhejiang University, China.
    Pang, Xiaodan
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems. KTH Royal Institute of Technology, Sweden.
    Bobrovs, V
    Riga Technical University, Latvia.
    Popov, Sergei
    KTH Royal Institute of Technology, Sweden.
    Wu, Yixin
    Huawei Technologies Company Ltd, China.
    Yu, Xiongbin
    Huawei Technologies Company Ltd, China.
    Ozolins, Oskars
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems. KTH Royal Institute of Technology, Sweden; Riga Technical University, Latvia.
    Yu, Xianbin
    Zhejiang University, China; Zhejiang Lab, China.
    Quantum Noise Secured Terahertz Communications2023In: 2023 Optical Fiber Communications Conference and Exhibition (OFC), 2023Conference paper (Refereed)
    Abstract [en]

    The quantum noise based terahertz signal encryption scheme is proposed, a 16 Gbits-1 secure terahertz communication system at 300 GHz with the optical communication realms is demonstrated, taking a significant step toward high-security wireless communications.

  • 11.
    Deniel, L.
    et al.
    C2N CNRS, France.
    Gay, M.
    University of Rennes CNRS, France.
    Pérez-Galacho, D.
    C2N CNRS, France.
    Baudot, C.
    STMicroelectronics, France.
    Bramerie, L.
    University of Rennes CNRS, France.
    Ozolins, Oskars
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Boeuf, F.
    STMicroelectronics, France.
    Vivien, L.
    C2N CNRS, France.
    Peucheret, C.
    University of Rennes CNRS, France.
    Marris-Morini, D.
    C2N CNRS, France.
    Generation of O-band PAM-4 signal using a silicon modulator driven by two binary sequences2019In: Proceedings of SPIE - The International Society for Optical Engineering, SPIE , 2019Conference paper (Refereed)
    Abstract [en]

    Silicon photonics is a promising solution for next generation of short-range optical communication systems. Silicon modulators have driven an important research activity over the past years, and many transmission links using on-off keying modulation format (OOK) were successfully demonstrated with a large diversity of modulator structures. In order to keep up with the demand of increasing bitrates for limited bandwidths in Datacom applications, higher modulation formats are explored, such as quadrature phase shift keying (QPSK) or 4-level pulse amplitude modulation (PAM-4). However, driving the modulators to generate PAM-4 signals commonly require expensive and power-hungry electronic devices such as digital-to-analog converters (DACs) for pulse-shaping and digital signal processors (DSP) for nonlinearity compensation. Lastly, new solutions were studied to overcome this issue, including new driving methods based on the use of two different input binary sequences applied directly on the modulator. While most of the reported works are focused on the C-band of communication, the O-band can present a definitive advantage due to the low dispersion of standard single-mode (SSMF) fiber. For those reasons, we demonstrate the generation of a 10-Gbaud DAC-less PAM-4 signal in the O-band using a depletion-based silicon traveling wave Mach-Zehnder modulator (TWMZM). An open eye diagram was obtained, and a bit error rate (BER) of 3.8×10 -3 was measured for a received optical power of about-6 dBm.

  • 12.
    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.

  • 13.
    Fan, Yuchuan
    et al.
    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.
    Udalcovs, Aleksejs
    RISE Research Institutes of Sweden.
    Natalino, C.
    Chalmers University of Technology, Sweden.
    Zhang, L.
    Zhejiang University, China; Zhejiang Lab, China.
    Bobrovs, V.
    Riga Technical University, Latvia.
    Schatz, R.
    KTH Royal Institute of Technology, Sweden.
    Yu, X.
    Zhejiang University, China; Zhejiang Lab, China.
    Furdek, M.
    Chalmers University of Technology, Sweden.
    Popov, S.
    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.
    Feedforward Neural Network-Based EVM Estimation: Impairment Tolerance in Coherent Optical Systems2022In: IEEE Journal of Selected Topics in Quantum Electronics, ISSN 1077-260X, E-ISSN 1558-4542, Vol. 28, no 4, article id 6000410Article in journal (Refereed)
    Abstract [en]

    Error vector magnitude (EVM) is commonly used for evaluating the quality of m-ary quadrature amplitude modulation (mQAM) signals. Recently proposed deep learning techniques for EVM estimation extend the functionality of conventional optical performance monitoring (OPM). In this article, we evaluate the tolerance of our developed EVM estimation scheme against various impairments in coherent optical systems. In particular, we analyze the signal quality monitoring capabilities in the presence of residual in-phase/quadrature (IQ) imbalance, fiber nonlinearity, and laser phase noise. We use feedforward neural networks (FFNNs) to extract the EVM information from amplitude histograms of 100 symbols per IQ cluster signal sequence captured before carrier phase recovery. We perform simulations of the considered impairments, along with an experimental investigation of the impact of laser phase noise. To investigate the tolerance of the EVM estimation scheme to each impairment type, we compare the accuracy for three training methods: 1) training without impairment, 2) training one model for all impairments, and 3) training an independent model for each impairment. Results indicate a good generalization of the proposed EVM estimation scheme, thus providing a valuable reference for developing next-generation intelligent OPM systems. 

  • 14.
    Fan, Yuchuan
    et al.
    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.
    Udalcovs, Aleksejs
    RISE Research Institutes of Sweden, Digital Systems.
    Natalino, C.
    Chalmers University of Technology, Sweden.
    Zhang, L.
    Zhejiang University, China.
    Spolitis, S.
    Riga Technical University, Sweden.
    Bobrovs, V.
    Riga Technical University, Latvia.
    Schatz, R.
    KTH Royal Institute of Technology, Sweden.
    Yu, X.
    Zhejiang University, China.
    Furdek, M.
    Chalmers University of Technology, Sweden.
    Popov, S.
    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.
    EVM Estimation for Performance Monitoring in Coherent Optical Systems: An Approach of Linear Regression2022In: Optics InfoBase Conference Papers, Optica Publishing Group (formerly OSA) , 2022Conference paper (Refereed)
    Abstract [en]

    We experimentally demonstrate the effectiveness of a simple linear regression scheme for optical performance monitoring when applied after modulation format identification. It outperforms the FFNN-based benchmark scheme providing 0.2% mean absolute error for EVM estimation., © 2022 The Author(s)

  • 15.
    Fan, Yuchuan
    et al.
    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.
    Udalcovs, Aleksejs
    RISE Research Institutes of Sweden.
    Natalino, Carlos
    Chalmers University of Technology, Sweden.
    Schatz, Richard
    KTH Royal Institute of Technology, Sweden.
    Furdek, Marija
    Chalmers University of Technology, Sweden.
    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.
    Laser Linewidth Tolerant EVM Estimation Approach for Intelligent Signal Quality Monitoring Relying on Feedforward Neural Networks2021In: 2021 European Conference on Optical Communication (ECOC), 2021Conference paper (Refereed)
    Abstract [en]

    Robustness against the large linewidth semiconductor laser-induced impairments in coherent systems is experimentally demonstrated for a feedforward neural network-enabled EVM estimation scheme. A mean error of 0.4% is achieved for 28 Gbaud square and circular QAM signals and linewidths up to 12.3 MHz.

  • 16.
    Fan, Yuchuan
    et al.
    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.
    Udalcovs, Aleksejs
    RISE Research Institutes of Sweden, Digital Systems.
    Natalino, Carlos
    Chalmers University of Technology, Sweden.
    Zhang, Lu
    Zhejiang University, Hangzhou, China; Zhejiang Lab, China.
    Spolitis, Sandis
    Riga Technical University, Latvia.
    Bobrovs, Vjaceslavs
    Riga Technical University, Latvia.
    Schatz, Richard
    KTH Royal Institute of Technology, Sweden.
    Yu, Xianbin
    Zhejiang University, Hangzhou, China; Zhejiang Lab, China.
    Furdek, Marija
    Chalmers University of Technology, Sweden.
    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; Zhejiang Lab, China.
    Linear Regression vs. Deep Learning for Signal Quality Monitoring in Coherent Optical Systems2022In: IEEE Photonics Journal, E-ISSN 1943-0655, Vol. 14, no 4, article id 8643108Article in journal (Refereed)
    Abstract [en]

    Error vector magnitude (EVM) is a metric for assessing the quality of m-ary quadrature amplitude modulation (mQAM) signals. Recently proposed deep learning techniques, e.g., feedforward neural networks (FFNNs) -based EVM estimation scheme leverage fast signal quality monitoring in coherent optical communication systems. Such a scheme estimates EVM from amplitude histograms (AHs) of short signal sequences captured before carrier phase recovery (CPR). In this work, we explore further complexity reduction by proposing a simple linear regression (LR) -based EVM monitoring method. We systematically compare the performance of the proposed method with the FFNN-based scheme and demonstrate its capability to infer EVM from an AH when the modulation format information is known in advance. We perform both simulation and experiment to show that the LR-based EVM estimation method achieves a comparable accuracy as the FFNN-based scheme. The technique can be embedded with modulation format identification modules to provide comprehensive signal information. Therefore, this work paves the way to design a fast-learning scheme with parsimony as a future intelligent OPM enabler. 

  • 17.
    Fan, Yuchuan
    et al.
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems.
    Udalcovs, Aleksejs
    RISE Research Institutes of Sweden.
    Natalino, Carlos
    Chalmers University of Technology, Sweden.
    Pang, Xiaodan
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems. KTH Royal Institute of Technology, Sweden.
    Schatz, Richard
    KTH Royal Institute of Technology, Sweden.
    Furdek, Marija
    Chalmers University of Technology, Sweden.
    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.
    Experimental validation of CNNs versus FFNNs for time- and energy-efficient EVM estimation in coherent optical systems2021In: Journal of Optical Communications and Networking, ISSN 1943-0620, E-ISSN 1943-0639, Vol. 13, no 10, p. E63-E71Article in journal (Refereed)
    Abstract [en]

    Error vector magnitude (EVM) has proven to be one of the optical performance monitoring metrics providing the quantitative estimation of error statistics. However, the EVM estimation efficiency has not been fully exploited in terms of complexity and energy consumption. Therefore, in this paper, we explore two deep-learning-based EVM estimation schemes. The first scheme exploits convolutional neural networks (CNNs) to extract EVM information from images of the constellation diagram in the in-phase/quadrature (IQ) complex plane or amplitude histograms (AHs). The second scheme relies on feedforward neural networks (FFNNs) extracting features from a vectorized representation of AHs. In both cases, we use short sequences of 32 Gbaud m-ary quadrature amplitude modulation (mQAM) signals captured before or after a carrier phase recovery. The impacts of the sequence length, neural network structure, and data set representation on the EVM estimation accuracy as well as the model training time are thoroughly studied. Furthermore, we validate the performance of the proposed schemes using the experimental implementation of 28 Gbaud 64QAM signals. We achieve a mean absolute estimation error below 0.15%, with short signals consisting of only 100 symbols per IQ cluster. Considering the estimation accuracy, the implementation complexity, and the potential energy savings, the proposed CNN- and FFNN-based schemes can be used to perform time-sensitive and accurate EVM estimation for mQAM signal quality monitoring purposes.

  • 18.
    Fan, Yuchuan
    et al.
    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.
    Pang, Xiaodan
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems. KTH Royal Institute of Technology, Sweden.
    Natalino, C.
    Chalmers University of Technology, Sweden.
    Furdek, M.
    Chalmers University of Technology, Sweden.
    Popov, S.
    KTH Royal Institute of Technology, Sweden.
    Ozolins, Oskars
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems. KTH Royal Institute of Technology, Sweden.
    Fast signal quality monitoring for coherent communications enabled by CNN-based EVM estimation2021In: Journal of Optical Communications and Networking, ISSN 1943-0620, E-ISSN 1943-0639, Vol. 13, no 4, p. B12-B20, article id 9326316Article in journal (Refereed)
    Abstract [en]

    We propose a fast and accurate signal quality monitoring scheme that uses convolutional neural networks for error vector magnitude (EVM) estimation in coherent optical communications. We build a regression model to extract EVM information from complex signal constellation diagrams using a small number of received symbols. For the additive-white-Gaussian-noise-impaired channel, the proposed EVM estimation scheme shows a normalized mean absolute estimation error of 3.7% for quadrature phase-shift keying, 2.2% for 16-Ary quadrature amplitude modulation (16QAM), and 1.1% for 64QAM signals, requiring only 100 symbols per constellation cluster in each observation period. Therefore, it can be used as a low-complexity alternative to conventional bit-error-rate estimation, enabling solutions for intelligent optical performance monitoring. 

  • 19.
    Fan, Yuchuan
    et al.
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems. KTH Royal Institute of Technology, Sweden.
    Udalcovs, Aleksejs
    RISE Research Institutes of Sweden.
    Pang, Xiaodan
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems. KTH Royal Institute of Technology, Sweden.
    Natalino, C.
    Chalmers University of Technology, Sweden.
    Schatz, Richard
    KTH Royal Institute of Technology, Sweden.
    Furdek, M.
    Chalmers University of Technology, Sweden.
    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.
    Deep learning assisted pre-carrier phase recovery EVM estimation for coherent transmission systems2021In: Optics InfoBase Conference Papers 2021 Article number STh1F.2, The Optical Society , 2021Conference paper (Refereed)
    Abstract [en]

    We exploit deep supervised learning and amplitude histograms of coherent optical signals captured before carrier phase recovery (CPR) to perform time-sensitive and accurate error vector magnitude (EVM) estimation for 32 Gbaud mQAM signal monitoring purposes. © OSA 2021, © 2021 The Author(s)

  • 20.
    Feng, Xingxing
    et al.
    Zhejiang University, China.
    Ye, Kangpeng
    Zhejiang University, China.
    Lou, Chaoteng
    Zhejiang University, Hangzhou, China.
    Suo, Xingmeng
    Zhejiang University, China.
    Song, Yujie
    Zhejiang University, China.
    Pang, Xiaodan
    KTH Royal Institute of Technology, Sweden.
    Ozolins, Oskars
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems. KTH Royal Institute of Technology, Sweden.
    Zhang, Lu
    Zhejiang University, China; Zhejiang Lab, China.
    Yu, Xianbin
    Zhejiang University, China; Zhejiang Lab, China.
    Human recognition with the optoelectronic reservoir-computing-based micro-Doppler radar signal processing2022In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 61, no 19, p. 5782-5789Article in journal (Refereed)
    Abstract [en]

    Current perception and monitoring systems, such as human recognition, are affected by several environmental factors, such as limited light intensity, weather changes, occlusion of targets, and public privacy. Human recognition using radar signals is a promising direction to overcome these defects; however, the low signal-to-noise ratio of radar signals still makes this task challenging. Therefore, it is necessary to use suitable tools that can efficiently deal with radar signals to identify targets. Reservoir computing (RC) is an efficient machine learning scheme that is easy to train and demonstrates excellent performance in processing complex time-series signals. The RC hardware implementation structure based on nonlinear nodes and delay feedback loops endows it with the potential for real-time fast signal processing. In this paper, we numerically study the performance of the optoelectronic RC composed of optical and electrical components in the task of human recognition with noisy micro-Doppler radar signals. A single-loop optoelectronic RC is employed to verify the application of RC in this field, and a parallel dual-loop optoelectronic RC scheme with a dual-polarization Mach–Zehnder modulator (DPol-MZM) is also used for performance comparison. The result is verified to be comparable with other machine learning tools, which demonstrates the ability of the optoelectronic RC in capturing gait information and dealing with noisy radar signals; it also indicates that optoelectronic RC is a powerful tool in the field of human target recognition based on micro-Doppler radar signals. 

  • 21.
    Gaiarin, Simone
    et al.
    DTU Technical University of Denmark, Denmark.
    Pang, Xiaodan
    RISE, Swedish ICT, Acreo.
    Ozolins, Oskars
    RISE, Swedish ICT, Acreo.
    Jones, Rasmus Thomas
    DTU Technical University of Denmark, Denmark.
    Da Silva, Edson Porto
    DTU Technical University of Denmark, Denmark.
    Schatz, Richard
    KTH Royal Institute of Technology, Sweden.
    Westergren, Urban
    KTH Royal Institute of Technology, Sweden.
    Popov, Sergei
    KTH Royal Institute of Technology, Sweden.
    Jacobsen, Gunnar
    RISE, Swedish ICT, Acreo.
    Zibar, Darko
    DTU Technical University of Denmark, Denmark.
    High speed PAM-8 optical interconnects with digital equalization based on neural network2016In: Asia Communications and Photonics Conference 2016, 2016, article id AS1C.1Conference paper (Refereed)
    Abstract [en]

    We experimentally evaluate a high-speed optical interconnection link with neural network equalization. Enhanced equalization performances are shown comparing to standard linear FFE for an EML-based 32 GBd PAM-8 signal after 4-km SMF transmission.

  • 22.
    Gyger, Samuel
    et al.
    KTH Royal Institute of Technology, Sweden.
    Zeuner, Katharina D.
    KTH Royal Institute of Technology, Sweden.
    Jöns, Klaus D.
    KTH Royal Institute of Technology, Sweden.
    Elshaari, Ali W.
    KTH Royal Institute of Technology, Sweden.
    Paul, Matthias
    KTH Royal Institute of Technology, Sweden.
    Popov, Sergei
    KTH Royal Institute of Technology, Sweden.
    Hedlund, Carl Reuterskiöld
    KTH Royal Institute of Technology, Sweden.
    Hammar, Mattias
    KTH Royal Institute of Technology, Sweden.
    Ozolins, Oskars
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo. KTH Royal Institute of Technology, Sweden.
    Zwiller, Val
    KTH Royal Institute of Technology, Sweden.
    Reconfigurable frequency coding of triggered single photons in the telecom C–band2019In: Optics Express, Vol. 27, no 10, p. 14400-14406Article in journal (Refereed)
    Abstract [en]

    In this work, we demonstrate reconfigurable frequency manipulation of quantum states of light in the telecom C–band. Triggered single photons are encoded in a superposition state of three channels using sidebands up to 53 GHz created by an off-the-shelf phase modulator. The single photons are emitted by an InAs/GaAs quantum dot grown by metal-organic vapor-phase epitaxy within the transparency window of the backbone fiber optical network. A cross-correlation measurement of the sidebands demonstrates the preservation of the single photon nature; an important prerequisite for future quantum technology applications using the existing telecommunication fiber network.

  • 23.
    Han, M.
    et al.
    Beijing Jiaotong University, China.
    Wang, M.
    Beijing Jiaotong University, China.
    Fan, Yuchuan
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems. KTH Royal Institute of Technology, Sweden.
    Cai, S.
    Beijing Jiaotong University, China.
    Guo, Y.
    Beijing Jiaotong University, China.
    Zhang, N.
    Beijing Jiaotong University, China.
    Schatz, Rickard
    KTH Royal Institute of Technology, Sweden.
    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.
    Simultaneous modulation format identification and OSNR monitoring based on optoelectronic reservoir computing2022In: Optics Express, E-ISSN 1094-4087, Vol. 30, no 26, p. 47515-47527Article in journal (Refereed)
    Abstract [en]

    An approach for simultaneous modulation format identification (MFI) and optical signal-to-noise ratio (OSNR) monitoring in digital coherent optical communications is proposed based on optoelectronic reservoir computing (RC) and the signal’s amplitude histograms (AHs) obtained after the adaptive post-equalization. The optoelectronic RC is implemented using a Mach-Zehnder modulator and optoelectronic delay feedback loop. We investigate the performance of the proposed model with the number of symbols, bins of AHs and the hyperparameters of optoelectronic RC. The results show that 100% MFI accuracy can be achieved simultaneously with accurate OSNR estimation for different modulation formats under study. The lowest achievable OSNR estimation mean absolute errors for the dual-polarization (DP)-quadrature phase-shift keying signal, the DP-16-ary quadrature amplitude modulation (16QAM) signal, and the DP-64QAM signal are 0.2 dB, 0.32 dB and 0.53 dB, respectively. The robustness of the proposed scheme is also evaluated when the optoelectronic RC is in presence of additive white Gaussian noises. Then, a proof of concept experiment is demonstrated to further verify our proposed method. The proposed approach offers a potential solution for next-generation intelligent optical performance monitoring in the physical layer.

  • 24.
    Han, M.
    et al.
    Beijing Jiaotong University, Sweden; KTH Royal Institute of Technology, Sweden.
    Wang, M.
    Beijing Jiaotong University, Sweden.
    Fan, Yuchuan
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems.
    Salgals, T.
    Riga Technical University, Latvia.
    Louchet, H.
    Keysight Technologies GmbH, Germany.
    Schatz, R.
    KTH Royal Institute of Technology, Sweden.
    Gruen, M.
    Keysight Technologies GmbH, Germany.
    Pittala, F.
    Keysight Technologies GmbH, Germany.
    Krüger, B.
    Keysight Technologies GmbH, Germany.
    Dippon, T.
    Keysight Technologies GmbH, Germany.
    Zhang, L.
    Zhejiang University, China; Zhejiang Lab, China.
    Yu, X.
    Zhejiang University, China; Zhejiang Lab, China.
    Spolitis, S.
    Riga Technical University, Latvia; .
    Bobrovs, V.
    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.
    Ozolins, Oskars
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems. KTH Royal Institute of Technology, Sweden.
    Optical amplification-free deep reservoir computing-assisted high-baudrate short-reach communication2023In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 48, no 8, p. 2122-2125Article in journal (Refereed)
    Abstract [en]

    An optical amplification-free deep reservoir computing (RC)-assisted high-baudrate intensity modulation direct detection (IM/DD) system is experimentally demonstrated using a 100G externally modulated laser operated in C-band. We transmit 112 Gbaud 4-level pulse amplitude modulation (PAM4) and 100 Gbaud 6-level PAM (PAM6) signals over a 200-m single-mode fiber (SMF) link without any optical amplification. The decision feedback equalizer (DFE), shallow RC, and deep RC are adopted in the IM/DD system to mitigate impairment and improve transmission performance. Both PAM transmissions over a 200-m SMF with bit error rate (BER) performance below 6.25% overhead hard-decision forward error correction (HD-FEC) threshold are achieved. In addition, the BER of the PAM4 signal is below the KP4-FEC limit after 200-m SMF transmission enabled by the RC schemes. Thanks to the use of a multiple-layer structure, the number of weights in deep RC has been reduced by approximately 50% compared with the shallow RC, whereas the performance is comparable. We believe that the optical amplification-free deep RC-assisted high-baudrate link has a promising application in intra-data center communications.

  • 25.
    Han, M.
    et al.
    Beijing Jiaotong University, China; KTH Royal Institute of Technology, Sweden.
    Wang, M.
    Beijing Jiaotong University, China.
    Fan, Yuchuan
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems. KTH Royal Institute of Technology, Sweden.
    Salgals, T.
    Riga Technical University, Latvia.
    Louchet, H.
    Keysight Technologies GmbH, Germany.
    Schatz, Richard
    KTH Royal Institute of Technology, Sweden.
    Gruen, M.
    Keysight Technologies GmbH, Germany.
    Pittala, F.
    Keysight Technologies GmbH, Germany.
    Krüger, B.
    Keysight Technologies GmbH, Germany.
    Dippon, T.
    Keysight Technologies GmbH, Germany.
    Zhang, L.
    Zhejiang University, China.
    Yu, X.
    Zhejiang University, China.
    Spolitis, S.
    Riga Technical University, Latvia.
    Bobrovs, V.
    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; 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.
    Deep Reservoir Computing for 100 Gbaud PAM6 IM/DD Transmission Impairment Mitigation2023In: Opt. Fiber Commun. Conf. Exhib., OFC - Proc., Institute of Electrical and Electronics Engineers Inc. , 2023Conference paper (Refereed)
    Abstract [en]

    We experimentally evaluate a deep Reservoir Computing (RC)-based post-equalization for 100 Gbaud PAM6 IM/DD transmissions. It achieves ∼1 dB higher sensitivity than DFE, and ∼50% implementation complexity reduction compared with the conventional RC configuration.

  • 26.
    Han, Mengyao
    et al.
    Beijing Jiaotong University, China; KTH Royal Institute of Technology, Sweden.
    Joharifar, Mahdieh
    KTH Royal Institute of Technology, Sweden.
    Wang, Muguang
    Beijing Jiaotong University, China.
    Fan, Yuchuan
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems.
    Maisons, Gregory
    MirSense, France.
    Abautret, Johan
    MirSense, France.
    Sun, Yan-Ting
    KTH Royal Institute of Technology, Sweden.
    Teissier, Roland
    MirSense, France.
    Zhang, Lu
    Zhejiang University, China; Zhejiang Lab, China.
    Bobrovs, Vjaceslavs
    Riga Technical University, Latvia.
    Yu, Xianbin
    Zhejiang University, China; Zhejiang Lab, China.
    Schatz, Richard
    KTH Royal Institute of Technology, Sweden.
    Popov, Sergei
    KTH Royal Institute of Technology, Sweden.
    Ozolins, Oskars
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems. Riga Technical University, Latvia.
    Pang, Xiaodan
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems. Riga Technical University, Latvia.
    Long-Wave Infrared Discrete Multitone Free-Space Transmission Using a 9.15-μm Quantum Cascade Laser2023In: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 35, no 9, p. 489-492Article in journal (Refereed)
    Abstract [en]

    A free-space optical (FSO) transmission system is experimentally demonstrated in the long-wave infrared (LWIR, 9.15μ m ) using a directly modulated quantum cascade laser (DM-QCL) and a commercial mercury-cadmium-telluride infrared photovoltaic detector. At room temperature, the DM-QCL is current-modulated by discrete multitone signals pre-processed with bit-/power-loading. Up to 5.1 Gbit/s data rate is achieved with bit error rate performance below the 6.25% overhead hard-decision forward error correction limit of 4.5× 10-3 , enabled by a frequency domain equalizer. The stability study of the FSO system is also performed at multiple temperature values. This study can provide a valuable reference for future terrestrial and space communications. 

  • 27.
    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 1558-2213Article 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

  • 28.
    Hong, Xuexhi
    et al.
    KTH Royal Institute of Technology, Sweden.
    Zhang, Lu
    KTH Royal Institute of Technology, Sweden.
    Pang, Xiaodan
    KTH Royal Institute of Technology, Sweden.
    Ozolins, Oskars
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo.
    Udalcovs, Aleksejs
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo.
    Guo, Changjian
    South China Normal University, China.
    Nordwall, Fredrik
    Tektronix AB, Sweden.
    Engenhardt, Klaus M.
    Tektronix GmbH, Germany.
    Kakkar, Aditya
    KTH Royal Institute of Technology, Sweden.
    Navarro, Jaime Rodrigo
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo.
    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.
    Xiao, Shilin
    Shanghai Jiao Tong University, China.
    Chen, Jiajia
    KTH Royal Institute of Technology, Sweden.
    200-Gbps DMT Transmission over 1.6-km SSMF with A Single EML/DAC/PD for Optical Interconnects at C-Band2017In: European Conference on Optical Communication, ECOC, 2017Conference paper (Refereed)
    Abstract [en]

    We report on the first experimental demonstration of 200-Gbps (net rate 166.7-Gbps) 1.55-μm DMT IMDD transmission over 1.6 km fiber using a single monolithically-integrated-EML, DAC and photodiode, achieving an effective electrical spectrum efficiency of 4.93 bit/s/Hz. © 2017 IEEE.

  • 29.
    Hong, Xuezhi
    et al.
    KTH Royal Institute of Technology, Sweden.
    Ozolins, Oskars
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo.
    Guo, Changjian
    South China Normal University, China.
    Pang, Xiaodan
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo.
    Zhang, Junwei
    South China Normal University, China.
    Navarro, Jaime Rodrigo
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo.
    Kakkar, Aditya
    KTH Royal Institute of Technology, Sweden.
    Schatz, Richard
    KTH Royal Institute of Technology, Sweden.
    Westergren, Urban
    KTH Royal Institute of Technology, Sweden.
    Jacobsen, Gunnar
    KTH Royal Institute of Technology, Sweden.
    Popov, Sergei
    KTH Royal Institute of Technology, Sweden.
    Chen, Jiajia
    KTH Royal Institute of Technology, Sweden.
    1.55-jnm EML-based DMT transmission with nonlinearity-aware time domain super-nyquist image induced aliasing2017In: 2017 Optical Fiber Communications Conference and Exhibition, OFC 2017 - Proceedings, 2017Conference paper (Refereed)
    Abstract [en]

    We experimentally demonstrate a DMT transmission system with 1.55-μm EML using nonlinearity-aware time domain super-Nyquist image induced aliasing. Compared with linear equalization, the capacity is improved by ∼16.8%(33.1%) with proposed method for 4(40) km transmission.

  • 30.
    Hong, Xuezhi
    et al.
    KTH Royal Institute of Technology, Sweden; South China Normal University, China.
    Ozolins, Oskars
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo.
    Guo, Changjian
    South China Normal University, China.
    Pang, Xiaodan
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo.
    Zhang, Junwei
    South China Normal University, China.
    Navarro, Jaime Rodrigo
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo.
    Kakkar, Aditya
    KTH Royal Institute of Technology, Sweden.
    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 Yu
    KTH Royal Institute of Technology, Sweden.
    Chen, Jiajia
    KTH Royal Institute of Technology, Sweden; South China Normal University, China.
    1.55-μm EML-based DMT transmission with nonlinearity- aware time domain super-nyquist image induced aliasing2017In: Optics InfoBase Conference Papers, OSA - The Optical Society , 2017Conference paper (Refereed)
    Abstract [en]

    We experimentally demonstrate a DMT transmission system with 1.55-μm EML using nonlinearity-aware time domain super-Nyquist image induced aliasing. Compared with linear equalization, the capacity is improved by ~16.8%(33.1%) with proposed method for 4(40) km transmission. © 2017 OSA.

  • 31.
    Hu, H.
    et al.
    DTU Technical University of Denmark, Denmark; University College London, UK.
    Jia, S.
    DTU Technical University of Denmark, Denmark.
    Lo, M. -C
    Universidad Carlos III de Madrid, Spain.
    Zhang, L.
    KTH Royal Institute of Technology, Sweden.
    Ozolins, Oskars
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo.
    Udalcovs, Aleksejs
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo.
    Kong, D.
    DTU Technical University of Denmark, Denmark.
    Pang, Xiaodan
    KTH Royal Institute of Technology, Sweden.
    Yu, X.
    Zhejiang University, China.
    Xiao, S.
    Shanghai Jiao Tong University, China.
    Popov, S.
    KTH Royal Institute of Technology, Sweden.
    Chen, J.
    KTH Royal Institute of Technology, Sweden.
    Carpintero, G.
    Universidad Carlos III de Madrid, Spain.
    Morioka, T.
    DTU Technical University of Denmark, Denmark.
    Oxenlowe, L.
    DTU Technical University of Denmark, Denmark.
    TuB4.1-chip based thz emitter for ultra-high speed THz wireless communication (Invited)2019In: IEEE Photonics Society Summer Topical Meeting Series 2019, SUM 2019, Institute of Electrical and Electronics Engineers Inc. , 2019Conference paper (Refereed)
    Abstract [en]

    By using a monolithically integrated dual-distributed feedback (DFB) laser chip attached to a photomixing uni-Travelling carrier photodiode (UTC-PD) with a THz antenna, single-channel THz photonic-wireless transmission system with a net rate of 131 Gbit/s over a wireless distance of 10.7 m has been achieved. 

  • 32.
    Jia, S.
    et al.
    DTU Technical University of Denmark, Denmark.
    Lo, MC
    Universidad Carlos III de Madrid, Spain.
    Zhang, L.
    KTH Royal Institute of Technology, Sweden; Shanghai Jiao Tong University, China.
    Ozolins, Oskars
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo. KTH Royal Institute of Technology, Sweden.
    Udalcovs, Aleksejs
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo.
    Kong, D.
    DTU Technical University of Denmark, Denmark.
    Pang, Xiaodan
    KTH Royal Institute of Technology, Sweden.
    Yu, X.
    Zhejiang University, China.
    Xiao, S.
    Shanghai Jiao Tong University, China.
    Popov, S.
    KTH Royal Institute of Technology, Sweden.
    Chen, J.
    KTH Royal Institute of Technology, Sweden.
    Carpintero, G.
    DTU Technical University of Denmark, Denmark.
    Morioka, T.
    Universidad Carlos III de Madrid, Spain.
    Hu, H.
    DTU Technical University of Denmark, Denmark.
    Oxenlowe, L. K.
    DTU Technical University of Denmark, Denmark.
    Integrated Dual-DFB Laser for 408 GHz Carrier Generation Enabling 131 Gbit/s Wireless Transmission over 10.7 Meters2019In: 2019 Optical Fiber Communications Conference and Exhibition, OFC 2019 - Proceedings, Institute of Electrical and Electronics Engineers Inc. , 2019, article id 8697005Conference paper (Refereed)
    Abstract [en]

    A monolithically integrated dual-DFB laser generates a 408 GHz carrier used for demonstrating a record-high single-channel bit rate of 131 Gbit/s transmitted over 10.7 m. 16-QAM-OFDM modulation and specific nonlinear equalization techniques are employed

  • 33.
    Jia, Shi
    et al.
    DTU Technical University of Denmark, Denmark.
    Lo, Mu-Chieh
    Universidad Carlos III de Madrid, Spain; University College London, UK.
    Zhang, Lu
    KTH Royal Institute of Technology, Sweden;Zhejiang University, China.
    Ozolins, Oskars
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems. KTH Royal Institute of Technology, Sweden; Riga Technical University, Latvia.
    Udalcovs, Aleksejs
    RISE Research Institutes of Sweden.
    Kong, Deming
    DTU Technical University of Denmark, Denmark.
    Pang, Xiaodan
    KTH Royal Institute of Technology, Sweden.
    Guzman, Robinson
    Universidad Carlos III de Madrid, Spain.
    Yu, Xianbin
    Zhejiang University, China.
    Xiao, Shilin
    Shanghai Jiao Tong University, China.
    Popov, Sergei
    KTH Royal Institute of Technology, Sweden.
    Chen, Jiajia
    KTH Royal Institute of Technology, Sweden.
    Carpintero, Guillermo
    Universidad Carlos III de Madrid, Spain.
    Morioka, Toshio
    DTU Technical University of Denmark, Denmark.
    Hu, Hao
    DTU Technical University of Denmark, Denmark.
    Oxenløwe, Leif
    DTU Technical University of Denmark, Denmark.
    Integrated dual-laser photonic chip for high-purity carrier generation enabling ultrafast terahertz wireless communications2022In: Nature Communications, E-ISSN 2041-1723, Vol. 13, no 1, article id 1388Article in journal (Refereed)
    Abstract [en]

    Photonic generation of Terahertz (THz) carriers displays high potential for THz communications with a large tunable range and high modulation bandwidth. While many photonics-based THz generations have recently been demonstrated with discrete bulky components, their practical applications are significantly hindered by the large footprint and high energy consumption. Herein, we present an injection-locked heterodyne source based on generic foundry-fabricated photonic integrated circuits (PIC) attached to a uni-traveling carrier photodiode generating high-purity THz carriers. The generated THz carrier is tunable within the range of 0–1.4 THz, determined by the wavelength spacing between the two monolithically integrated distributed feedback (DFB) lasers. This scheme generates and transmits a 131 Gbits−1 net rate signal over a 10.7-m distance with −24 dBm emitted power at 0.4 THz. This monolithic dual-DFB PIC-based THz generation approach is a significant step towards fully integrated, cost-effective, and energy-efficient THz transmitters. © 2022, The Author(s).

  • 34.
    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.

  • 35.
    Joharifar, Mahdieh
    et al.
    KTH Royal Institute of Technology, Sweden.
    Han, Mengyao
    KTH Royal Institute of Technology, Sweden; Beijing Jiaotong University, China.
    Schatz, Richard
    KTH Royal Institute of Technology, Sweden.
    Puerta, Rafael
    KTH Royal Institute of Technology, Sweden; Ericsson AB, Sweden.
    Sun, Yan-Ting
    KTH Royal Institute of Technology, Sweden.
    Fan, Yuchuan
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems.
    Maisons, Gregory
    mirSense, France.
    Abautret, Johan
    mirSense, France.
    Teissier, Roland
    mirSense, France.
    Zhang, Lu
    Zhejiang University, China.
    Spolitis, Sandis
    Riga Technical University, Latvia.
    Wang, Muguang
    Beijing Jiaotong University, China.
    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; Riga Technical University, Latvia.
    Pang, Xiaodan
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems. KTH Royal Institute of Technology, Sweden; Riga Technical University, Latvia.
    8.1 Gbps PAM8 Long-Wave IR FSO Transmission using a 9.15-µm Directly-Modulated QCL with an MCT Detector2023In: Optical Fiber Communication Conference (OFC) 2023, 2023Conference paper (Refereed)
    Abstract [en]

    We experimentally demonstrate a Long-Wave IR FSO link with a 9.15-µm directly modulated quantum cascade laser at room temperature. Up to 8.1 Gb/s PAM8 transmission over 1.4 meter is achieved with a wideband MCT detector.

  • 36.
    Kakkar, Aditya
    et al.
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo. KTH Royal Institute of Technology, Sweden.
    Navarro, Jaime Rodrigo
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo. 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.
    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.
    Low complexity timing recovery algorithm for PAM-8 in high speed direct detection short range links2017In: Optics InfoBase Conference Papers, 2017, article id W2A.54Conference paper (Refereed)
    Abstract [en]

    We propose a low complexity timing algorithm for high order PAM. Experimental results demonstrate higher performance and lower complexity than conventional algorithms in a 32 Gbaud PAM-8 transmission over 4 km SMF links.

  • 37.
    Kakkar, Aditya
    et al.
    RISE, Swedish ICT, Acreo.
    Navarro, Jaime Rodrigo
    RISE, Swedish ICT, Acreo.
    Schatz, Richard
    KTH Royal Institute of Technology, Sweden.
    Louchet, Hadrien
    VPIPhotonics GmBH, Germany.
    Pang, Xiaodan
    RISE, Swedish ICT, Acreo.
    Ozolins, Oskars
    RISE, Swedish ICT, Acreo.
    Jacobsen, Gunnar
    RISE, Swedish ICT, Acreo.
    Popov, Sergei
    KTH Royal Institute of Technology, Sweden.
    Comprehensive Study of Equalization-Enhanced Phase Noise in Coherent Optical Systems2015In: IEEE transactions on intelligent transportation systems (Print), ISSN 1524-9050, E-ISSN 1558-0016, Vol. 33, no 23, p. 4834 -4841Article in journal (Refereed)
    Abstract [en]

    A thorough analysis of equalization-enhanced phase noise (EEPN) and its impact on the coherent optical system is presented. We show with a time-domain analysis that EEPN is caused due to the interference of multiple delayed versions of the dispersed signal, generated by intermixing of the received dispersed signal, and the noise side bands of the local oscillator (LO) in the photodetectors. We derive statistical properties such as the mean, variance, and error vector magnitude of the received signal influenced with EEPN. We show that in coherent optical systems utilizing electronic dispersion compensation, this noise corresponds to multipath fading in wireless communication systems. Closed-form expressions of necessary LO linewidth and/or mitigation bandwidth for a general system configuration and specified OSNR penalty are given. The expressions for system design parameters, validated with system simulations, show that higher order modulation formats, such as 16-quadrature amplitude modulation and beyond, put stringent demands on the LO linewidth unless a mitigation technique is used.

  • 38.
    Kakkar, Aditya
    et al.
    KTH Royal Institute of Technology, Sweden.
    Navarro, Jaime Rodrigo
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo.
    Schatz, Richard
    KTH Royal Institute of Technology, Sweden.
    Pang, Xiaodan
    RISE, Swedish ICT, Acreo.
    Ozolins, Oskars
    RISE, Swedish ICT, Acreo.
    Louchet, Hadrien
    VPIphotonics GmBH, Germany.
    Jacobsen, Gunnar
    RISE, Swedish ICT, Acreo.
    Popov, Sergei
    KTH Royal Institute of Technology, Sweden.
    Equalization enhanced phase noise in coherent optical systems with digital pre-and post-processing2016In: Photonics, ISSN 2304-6732, Vol. 3, no 2, article id 12Article in journal (Refereed)
    Abstract [en]

    We present an extensive study of equalization enhanced phase noise (EEPN) in coherent optical system for all practical electronic dispersion compensation configurations. It is shown that there are only eight practicable all-electronic impairment mitigation configurations. The non-linear and time variant analysis reveals that the existence and the cause of EEPN depend on the digital signal processing (DSP) schemes. There are three schemes that in principle do not cause EEPN. Analysis further reveals the statistical equivalence of the remaining five system configurations resulting in EEPN. In three of them, EEPN is due to phase noise of the transmitting laser, while in the remaining two, EEPN is caused by the local oscillator. We provide a simple look-up table for the system designer to make an informative decision regarding practicable configuration choice and design.

  • 39.
    Kakkar, Aditya
    et al.
    RISE, Swedish ICT, Acreo.
    Navarro, Jaime Rodrigo
    RISE, Swedish ICT, Acreo.
    Schatz, Richard
    KTH Royal Institute of Technology, Sweden.
    Pang, Xiaodan
    RISE, Swedish ICT, Acreo.
    Ozolins, Oskars
    RISE, Swedish ICT, Acreo.
    Louchet, Hadrien
    VPI Photonics GmBH, Germany.
    Jacobsen, Gunnar
    RISE, Swedish ICT, Acreo.
    Popov, Sergei
    KTH Royal Institute of Technology, Sweden.
    Mitigation of EEPN in Coherent Optical Systems with Low Speed Digital Coherence Enhancement2015In: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 27, no 18, p. 1942-1945, article id 7128718Article in journal (Refereed)
    Abstract [en]

    A method for mitigating local oscillator (LO) phase noise-induced impairment, also known as equalization-enhanced phase noise, in coherent optical systems is discussed. The method is suitable for real-time implementation and requires hardware with a bandwidth much lower than the signal baud rate, even for a system utilizing conventional semiconductor laser as LO. We evaluate the required parameters like interpolation technique, electrical signal-to-noise ratio at digital coherence enhancement (DCE) front end, for long haul transmission links having quadrature phase shift keying and 16-quadrature amplitude modulation formats. We show that the method can be implemented using a low-speed DCE front end and a simple digital linear interpolator with small (<1 dB) implementation penalty even in cases that would otherwise result inerror floor.

  • 40.
    Kakkar, Aditya
    et al.
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo. KTH Royal Institute of Technology, Sweden.
    Navarro, Jaime Rodrigo
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo. KTH Royal Institute of Technology, Sweden.
    Schatz, Richard
    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.
    Nordwall, Fredrik
    Tektronix AB, Sweden.
    Zibar, Dakar
    DTU Technical University of Denmark, Denmark.
    Jacobsen, Gunnar
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo.
    Popov, Sergei
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo.
    Influence of lasers with non-white frequency noise on the design of coherent optical links2017In: Optical Fiber Communication Conference OSA Technical Digest (online) (Optical Society of America, 2017)Los Angeles, California United States19–23 March 2017, 2017, article id Th2A.55Conference paper (Refereed)
    Abstract [en]

    We experimentally demonstrate for a 28 Gbaud 64-QAM metro link that the LO frequency noise causes timing impairment. Results show the existence of LO frequency noise spectrum regimes where different design criteria apply.

  • 41.
    Kakkar, Aditya
    et al.
    KTH Royal Institute of Technology, Sweden.
    Navarro, Jaime Rodrigo
    KTH Royal Institute of Technology, Sweden.
    Schatz, Richard
    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.
    Nordwall, Fredrik
    Tektronix GmbH, Germany.
    Zibar, Darko
    DTU Technical University of Denmark, Denmark.
    Jacobsen, Gunnar
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo.
    Popov, Sergei
    KTH Royal Institute of Technology, Sweden.
    Influence of lasers with non-white frequency noise on the design of coherent optical links2017In: 2017 Optical Fiber Communications Conference and Exhibition, OFC 2017 - Proceedings, 2017Conference paper (Refereed)
    Abstract [en]

    We experimentally demonstrate for a 28 Gbaud 64-QAM metro link that the LO frequency noise causes timing impairment. Results show the existence of LO frequency noise spectrum regimes where different design criteria apply.

  • 42.
    Kakkar, Aditya
    et al.
    KTH Royal Institute of Technology, Sweden.
    Olmedo, Miguel Iglesias
    KTH Royal Institute of Technology, Sweden.
    Ozolins, Oskars
    RISE, Swedish ICT, Acreo.
    Navarro, Jaime Rodrigo
    RISE, Swedish ICT, Acreo.
    Pang, Xiaodan
    RISE, Swedish ICT, Acreo.
    Schatz, Richard
    KTH Royal Institute of Technology, Sweden.
    Louchet, Hadrien
    VPIphotonics GmbH, Germany.
    Jacobsen, Gunnar
    RISE, Swedish ICT, Acreo.
    Popov, Sergei
    KTH Royal Institute of Technology, Sweden.
    Overcoming EEPN in coherent transmission systems2016In: 2016 Conference on Lasers and Electro-Optics (CLEO), 2016, article id 7788753Conference paper (Refereed)
    Abstract [en]

    We for the first time experimentally demonstrate a simple technique to overcome EEPN. Performance recovery from above FEC to <1 dB penalty for 28 Gbd 16-QAM over 520 km with high LO linewidth is achieved.

  • 43.
    Kakkar, Aditya
    et al.
    KTH Royal Institute of Technology, Sweden.
    Ozolins, Oskars
    RISE, Swedish ICT, Acreo.
    Navarro, Jaime Rodrigo
    RISE, Swedish ICT, Acreo.
    Pang, Xiaodan
    RISE, Swedish ICT, Acreo.
    Olmedo, Miguel Iglesias
    KTH Royal Institute of Technology, Sweden.
    Schatz, Richard
    KTH Royal Institute of Technology, Sweden.
    Louchet, Hadrien
    VPIphotonics GmbH, Germany.
    Jacobsen, Gunnar
    RISE, Swedish ICT, Acreo.
    Popov, Sergei
    KTH Royal Institute of Technology, Sweden.
    Design of coherent optical systems impaired by EEPN2016In: 2016 Optical Fiber Communications Conference and Exhibition (OFC 2016), 2016, article id 7537506Conference paper (Refereed)
    Abstract [en]

    We present experimental validation of novel analytical expressions essential for the design of coherent optical systems impaired by EEPN. These expressions enable a simple and accurate EEPN analysis for any system specification.

  • 44.
    Kakkar, Aditya
    et al.
    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.
    Navarro, Jaime Rodrigo
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo.
    Louchet, Hadrien
    VPIphotonics GmBH, Germany.
    Jacobsen, Gunnar
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo.
    Popov, Sergei
    KTH Royal Institute of Technology, Sweden.
    A path to use large linewidth LO in 28 Gbd 16-QAM metro links2015In: 2015 European Conference on Optical Communication (ECOC), 2015, article id 7341948Conference paper (Refereed)
    Abstract [en]

    We experimentally investigate the possibility to mitigate local oscillator induced Equalization Enhanced Phase Noise penalty. The results pave the way for the use of even 10 MHz linewidth local oscillator lasers in 28 Gbd 16-QAM metro links.

  • 45.
    Kakkar, Aditya
    et al.
    RISE, Swedish ICT, Acreo. KTH Royal Institute of Technology, Sweden.
    Schatz, Richard
    KTH Royal Institute of Technology, Sweden.
    Pang, Xiaodan
    RISE, Swedish ICT, Acreo.
    Navarro, Jaime Rodrigo
    RISE, Swedish ICT, Acreo.
    Louchet, Hadrien
    VPIphotonics GmbH, Germany.
    Ozolins, Oskars
    RISE, Swedish ICT, Acreo.
    Jacobsen, Gunnar
    RISE, Swedish ICT, Acreo.
    Popov, Sergei
    KTH Royal Institute of Technology, Sweden.
    Impact of local oscillator frequency noise on coherent optical systems with electronic dispersion compensation2015In: Optics Express, E-ISSN 1094-4087, Vol. 23, no 9, p. 11221-11226Article in journal (Refereed)
    Abstract [en]

    A theoretical investigation of the equalization-enhanced phase noise (EEPN) and its mitigation is presented. We show with a frequency domain analysis that the EEPN results from the non-linear inter-mixing between the sidebands of the dispersed signal and the noise sidebands of the local oscillator. It is further shown and validated with system simulations that the transmission penalty is mainly due to the slow optical frequency fluctuations of the local oscillator. Hence, elimination of the frequency noise below a certain cut-off frequency significantly reduces the transmission penalty, even when frequency noise would otherwise cause an error floor. The required cut-off frequency increases linearly with the white frequency noise level and hence the linewidth of the local oscillator laser, but is virtually independent of the symbol rate and the accumulated dispersion.

  • 46.
    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.

  • 47.
    Kerrebrouck, Joris Van
    et al.
    Ghent University, Belgium.
    Zhang, Liu
    KTH Royal Institute of Technology, Sweden; Shanghai Jiao Tong University, China.
    Lin, Rui
    KTH Royal Institute of Technology, Sweden; Huazhong University of Science and Technology, China.
    Pang, Xiaodan
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo. KTH Royal Institute of Technology, Sweden.
    Udalcovs, Aleksejs
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo.
    Ozolins, Oskars
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo.
    Spiga, Silvia
    Walter Schottky Institut, Germany.
    Amann, Markus Christian
    Walter Schottky Institut, Germany.
    van Steenberge, Geert
    Ghent University, Belgium.
    Gan, Lei
    Huazhong University of Science and Technology, China.
    Tang, Ming
    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, Di
    Huazhong University of Science and Technology, China.
    Tong, Weijun
    YOFC Yangtze Optical Fiber and Cable, China.
    Xiao, Shiyi
    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.
    726.7-Gb/s 1.5-μm single-mode VCSEL discrete multi-tone transmission over 2.5-km multicore fiber2018Conference paper (Refereed)
    Abstract [en]

    A 107Gb/s net-rate DMT optical signal was generated using a single-mode long-wavelength VCSEL with a modulation bandwidth of 23 GHz. We experimentally demonstrated a total net-rate up to 726.7Gb/s at 1.5&amp;#x03BC;m over 2.5km 7-core dispersion-uncompensated MCF.

  • 48.
    Kolpakov, S.
    et al.
    Aston University, UK.
    Sergeyev, S. V.
    Aston University, UK.
    Udalcovs, Aleksejs
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems.
    Pang, Xiaodan
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems. KTH Royal Institute of Technology, Sweden.
    Ozolins, Oskars
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems. KTH Royal Institute of Technology, Sweden.
    Schatz, Richard
    KTH Royal Institute of Technology, Sweden.
    Popov, Sergei
    KTH Royal Institute of Technology, Sweden.
    Optical rogue waves in coupled fiber Raman lasers2020In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 45, no 17, p. 4726-4729Article in journal (Refereed)
    Abstract [en]

    For coupled linear cavity-random fiber Raman lasers, for the first time, to the best of our knowledge, we demonstrate a new mechanism of emergence of the random pulses, with the anomalous statistics satisfying optical rogue waves’ criteria experimentally. The rogue waves appear as a result of the coupling of two Raman cascades, namely, a linear cavity laser with a wavelength of 1.55 µm and a random laser with a wavelength nearly 1.67 µm, along with coupling of the orthogonal states of polarization (SOPs). The coherent coupling of SOPs causes localization of the trajectories in the vicinity of these states, whereas polarization instability drives escape taking the form of chaotic oscillations. Antiphase dynamics in two cascades result in the suppression of low amplitude chaotic oscillations and enable the anomalous spikes, satisfying rogue waves criteria. 

  • 49.
    Kolpakov, Stanislav
    et al.
    Aston University, UK.
    Sergeyev, Sergey
    Aston University, UK.
    Udalcovs, Aleksejs
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems.
    Pang, Xiaodan
    KTH Royal Institute of Technology, Sweden.
    Ozolins, Oskars
    KTH Royal Institute of Technology, Sweden.
    Schatz, Richard
    KTH Royal Institute of Technology, Sweden.
    Popov, Sergei
    KTH Royal Institute of Technology, Sweden.
    Polarization Dynamics of Coupled Raman Lasers2020In: 2020 22nd International Conference on Transparent Optical Networks (ICTON), 2020Conference paper (Refereed)
    Abstract [en]

    We experimentally demonstrated a new mechanism of generation of random pulses with the anomalous statistics (optical rogue waves) in a system of coupled Raman lasers. The pump laser with a linear cavity and wavelength of 1550 nm was coupled to a random laser generating nearby 1670 nm. These rogue waves appeared as a result of the interactions between Raman cascades and a coupling of the orthogonal states of polarization (SOPs). The desynchronization of SOPs caused by polarization instability led to chaotic oscillations. Due to the antiphase dynamics in two cascades, these chaotic oscillations were transformed into anomalous spikes satisfying rogue waves criteria.

  • 50.
    Lavrinovica, Ingrida
    et al.
    Riga Technical University, Latvia.
    Supe, Andis
    Riga Technical University, Latvia.
    Udalcovs, Aleksejs
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Ozolins, Oskars
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Popov, Sergei
    KTH Royal Institute of Technology, Sweden.
    Porins, Jurgis
    Riga Technical University, Latvia.
    Exploration of Optical Amplifiers Based on Erbium (Er3+) and Ytterbium (Yb3+) Doped Fiber Segments and Its Emerging Applications2018Conference paper (Refereed)
    Abstract [en]

    This paper proposes the improvement of EDFA amplifier properties by adding additional segments of Yb<sup>3+</sup> doped fiber. Experimental demonstration of a combined erbium-ytterbium doped fiber amplifier (EYDFA) performance using 5 m long erbium-doped fiber (EDF) and 5 m long ytterbium-doped fiber (YDF) is presented.

1234 1 - 50 of 170
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