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  • 1.
    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
    KTH Royal Institute of Technology, Sweden.
    Ozolins, Oskars
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Udalcovs, Aleksejs
    RISE - Research Institutes of Sweden, 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).

  • 2.
    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. 

  • 3.
    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.

  • 4.
    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. 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. 

  • 5.
    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. 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)

  • 6.
    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. 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.

  • 7.
    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. 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. 

  • 8.
    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. 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.

  • 9.
    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. 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. 

  • 10.
    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. 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)

  • 11.
    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, ICT, Acreo.
    Udalcovs, Aleksejs
    RISE - Research Institutes of Sweden, 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, 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, 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.

  • 12.
    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, ICT, Acreo.
    Udalcovs, Aleksejs
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Kong, D.
    DTU Technical University of Denmark, Denmark.
    Pang, X.
    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. 

  • 13.
    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, ICT, Acreo. KTH Royal Institute of Technology, Sweden.
    Udalcovs, Aleksejs
    RISE - Research Institutes of Sweden, 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

  • 14.
    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).

  • 15.
    Joharifar, Mahdieh
    et al.
    KTH Royal Institute of Technology, Sweden.
    Dely, Hamza
    Sorbonne University, France.
    Pang, Xiaodan
    KTH Royal Institute of Technology, Sweden.
    Schatz, Richard
    KTH Royal Institute of Technology, Sweden.
    Gacemi, Djamal
    Sorbonne University, France.
    Salgals, Toms
    Riga Technical University, Latvia.
    Udalcovs, Aleksejs
    RISE Research Institutes of Sweden, Digital Systems.
    Sun, Yan-Ting
    KTH Royal Institute of Technology, Sweden.
    Fan, Yuchuan
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems. KTH Royal Institute of Technology, Sweden.
    Zhang, Lu
    Zhejiang University, China.
    Rodriguez, Etienne
    Sorbonne University, France.
    Spolitis, Sandis
    Riga Technical University, Latvia.
    Bobrovs, Vjaceslavs
    Riga Technical University, Latvia.
    Yu, Xianbin
    Zhejiang University, China.
    Lourdudoss, Sebastian
    KTH Royal Institute of Technology, Sweden.
    Popov, Sergei
    KTH Royal Institute of Technology, Sweden.
    Vasanelli, Angela
    Sorbonne University, France.
    Ozolins, Oskars
    KTH Royal Institute of Technology, Sweden.
    Sirtori, Carlo
    Sorbonne University, France.
    High-Speed 9.6-μm Long-Wave Infrared Free- Space Transmission with a Directly-Modulated QCL and a Fully-Passive QCD2023In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 41, no 4, p. 1087-Article in journal (Refereed)
    Abstract [en]

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

  • 16.
    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.

  • 17.
    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, Xioadan
    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.

  • 18.
    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. 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. 

  • 19.
    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.

  • 20.
    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.

  • 21.
    Lin, R.
    et al.
    KTH Royal Institute of Technology, Sweden; Huazhong University of Science and Technology, China.
    Gan, L.
    Huazhong University of Science and Technology, China.
    Udalcovs, Aleksejs
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Ozolins, Oskars
    RISE - Research Institutes of Sweden, ICT, Acreo. KTH Royal Institute of Technology, Sweden.
    Pang, Xiaodan
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Shen, L.
    Huazhong University of Science and Technology, China.
    Popov, S.
    KTH Royal Institute of Technology, Sweden.
    Tang, M.
    Huazhong University of Science and Technology, China.
    Fu, S.
    Huazhong University of Science and Technology, China.
    Tong, W.
    Yangtze Optical Fiber and Cable Joint Stock Ltd Co, China.
    Liu, D.
    Huazhong University of Science and Technology, China.
    Da Silva, T. F.
    National Institute of Metrology, Brazil.
    Xavier, G. B.
    Linköping University, Sweden.
    Chen, J.
    KTH Royal Institute of Technology, Sweden.
    Spontaneous Raman Scattering Effects in Multicore Fibers: Impact on Coexistence of Quantum and Classical Channels2019In: 2019 Optical Fiber Communications Conference and Exhibition, OFC 2019 - Proceedings, Institute of Electrical and Electronics Engineers Inc. , 2019, article id 8696422Conference paper (Refereed)
    Abstract [en]

    We measure spontaneous Raman scattering (SRS) effects in C-band and observe trench-assisted MCF is robust to SRS noise, making it possible to run quantum channels in the neighboring and/or the same core as data channels.

  • 22.
    Lin, R.
    et al.
    Chalmers Tekniska Högskola, Sweden.
    Udalcovs, Aleksejs
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Ozolins, Oskars
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Tang, M.
    Huazhong University of Science and Technology, China.
    Fu, S.
    Huazhong University of Science and Technology, China.
    Popov, Sergei
    KTH Royal institute of Technology, Sweden.
    Da Silva, T. F.
    National Institute of Metrology, Brazil.
    Xavier, G. B.
    Linköpings Universitet, Sweden.
    Chen, J.
    Chalmers Tekniska Högskola, Sweden.
    Embedding quantum key distribution into optical telecom communication systems2019In: International Conference on Transparent Optical Networks, IEEE Computer Society , 2019Conference paper (Refereed)
    Abstract [en]

    Quantum key distribution (QKD) together with one-time pad cryptography provides unconditional security for the sensitive information. However, the lack of telecom compatibility hinders massive deployment of QKD. In this talk we will discuss the approaches of embedding QKD in optical communication systems and the recent progress.

  • 23.
    Lin, Rui
    et al.
    Huazhong University of Science and Technology, China; KTH Royal Institute of Technology, Sweden.
    Kerrebrouck, Joris
    Ghent University, Belgium.
    Pang, Xiaodan
    RISE - Research Institutes of Sweden, ICT, Acreo. KTH Royal Institute of Technology, Sweden.
    Verplaetse, Michiel
    Ghent University, Belgium.
    Ozolins, Oskars
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Udalcovs, Aleksejs
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Zhang, Lu
    KTH Royal Institute of Technology, Sweden; Shanghai Jiao Tong Universit, China.
    Gan, Lin
    Huazhong University of Science and Technology, China.
    Tang, Ming
    Huazhong University of Science and Technology, China.
    Fu, Songnian
    Huazhong University of Science and Technology, China.
    Schatz, Richard
    KTH Royal Institute of Technology, Sweden.
    Westergren, Urban
    KTH Royal Institute of Technology, Sweden.
    Popov, Sergei
    KTH Royal Institute of Technology, Sweden.
    Liu, Deming
    Huazhong University of Science and Technology, China.
    Tong, Weijun
    fYangtze Optical fiber and Cable Joint Stock Limited Company, China.
    Keulenaer, Timothy
    Ghent University, Belgium.
    Torfs, Guy
    Ghent University, Belgium.
    Bauwelinck, Johan
    Ghent University, Belgium.
    Yin, Xin
    Ghent University, Belgium.
    Chen, Jiajia
    KTH Royal Institute of Technology, Sweden.
    Real-time 100 Gbps/λ/core NRZ and EDB IM/DD transmission over multicore fiber for intra-datacenter communication networks2018In: Optics Express, E-ISSN 1094-4087, Vol. 26, no 8, p. 10519-10526Article in journal (Refereed)
    Abstract [en]

    A BiCMOS chip-based real-time intensity modulation/direct detection spatial division multiplexing system is experimentally demonstrated for both optical interconnects. 100 Gbps/λ/core electrical duobinary (EDB) transmission over 1 km 7-core multicore fiber (MCF) is carried out, achieving KP4 forward error correction (FEC) limit (BER < 2E-4). Using optical dispersion compensation, 7 × 100 Gbps/λ/core transmission of both non-return-to-zero (NRZ) and EDB signals over 10 km MCF transmission is achieved with BER lower than 7% overhead hard-decision FEC limit (BER < 3.8E-3). The integrated low complexity transceiver IC and analog signal processing approach make such a system highly attractive for the high-speed intra-datacenter interconnects..

  • 24.
    Lin, Rui
    et al.
    KTH Royal Institute of Technology, Sweden.
    Kerrebrouck, Joris Van
    Ghent University, Belgium.
    Pang, Xiaodan
    KTH Royal Institute of Technology, Sweden.
    Verplaetse, Michiel
    Ghent University, Belgium.
    Ozolins, Oskars
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Udalcovs, Aleksejs
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Zhang, Lu
    KTH Royal Institute of Technology, Sweden.
    Gan, Lin
    Huazhong University of Science and Technology, China.
    Tang, Ming
    Huazhong University of Science and Technology, China.
    Fu, Songnian
    Huazhong University of Science and Technology, China.
    Schatz, Richard
    KTH Royal Institute of Technology, Sweden.
    Westergren, Urban
    KTH Royal Institute of Technology, Sweden.
    Popov, Sergei
    KTH Royal Institute of Technology, Sweden.
    Liu, Deming
    Huazhong University of Science and Technology, China.
    Tong, Weijun
    YOFC Yangtze Optical Fiber and Cable, China.
    Keulenaer, Timothy De
    Ghent University, Belgium.
    Torfs, Guy
    Ghent University, Belgium.
    Bauwelinck, Johan
    Ghent University, Belgium.
    Yin, Xin
    Ghent University, Belgium.
    Chen, Jiajia
    KTH Royal Institute of Technology, Sweden.
    Spatial division multiplexing for optical data center networks2018Conference paper (Refereed)
    Abstract [en]

    Emerging mobile and cloud applications drive ever-increasing capacity demands, particularly for short-reach optical communications, where low-cost and low-power solutions are highly required. Spatial division multiplexing (SDM) techniques provide a promising way to scale up the lane count per fiber, while reducing the number of fiber connections and patch cords, and hence simplifying cabling complexity. This talk will address challenges on both system and network levels, and report our recent development on SDM techniques for optical data center networks.

  • 25.
    Lin, Rui
    et al.
    KTH Royal Institute of Technology, Sweden.
    Lu, Yang
    KTH Royal Institute of Technology, Sweden.
    Pang, Xiaodan
    KTH Royal Institute of Technology, Sweden.
    Ozolins, Oskars
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Cheng, Yuxin
    KTH Royal Institute of Technology, Sweden.
    Udalcovs, Aleksejs
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Popov, Sergei
    KTH Royal Institute of Technology, Sweden.
    Jacobsen, Gunnar
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Tang, Ming
    Huazhong University of Science and Technology, China.
    Liu, Deming
    Huazhong University of Science and Technology, China.
    Chen, Jiajia
    KTH Royal Institute of Technology, Sweden.
    First Experimental Demonstration of Physical-Layer Network Coding in PAM4 System for Passive Optical Interconnects2018In: European Conference on Optical Communication, ECOC, 2018Conference paper (Refereed)
    Abstract [en]

    We propose to implement physical-layer network coding (PLNC) in coupler-based passive optical interconnects. The PLNC over PAM4 system is for the first time experimentally validated, where simultaneous mutual communications can be kept within the same wavelength channel, doubling spectrum efficiency.

  • 26.
    Lin, Rui
    et al.
    Huazhong University of Science and Technology, China.
    Pang, Xiaodan
    KTH Royal Institute of Technology, Sweden.
    Kerrebrouck, Joris Van
    Ghent University, Belgium.
    Verplaetse, Michiel
    Ghent University, Belgium.
    Ozolins, Oskars
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Udalcovs, Aleksejs
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Zhang, Lu
    KTH Royal Institute of Technology, Sweden.
    Gan, Lin
    Huazhong University of Science and Technology, China.
    Tang, Ming
    Huazhong University of Science and Technology, China.
    Fu, Songnian
    Huazhong University of Science and Technology, China.
    Schatz, Richard
    KTH Royal Institute of Technology, Sweden.
    Westergren, Urban
    KTH Royal Institute of Technology, Sweden.
    Popov, Sergei
    KTH Royal Institute of Technology, Sweden.
    Liu, Deming
    Huazhong University of Science and Technology, China.
    Tong, Weijun
    YOFC Yangtze Optical Fiber and Cable, China.
    Keulenaer, Timothy De
    Ghent University, Belgium.
    Torfs, Guy
    Ghent University, Belgium.
    Bauwelinck, Johan
    Ghent University, Belgium.
    Yin, Xin
    Ghent University, Belgium.
    Chen, Jiajia
    KTH Royal Institute of Technology, Sweden.
    Real-time 100 Gbps/lambda/core NRZ and EDB IM/DD Transmission over 10 km Multicore Fiber2018In: 2018 Optical Fiber Communications Conference and Exposition (OFC), 2018, p. 1-3Conference paper (Refereed)
    Abstract [en]

    A BiCMOS chip-based real-time IM/DD spatial division multiplexing system is experimentally demonstrated for short-reach communications. 100 Gbps/&amp;#x03BB;/core NRZ and EDB transmission is achieved below 7%-overhead HD-FEC limit after 10km 7-core fiber with optical dispersion compensation.

  • 27.
    Lin, Rui
    et al.
    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.
    Pang, Xiaodan
    KTH Royal Institute of Technology, Sweden.
    Gan, L
    Huazhong University of Science and Technology, China.
    Shen, L
    Huazhong University of Science and Technology, China.
    Tang, M.
    Huazhong University of Science and Technology, China.
    Fu, S.
    Huazhong University of Science and Technology, China.
    Popov, Sergei
    KTH Royal Institute of Technology, Sweden.
    Yang, C.
    YOFC Yangtze Optical Fiber and Cable, China.
    Tong, W.
    YOFC Yangtze Optical Fiber and Cable, China.
    Liu, D.
    Huazhong University of Science and Technology, China.
    Silva, T. F. da
    National Institute of Metrology, Brazil.
    Xavier, G. B.
    Linköping University, Sweden.
    Chen, J.
    KTH Royal Institute of Technology, Sweden.
    Telecom Compatibility Validation of Quantum Key Distribution Co-Existing with 112 Gbps/$\boldsymbol{\lambda}$/core Data Transmission in Non-Trench and Trench-Assistant Multicore Fibers2018Conference paper (Refereed)
    Abstract [en]

    We experimentally characterize photon leakage from 112Gb/s data channels in both non-trench and trench-assistant 7-core fibers, demonstrating telecom compatibility for QKD co-existing with high-speed data transmission when a proper core/wavelength allocation is carried out.

  • 28.
    Lin, Rui
    et al.
    KTH Royal Institute of Technology, Sweden.
    Udalcovs, Aleksejs
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Ozolins, Oskars
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Pang, Xiaodan
    KTH Royal Institute of Technology, Sweden.
    Gan, Lin
    Huazhong University of Science and Technology, China.
    Shen, Li
    Huazhong University of Science and Technology, China.
    Tang, Ming
    Huazhong University of Science and Technology, China.
    Fu, Songnian
    Huazhong University of Science and Technology, China.
    Yang, Chen
    YOFC Yangtze Optical fiber and Cable, China.
    Tong, Weijun
    YOFC Yangtze Optical fiber and Cable, China.
    Liu, Deming
    Huazhong University of Science and Technology, China.
    Silva, Thiago
    National Institute of Metrology, Brazil.
    Xavier, Guilherme
    Linköping University, Sweden.
    Chen, Jiajia
    KTH Royal Institute of Technology, Sweden.
    Integrating Quantum Key Distribution with the Spatial Division Multiplexing Enabled High Capacity Optical Networks2018In: 2018 Asia Communications and Photonics Conference (ACP), 2018Conference paper (Refereed)
    Abstract [en]

    In this talk, we discuss integrating the quantum key distribution (QKD) with the spatial division multiplexing (SDM) enabled optical communication network for the cyber security.

  • 29.
    Lin, Rui
    et al.
    Chalmers University of Technology, Sweden.
    Udalcovs, Aleksejs
    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.
    Pang, Xiaodan
    KTH Royal Institute of Technology, Sweden.
    Gan, Lin
    Huazhong University of Science and Technology, China.
    Tang, Ming
    Huazhong University of Science and Technology, China.
    Fu, Songnian
    Huazhong University of Science and Technology, China.
    Popov, Sergei
    KTH Royal Institute of Technology, Sweden.
    Silva, Thiago
    National Institute of Metrology, Quality and Technology, Brazil.
    Xavier, Guilherme
    Linköping University, Sweden.
    Chen, Jiajia
    Chalmers University of Technology, Sweden.
    Telecommunication compatibility evaluation for co-existing quantum key distribution in homogenous multicore fiber2020In: IEEE Access, E-ISSN 2169-3536, Vol. 8, p. 78836-78846, article id 9078126Article in journal (Refereed)
    Abstract [en]

    Quantum key distribution (QKD) is regarded as an alternative to traditional cryptography methods for securing data communication by quantum mechanics rather than computational complexity. Towards the massive deployment of QKD, embedding it with the telecommunication system is crucially important. Homogenous optical multi-core fibers (MCFs) compatible with spatial division multiplexing (SDM) are essential components for the next-generation optical communication infrastructure, which provides a big potential for co-existence of optical telecommunication systems and QKD. However, the QKD channel is extremely vulnerable due to the fact that the quantum states can be annihilated by noise during signal propagation. Thus, investigation of telecom compatibility for QKD co-existing with high-speed classical communication in SDM transmission media is needed. In this paper, we present analytical models of the noise sources in QKD links over heterogeneous MCFs. Spontaneous Raman scattering and inter-core crosstalk are experimentally characterized over spans of MCFs with different refractive index profiles, emulating shared telecom traffic conditions. Lower bounds for the secret key rates and quantum bit error rate (QBER) due to different core/wavelength allocation are obtained to validate intra- and inter-core co-existence of QKD and classical telecommunication

  • 30.
    Lu, Yang
    et al.
    KTH Royal Institute of Technology, Sweden ; Hangzhou Dianzi University, China.
    Agrell, Erik
    Chalmers University of Technology, Sweden.
    Pang, Xiaodan
    KTH Royal Institute of Technology, Sweden.
    Ozolins, Oskars
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Hong, Xuexhi
    KTH Royal Institute of Technology, Sweden.
    Lin, Rui
    KTH Royal Institute of Technology, Sweden.
    Cheng, Yuxin
    KTH Royal Institute of Technology, Sweden.
    Udalcovs, Aleksejs
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Popov, Sergei
    KTH Royal Institute of Technology, Sweden.
    Jacobsen, Gunnar
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Chen, Jiajia
    KTH Royal Institute of Technology, Sweden.
    Matrix Receiving Scheme Supporting Arbitrary Multiple-Wavelength Reception for Optical Interconnects2017In: European Conference on Optical Communication, ECOC, 2017Conference paper (Refereed)
    Abstract [en]

    An arbitrary multiple-wavelength reception scheme using only a few fixed-wavelength filters is proposed for optical interconnects. Filter matrices design based on error-control coding theory is devised. The feasibility of the proposed scheme is demonstrated in a four-wavelength reception experiment.

  • 31.
    Lu, Yang
    et al.
    Hangzhou Dianzi University, China.
    Agrell, Erik
    Chalmers University of Technology, Sweden.
    Pang, Xiaodan
    RISE - Research Institutes of Sweden, ICT, Acreo. KTH Royal Institute of Technology, Sweden.
    Ozolins, Oskars
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Hong, Xuezhi
    South China Normal University, China .
    Lin, Rui
    KTH Royal Institute of Technology, Sweden.
    Cheng, Yuxin
    KTH Royal Institute of Technology, Sweden.
    Udalcovs, Aleksejs
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Popov, Sergei
    KTH Royal Institute of Technology, Sweden.
    Jacobsen, Gunnar
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Chen, Jiajia
    KTH Royal Institute of Technology, Sweden ; South China Normal University, China .
    Multi-channel collision-free reception for optical interconnects2018In: Optics Express, E-ISSN 1094-4087, Vol. 26, no 10, p. 13214-13222Article in journal (Refereed)
    Abstract [en]

    A multi-channel reception scheme that allows each node to receive an arbitrary set of wavelengths simultaneously (i.e., collision-free) is proposed for optical interconnects. The proposed scheme only needs to use a few receivers and fixed-wavelength filters that are designed based on error-control coding theory. Experiments with up to four channel collision-free reception units are carried out to demonstrate the feasibility of the proposed scheme.

  • 32.
    Mardoyan, Haik
    et al.
    Nokia Bell Labs, France.
    Jorge, Filipe
    III-V Lab, France.
    Ozolins, Oskars
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Estaran, Jose Manuel
    Nokia Bell Labs, France.
    Udalcovs, Aleksejs
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Konczykowska, Agnieszka
    III-V Lab, France.
    Riet, Muriel
    III-V Lab, France.
    Duval, Bernadette
    III-V Lab, France.
    Nodjiadjim, Virginie
    III-V Lab, France.
    Dupuy, Jean-Yves
    III-V Lab, 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.
    204-GBaud On-Off Keying Transmitter for Inter-Data Center Communications2018In: Optical Fiber Communication Conference Postdeadline Papers OSA Technical Digest (online) (Optical Society of America, 2018), paper Th4A.4, 2018, article id Th4A.4Conference paper (Refereed)
    Abstract [en]

    We demonstrate an on-off keyed transmitter with direct detection, at record symbol rates of 204Gbaud and 140Gbaud, over 10km and 80km, respectively, powered by a high-speed InP-based 2:1 selector and travelling-wave electro-absorption laser-modulator.

  • 33.
    Marinins, A.
    et al.
    KTH Royal Institute of Technology, Sweden.
    Ozolins, Oskars
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Pang, Xiaodan
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Udalcovs, Aleksejs
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Navarro, Jaime Rodrigo
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Kakkar, Aditya
    KTH Royal Institute of Technology, Sweden.
    Schatz, Richard
    KTH Royal Institute of Technology, Sweden.
    Jacobsen, Gunnar
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Popov, Sergei
    KTH Royal Institute of Technology, Sweden.
    Cylindrical polymer optical waveguides with polarization independent performance2017In: 2017 Conference on Lasers and Electro-Optics, CLEO 2017 - Proceedings, 2017, p. 1-2Conference paper (Refereed)
    Abstract [en]

    Heating of poly(methyl methacrylate) ridge optical waveguides slightly above glass transition temperature minimizes surface roughness and provides cylindrical shape. We experimentally demonstrate propagation loss decrease and polarization insensitivity as a result of waveguide thermal treatment.

  • 34.
    Marinins, A.
    et al.
    KTH Royal Institute of Technology, Sweden.
    Udalcovs, Aleksejs
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Ozolins, Oskars
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Pang, Xiaodan
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Veinot, J.
    University of Alberta, Canada.
    Jacobsen, Gunnar
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Sychugov, I.
    KTH Royal Institute of Technology, Sweden.
    Linnros, J.
    KTH Royal Institute of Technology, Sweden.
    Popov, Sergei
    KTH Royal Institute of Technology, Sweden.
    All-optical intensity modulation in polymer waveguides doped with si quantum dots2018In: Conference on Lasers and Electro-Optics OSA Technical Digest (online) (Optical Society of America, 2018), paper JW2A.31, 2018Conference paper (Refereed)
    Abstract [en]

    We demonstrate all-optical intensity modulation in integrated PMMA optical waveguides doped with silicon quantum dots. The 1550 nm probe signal is absorbed by free carriers excited in silicon quantum dots with 405 nm pump light.

  • 35.
    Marinins, Aleksandrs
    et al.
    KTH Royal Institute of Technology, Sweden.
    Ozolins, Oskars
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Pang, Xiaodan
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Udalcovs, Aleksejs
    KTH Royal Institute of Technology, Sweden.
    Navarro, Jaime Rodrigo
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Kakkar, Aditya
    KTH Royal Institute of Technology, Sweden.
    Schatz, Richard
    KTH Royal Institute of Technology, Sweden.
    Jacobsen, Gunnar
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Popov, Sergei
    KTH Royal Institute of Technology, Sweden.
    Cylindrical polymer optical waveguides with polarization independent performance2017In: Optics InfoBase Conference Papers, 2017, article id SF1J.6Conference paper (Refereed)
    Abstract [en]

    Heating of poly(methyl methacrylate) ridge optical waveguides slightly above glass transition temperature minimizes surface roughness and provides cylindrical shape. We experimentally demonstrate propagation loss decrease and polarization insensitivity as a result of waveguide thermal treatment.

  • 36.
    Marinins, Aleksandrs
    et al.
    KTH Royal Institute of Technology, Sweden.
    Ozolins, Oskars
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Pang, Xiaodan
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Udalcovs, Aleksejs
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Navarro, Jaime Rodrigo
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Kakkar, Aditya
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Schatz, Richard
    KTH Royal Institute of Technology, Sweden.
    Jacobsen, Gunnar
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Popov, Sergei
    KTH Royal Institute of Technology, Sweden.
    Thermal reflow engineered cylindrical polymer waveguides for optical interconnects2018In: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 30, no 5, p. 447-450Article in journal (Refereed)
    Abstract [en]

    Integrated polymer photonics brings low cost and high fabrication flexibility to optoelectronic industry. However, this platform needs to overcome several issues to be effective enough for practical applications. In this work, we experimentally demonstrate a decrease of propagation losses and polarization sensitivity of polymer waveguide-based devices as a result of thermal treatment. Heating of poly(methyl methacrylate) strip optical waveguides above the glass transition temperature initiates a waveguide surface reflow due to a decrease of the polymer viscosity and surface tension energy. This results in a decrease of surface roughness and shape change from rectangular to cylindrical. Thus, scattering losses and polarization sensitivity are minimized. IEEE

  • 37.
    Matsenko, Svitlana
    et al.
    Riga Technical University, Latvia.
    Borysenko, Oleksiy
    Sumy State University, Ukraine.
    Spolitis, Sandis
    Riga Technical University, Latvia.
    Udalcovs, Aleksejs
    RISE Research Institutes of Sweden.
    Gegere, Lilita
    Riga Technical University, Latvia.
    Krotov, Aleksandr
    Riga Technical University, Latvia.
    Ozolins, Oskars
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems. Riga Technical University, Latvia; KTH Royal Institute of Technology, Sweden.
    Bobrovs, Vjaceslavs
    Riga Technical University, Latvia.
    FPGA-Implemented Fractal Decoder with Forward Error Correction in Short-Reach Optical Interconnects2022In: Entropy, E-ISSN 1099-4300, Vol. 24, no 1, article id 122Article in journal (Refereed)
    Abstract [en]

    Forward error correction (FEC) codes combined with high-order modulator formats, i.e., coded modulation (CM), are essential in optical communication networks to achieve highly efficient and reliable communication. The task of providing additional error control in the design of CM systems with high-performance requirements remains urgent. As an additional control of CM systems, we propose to use indivisible error detection codes based on a positional number system. In this work, we evaluated the indivisible code using the average probability method (APM) for the binary symmetric channel (BSC), which has the simplicity, versatility and reliability of the estimate, which is close to reality. The APM allows for evaluation and compares indivisible codes according to parameters of correct transmission, and detectable and undetectable errors. Indivisible codes allow for the end-to-end (E2E) control of the transmission and processing of information in digital systems and design devices with a regular structure and high speed. This study researched a fractal decoder device for additional error control, implemented in field-programmable gate array (FPGA) software with FEC for short-reach optical interconnects with multilevel pulse amplitude (PAM-M) modulated with Gray code mapping. Indivisible codes with natural redundancy require far fewer hardware costs to develop and implement encoding and decoding devices with a sufficiently high error detection efficiency. We achieved a reduction in hardware costs for a fractal decoder by using the fractal property of the indivisible code from 10% to 30% for different n while receiving the reciprocal of the golden ratio. © 2022 by the authors. 

  • 38.
    Murnieks, Rihards
    et al.
    Riga Technical University, Latvia.
    Salgals, Toms
    Riga Technical University, Latvia.
    Alnis, Janis
    University of Latvia, Latvia.
    Ostrovskis, Armands
    Riga Technical University, Latvia.
    Ozolins, Oskars
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems. Riga Technical University, Latvia; KTH Royal Institute of Technology, Sweden.
    Brice, Inga
    University of Latvia, Latvia.
    Sedulis, Arvids
    Riga Technical University, Latvia; University of Latvia, Latvia.
    Draguns, Kristians
    University of Latvia, Latvia.
    Lyashuk, Ilya
    Riga Technical University, Latvia.
    Berkis, Roberts
    University of Latvia, Latvia; University of Innsbruck, Austria.
    Udalcovs, Aleksejs
    RISE Research Institutes of Sweden.
    Bi, Toby
    Max Planck Institute, Germany; Friedrich-Alexander-Universität Erlangen-Nürnberg, Germany.
    Pang, Xiaodan
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems. Riga Technical University, Latvia; KTH Royal Institute of Technology, Sweden.
    Porins, Jurgis
    Riga Technical University, Latvia.
    Spolitis, Sandis
    Riga Technical University, Latvia.
    Del' Haye, Pascal
    Max Planck Institute, Germany; Friedrich-Alexander-Universität Erlangen-Nürnberg, Germany.
    Bobrovs, Vjaceslavs
    Riga Technical University, Latvia.
    Silica micro-rod resonator-based Kerr frequency comb for high-speed short-reach optical interconnects.2023In: Optics Express, E-ISSN 1094-4087, Vol. 31, no 12, p. 20306-20320Article in journal (Refereed)
    Abstract [en]

    Conventional data center interconnects rely on power-hungry arrays of discrete wavelength laser sources. However, growing bandwidth demand severely challenges ensuring the power and spectral efficiency toward which data center interconnects tend to strive. Kerr frequency combs based on silica microresonators can replace multiple laser arrays, easing the pressure on data center interconnect infrastructure. Therefore, we experimentally demonstrate a bit rate of up to 100 Gbps/λ employing 4-level pulse amplitude modulated signal transmission over a 2 km long short-reach optical interconnect that can be considered a record using any Kerr frequency comb light source, specifically based on a silica micro-rod. In addition, data transmission using the non-return to zero on-off keying modulation format is demonstrated to achieve 60 Gbps/λ. The silica micro-rod resonator-based Kerr frequency comb light source generates an optical frequency comb in the optical C-band with 90 GHz spacing between optical carriers. Data transmission is supported by frequency domain pre-equalization techniques to compensate amplitude–frequency distortions and limited bandwidths of electrical system components. Additionally, achievable results are enhanced with offline digital signal processing, implementing post-equalization using feed-forward and feedback taps.

  • 39.
    Natalino, C.
    et al.
    Chalmers University of Technology, Sweden.
    Udalcovs, Aleksejs
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Wosinska, L.
    Chalmers University of Technology, Sweden.
    Ozolins, Oskars
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Furdek, M.
    Chalmers University of Technology, Sweden.
    One-shot learning for modulation format identification in evolving optical networks2017In: Optics InfoBase Conference Papers, OSA - The Optical Society , 2017Conference paper (Refereed)
    Abstract [en]

    We report on the first successful application of one-shot machine learning scheme that identifies new modulation formats based on a single constellation diagram without re-training. 100% accuracy is achieved when expanding from 2 to 5 supported modulation formats. © 2019 The Author(s).

  • 40.
    Natalino, Carlos
    et al.
    Chalmers University of Technology, Sweden.
    Udalcovs, Aleksejs
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems.
    Wosinska, Lena
    Chalmers University of Technology, Sweden.
    Ozolins, Oskars
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems.
    Furdek, Marija
    Chalmers University of Technology, Sweden.
    Spectrum Anomaly Detection for Optical Network Monitoring using Deep Unsupervised Learning2021In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 25, no 5, p. 1583-1586Article in journal (Refereed)
    Abstract [en]

    Accurate and efficient anomaly detection is a key enabler for the cognitive management of optical networks, but traditional anomaly detection algorithms are computationally complex and do not scale well with the amount of monitoring data. Therefore, we propose an optical spectrum anomaly detection scheme that exploits computer vision and deep unsupervised learning to perform optical network monitoring relying only on constellation diagrams of received signals. The proposed scheme achieves 100% detection accuracy even without prior knowledge of the anomalies. Furthermore, operation with encoded images of constellation diagrams reduces the runtime by up to 200 times. 

  • 41.
    Navarro, Jaime Rodrigo
    et al.
    RISE - Research Institutes of Sweden, ICT, Acreo. KTH Royal Institute of Technology, Sweden.
    Kakkar, Aditye
    RISE - Research Institutes of Sweden, ICT, Acreo. KTH Royal Institute of Technology, Sweden.
    Schatz, Richard
    KTH Royal Institute of Technology, Sweden.
    Pang, Xiaodan
    KTH Royal Institute of Technology, Sweden.
    Ozolins, Oskars
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Udalcovs, Aleksejs
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Popov, Sergei
    KTH Royal Institute of Technology, Sweden.
    Jacobsen, Gunnar
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Blind phase search with angular quantization noise mitigation for efficient carrier phase recovery2017In: Photonics, ISSN 2304-6732, Vol. 4, no 2, article id 37Article in journal (Refereed)
    Abstract [en]

    The inherent discrete phase search nature of the conventional blind phase search (C-BPS) algorithm is found to introduce angular quantization noise in its phase noise estimator. The angular quantization noise found in the C-BPS is shown to limit its achievable performance and its potential low complexity implementation. A novel filtered BPS algorithm (F-BPS) is proposed and demonstrated to mitigate this quantization noise by performing a low pass filter operation on the C-BPS phase noise estimator. The improved performance of the proposed F-BPS algorithm makes it possible to significantly reduce the number of necessary test phases to achieve the C-BPS performance, thereby allowing for a drastic reduction of its practical implementation complexity. The proposed F-BPS scheme performance is evaluated on a 28-Gbaud 16QAM and 64QAM both in simulations and experimentally. Results confirm a substantial improvement of the performance along with a significant reduction of its potential implementation complexity compared to that of the C-BPS.

  • 42.
    Osorio, Camilo
    et al.
    University of Campinas, Brazil.
    Udalcovs, Aleksejs
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo.
    Barreto, Andre
    University of Campinas, Brazil.
    Monti, Paolo
    University of Campinas, Brazil.
    Ozolins, Oskars
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo.
    Mello, Darli
    University of Campinas, Brazil.
    Dual-Mode Distance-Adaptive Transceiver Architecture for 5G Optical Fiber Fronthaul2018Conference paper (Refereed)
    Abstract [en]

    We propose a transceiver architecture for 5G fronthaul that adapts the modulation format according to the channel quality. The proposed solution operates in dual-mode using digital signal processing (DSP)-assisted analog radio-over-fiber (A-RoF) and digital radio-over-fiber (D-RoF) with multiple modulation orders. The system performance is assessed through Monte-Carlo simulations of the optical fiber link conveying wireless waveforms that utilize the filter bank multicarrier (FBMC) and orthogonal frequency-division multiplexing (OFDM) formats. The simulation results highlight the benefits of having both digital and DSP-assisted analog transmission capabilities to optimize the reach versus spectral efficiency trade-off in optical fronthaul.

  • 43.
    Ozolins, Oskars
    et al.
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems. KTH Royal Institute of Technology, Sweden; Riga Technical University, Latvia.
    Fan, Yuchuan
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems.
    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; Riga Technical University, Latvia.
    106.25 Gbaud 4-Level Pulse Amplitude Modulation Links Supporting (2x)100Gigabit Ethernet on Single Lambda2023In: 2023 Optical Fiber Communications Conference and Exhibition, OFC 2023 - Proceedings. 2023 Article number Tu3I.1, Institute of Electrical and Electronics Engineers Inc. , 2023Conference paper (Refereed)
    Abstract [en]

    We experimentally demonstrate and compare EML- and DML-based optical interconnects with 106.25 Gbaud NRZ-OOK and PAM4 for computing applications. The results show that both transmitters can be used to enable optical-amplification-free transmissions with low-complexity DSP. © 2023 The Author(s).

  • 44.
    Ozolins, Oskars
    et al.
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems. KTH Royal Institute of Technology, Sweden; Riga Technical University, Latvia.
    Fan, Yuchuan
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems.
    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; Riga Technical University, Latvia.
    High Baudrate Short-Reach Communication2022In: OECC/PSC 2022 - 27th OptoElectronics and Communications Conference/International Conference on Photonics in Switching and Computing 2022, Institute of Electrical and Electronics Engineers Inc. , 2022Conference paper (Refereed)
    Abstract [en]

    We demonstrate a 200 Gbps IM/DD link without any optical amplification using C-band externally modulated laser with 3.3 dBm of modulated output power and O-band directly modulated laser with 7.3 dBm of modulated output power. 

  • 45.
    Ozolins, Oskars
    et al.
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems.
    Joharifar, Mahdieh
    KTH Royal Institute of Technology, Sweden.
    Salgals, Toms
    Riga Technical University, Latvia.
    Louchet, Hadrien
    Keysight Technologies GmbH, Germany.
    Schatz, Richard
    KTH Royal Institute of Technology, Sweden.
    Gruen, Markus
    Keysight Technologies GmbH, Germany.
    Dippon, Thomas
    Keysight Technologies GmbH, Germany.
    Kruger, Benjamin
    Keysight Technologies GmbH, Germany.
    Pittala, Fabio
    Keysight Technologies GmbH, Germany.
    Che, Di
    Nokia Bell Labs, USA.
    Matsui, Yasuhiro
    II-VI Incorporated, USA.
    Fan, Yuchuan
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems. KTH Royal Institute of Technology, Sweden.
    Udalcovs, Aleksejs
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems.
    Westergren, Urban
    KTH Royal Institute of Technology, Sweden.
    Zhang, Lu
    Zhejiang Universitsy, China.
    Yu, Xianbin
    Zhejiang Universitsy, China.
    Spolitis, Sandis
    Riga Technical University, Latvia.
    Bobrovs, Vjaceslavs
    Riga Technical University, Latvia.
    Popov, Sergei
    KTH Royal Institute of Technology, Sweden.
    Pang, Xiaodan
    KTH Royal Institute of Technology, Sweden.
    Optical Amplification-Free High Baudrate Links for Intra-Data Center Communications2023In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213Article in journal (Refereed)
    Abstract [en]

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

  • 46.
    Ozolins, Oskars
    et al.
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Pang, Xiaodan
    RISE - Research Institutes of Sweden, ICT, Acreo. KTH Royal Institute of Technology, Sweden.
    Udalcovs, Aleksejs
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Lin, Rui
    KTH Royal Institute of Technology, Sweden; Huazhong University of Science and Technology, China.
    Van Kerrebrouck, Jóris
    Ghent University, Belgium.
    Gan, Lin
    Huazhong University of Science and Technology, China.
    Zhang, Lu
    KTH Royal Institute of Technology, Sweden.
    Tang, Ming
    Huazhong University of Science and Technology, China.
    Fu, Songnian
    Huazhong University of Science and Technology, China.
    Schatz, Richard
    KTH Royal Institute of Technology, Sweden.
    Westergren, Urban
    KTH Royal Institute of Technology, Sweden.
    Jacobsen, Gunnar
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Liu, Deming
    KTH Royal Institute of Technology, Sweden.
    Tong, Weijun
    YOFC Yangtze Optical fiber and Cable, China.
    Torfs, Guy
    Ghent University, Belgium.
    Bauwelinck, Johan
    Ghent University, Belgium.
    Chen, Jiajia
    KTH Royal Institute of Technology, Sweden.
    Popov, Sergei
    KTH Royal Institute of Technology, Sweden.
    Yin, Xin
    Ghent University, Belgium.
    7×149 Gbit/s PAM4 transmission over 1 km multicore fiber for short-reach optical interconnects2018In: Conference on Lasers and Electro-Optics OSA Technical Digest (online) (Optical Society of America, 2018), paper SM4C.4, 2018Conference paper (Refereed)
    Abstract [en]

    We transmit 80 Gbaud/λ/core PAM4 signal enabled by 1.55 μm EML over 1 km 7-core fiber. The solution achieves single-wavelength and single-fiber 1.04 Tbit/s post-FEC transmission enhancing bandwidth-density for short-reach optical interconnects.

  • 47.
    Ozolins, Oskars
    et al.
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems. KTH Royal Institute of Technology, Sweden; Riga Technical University, Latvia.
    Pang, Xiaodan
    KTH Royal Institute of Technology, Sweden.
    Udalcovs, Aleksejs
    RISE Research Institutes of Sweden.
    Schatz, Richard
    KTH Royal Institute of Technology, Sweden.
    Spolitis, Sandis
    Riga Technical University, Latvia.
    Bobrovs, Vjaceslavs
    Riga Technical University, Latvia.
    Jacobsen, Gunnar
    RISE Research Institutes of Sweden.
    Popov, Sergei
    KTH Royal Institute of Technology, Sweden.
    100 gbaud on–off keying/pulse amplitude modulation links in c-band for short-reach optical interconnects2021In: Applied Sciences, E-ISSN 2076-3417, Vol. 11, no 9, article id 4284Article in journal (Refereed)
    Abstract [en]

    We experimentally evaluate the high-speed on–off keying (OOK) and four-level pulse amplitude modulation (PAM4) transmitter’s performance in C-band for short-reach optical interconnects. We demonstrate up to 100 Gbaud OOK and PAM4 transmission over a 400 m standard single-mode fiber with a monolithically integrated externally modulated laser (EML) having 100 GHz 3 dB bandwidth with 2 dB ripple. We evaluate its capabilities to enable 800 GbE client-side links based on eight, and even four, optical lanes for optical interconnect applications. We study the equalizer’s complexity when increasing the baud rate of PAM4 signals. Furthermore, we extend our work with numerical simulations showing the required received optical power (ROP) for a certain bit error rate (BER) for the different combinations of the effective number of bits (ENOB) and extinction ratio (ER) at the transmitter. We also show a possibility to achieve around 1 km dispersion uncompensated transmission with a simple decision feedback equalizer (DFE) for a 100 Gbaud OOK, PAM4, and eight-level PAM (PAM8) link having the received power penalty of around 1 dB. © 2021 by the authors. 

  • 48.
    Ozolins, Oskars
    et al.
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Pang, Xiaodan
    KTH Royal Institute of Technology, Sweden.
    Udalcovs, Aleksejs
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Schatz, Richard
    KTH Royal Institute of Technology, Sweden.
    Westergren, Urban
    KTH Royal Institute of Technology, Sweden.
    Navarro, Jaime Rodrigo
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Kakkar, Aditya
    KTH Royal Institute of Technology, Sweden.
    Nordwall, Fredrik
    Tektronix AB, Sweden.
    Engenhardt, Klaus
    Tektronix GmbH, Germany.
    Chen, Jiajia
    KTH Royal Institute of Technology, Sweden.
    Popov, Sergei
    KTH Royal Institute of Technology, Sweden.
    Jacobsen, Gunnar
    RISE - Research Institutes of Sweden, ICT, Acreo.
    100 Gbaud 4PAM Link for High Speed Optical Interconnects2017Conference paper (Refereed)
    Abstract [en]

    We demonstrate 100 Gbaud 4PAM transmission over 400 meters SMF with monolithically integrated 1550 nm DFB-TWEAM having 100 GHz 3-dB bandwidth with 2 dB ripple. We evaluate its capabilities to enable two lanes 400 GbE client-side links for optical interconnects. © 2017 IEEE.

  • 49.
    Ozolins, Oskars
    et al.
    RISE - Research Institutes of Sweden, ICT, Acreo. KTH Royal Institute of Technology, Sweden.
    Pang, Xiaodan
    RISE - Research Institutes of Sweden, ICT, Acreo. KTH Royal Institute of Technology, Sweden.
    Udalcovs, Aleksejs
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Zhang, Lu
    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, ICT, Acreo.
    Chen, Jiajia
    KTH Royal Institute of Technology, Sweden.
    Popov, Sergei
    KTH Royal Institute of Technology, Sweden.
    Multilevel modulation at 100 gbaud for short reach C-band links2019In: International Conference on Transparent Optical Networks, IEEE Computer Society , 2019Conference paper (Refereed)
    Abstract [en]

    Datacenters experience an enormous traffic growth due to the vast amount of data to be stored, transmitted and processed [1]-[4]. Technical and economic challenges arise to keep up the bandwidth scalability. Therefore, cost-efficient short reach optical interconnects for 400 GbE intra-datacenter links are critical. Attractive solutions are proposed based on eight optical lanes thanks to compatibility with 100 GbE building blocks, where two optical lanes based 100 GbE solution is already being deployed [4]. Solutions for 400 GbE based on four optical lanes or even two optical lanes using high bandwidth components may be more attractive to reduce cost, power consumption and complexity of parallelism [5], [6]. In this talk, we report on several experimental demonstrations for short reach optical interconnects in C-band. We experimentally evaluate high-speed on-off keying (OOK) and 4-level pulse amplitude modulation (PAM4) and 8-level PAM8 transmitter performance in C-band for short reach optical interconnects. We demonstrate 100 Gbaud PAM4 transmission over 400 meters long standard single mode fiber without optical amplification. We also show results of numerical simulations showing achievable transmission reach in C-band for multilevel modulation at 100 Gbaud over standard single mode fiber with simple decision feedback equalizer. This paves the way for cost-effective short reach optical interconnects with multilevel modulation at 100 Gbaud and higher. 

  • 50.
    Ozolins, Oskars
    et al.
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Pang, Xiaodan
    KTH Royal Institute of Technology, Sweden.
    Udalcovs, Aleksejs
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Zhang, Lu
    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, ICT, Acreo.
    Popov, Sergei
    KTH Royal Institute of Technology, Sweden.
    Chen, Jiajia
    KTH Royal Institute of Technology, Sweden.
    Short Reach Optical Interconnects with Single Externally Modulated Laser Operated in C-Band2018Conference paper (Refereed)
    Abstract [en]

    Datacenters experience massive traffic growth due to expansive growth of cloud services and online gaming [1]. This trend leads to technical and economic challenges to keep up scalability for bandwidth in short reach optical interconnects. It is of critical importance to enable a cost-efficient solution for 400 Gbps links [2]. Solution for 400 GbE based on four optical lanes [3] or even two optical lanes [4] may be more attractive to reduce power consumption and complexity of parallelism. This requires InP and silicon opto-electronic components with more than 70 GHz bandwidth [2]. In this talk, we report on several experimental demonstrations for short reach optical interconnects in C-band. We review demonstrations of up to 200 Gbit/s 4-pulse amplitude modulation (PAM) [4] and up to 200 Gbit/s discrete multitone (DMT) [5] transmission with a cost-efficient monolithically integrated externally modulated laser (EML) with large bandwidth. Related digital signal processing techniques are also discussed in terms of practical implementation and complexity, paving the way for cost-effective interconnects using high speed advanced modulation formats.

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