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  • 1.
    Hong, Xuezhi
    et al.
    KTH, School of Information and Communication Technology (ICT). South China Normal University, China.
    Ozolins, O.
    Guo, C.
    Pang, X.
    Zhang, J.
    Navarro, J. R.
    Kakkar, Aditya
    KTH, School of Information and Communication Technology (ICT).
    Schatz, Richard
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Westergren, Urban
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Jacobsen, G.
    Popov, Sergei
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Chen, Jiajia
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab). South China Normal University, China.
    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, Institute of Electrical and Electronics Engineers Inc. , 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.

  • 2.
    Hong, Xuezhi
    et al.
    KTH, School of Information and Communication Technology (ICT). South China Normal Univ, Peoples R China.
    Ozolins, O.
    Guo, C.
    Pang, Xiaodan
    RISE ACREO AB.
    Zhang, J.
    Navarro, J. R.
    Kakkar, Aditya
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Schatz, Richard
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Westergren, Urban
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Jacobsen, G.
    Popov, Sergei
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Chen, Jiajia
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab). South China Normal Univ, Peoples R China.
    1.55-μm EML-based DMT transmission with nonlinearity- aware time domain super-nyquist image induced aliasing2017In: Optics InfoBase Conference Papers, Optics Info Base, Optical Society of America, 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.

  • 3.
    Hong, Xuezhi
    et al.
    KTH, School of Information and Communication Technology (ICT). South China Normal Univ, Peoples R China.
    Ozolins, Oskars
    Guo, Changjian
    Pang, Xiaodan
    Zhang, Junwei
    Navarro, Jaime Rodrigo
    Kakkar, Aditya
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Schatz, Richard
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Westergren, Urban
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Jacobsen, Gunnar
    Popov, Sergei
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Chen, Jiajia
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab). South China Normal Univ, Peoples R China.
    1.55-mu m EML-based DMT Transmission with Nonlinearity-Aware Time Domain Super-Nyquist Image Induced Aliasing2017In: 2017 OPTICAL FIBER COMMUNICATIONS CONFERENCE AND EXHIBITION (OFC), IEEE , 2017Conference paper (Refereed)
    Abstract [en]

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

  • 4.
    Hong, Xuezhi
    et al.
    KTH, School of Information and Communication Technology (ICT). South China Normal Univ, ZJU SCNU Joint Res Ctr Photon, Guangzhou, Guangdong, Peoples R China..
    Zhang, Lu
    KTH, School of Electrical Engineering and Computer Science (EECS), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Pang, Xiaodan
    KTH, School of Electrical Engineering and Computer Science (EECS), Communication Systems, CoS, Optical Network Laboratory (ON Lab). RISE Acreo AB, Networking & Transmiss Lab, Kista, Sweden..
    Ozolins, Oskars
    RISE Acreo AB, Networking & Transmiss Lab, Kista, Sweden..
    Udalcovs, Aleksejs
    RISE Acreo AB, Networking & Transmiss Lab, Kista, Sweden..
    Guo, Changjian
    South China Normal Univ, ZJU SCNU Joint Res Ctr Photon, Guangzhou, Guangdong, Peoples R China..
    Nordwall, Fredrik
    Tektronix AB, Stockholm, Sweden..
    Engenhardt, Klaus M.
    Tektronix GmbH, Stuttgart, Germany..
    Kakkar, Aditya
    KTH, School of Electrical Engineering and Computer Science (EECS).
    Rodrigo Navarro, Jaime
    KTH, School of Electrical Engineering and Computer Science (EECS).
    Schatz, Richard
    KTH, School of Engineering Sciences (SCI), Applied Physics, Photonics.
    Westergren, Urban
    KTH, School of Engineering Sciences (SCI), Applied Physics, Photonics.
    Jacobsen, Gunnar
    RISE Acreo AB, Networking & Transmiss Lab, Kista, Sweden..
    Popov, Sergei
    KTH, School of Engineering Sciences (SCI), Applied Physics, Photonics.
    Xiao, Shilin
    Shanghai Jiao Tong Univ, State Key Lab Adv Opt Commun Syst & Networks, Shanghai, Peoples R China..
    Chen, Jiajia
    KTH, School of Electrical Engineering and Computer Science (EECS), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    200-Gbps DMT Transmission over 1.6-km SSMF with A Single EML/DAC/PD for Optical Interconnects at C-Band2017In: 43RD EUROPEAN CONFERENCE ON OPTICAL COMMUNICATION (ECOC 2017), IEEE , 2017Conference paper (Refereed)
    Abstract [en]

    We report on the first experimental demonstration of 200-Gbps (net rate 166.7-Gbps) 1.55-mu m 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.

  • 5.
    Kakkar, Aditya
    KTH, School of Engineering Sciences (SCI), Applied Physics, Optics and Photonics, OFO.
    Frequency Noise in Coherent Optical Systems: Impact and Mitigation Methods2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The increase in capacity demand along with the advancement in digital signal processing (DSP) have recently revived the interest in coherent optical communications and led to its commercialization. However, design and development of robust DSP algorithms for example for carrier phase recovery (CPR) becomes complex as we opt for high order modulation formats such as 16QAM and beyond. Further, electrical-domain dispersion compensation (EDC), while providing many advantages, makes the system more susceptible to laser frequency noise (FN). For instance, in coherent optical links with post-reception EDC, while the transmitter frequency noise causes only phase impairment, the local oscillator (LO) FN in these systems results in a noise enhancement in both amplitude and phase. This noise is commonly known as equalization enhanced phase noise (EEPN). It results in asymmetric requirements for transmitter laser and LO laser. Further, the system design in the presence of lasers with non-white frequency noise becomes increasingly challenging for increased capacity-distance product.

    The main contributions of this thesis are, firstly, an experimentally validated theory of coherent optical links with lasers having general non-white frequency noise spectrum and corresponding system/laser design criteria and mitigation technique. Secondly, low complexity and high phase noise tolerant CPR for high order modulation formats.

    The general theory propounded in this thesis elucidates the origin of the laser frequency noise induced noise enhancement in coherent optical links with different DSP configurations. The thesis establishes the existence of multiple frequency noise regimes and shows that each regime results in different set of impairments. The influence of the impairments due to some regimes can ideally be reduced by optimizing the corresponding mitigation algorithms, while other regimes cause irretrievable impairments. Experimentally validated theoretical boundaries of these regimes and corresponding criteria applicable to system/laser design are provided. Further, an EEPN mitigation method and its two possible implementations are proposed and discussed.

    The thesis also demonstrates an intrinsic limitation of the conventional Blind Phase Search (BPS) algorithm due to angular quantization and provides methods to overcome it. Finally, this thesis proposes and demonstrates single stage and multi-stage carrier phase recovery algorithms for compensation of phase impairments due to the two lasers for higher order circular and square modulations. The proposed methods outperform the state of art algorithms both in performance and in complexity.

  • 6.
    Kakkar, Aditya
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Navarro, J. R.
    Schatz, Richard
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Louchet, H.
    Pang, Xiaodan
    RISE ACREO AB.
    Ozolins, O.
    Jacobsen, G.
    Popov, Sergei Yu
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Comprehensive study of equalization-enhanced phase noise in coherent optical systems2015In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 33, no 23, p. 4834-4841, article id 7299252Article 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.

  • 7.
    Kakkar, Aditya
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Navarro, Jaime Rodrigo
    Schatz, Richard
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Fotonik och mikrovågsteknik, FMI.
    Pang, Xiaodan
    Ozolins, Oskars
    Louchet, Hadrien
    Jacobsen, Gunnar
    Popov, Sergei
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    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.

  • 8.
    Kakkar, Aditya
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Navarro, Jaime Rodrigo
    Acreo Swedish ICT AB, Network & Transmiss Lab, S-16425 Kista, Sweden..
    Schatz, Richard
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Pang, Xiaodan
    Acreo Swedish ICT AB, Network & Transmiss Lab, S-16425 Kista, Sweden..
    Ozolins, Oskars
    Acreo Swedish ICT AB, Network & Transmiss Lab, S-16425 Kista, Sweden..
    Louchet, Hadrien
    VPI Photon GmBH, D-10587 Berlin, Germany..
    Jacobsen, Gunnar
    Acreo Swedish ICT AB, Network & Transmiss Lab, S-16425 Kista, Sweden..
    Popov, Sergei
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    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. 1942-1945Article 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 in error floor.

  • 9.
    Kakkar, Aditya
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Navarro, Jaime Rodrigo
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO. Networking and Transmission Laboratory (NETLAB), Acreo Swedish ICT, AB, SE-16425, Kista, Sweden.
    Schatz, Richard
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Pang, Xiaodan
    Ozolins, Oskars
    Udalcovs, Aleksejs
    Louchet, Hadrien
    Popov, Sergei
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Jacobsen, Gunnar
    Laser Frequency Noise in Coherent Optical Systems: Spectral Regimes and Impairments2017In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 7, article id 844Article in journal (Refereed)
    Abstract [en]

    Coherent communication networks are based on the ability to use multiple dimensions of the lightwave together with electrical domain compensation of transmission impairments. Electrical-domain dispersion compensation (EDC) provides many advantages such as network flexibility and enhanced fiber nonlinearity tolerance, but makes the system more susceptible to laser frequency noise (FN), e.g. to the local oscillator FN in systems with post-reception EDC. Although this problem has been extensively studied, statistically, for links assuming lasers with white-FN, many questions remain unanswered. Particularly, the influence of a realistic non-white FN-spectrum due to e.g., the presence of 1/f-flicker and carrier induced noise remains elusive and a statistical analysis becomes insufficient. Here we provide an experimentally validated theory for coherent optical links with lasers having general non-white FN-spectrum and EDC. The fundamental reason of the increased susceptibility is shown to be FN-induced symbol displacement that causes timing jitter and/or inter/intra symbol interference. We establish that different regimes of the laser FN-spectrum cause a different set of impairments. The influence of the impairments due to some regimes can be reduced by optimizing the corresponding mitigation algorithms, while other regimes cause irretrievable impairments. Theoretical boundaries of these regimes and corresponding criteria applicable to system/laser design are provided.

  • 10.
    Kakkar, Aditya
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Olmedo, Miguel Iglesias
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Ozolins, Oskars
    Navarro, Jaime Rodrigo
    Pang, Xiaodan
    Schatz, Richard
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Louchet, Hadrien
    Jacobsen, Gunnar
    Popov, Sergei
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Overcoming EEPN in Coherent Transmission Systems2016In: 2016 CONFERENCE ON LASERS AND ELECTRO-OPTICS (CLEO), IEEE conference proceedings, 2016Conference 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.

  • 11.
    Kakkar, Aditya
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Ozolins, O.
    Navarro, J. R.
    Pang, Xiaodan
    RISE ACREO AB.
    Olmedo, Miguel Iglesias
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Schatz, Richard
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Fotonik och mikrovågsteknik, FMI.
    Louchet, H.
    Jacobsen, G.
    Popov, Sergei
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Design of coherent optical systems impaired by EEPN2016In: 2016 Optical Fiber Communications Conference and Exhibition, OFC 2016, Institute of Electrical and Electronics Engineers (IEEE), 2016Conference 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. 

  • 12.
    Kakkar, Aditya
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Pang, Xiaodan
    RISE ACREO AB.
    Ozolins, O.
    Schatz, Richard
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Navarro, J. R.
    Louchet, H.
    Jacobsen, G.
    Popov, Sergei
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    A path to use large linewidth LO in 28 Gbd 16-QAM metro links2015In: European Conference on Optical Communication, ECOC, IEEE , 2015Conference 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.

  • 13.
    Kakkar, Aditya
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO. Acreo Swedish ICT AB, Sweden.
    Rodrigo Navarro, Jaime
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO. Acreo Swedish ICT AB, Sweden.
    Pang, Xiaodan
    Ozolins, Oskars
    Schatz, Richard
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Westergren, Urban
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Jacobsen, Gunnar
    Popov, Sergei
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Low Complexity Timing Recovery Algorithm for PAM-8 in High Speed Direct Detection Short Range Links2017In: Optics InfoBase Conference Papers, Volume Part F40-OFC 2017, 2017, IEEE , 2017Conference 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 kin SMF links.

  • 14.
    Kakkar, Aditya
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Optics and Photonics, OFO.
    Rodrigo Navarro, Jaime
    KTH, School of Engineering Sciences (SCI), Applied Physics, Optics and Photonics, OFO.
    Schatz, Richard
    KTH, School of Engineering Sciences (SCI), Applied Physics, Optics and Photonics, OFO.
    Pang, Xiaodan
    RISE ACREO AB.
    Ozolins, Oskars
    Nordwall, Fredrik
    Zibar, Darko
    Jacobsen, Gunnnar
    Popov, Sergei
    KTH, School of Engineering Sciences (SCI), Applied Physics, Optics and Photonics, OFO.
    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, 2017, article id 7937006Conference 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.

  • 15.
    Kakkar, Aditya
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Schatz, Richard
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Pang, Xiaodan
    Navarro, Jaime Rodrigo
    Louchet, Hadrien
    Ozolins, Oskars
    Jacobsen, Gunnar
    Popov, Sergei
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Impact of local oscillator frequency noise on coherent optical systems with electronic dispersion compensation2015In: Optics Express, ISSN 1094-4087, 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.

  • 16.
    Marinins, Aleksandrs
    et al.
    KTH, School of Engineering Sciences (SCI).
    Ozolins, O.
    Pang, X.
    Udalcovs, A.
    Navarro, J. R.
    Kakkar, Aditya
    KTH, School of Engineering Sciences (SCI).
    Schatz, Richard
    KTH, School of Engineering Sciences (SCI).
    Jacobsen, G.
    Popov, Sergei
    KTH, School of Engineering Sciences (SCI).
    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 letter, 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. 

  • 17.
    Marinins, Aleksandrs
    et al.
    KTH.
    Ozolins, Oskars
    Pang, Xiaodan
    RISE ACREO AB.
    Udalcovs, Aleksejs
    Navarro, Jaime Rodrigo
    Kakkar, Aditya
    KTH.
    Schatz, Richard
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Jacobsen, Gunnar
    Popov, Sergei
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Cylindrical Polymer Optical Waveguides with Polarization Independent Performance2017In: CLEO: Science and Innovations, OSA Publishing , 2017Conference 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.

  • 18.
    Marinins, Aleksandrs
    et al.
    KTH, School of Engineering Sciences (SCI).
    Ozolins, Oskars
    Pang, Xiaodan
    Udalcovs, Aleksejs
    Navarro, Jaime Rodrigo
    Kakkar, Aditya
    KTH, School of Engineering Sciences (SCI).
    Schatz, Richard
    KTH, School of Engineering Sciences (SCI).
    Jacobsen, Gunnar
    Popov, Sergei
    KTH, School of Engineering Sciences (SCI).
    Thermal reflow engineered cylindrical polymer waveguides for optical interconnectsManuscript (preprint) (Other academic)
    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 efficient 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) (PMMA) strip optical waveguides above the glass transition temperature initiates a waveguide surface reflow due to a decrease of a 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.

  • 19. Navarro, J. R.
    et al.
    Olmedo, Miguel Iglesias
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Kakkar, Aditya
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Pang, Xiaodan
    RISE ACREO AB.
    Ozolins, O.
    Schatz, Richard
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Jacobsen, G.
    Popov, Sergei Yu
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Zibar, D.
    Phase noise tolerant carrier recovery scheme for 28 Gbaud circular 16QAM2015In: European Conference on Optical Communication, ECOC, Institute of Electrical and Electronics Engineers (IEEE), 2015Conference paper (Refereed)
    Abstract [en]

    We propose a novel carrier phase recovery scheme for circular 16QAM coherent transmission systems. Experimental results show low penalties (<1.4 dB) even for linewidths where square 16QAM exhibits irretrievable (above the FEC limit) error floor.

  • 20. Navarro, J. R.
    et al.
    Udalcovs, A.
    Pang, Xiaodan
    KTH, School of Information and Communication Technology (ICT).
    Ozolins, O.
    Kakkar, Aditya
    KTH, School of Engineering Sciences (SCI).
    Schatz, Richard
    KTH, School of Engineering Sciences (SCI).
    Nordwall, F.
    Popov, Sergei
    KTH, School of Engineering Sciences (SCI), Applied Physics, Photonics.
    Jacobsen, G.
    High phase noise tolerant circular-64QAM with efficient phase recovery for coherent optical systems2017In: Optics InfoBase Conference Papers, OSA - The Optical Society , 2017Conference paper (Refereed)
    Abstract [en]

    We experimentally demonstrate the significant phase noise tolerance increase of 28Gbaud circular-64QAM constellations against its square-64QAM counterpart with a novel, low complexity and high-performance phase recovery scheme employing only 8 test phases.

  • 21. Navarro, Jaime Rodrigo
    et al.
    Kakkar, Aditya
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Pang, Xiaodan
    Olmedo, Miguel Iglesias
    KTH.
    Ozolins, Oskars
    Da Ros, Francesco
    Piels, Molly
    Schatz, Richard
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Fotonik och mikrovågsteknik, FMI.
    Zibar, Darko
    Jacobsen, Gunnar
    Popov, Sergei
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Two-Stage n-PSK Partitioning Carrier Phase Recovery Scheme for Circular mQAM Coherent Optical Systems2016In: PHOTONICS, ISSN 2304-6732, Vol. 3, no 2, article id 37Article in journal (Refereed)
    Abstract [en]

    A novel two-stage n-PSK partitioning carrier phase recovery (CPR) scheme for circular multilevel quadrature amplitude modulation (C-mQAM) constellations is presented. The first stage of the algorithm provides an initial rough estimation of the received constellation, which is utilized in the second stage for CPR. The performance of the proposed algorithm is studied through extensive simulations at the forward error correction bit error rate targets of 3.8 x 10(-3) and 1 x 10(-2) and is compared with different CPR algorithms. A significant improvement in the combined linewidth symbol duration product (Delta vT(s)) tolerance is achieved compared to the single-stage n-PSK partitioning scheme. Superior performance in the Delta vT(s) tolerance compared to the blind phase search algorithm is also reported. The relative improvements with respect to other CPR schemes are also validated experimentally for a 28-Gbaud C-16QAM back-to-back transmission system. The computational complexity of the proposed CPR scheme is studied, and reduction factors of 24.5 broken vertical bar 30.1 and 59.1 broken vertical bar 63.3 are achieved for C-16QAM and C-64QAM, respectively, compared to single-stage BPS in the form of multipliers broken vertical bar adders.

  • 22. Navarro, Jaime Rodrigo
    et al.
    Kakkar, Aditya
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Pang, Xiaodan
    Ozolins, Oskars
    Schatz, Richard
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Olmedo, Miguel Iglesias
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Jacobsen, Gunnar
    Popov, Sergei
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Carrier Phase Recovery Algorithms for Coherent Optical Circular mQAM Systems2016In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 34, no 11, p. 2717-2723Article in journal (Refereed)
    Abstract [en]

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

  • 23. Ozolins, O.
    et al.
    Iglesias Olmedo, Miguel
    KTH, School of Information and Communication Technology (ICT).
    Pang, X.
    Gaiarin, S.
    Kakkar, A.
    KTH, School of Information and Communication Technology (ICT).
    Udalcovs, A.
    KTH, School of Information and Communication Technology (ICT).
    Engenhardt, K. M.
    Asyngier, T.
    Schatz, R.
    KTH, School of Information and Communication Technology (ICT).
    Li, J.
    Nordwall, F.
    Westergren, U.
    KTH, School of Information and Communication Technology (ICT).
    Zibar, D.
    Popov, S.
    KTH, School of Information and Communication Technology (ICT).
    Jacobsen, G.
    100 GHz EML for high speed optical interconnect applications2016In: European Conference on Optical Communication, ECOC, Institute of Electrical and Electronics Engineers Inc. , 2016, p. 127-129Conference paper (Refereed)
    Abstract [en]

    We report on a 116 Gbit/s OOK, 4PAM and 105 Gbit/s 8PAM optical transmitter using InP-based integrated EML for interconnect applications with up to 30 dB static extinction ratio and over 100 GHz 3 dB bandwidth with 2 dB ripple. © VDE VERLAG GMBH. Berlin. Offenbach.

  • 24. Ozolins, O
    et al.
    Pang, Xiaodan
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab). RISE ACREO AB.
    Olmedo, M. Iglesias
    KTH, School of Information and Communication Technology (ICT).
    Kakkar, Aditya
    KTH, School of Information and Communication Technology (ICT).
    Udalcovs, A
    Navarro, J R
    Schatz, Richard
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Westergren, Urban
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Jacobsen, G
    Popov, Sergei
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    High-speed optical interconnects with integrated externally modulated laser2017In: Transparent Optical Networks (ICTON), 2017 19th International Conference on, Institute of Electrical and Electronics Engineers (IEEE), 2017, p. 1-1Conference paper (Refereed)
    Abstract [en]

    The cloud services together with the huge size datasets are driving demand for bandwidth in datacenters [1]. The 400 Gbps client-side links are demanding cost efficient solution: to reduce the number of lanes and increase the bandwidth for a single lane. The intensity modulation and direct-detection systems together with integrated semiconductor lasers and modulators appear as promising solution in four optical lanes at 100G since it reduces complexity, power consumption and costs [2]. However, it requires silicon and InP opto-electronic components with more than 70 GHz bandwidth [3]. In this talk, we report on a cost-efficient integrated externally modulated laser (EML) with high bandwidth for record high-speed intensity modulation and direct detection system demonstration with up to 100G OOK, PAM4/8 and duobinary signaling, as well as analog modulations e.g. DMT, paving the way for high speed multilevel modulation formats [4–6]. Related techniques including digital signal processing algorithms for timing recovery, adaptive/static equalization are also discussed in terms of practical implementation and complexity. In addition, techniques constructively using time domain super-Nyquist image induced aliasing for mitigating modulator driver nonlinearity for high speed DMT transmission will be presented [6], [7].

  • 25. Ozolins, Oskars
    et al.
    Pang, Xiaodan
    Iglesias Olmedo, Miguel
    KTH, School of Information and Communication Technology (ICT).
    Kakkar, Aditya
    KTH, School of Information and Communication Technology (ICT).
    Udalcovs, Aleksejs
    Gaiarin, Simone
    KTH, School of Information and Communication Technology (ICT).
    Navarro, Jaime Rodrigo
    Engenhardt, Klaus M.
    Asyngier, Tadeusz
    Schatz, Richard
    KTH, School of Information and Communication Technology (ICT).
    Li, Jie
    Nordwall, Fredrik
    Westergren, Urban
    KTH, School of Information and Communication Technology (ICT).
    Zibar, Darko
    Popov, Sergei
    KTH, School of Information and Communication Technology (ICT).
    Jacobsen, Gunnar
    100 GHz Externally Modulated Laser for Optical Interconnects2017In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 35, no 6, p. 1174-1179Article in journal (Refereed)
    Abstract [en]

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

  • 26. Ozolins, Oskars
    et al.
    Pang, Xiaodan
    RISE ACREO AB.
    Olmedo, Miguel Iglesias
    KTH, School of Information and Communication Technology (ICT).
    Udalcovs, Aleksejs
    KTH, School of Information and Communication Technology (ICT).
    Kakkar, Aditya
    KTH, School of Information and Communication Technology (ICT).
    Navarro, Jaime Rodrigo
    Schatz, Richard
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Westergren, Urban
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Popov, Sergei
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Jacobsen, Gunnar
    High-speed optical and wireless transmission-challenges and achievements2016In: Advances in Wireless and Optical Communications (RTUWO), 2016, IEEE, 2016Conference paper (Refereed)
    Abstract [en]

    The cloud services together with the huge size datasets are driving demand for bandwidth in datacenters. The 400 Gbps client-side links are demanding a solution. The intensity modulation and direct-detection systems together with integrated semiconductor lasers and modulators appear as promising solution in four optical lanes at 100 Gbps net rate in order to reduce complexity, size, power consumption and cost.

  • 27.
    Ozolins, Oskars
    et al.
    RISE Acreo AB, Networking & Transmiss Lab, Kista, Sweden..
    Pang, Xiaodan
    RISE Acreo AB, Networking & Transmiss Lab, Kista, Sweden.;KTH Royal Inst Technol, Sch ICT, Stockholm, Sweden.;KTH Royal Inst Technol, Sch SCI, Stockholm, Sweden..
    Udalcovs, Aleksejs
    RISE Acreo AB, Networking & Transmiss Lab, Kista, Sweden..
    Schatz, Richard
    KTH, School of Engineering Sciences (SCI), Applied Physics, Photonics.
    Westergren, Urban
    KTH, School of Engineering Sciences (SCI), Applied Physics, Photonics.
    Rodrigo Navarro, Jaime
    Kakkar, Aditya
    KTH.
    Nordwall, Fredrik
    Tektronix AB, Stockholm, Sweden..
    Engenhardt, Klaus M.
    Tektronix GmbH, Stuttgart, Germany..
    Chen, Jiajia
    KTH, School of Electrical Engineering and Computer Science (EECS), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Popov, Sergei
    KTH, School of Engineering Sciences (SCI), Applied Physics, Photonics.
    Jacobsen, Gunnar
    RISE Acreo AB, Networking & Transmiss Lab, Kista, Sweden..
    100 Gbaud 4PAM Link for High Speed Optical Interconnects2017In: 43RD EUROPEAN CONFERENCE ON OPTICAL COMMUNICATION (ECOC 2017), IEEE , 2017Conference 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.

  • 28.
    Pang, Xiaodan
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Ozolins, O.
    RISE Acreo AB, NETLAB Networking & Transmiss Lab, Isafjordsgatan 22, S-16440 Kista, Sweden..
    Navarro, Julien R. G.
    Udalcovs, A.
    RISE Acreo AB, NETLAB Networking & Transmiss Lab, Isafjordsgatan 22, S-16440 Kista, Sweden..
    Kakkar, Aditya
    KTH, School of Electrical Engineering and Computer Science (EECS).
    Lin, Rui
    KTH, School of Electrical Engineering and Computer Science (EECS), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Schatz, Richard
    KTH, School of Engineering Sciences (SCI), Applied Physics, Photonics. KTH Royal Inst Technol, Isafjordsgatan 22, S-16440 Kista, Sweden..
    Tang, M.
    Huazhong Univ Sci & Technol, Wuhan, Hubei, Peoples R China..
    Fu, S.
    Huazhong Univ Sci & Technol, Wuhan, Hubei, Peoples R China..
    Liu, D.
    Huazhong Univ Sci & Technol, Wuhan, Hubei, Peoples R China..
    Jacobsen, G.
    RISE Acreo AB, NETLAB Networking & Transmiss Lab, Isafjordsgatan 22, S-16440 Kista, Sweden..
    Popov, Sergei
    KTH, School of Engineering Sciences (SCI), Applied Physics, Photonics.
    Chen, Jiajia
    KTH, School of Electrical Engineering and Computer Science (EECS), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Low-Complexity Digital Signal Processing Techniques to Enable Coherent Optical Systems for Metro and Access networks2018In: 23RD OPTO-ELECTRONICS AND COMMUNICATIONS CONFERENCE (OECC2018), IEEE , 2018Conference paper (Refereed)
    Abstract [en]

    We summarize our recent research works on enabling coherent optical transmission systems for metro and access networks with low-complexity digital signal processing techniques, focusing on reduction of laser linewidth requirement with efficient carrier phase recovery.

  • 29.
    Pang, Xiaodan
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Ozolins, Oscar
    Gaiarin, S.
    Kakkar, Aditya
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Rodrigo Navarro, J.
    Iglesias Olmedo, M.
    Schatz, Richard
    KTH, School of Engineering Sciences (SCI), Applied Physics. KTH, School of Information and Communication Technology (ICT), Centres, Kista Photonics Research Center, KPRC.
    Udalcovs, A.
    Westergren, U.
    Zibar, D.
    Popov, Sergei
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Jacobsen, Gunnar
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Experimental Study of 1.55-μ m EML-Based Optical IM/DD PAM-4/8 Short Reach Systems2017In: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 29, no 6, p. 523-526, article id 7839925Article in journal (Refereed)
    Abstract [en]

    We experimentally evaluate high-speed intensity modulation/direct detection (IM/DD) transmissions with a 1.55-μ text broadband electro-Absorption modulated laser and pulse amplitude modulations (PAM). We demonstrate 80 Gb/s/ λ PAM-4 and 96 Gb/s/ λ PAM-8 transmissions with low-complexity digital equalizers at the receiver. Performance comparison with different types of equalizers are performed, including linear symbol-spaced feed-forward equalizer (FFE), fractional (half-symbol) spaced FFE and decision feedback equalizer (DFE), with different tap number. It is found that for both cases, a 6-Tap symbol-spaced FFE is sufficient to achieve a stable performance with bit-error-rate below the 7% overhead hard decision forward error correction (7%-OH HD-FEC) threshold over a 4 km standard single mode fiber link. Practical considerations including comparison between adaptive and static equalizer implementation and tolerable fiber chromatic dispersion are discussed.

  • 30.
    Pang, Xiaodan
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab). RISE Acreo AB.
    Ozolins, Oskars
    Schatz, Richard
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Storck, Joakim
    Udalcovs, Aleksejs
    Navarro, Jaime Rodrigo
    Kakkar, Aditya
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Maisons, Gregory
    Carras, Mathieu
    Jacobsen, Gunnar
    Popov, Sergei
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Lourdudoss, Sebastian
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Gigabit free-space multi-level signal transmission with a mid-infrared quantum cascade laser operating at room temperature2017In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 42, no 18, p. 3646-3649Article in journal (Refereed)
    Abstract [en]

    Gigabit free-space transmissions are experimentally demon-strated with a quantum cascaded laser (QCL) emitting at mid-wavelength infrared of 4.65 mu m, and a commercial infrared photovoltaic detector. The QCL operating at room temperature is directly modulated using on - off keying and, for the first time, to the best of our knowledge, four-and eight-level pulse amplitude modulations (PAM-4, PAM-8). By applying pre- and post-digital equalizations, we achieve up to 3 Gbit/s line data rate in all three modulation configurations with a bit error rate performance of below the 7% overhead hard decision forward error correction limit of 3.8 x 10(-3). The proposed transmission link also shows a stable operational performance in the lab environment.

  • 31.
    Pang, Xiaodan
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Rodrigo Navarro, Jaime
    KTH, School of Engineering Sciences (SCI), Applied Physics, Optics and Photonics, OFO.
    Kakkar, Aditya
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Olmedo, Miguel Iglesias
    Ozolins, Oskars
    KTH, School of Engineering Sciences (SCI), Applied Physics, Optics and Photonics, OFO.
    Schatz, Richard
    KTH, School of Information and Communication Technology (ICT), Centres, Kista Photonics Research Center, KPRC. KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Udalcovs, Aleksejs
    KTH, School of Engineering Sciences (SCI), Applied Physics, Optics and Photonics, OFO.
    Popov, Sergei
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Jacobsen, Gunnar
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Advanced Modulations and DSP Enabling High-speed Coherent Communication Using Large Linewidth Lasers2016In: 2016 PROGRESS IN ELECTROMAGNETICS RESEARCH SYMPOSIUM (PIERS), IEEE , 2016, p. 4849-4849Conference paper (Refereed)
  • 32.
    Popov, Sergei
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Kakkar, Aditya
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Navarro, J. R.
    Pang, Xiaodan
    Ozolins, O.
    Schatz, Richard
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Louchet, H.
    Jacobsen, G.
    Equalization-Enhanced Phase Noise in Coherent Optical Communications Systems2016In: 2016 18TH INTERNATIONAL CONFERENCE ON TRANSPARENT OPTICAL NETWORKS (ICTON), IEEE, 2016Conference paper (Refereed)
    Abstract
  • 33.
    Rodrigo Navarro, Jaime
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Optics and Photonics, OFO.
    Kakkar, Aditya
    KTH, School of Engineering Sciences (SCI), Applied Physics, Optics and Photonics, OFO.
    Pang, Xiaodan
    Ozolins, Oskars
    Udalcovs, Aleksejs
    Schatz, Richard
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Popov, Sergei
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Jacobsen, Gunnar
    Design of Multi-Stage Carrier Phase Recovery Schemes for  high  order  Coherent  Optical  mQAM  SystemsArticle in journal (Refereed)
  • 34.
    Rodrigo Navarro, Jaime
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Optics and Photonics, OFO. Acreo Swedish ICI'AB, Sweden.
    Kakkar, Aditya
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO. Acreo Swedish ICI'AB, Sweden.
    Schatz, Richard
    KTH, School of Engineering Sciences (SCI), Applied Physics, Optics and Photonics, OFO.
    Pang, X.
    Ozolins, O.
    Nordwall, F.
    Louchet, H.
    Popov, Sergei
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Jacobsen, G.
    High performance and low complexity carrier phase recovery schemes for 64-QAM coherent optical systems2017In: 2017 Optical Fiber Communications Conference and Exhibition, OFC 2017 - Proceedings, Institute of Electrical and Electronics Engineers Inc. , 2017Conference paper (Refereed)
    Abstract [en]

    We experimentally validate two novel CPR schemes outperforming existing CPRs in complexity and performance. A complexity reduction of at least a factor of 4 is reported compared to the BPS algorithm for a 64QAM system.

  • 35.
    Rodrigo Navarro, Jaime
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Optics and Photonics, OFO.
    Kakkar, Aditya
    KTH, School of Engineering Sciences (SCI), Applied Physics, Optics and Photonics, OFO.
    Schatz, Richard
    KTH, School of Engineering Sciences (SCI), Applied Physics, Optics and Photonics, OFO.
    Pang, Xiaodan
    Acreo Swedish, Sweden.
    Ozolins, Oskars
    Acreo Swedish, Sweden.
    Fredrik, Nordwall
    Louchet, Hadrien
    Popov, Sergei
    KTH, School of Engineering Sciences (SCI), Applied Physics, Optics and Photonics, OFO.
    Jacobsen, Gunnnar
    High Performance and Low Complexity Carrier Phase Recovery Schemes for 64-QAM Coherent Optical Systems2017In: Optics InfoBase Conference Papers, Optical Society of America, 2017Conference paper (Refereed)
    Abstract [en]

    We experimentally validate two novel CPR schemes outperforming existing CPRs in complexity and performance. A complexity reduction of at least a factor of 4 is reported compared to the BPS algorithm for a 64QAM system.

  • 36.
    Rodrigo Navarro, Jaime
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Optics and Photonics, OFO.
    Kakkar, Aditya
    KTH, School of Engineering Sciences (SCI), Applied Physics, Optics and Photonics, OFO.
    Schatz, Richard
    KTH, School of Engineering Sciences (SCI).
    Pang, Xiaodan
    RISE ACREO AB.
    Ozolins, Oskars
    Udalcovs, Aleksejs
    Popov, Sergei
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Jacobsen, Gunnnar
    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.

  • 37.
    Rodrigo Navarro, Jaime
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO. Acreo Swedish, Sweden.
    Pang, Xiaodan
    Kakkar, Aditya
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Ozolins, Oskars
    Schatz, Richard
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Jacobsen, Gunnar
    Popov, Sergei
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Adaptive Boundaries Scheme for Cycle-Slip Mitigation in C-mQAM Coherent Systems2015In: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 27, no 20, p. 2154-2157Article in journal (Refereed)
    Abstract [en]

    We propose a method for cycle-slip mitigation in circular multilevel quadrature amplitude modulation (C-mQAM) coherent optical systems, with constellation rotational asymmetry, based on an adaptive boundaries approach. The impact of cycle-slips in C-mQAM coming from Viterbi-Viterbi algorithm limits the phase noise tolerance. By introducing adaptive boundaries and a differential coding scheme, the ambiguity of asymmetrical rotation of constellation can be effectively removed. Performance of the proposed method is evaluated for a C-16QAM and C-64QAM for various laser linewidths. Results show a noticeable improvement in linewidth symbol duration product (Delta(upsilon) . T-S) tolerance compared with the previous studies on C-mQAM and mQAM constellations. The Delta(upsilon) . T-S tolerance reaches 4 x 10(-4) and 1.1 x 10(-4) for C-16QAM and C-64QAM, respectively, for 1 dB penalty at a symbol error rate of 10(-3).

  • 38.
    Udalcovs, Aleksejs
    et al.
    KTH.
    Schatz, Richard
    KTH, School of Engineering Sciences (SCI), Applied Physics, Photonics.
    Monti, Paolo
    KTH, School of Electrical Engineering and Computer Science (EECS), Communication Systems, CoS.
    Ozolins, Oskars
    KTH, School of Engineering Sciences (SCI), Applied Physics, Photonics.
    Pang, Xiaodan
    KTH, School of Electrical Engineering and Computer Science (EECS), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Navarro, Julien R. G.
    KTH, School of Engineering Sciences (SCI).
    Kakkar, Aditya
    KTH, School of Engineering Sciences (SCI).
    Louchet, H.
    Popov, Sergei
    KTH, School of Engineering Sciences (SCI), Applied Physics, Photonics.
    Wosinska, Lena
    KTH, School of Electrical Engineering and Computer Science (EECS), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Jacobsen, Gunnar
    Quantifying spectral and energy efficiency limitations of WDM networks due to crosstalk in optical nodes2017In: Optics InfoBase Conference Papers, OSA - The Optical Society , 2017Conference paper (Refereed)
    Abstract [en]

    We demonstrate the significant impact of crosstalk between add and drop ports at optical nodes on energy-efficiency per Hertz in WDM networks employing 32/64 Gbd DP-16QAM transmission, especially when the isolation is reduced to 30dB.

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