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  • 1. El-Taher, Atalla
    et al.
    Pang, Xiaodan
    RISE ACREO AB.
    Schatz, Richard
    KTH, School of Engineering Sciences (SCI), Applied Physics, Optics and Photonics, OFO.
    Jacobsen, Gunnar
    Popov, Sergei
    KTH, School of Engineering Sciences (SCI), Applied Physics, Optics and Photonics, OFO.
    Sergeyev, Sergey
    Noise characterization and transmission evaluation of unrepeated Raman amplified DP-16QAM link2015In: Optical Fiber Communication Conference, 2015Conference paper (Refereed)
    Abstract [en]

    Impairments characterization and performance evaluation of Raman amplified unrepeated DP-16QAM transmissions arc conducted, Experimental results indicate that small gain in forward direction enhance the system signal-to-noise ratio for longer reach without introducing noticeable penalty.

  • 2.
    Iglesias Olmedo, Miguel
    KTH, School of Engineering Sciences (SCI), Applied Physics, Optics and Photonics, OFO.
    Impairment Mitigation in High Capacity and Cost-efficient Optical Data Links2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The work presented in this thesis fits within the broader area of fiber optics communications. This is an important area of research as it provides a breeding ground for the present and future technologies supporting the Internet. Due to the ever-increasing bandwidth demands worldwide, the network infrastructures that make up the Internet are continuously being upgraded. This thesis aims to identify key segments of the Internet that are deemed to become the Internet's bottleneck if new technology does not replace the current one. These are datacenter intra and inter-connects, and metropolitan core area networks. In each category, we provide a comprehensive overview of the state of the art, identify key impairments affecting data transmission, and suggest solutions to overcome them.

     

    For datacenter intra and inter-connects, the key impairments are lack of bandwidth from electro-optic devices, and dispersion. Solutions attempting to tackle these impairments must be constrained by cost and power consumption. The provided solution is MultiCAP, an alternative advanced modulation format that is more tolerable to dispersion and provides bandwidth management features, while being flexible enough to sacrifice performance in order to gain simplicity. MultiCAP was the first advanced modulation format to achieve over 100~Gb/s in 2013 for a data-center interconnect and set the world record on data transmission over a single VCSEL in 2014 for a short reach data link. 

     

    On metro-core networks, the challenge is to efficiently mitigate carrier induced frequency noise generated by modern semiconductor lasers. We point out that, when such lasers are employed, the commonly used laser linewidth fails to estimate system performance, and we propose an alternative figure of merit we name "Effective Linewidth". We derive this figure of merit analytically, explore it by numerical simulations and experimentally validate our results by transmitting a 28~Gbaud DP-16QAM over an optical link.

  • 3.
    Ivanov, Ruslan
    KTH, School of Engineering Sciences (SCI), Applied Physics, Optics and Photonics, OFO.
    Impact of carrier localization on recombination in InGaN quantum wells with nonbasal crystallographic orientations2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The modern InGaN technology demonstrates high efficiencies only in the blue spectral region and low current operation modes. The growth of InGaN quantum wells (QWs) on nonbasal crystallographic planes (NBP) has potential to deliver high-power blue and green light emitting diodes and lasers. The emission properties of these QWs are largely determined by the localization of carriers in the minima of spatially inhomogeneous band potential, which affects the recombination dynamics, spectral characteristics of the emission, its optical polarization and carrier transport. Understanding it is crucial for increasing the efficiency of NBP structures to their theoretical limit.

    In this thesis, the influence of carrier localization on the critical aspects of light emission has been investigated in semipolar  and nonpolar  InGaN QWs. For this purpose, novel multimode scanning near-field optical microscopy configurations have been developed, allowing mapping of the spectrally-, time-, and polarization-resolved emission.

    In the nonpolar QW structures the sub-micrometer band gap fluctuations could be assigned to the selective incorporation of indium on different slopes of the undulations, while in the smoother semipolar QWs – to the nonuniformity of QW growth. The nanoscale band potential fluctuations and the carrier localization were found to increase with increasing indium percentage in the InGaN alloy. In spite to the large depth of the potential minima, the localized valence band states were found to retain properties of the corresponding bands. The reduced carrier transfer between localization sites has been suggested as a reason for the long recombination times in the green-emitting semipolar QWs. Sharp increase of the radiative lifetimes has been assigned to the effect of nanoscale electric fields resulting from nonplanar QW interfaces. Lastly, the ambipolar carrier diffusion has been measured, revealing ~100 nm diffusion length and high anisotropy.

  • 4.
    Ivanov, Ruslan
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Optics and Photonics, OFO.
    Marcinkevičius, Saulius
    KTH, School of Engineering Sciences (SCI), Applied Physics, Optics and Photonics, OFO.
    Mensi, Mounir D.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Optics and Photonics, OFO.
    Martinez, Oscar
    KTH, School of Engineering Sciences (SCI), Applied Physics. GdS Optronlab, Física Materia Condensada, Universidad de Valladolid, Valladolid, Spain.
    Kuritzky, L. Y.
    Myers, D. J.
    Nakamura, S.
    Speck, J. S.
    Polarization-Resolved Near-Field Spectroscopy of Localized States in m -Plane InxGa1-x N/Ga N Quantum Wells2017In: Physical Review Applied, Vol. 7, no 6Article in journal (Refereed)
    Abstract [en]

    We present a polarization, spectrally, and spatially resolved near-field photoluminescence (PL) measurement technique and apply it to the study of wide m-plane InxGa1-xN/GaN quantum wells grown on on-axis and miscut GaN substrates. It is found that PL originates from localized states; nevertheless, its degree of linear polarization (DLP) is high with little spatial variation. This allows an unambiguous assignment of the localized states to InxGa1-xN composition-related band potential fluctuations. Spatial PL variations, occurring due to morphology features of the on-axis samples, play a secondary role compared to the variations of the alloy composition. The large PL peak wavelength difference for polarizations parallel and perpendicular to the c axis, the weak correlation between the peak PL wavelength and the DLP, and the temperature dependence of the DLP suggest that effective potential variations and the hole mass in the second valence-band level are considerably smaller than that for the first level. DLP maps for the long wavelength PL tails have revealed well-defined regions with a small DLP, which have been attributed to a partial strain relaxation around dislocations.

  • 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 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.

  • 7.
    Lobov, Gleb
    KTH, School of Engineering Sciences (SCI), Applied Physics, Optics and Photonics, OFO.
    Electro-optical properties of one-dimensional organic crystals2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The recent development of photonics and applications puts new challenges for systems using emission, transmission and modulation of light. For these reasons, novel optical materials attract a special interest for their enabling properties for novel technologies.

    In this work, we performed the research on fundamental properties and the possibility of implementation of electro-optical response of Poly-3-hexylthiophene-2,5-diyl (P3HT) nanofibers, which belong to the class of organic semiconductor crystalline materials. Our research demonstrated that an external electric field allows controlling the orientation of nanofibers dispersed in a solution by changing the electrical properties of P3HT crystals. This method was used to introduce a collective alignment of P3HT nanofibers and to impact the optical properties of the colloid. The spectroscopic and polarization measurements show that P3HT nanofibers possess optical anisotropy in a wide range of visible spectrum. This property combined with the ability to manipulate the orientation of nanofibers dynamically, was used for direct phase and intensity modulation of transmitted light. Along with these investigations, several engineering and technology tasks were solved. We have designed the transverse electro-optical cell using all-optical-fiber approach, as well as the longitudinal electro-optical cell was fabricated using a novel polymer molding technique.

    The obtained research results demonstrate the potential of P3HT crystalline nanofibers as a material class of large niche of applications, not only limited to photovoltaics but also being implemented in electro-optical systems to control light polarization and propagation.

  • 8.
    Mounir, Mensi
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Optics and Photonics, OFO.
    Ivanov, Ruslan
    KTH, School of Engineering Sciences (SCI), Applied Physics, Optics and Photonics, OFO.
    Uždavinys, Tomas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Optics and Photonics, OFO.
    Kelchner, Kathryn
    Materials Department, University of California, Santa Barbara.
    Nakamura, Shuji
    Materials Department, University of California, Santa Barbara.
    DenBaars, Steven P.
    Materials Department, University of California, Santa Barbara.
    Speck, James S.
    Materials Department, University of California, Santa Barbara.
    Marcinkevičius, Saulius
    KTH, School of Engineering Sciences (SCI), Applied Physics, Optics and Photonics, OFO.
    Direct measurement of nanoscale lateral carrier diffusion: toward scanning diffusion microscopy2017In: ACS Photonics, E-ISSN 2330-4022Article in journal (Other academic)
    Abstract [en]

    A multimode scanning near-field optical microscopy technique allowing to map surface morphology, photoluminescence (PL) spectra in illumination and illumination-collection modes, as well as PL dynamics, all in one scan, has been developed along with a method to use it for evaluation of carrier diffusion. The method allows to measure diffusion lengths as small as ~100 nm, their anisotropy and spatial distribution, parameters remaining inaccessible to conventional far-field techniques. The procedure has been applied to study ambipolar carrier diffusion in a nonpolar m-plane InGaN/GaN quantum well. The diffusion was found to be highly anisotropic with diffusion coefficients along and perpendicular to the wurtzite c axis equal to 0.4 and 1.9 cm2/s, respectively. The large diffusion anisotropy confirms band structure calculations that suggest that the top-most valence band in m-plane InGaN quantum well is highly anisotropic

  • 9.
    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)
  • 10.
    Popov, Sergei
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Optics and Photonics, OFO.
    Pang, Xiaodan
    RISE ACREO AB.
    Ozolins, Oskars
    Olmedo, Miguel I
    Kakkar, Aditya
    Gaiarin, Simone
    Udalcovs, Aleksejs
    Lin, Rui
    Schatz, Richard
    KTH, School of Engineering Sciences (SCI), Applied Physics, Fotonik och mikrovågsteknik.
    Navarro, Jaime R
    Djupsjöbacka, Anders
    Zibar, Darko
    Chen, Jiajia
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Westergren, Urban
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Jacobsen, Gunnar
    Ultra-Broadband High-Linear Integrated Transmitter for Low Complexity Optical Interconnect Applications2016In: Optics InfoBase Conference Papers, Optics Info Base, Optical Society of America, 2016Conference paper (Refereed)
    Abstract [en]

    We report on a high-speed optical transmitter using InP-based integrated externally modulated laser for optical interconnect applications with up to 30 dB static extinction ratio and over 100 GHz 3 dB bandwidth with 2 dB ripple. It is evaluated with up to 116 Gbit/s on-offkeying, 4-pulse amplitude modulation (PAM) and up to 105 Gbit/s 8-PAM optical signals with different digital equalization implementations. Low number of taps is required for a high and stable performance. Results reveal that digital equalization significantly boosts the passive optical interconnect scalability.

  • 11.
    Rodrigo Navarro, Jaime
    KTH, School of Engineering Sciences (SCI), Applied Physics, Optics and Photonics, OFO. ACREO Swedish ICT.
    Phase Noise Tolerant Modulation Formats and DSP Algorithms for Coherent Optical Systems2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Coherent detection together with multilevel modulation formats has the potential to significantly increase the capacity of existing optical communication systems at no extra cost in signal bandwidth. However, these modulation formats are more susceptible to the impact of different noise sources and distortions as the distance between its constellation points in the complex plane reduces with the modulation index. In this context, digital signal processing (DSP) plays a key role as it allows compensating for the impairments occurring during signal generation, transmission and/or detection relaxing the complexity of the overall system. The transition towards pluggable optical transceivers, offers flexibility for network design/upgrade but sets strict requirements on the power consumption of the DSP thus limiting its complexity. The DSP module complexity however, scales with the modulation order and, in this scenario, low complex yet high performance DSP algorithms are highly desired.

    In this thesis, we mainly focus on the impact of laser phase noise arising from the transmitter and local oscillator (LO) lasers in coherent optical communication systems employing high order modulation formats. In these systems, the phase noise of the transmitting and LO lasers translate into phase noise in the received constellation impeding the proper recovery of the transmitted data. In order to increase the system phase noise tolerance, we firstly explore the possibility of re-arranging the constellation points in a circularly shaped mQAM (C-mQAM) constellation shape to exploit its inherent phase noise tolerance. Different low-complex carrier phase recovery (CPR) schemes applicable to these constellations are proposed along with a discussion on its performance and implementation complexity. Secondly, the design guidelines of high performance and low complex CPR schemes for conventional square mQAM constellations are presented. We identify the inherent limitation of the state-of-the-art blind phase search (BPS) carrier phase recovery algorithm which hinders its achievable performance and implementation complexity and present a low complex solution to overcome it. The design guidelines of multi-stage CPR schemes for high order modulation formats, where the BPS algorithm is employed at any of the stages, are also provided and discussed. Finally, the interplay between the received dispersed signal and the LO phase noise is analytically investigated to characterize the origin of the equalization enhanced phase noise phenomena.

  • 12.
    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)
  • 13.
    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.

  • 14.
    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.

  • 15.
    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.

  • 16.
    Sun, Xu
    KTH, School of Engineering Sciences (SCI), Applied Physics, Optics and Photonics, OFO. KTH.
    Hybrid Plasmonic Devices for Optical Communication and Sensing2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Hybrid plasmonic (HP) waveguides, a multi-layer waveguide structure supporting a hybrid mode of surface plasmonics and Si photonics, is a compromise way to integrate plasmonic materials into Si or SOI platforms, which can guide optical waves of sub-wavelength size, and with relative low propagation loss. In this thesis, several HP waveguides and devices are developed for the purposes of optical communications and sensing. The single-slot HP ring resonator sensor with 2.6µm radius can give a quality factor (factor) of 1300 at the communication wavelength of 1.5µm with a device sensitivity of 102nm/RIU (refractive index unit). The Mach-Zehnder interferometer (MZI) with a 40µm double-slot HP waveguide has a device sensitivity around 474nm/RIU. The partly open silicon side-coupled double-slot HP ring resonator has a device sensitivity of 687.5nm/RIU, with a Q factor over 1000 after optimization. Further, an all-optical switching HP donut resonator with a photothermal plasmonic absorber is developed, utilizing the thermal expansion effect of silicon to shift the resonant peak of the HP resonator. The active area has a radius of 10µm to match the core size of a single-mode fiber. By applying 10mW power of the driving laser to the absorber, the resonator transmitted power can be changed by 15dB, with an average response time of 16µs. Using the same fabrication flow, and removing the oxide materials using hydrogen fluoride wet etching, a hollow HP waveguide is fabricated for liquid sensing applications. The experimentally demonstrated waveguide sensitivity is about 0.68, which is more than twice that of pure Si waveguide device. Microelectromechanical systems (MEMS) can also be integrated into vertical HP waveguides. By tuning the thickness of the air gap, over 20dB transmitted power change was experimentally demonstrated. This can be used for optical switching applications by either changing the absorption or phase of the HP devices.

  • 17.
    Sun, Xu
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Optics and Photonics, OFO. KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Thylén, Lars
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology. KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Wosinski, L.ech
    KTH, School of Engineering Sciences (SCI), Applied Physics, Optics and Photonics, OFO. KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Hollow hybrid plasmonic Mach-Zehnder sensor2017In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 42, no 4Article in journal (Refereed)
    Abstract [en]

    A Mach–Zehnder interferometer (MZI)-based liquid refractiveindex sensor, utilizing a hollow hybrid plasmonic (HP)waveguide as the sensing element, has been investigated,showing large sensitivity to the refractive index changesof the tested liquids, as well as lower propagation loss incomparison to typical plasmonic waveguide-based ones.The sensor is fabricated using conventional silicon-oninsulator(SOI) technology; therefore, it is compatible toother standard SOI devices. The waveguide sensitivity, Sw,is experimentally demonstrated to be 0.64, with a propagationloss less than 0.25 dB/μm. Using a 20 μm long hollowHP waveguide in the sensing arm, the sensitivity of the MZIsensor (device sensitivity, Sd ) is about 160 nm/RIU, with anextinction ratio larger than 40 dB.

  • 18.
    Sun, Xu
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Optics and Photonics, OFO. KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Thylén, Lars
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology. KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Wosinski, Lech
    KTH, School of Engineering Sciences (SCI), Applied Physics, Optics and Photonics, OFO. KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Hollow Hybrid Plasmonic Waveguide Used for Electro-optic Phase Modulation2016In: Optics InfoBase Conference Papers, Optical Society of America, 2016, p. AF3F.2-Conference paper (Refereed)
    Abstract [en]

    An electro-optic polymer-based hollow hybrid plasmonic phase modulator has beenproposed. Estimating from our preliminary experimental results, related to a hollow HP liquidsensor, the proposed device shows unique advantages in high speed modulation applications.

  • 19.
    Sun, Xu
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Optics and Photonics, OFO. KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Thylén, Lars
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology. KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Wosinski, L.ech
    KTH, School of Engineering Sciences (SCI), Applied Physics, Optics and Photonics, OFO. KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    MEMS Tunable Hybrid Plasmonic-Si Waveguide2017In: OSA Technical Digest (online), 2017, p. Th2A.6-Conference paper (Refereed)
    Abstract [en]

    A MEMS tunable hybrid plasmonic-Si (HP) waveguide is investigated, showing verylarge changes of both effective refractive index and propagation loss when applying bias voltage.Preliminary experimental results show that: with 15μm MEMS structure in Si waveguideplatform, the extinction ratio can be over 20dB between “on” and “off” states.

  • 20.
    Udalcovs, Aleksejs
    et al.
    KTH, School of Information and Communication Technology (ICT).
    Schatz, Richard
    KTH, School of Engineering Sciences (SCI), Applied Physics, Optics and Photonics, OFO.
    Wosinska, Lena
    KTH, School of Information and Communication Technology (ICT).
    Monti, Paolo
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Analysis of Spectral and Energy Efficiency Tradeoff in Single-Line Rate WDM Links2017In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 35, no 10, p. 1847-1857Article in journal (Refereed)
    Abstract [en]

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

  • 21. Yin, Xin
    et al.
    Verplaetse, Michiel
    Lin, Rui
    Van Kerrebrouck, Joris
    Ozolins, Oskars
    De Keulenaer, Timothy
    Pang, Xiaodan
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab). RISE ACREO AB.
    Pierco, Ramses
    Vaernewyck, Renato
    Vyncke, Arno
    Schatz, Richard
    KTH, School of Engineering Sciences (SCI), Applied Physics, Fotonik och mikrovågsteknik.
    Westergren, Urban
    Jacobsen, Gunnar
    Popov, Sergei
    KTH, School of Engineering Sciences (SCI), Applied Physics, Optics and Photonics, OFO.
    Chen, Jiajia
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Torfs, Guy
    Bauwelinck, Johan
    First demonstration of real-time 100 Gbit/s 3-Level duobinary transmission for optical interconnects2016In: ECOC 2016-Post Deadline Paper; 42nd European Conference on Optical Communication; Proceedings of, 2016, p. 1-3Conference paper (Refereed)
  • 22. Zawistowski, Zygmunt J.
    et al.
    Jaskorzynska, Bozena
    KTH, School of Engineering Sciences (SCI), Applied Physics, Optics and Photonics, OFO.
    Modeling structures of 1D PhC for telecommunication applications2016In: PHOTONICS APPLICATIONS IN ASTRONOMY, COMMUNICATIONS, INDUSTRY, AND HIGH-ENERGY PHYSICS EXPERIMENTS 2016, SPIE - International Society for Optical Engineering, 2016, article id UNSP 100310ZConference paper (Refereed)
    Abstract [en]

    Effective method of modeling 1-dimensional photonic crystals structures is presented. As an illustration of the method a concept of widely tunable narrow band drop filter is described. As an active electro-optic material a liquid crystal is used. Very good parameters are obtained so the presented structure is suitable for fast packet switched wavelength division multiplexing networks (WDM).

  • 23.
    Zhang, Lu
    et al.
    KTH, School of Information and Communication Technology (ICT). State Key Laboratory of Advanced Optical Communication System and Networks, Shanghai Jiao Tong University, Shanghai 200240, China.
    Hong, Xuezhi
    KTH, School of Information and Communication Technology (ICT). MOE International Laboratory for Optical Information Technologies, South China Academy of Advanced Optoelectronics, South China Normal University, Guangzhou 510006, China.
    Pang, Xiaodan
    KTH, School of Information and Communication Technology (ICT). Networking and Transmission Laboratory, RISE Acreo AB, Kista 16425, Sweden.
    Ozolins, Oskars
    Udalcovs, Aleksejs
    Schatz, Richard
    KTH, School of Engineering Sciences (SCI), Applied Physics, Optics and Photonics, OFO.
    Guo, Changjian
    Zhang, Junwei
    Nordwall, Fredrik
    Engenhardt, Klaus M.
    Westergren, Urban
    KTH, School of Engineering Sciences (SCI), Applied Physics, Optics and Photonics, OFO.
    Popov, Sergei
    KTH, School of Engineering Sciences (SCI), Applied Physics, Optics and Photonics, OFO.
    Jacobsen, Gunnar
    Xiao, Shilin
    Hu, Weisheng
    Chen, Jiajia
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab). MOE International Laboratory for Optical Information Technologies, South China Academy of Advanced Optoelectronics, South China Normal University, Guangzhou 510006, China.
    Nonlinearity-aware 200 Gbit/s DMT transmission for C-band short-reach optical interconnects with a single packaged electro-absorption modulated laser2018In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 43, no 2, p. 182-185Article in journal (Refereed)
    Abstract [en]

    We experimentally demonstrate the transmission of a 200 Gbit/s discrete multitone (DMT) at the soft forward error correction limit in an intensity-modulation directdetection system with a single C-band packaged distributed feedback laser and traveling-wave electro absorption modulator (DFB-TWEAM), digital-to-analog converter and photodiode. The bit-power loaded DMT signal is transmitted over 1.6 km standard single-mode fiber with a net rate of 166.7 Gbit/s, achieving an effective electrical spectrum efficiency of 4.93 bit/s/Hz. Meanwhile, net rates of 174.2 Gbit/s and 179.5 Gbit/s are also demonstrated over 0.8 km SSMF and in an optical back-to-back case, respectively. The feature of the packaged DFB-TWEAM is presented. The nonlinearity-aware digital signal processing algorithm for channel equalization is mathematically described, which improves the signal-to-noise ratio up to 3.5 dB. 

1 - 23 of 23
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