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  • 1.
    Ahmed, Jawwad
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Cavdar, Cicek
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Monti, Paolo
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Wosinska, Lena
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    A Dynamic Bulk Provisioning Framework for Concurrent Optimization in PCE-Based WDM Networks2012In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 30, no 14, p. 2229-2239Article in journal (Refereed)
    Abstract [en]

    A centralized network control and management plane, such as the one based on a path computation element (PCE), is highly beneficial in terms of resource optimization in wavelength division multiplexing optical networks. Benefits of centralized provisioning are even more evident when connection requests are provisioned in batches, i.e., they allow a better use of network resources via concurrent optimization. In this study, a dynamic bulk provisioning framework is presented with the objective of optimizing the use of network resources that also presents, as an additional benefit, the ability to yield a reduction of the control plane overhead. The rationale behind the proposed framework is based on a mechanism in which the PCE client is allowed to bundle and simultaneously send multiple labeled switch path (LSP) requests to the PCE where, in turn, several bundles can be concurrently processed together as a single bulk. From the network deployment perspective, a PCE-based network architecture is proposed to practically realize this approach. For dynamic bulk provisioning of optical LSP requests, a time-efficient integer linear programming (ILP) model (LSP BP ILP) is presented to minimize the request blocking, the network resource consumption, and the network congestion. In addition, a heuristic based on a greedy randomized adaptive search procedure (GRASP), namely LSP_BP_GRASP, is also proposed as a scalable alternative. The presented results demonstrate significant advantages of the proposed PCE bulk provisioning framework based on concurrent optimization in terms of reduced blocking probability and control overhead when compared with conventional dynamic connection provisioning approaches processing a single connection request at a time.

  • 2.
    Björk, Gunnar
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum Electronics and Quantum Optics, QEO. AlbaNova University Center, Sweden.
    Stensson, Katarina
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum Electronics and Quantum Optics, QEO. AlbaNova University Center, Sweden.
    Karlsson, Magnus
    Proposed Implementation of "Non-Physical" Four-Dimensional Polarization Rotations2016In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 34, no 14, p. 3317-3322Article in journal (Refereed)
    Abstract [en]

    Recently one of us proposed a new formalism for modeling electromagnetic wave transformations for coherent communication using a real, four-vector description instead of the conventionally used Jones calculus or the Mueller matrices. The four-vector can then handle all superpositions of two orthogonal polarization basis and two orthogonal time bases (e.g., the in-phase and quadrature phase). In developing this formulation it was found that to provide a general but minimal framework for such rotations, it is natural to divide the six generators of four-dimensional (4d) rotations into two groups of three generators, the right-and the left-isoclinic matrices. Of the six transformations these generators define, it was furthermore found that four of them are readily implemented by linear optical components, while two of then were impossible to implement by such means. In this paper, we detail the reason these two "unphysical" rotations cannot be implemented with linear optics. We also suggest how they can be implemented, but at a cost in the signal-to-noise ratio, and give this minimum cost.

  • 3.
    Campi, Roberta
    et al.
    TTC-Agilent Technol., Turin.
    Söderström, David
    TTC-Agilent Technol., Turin.
    et al.,
    Highly reliable and high-yield 1300-nm InGaAlAs directly modulated ridge fabry-Perot lasers, operating at 10-gb/s, up to 110°C, with constant current swing2006In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 24, no 1, p. 143-149Article in journal (Refereed)
    Abstract [en]

    Transceivers for 300-m multimode links, based on a serial 10-Gb/s laser source and incorporating a receiver based on electronic dispersion compensation (EDC), are creating the first high-volume application for a 10-Gb Fabry-Perot (FP). A highly reliable and high-yield uncooled ridge FP laser is presented. The device shows excellent power characteristics in the 25 divided by 150 degrees C temperature range with very high To (95 K in the temperature range 0 divided by 85 C and still 78 K at 150 degrees C). Outstanding dynamic performances are also shown: 6 dB of extinction ratio can be achieved up to 110 degrees C by using a constant current swing of 50 mA. Because of their enhanced performances, these devices have enabled single temperature setting of the optical module, leading to a significant test cost reduction.

  • 4. Carlsson, C.
    et al.
    Martinsson, H.
    Schatz, Richard
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Halonen, J.
    Larsson, A.
    Analog modulation properties of oxide confined VCSELs at microwave frequencies2002In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 20, no 9, p. 1740-1749Article in journal (Refereed)
    Abstract [en]

    Motivated by the need for affordable, high-performance fiber-optic microwave links in fiber-fed microcellular networks and radar systems, we have performed a comprehensive experimental evaluation of the microwave modulation characteristics of high-speed oxide-confined vertical cavity surface emitting lasers (VCSELs) emitting at 840 inn. VCSELs with different oxide aperture diameters, including both single- and multimode lasers, have been used to track the dependence on modal behavior. The study includes both static and dynamic characteristics, with an emphasis on those of major importance for analog modulation. This includes the small-signal modulation response (S-11 and S-21), the relative intensity noise (RIN), and the intermodulation distortion. From this, we determine the spurious free dynamic range, the impedance characteristics, and the speed limitations.

  • 5.
    Cavdar, Cicek
    et al.
    University of California; Istanbul Technical University.
    Tornatore, Massimo
    Buzluca, Feza
    Mukherjee, Biswanath
    Shared-Path Protection With Delay Tolerance (SDT) in Optical WDM Mesh Networks2010In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 28, no 14, p. 2068-2076Article in journal (Refereed)
    Abstract [en]

    Optical wavelength-division-multiplexing (WDM) networks have emerged as an ideal backbone for the dynamic transport of bandwidth-intensive applications. Most emerging applications require end-to-end survivable connections to be set up for specific time durations that have sliding or fixed setup times (such as IPTV, grid computing backup storage). It is critical for the development of future network infrastructure that user-centric, dynamic, and end-to-end management and control mechanisms are devised to bridge the gap between the transport capacity and the needs of new applications at the customer edges. In this paper, we study the problem of dynamic provisioning of user-controlled connection requests that have specified holding times and delay tolerances. Delay tolerance is a measure of customer patience, and it is defined as the duration a connection request can be held until it is set up. A connection that cannot be established at the instant of its request could potentially be set up in the remaining duration of its delay tolerance. In this study, different dynamic scheduling algorithms are developed and compared by giving priority to connections according to their arrival rates, delay tolerances, and holding times. Using a mathematical model for impatient requests and simulation experiments, we show that delay tolerance flexibility in the traffic model provides a reduction of up to 50% on blocking probability, without the use of extra backup capacity.

  • 6. Cen, Min
    et al.
    Chen, Jiajia
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Moeyaert, Veronique
    Megret, Patrice
    Wuilpart, Marc
    Advanced Fault-Monitoring Scheme for Ring-Based Long-Reach Optical Access Networks2017In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 35, no 10, p. 1876-1886Article in journal (Refereed)
    Abstract [en]

    This paper presents a novel fiber fault-monitoring system for long-reach optical access networks based on a transmission-reflection analysis approach. By launching an un-modulated continuous-wave optical signal into the feeder ring and measuring the transmitted and reflected/backscattered optical powers, the proposed monitoring scheme is able to detect, identify, and localize any major fault (covering both reflective and nonreflective events) with a good spatial accuracy (<= 10 m) and a high detection speed (3 s). Both experimental and simulation results have demonstrated that the proposed system provides fiber monitoring functionality better than that obtained by the conventional methods.

  • 7.
    Chacinski, Marek
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP. KTH, School of Information and Communication Technology (ICT), Centres, Kista Photonics Research Center, KPRC.
    Westergren, Urban
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics. KTH, School of Information and Communication Technology (ICT), Centres, Kista Photonics Research Center, KPRC.
    Stoltz, Björn
    Syntune AB, Kista, Sweden.
    Hammerfeldt, Stefan
    Thylén, Lars
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics. KTH, School of Information and Communication Technology (ICT), Centres, Kista Photonics Research Center, KPRC.
    Monolithically Integrated 100 GHz DFB-TWEAM2009In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 7, no 16, p. 3410-3415Article in journal (Refereed)
    Abstract [en]

    A monolithically integrated distributed feedback (DFB) laser and traveling-wave electro-absorption modulator (TWEAM) with >= 100 GHz -dBe bandwidth suitable for Non-return-to-zero (NRZ) operation with on-off keying (OOK) is presented. The steady-state, small-signal modulation response, microwave reflection, chirp characteristic, and both data operation and transmission were investigated. The DFB-TWEAM was found to be an attractive candidate for future short distance communication in high bitrates systems.

  • 8. Chen, D. R.
    et al.
    Liu, W. S.
    Jiang, M.
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    High-Resolution Strain/Temperature Sensing System Based on a High-Finesse Fiber Cavity and Time-Domain Wavelength Demodulation2009In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 27, no 13, p. 2477-2481Article in journal (Refereed)
    Abstract [en]

    A high-resolution strain/temperature sensing system based on a fiber Bragg grating-Fabry-Perot cavity (FBG-FPC) and a wavelength-swept single-longitudinal-mode laser diode (modulated by a sawtooth signal) is proposed. The high-finesse (similar to 627) FBG-FPC formed by two uniform FBGs of high reflectivity (similar to 99.5%) is used both as a strain/temperature sensor and a FPC with ultranarrow (similar to 0.12 pm) transmission bands. Using a photodetector to detect the transmissive light of the laser diode through the FBG-FPC, wavelength demodulation is achieved by mapping wavelength measurement to time measurement. Both strain sensing and temperature sensing with a resolution of 0.11 mu epsilon and 0.014 degrees C, respectively, have been demonstrated.

  • 9. Dai, D. X.
    et al.
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Tsang, H. K.
    Bilevel mode converter between a silicon nanowire waveguide and a larger waveguide2006In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 24, no 6, p. 2428-2433Article in journal (Refereed)
  • 10. Dai, D. X.
    et al.
    Liu, S. Z.
    He, Sailing
    KTH, Superseded Departments, Electromagnetic Theory.
    Zhou, Q. C.
    Optimal design of an MMI coupler for broadening the spectral response of an AWG demultiplexer2002In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 20, no 11, p. 1957-1961Article in journal (Refereed)
  • 11. Dai, D. X.
    et al.
    Yang, L.
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Ultrasmall thermally tunable microring resonator with a submicrometer heater on Si nanowires2008In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 26, no 5-8, p. 704-709Article in journal (Refereed)
    Abstract [en]

    An ultracompact widely tunable thermooptical (TO) microring resonator (MRR) filter based on Si nanowires is presented. The Si nanowire waveguide has a SiO2 insulator, Si core, a SiO2 up-cladding, and a thin metal film at the top. The metal circuit along the microring is used as a submicrometer heater which has the same width as the Si nanowire waveguide. The up-cladding is optimized to reduce the light absorption of the metal as well as to have a good heat-conduction from the heater to the Si core. Two pads used as the contact points for the probes connecting to the electrical power are perpendicularly connected to the microring by using optimized T-junctions (with a low excess loss of about 0.06 dB per T-junction). With such a design, the present thermally tunable microring resonator (MRR) can be fabricated by using a standard fabrication process with a single lithography process, which is much simpler than the fabrication with double lithography processes used for the conventional TO components. Finally, the simulation results show that the designed MRR has a wide tuning range of about 20 nm with a low heating power of 5 mW.

  • 12.
    Dai, Daoxin
    et al.
    Centre for Optical and Electromagnetic Research, State Key Laboratory for Modern Optical Instrumentation, Zhejiang University.
    Shi, Yaocheng
    Centre for Optical and Electromagnetic Research, State Key Laboratory for Modern Optical Instrumentation, Zhejiang University.
    Deeply etched SiO2 ridge waveguide for sharp bends2006In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 24, no 12, p. 5019-5024Article in journal (Refereed)
    Abstract [en]

    A deeply etched SiO2 ridge waveguide including the buffer, core, and cladding is presented for realizing sharp bends. The present SiO2 ridge waveguide has a strong confinement at the lateral direction, while it has a weak confinement at the vertical direction. Due to the strong confinement, a sharp bend (with a very small bending radius of about 10 mu m) is obtained for an acceptable bending loss. A detailed analysis of the loss in a bent waveguide is given by using a finite-difference method. In order to reduce the transition loss, a narrow bending section with an optimal lateral offset is used. A low leakage loss is obtained by using wide straight waveguides, and linear tapers are used to connect the wide straight section and narrow bent sections.

  • 13. Dai, Daoxin
    et al.
    Yang, Liu
    Sheng, Z.
    Yang, Bo
    He, Sailing
    Compact Microring Resonator With 2 x 2 Tapered Multimode Interference Couplers2009In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 27, no 21, p. 4878-4883Article in journal (Refereed)
    Abstract [en]

    Compact microring resonator devices are realized by using a small SU-8 polymer strip waveguide that has an SU-8 polymer core (n similar to 1.573), an SiO2 buffer (n similar to 1.445), and an air cladding. Due to the high index contrast of the optical waveguide, a small bending radius (similar to 150 mu m) is used for the MRR. To enhance the coupling between the access optical waveguides and the microring, 2 x 2 multimode interference couplers are used. The measured spectral response of the through port shows a high extinction ratio of over 15 dB and a 3-dB bandwidth of about 0.38 nm (corresponding to a moderate Q-value of similar to 4500).

  • 14. de Rossi, S.
    et al.
    Sagnes, I.
    Legratiet, L.
    Talneau, A.
    Berrier, A.
    Mulot, M.
    Anand, Srinivasan
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Gentner, J. L.
    Longitudinal mode selection in constricted photonic crystal guides and electrically injected lasers2005In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 23, no 3, p. 1363-1368Article in journal (Refereed)
    Abstract [en]

    Locally reducing the width of a wide photonic crystal (PhC) waveguide generates a constriction which acts as an internal reflector. We have simulated and measured the spectral behavior of a wide PhC waveguide locally constricted to a narrower PhC waveguide and ended by two cleaved facets, thus generating two coupled cavities. Passive structures as well as electrically injected active structures have been investigated. The multimode behavior of wide PhC waveguides is evidenced to play a deciding role. Modal reflection and transmission at the constriction are simulated and measured on passive PhC waveguides, when varying the constrictions' hole size and length. The spectral behavior of full-PhC electrically pumped lasers including such a constriction is measured and analyzed according to the constriction geometry. Design rules are finally proposed to take advantage of this coupled-cavities behavior for high rejection and high external efficiency monomode laser operation.

  • 15. Drummond, Miguel V.
    et al.
    Nogueira, Rogerio N.
    Monteiro, Paulo P.
    Violas, Manuel A.
    Sterner, Carola
    KTH, School of Information and Communication Technology (ICT), Centres, Kista Photonics Research Center, KPRC.
    Fonjallaz, Pierre-Yves
    KTH, School of Information and Communication Technology (ICT), Centres, Kista Photonics Research Center, KPRC.
    Tunable Optical Dispersion Compensator Based on Power Splitting Between Two Dispersive Media2010In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 28, no 8, p. 1164-1175Article in journal (Refereed)
    Abstract [en]

    In this paper, we propose and experimentally demonstrate a novel tunable optical dispersion compensator (TODC). Dispersion compensation is achieved by splitting the input signal between two dispersive media and adding the resulting signals thereafter. Tunable compensation is attained by controlling the power splitting ratio of the input signal between both dispersive media. The frequency response of the TODC is theoretically assessed considering signal addition in the optical and electrical domains. The latter case is enabled by using optical single side-band (OSSB) modulation, which allows preserving the phase information of dispersive media output signals after direct detection. This is the only case experimentally tested, since it avoids stability problems related with coherent addition of optical signals. A TODC with a tuning range of -340 to 0 ps/nm was designed and experimentally assessed for a 40 Gb/s nonreturn-to-zero OSSB signal. The tunable power splitter consisted of an automatic polarization controller and a polarization beam splitter, which offered a tuning time lower than 150 mu s. A bit error rate lower than 10(-8) was measured on the entire compensation range with a maximum power penalty of 3.3 dB relatively to an SSB signal in back-to-back.

  • 16. Fei, Chao
    et al.
    Zhang, Junwei
    Zhang, Guowu
    Wu, Yujian
    Hong, Xuezhi
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering. Zhejiang Univ, Ctr Opt & Electromagnet Res, State Key Lab Modern Opt Instrumentat, Hangzhou 310027, Zhejiang, Peoples R China.
    Demonstration of 15-M 7.33-Gb/s 450-nm Underwater Wireless Optical Discrete Multitone Transmission Using Post Nonlinear Equalization2018In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 36, no 3, p. 728-734Article in journal (Refereed)
    Abstract [en]

    In this paper, we experimentally demonstrate an underwater wireless optical communication (UWOC) system using a 450-nm gallium nitride (GaN) laser and adaptive bit-power loading discrete multitone (DMT). To enhance the system capacity, a post nonlinear equalizer based on the simplified Volterra series is employed at the receiver to mitigate the nonlinear impairments of the UWOC system. By combining the adaptive bit-power loading with nonlinear equalization, 7.33-Gb/s DMT-modulated UWOC under 15-m tap water is achieved at a bit error rate below the 7% hard-decision forward error correction (FEC) limit 3.8 x 10(-3). The electrical signal bandwidth is 1.25 GHz, which corresponds to an electrical spectrum efficiency of similar to 6 bit/s/Hz. The capacity-distance product reaches 109.95 Gb/s-m in a single channel UWOC system with tap water. Compared with the linear equalization case, the system capacity at the FEC limit for 15-m underwater transmission is improved by similar to 18% with the nonlinear equalization. Furthermore, the impact of turbidity on the performance of UWOC system is investigated by measuring the signal-to-noise ratio (SNR) under different suspension concentrations of Al(OH)(3) and Mg(OH)(2). The results show that significant SNR gains (>3 dB for transmission distance up to 11 m) can be obtained by the nonlinear equalization over a wide range of water turbidity levels representing "clear ocean," "coastal ocean," and "harbor water," which demonstrates the robustness of the proposed scheme in various ocean environments.

  • 17.
    Furdek, Marija
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Skorin-Kapov, Nina
    Wosinska, Lena
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Attack-aware dedicated path protection in optical networks2016In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 34, no 4, p. 1050-1061Article in journal (Refereed)
    Abstract [en]

    Due to the high data rates in optical networks,physical-layer attacks targeting service degradation, such as powerjamming, can potentially lead to large data and revenue losses.Conventional network survivability approaches which establishlink-disjoint working and backup paths to protect from componentfaults may not provide adequate protection for such attacks.Namely, the working and the backup paths, although link-disjoint,might both be affected by a single attack scenario due to specificattack propagation characteristics. To enhance the existing survivabilityapproaches, we utilize the concept of an attack group(AG) which incorporates these characteristics to identify connectionswhich can simultaneously be affected by a single attack. Weapply this concept to dedicated path protection (DPP) and developattack-aware DPP (AA-DPP) approaches which aim to establishAG-disjoint primary and backup paths in a cost-effective manner.We provide a two-step ILP formulation for the routing and wavelengthassignment of the working and backup paths, as well as aheuristic for larger problem instances. Numerical results indicatethat the proposed approaches provide dedicated path protectionschemes with enhanced attack protection without using more resources(i.e., wavelengths, average path lengths) than standardDPPmethods.

  • 18.
    Gao, Ying
    et al.
    KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Xu, Lei
    He, Sailing
    KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Optical Multi-Level Signal Generation Using Four-Wave-Mixing2011In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 29, no 14, p. 2166-2172Article in journal (Refereed)
    Abstract [en]

    We propose and demonstrate a novel optical method to generate multi-level signals with reduced driving voltage through degenerate four-wave mixing processes. With the present approach, it is possible to extend the size of the signal constellations and at the same time reduce the modulator driving voltage without bandwidth degradations. In our experiments, one amplitude shift keying (ASK) signal and one differential phase shift keying (DPSK) signal are used to generate one ASK-DPSK signal with clearly opened eye-diagrams and error-free demodulation results. Our numerical simulations show that the proposed method is applicable for generating several 8-ary and 16-ary quadrature amplitude modulation (QAM) signals with silicon waveguides at a higher modulation baud rate.

  • 19. Guan, Zu-Guang
    et al.
    Chen, Daru
    He, Sailing
    Coherence multiplexing of distributed sensors based on pairs of fiber Bragg gratings of low reflectivity2007In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 25, no 8, p. 2143-2148Article in journal (Refereed)
  • 20. Guo, Changjian
    et al.
    Nix, Michael
    Yam, Scott S. -H.
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Picosecond and Sub-Picosecond Flat-Top Pulse Shaping Using Abrupt Taper Interferometers2010In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 28, no 6, p. 876-881Article in journal (Refereed)
    Abstract [en]

    A picosecond flat-top pulse shaper using an abrupt taper interferometer is proposed and experimentally demonstrated. A theoretical model based on coupled mode equations is also derived to simulate the propagation of picosecond pulses through the abrupt taper interferometer. Through properly designing the abrupt taper interferometer, a 3.8-ps flat-top pulse with less than 4% ripple is successfully generated from a 2.2-ps Gaussian pulse. The proposed technique can also be used in the sub-picosecond regime.

  • 21. Hu, R.
    et al.
    Dai, D. X.
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    A Small Polymeric Ridge Waveguide With a High Index Contrast2008In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 26, no 13-16, p. 1964-1968Article in journal (Refereed)
    Abstract [en]

    In this paper, an optimal design of a small polymeric ridge waveguide with a high index contrast is presented. In order to reduce the leakage to the substrate and pure bending losses, the buffer layer of the present waveguide is etched partially. The single-mode condition, the bending characteristics, and the birefringence of the present small polymeric ridge waveguide are also studied. By adjusting the core width and the core height, it is possible to obtain a polarization-insensitive small polymer ridge waveguide. For the bending loss, the numerical results show that the dominant part is the transition loss between the straight and bending sections (other than the pure bending loss) and the transition loss could be reduced greatly by introducing a lateral offset. However, the transition loss is still too large to obtain a very small bending radius (e.g., 10 mu m). When only the pure bending loss is necessary to consider in some special case (e.g., microrings without any transitions), one can have a bending radius less than 10 mu n due to the possibility of low pure bending loss.

  • 22.
    Iglesias Olmedo, Miguel
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO. DTU Fotonik, Department of Photonics Engineering, Technical University of Denmark2800 Kgs. Lyngby, Denmark .
    Suhr, Lau
    Prince, Kamau
    Rodes, Roberto
    Mikkelsen, Christian
    Hviid, Erling
    Neumeyr, Christian
    Vollrath, Gunther
    Goobar, Edgard
    Ohlen, Peter
    Monroy, Idelfonso Tafur
    Gigabit Access Passive Optical Network Using Wavelength Division Multiplexing-GigaWaM2014In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 32, no 22Article in journal (Refereed)
    Abstract [en]

    This paper summarizes the research and technical achievements done under the EU project GigaWaM. The goal of this project was to develop a cost-effective solution that can meet the increasing bandwidth demands in access networks. The approach was to use a novel wavelength division multiplexing passive optical network (WDM-PON) architecture that can deliver symmetric 1 Gb/s to 64 users over 20 km standard single mode fiber using the L and C bands for down and upstream, respectively. During the course of the project, a number of key enabling technologies were developed including tunable transceivers, athermal 50 GHz spaced arrayed waveguide grating multiplexer devices, novel hybridization technologies for integration of passive and active electro-optic devices, and system-level algorithms that ensure the quality of service. The outcome of the project proved a reliable, cost-effective, flexible, and upgradable WDM-PON solution, achieving per-user datarates of 2.5 and 10 Gb/s for up and downstream, respectively. The proposed solution is not only suitable for access networks, but also for metro aggregation and mobile backhaul.

  • 23.
    Iglesias Olmedo, Miguel
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Zuo, Tianjian
    Jensen, Jesper Bevensee
    Zhong, Qiwen
    Xu, Xiaogeng
    Popov, Sergei
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Monroy, Idelfonso Tafur
    Multiband Carrierless Amplitude Phase Modulation for High Capacity Optical Data Links2014In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 32, no 4, p. 798-804Article in journal (Refereed)
    Abstract [en]

    Short range optical data links are experiencing bandwidth limitations making it very challenging to cope with the growing data transmission capacity demands. Parallel optics appears as a valid short-term solution. It is, however, not a viable solution in the long-term because of its complex optical packaging. Therefore, increasing effort is now put into the possibility of exploiting higher order modulation formats with increased spectral efficiency and reduced optical transceiver complexity. As these type of links are based on intensity modulation and direct detection, modulation formats relying on optical coherent detection can not be straight forwardly employed. As an alternative and more viable solution, this paper proposes the use of carrierless amplitude phase (CAP) in a novel multiband approach (MultiCAP) that achieves record spectral efficiency, increases tolerance towards dispersion and bandwidth limitations, and reduces the complexity of the transceiver. We report on numerical simulations and experimental demonstrations with capacity beyond 100 Gb/s transmission using a single externally modulated laser. In addition, an extensive comparison with conventional CAP is also provided. The reported experiment uses MultiCAP to achieve 102.4 Gb/s transmission, corresponding to a data payload of 95.2 Gb/s error free transmission by using a 7% forward error correction code. The signal is successfully recovered after 15 km of standard single mode fiber in a system limited by a 3 dB bandwidth of 14GHz.

  • 24.
    Jamid, H. A.
    et al.
    Electrical Engineering Department, King Fahd Univ. Petrol. and Minerals, Saudi Arabia.
    Akram, Nadeem
    Electrical Engineering Department, King Fahd Univ. Petrol. and Minerals, Saudi Arabia.
    A new higher order finite-difference approximation scheme for the method of lines2001In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 19, no 3, p. 398-404Article in journal (Refereed)
    Abstract [en]

    A new 5-point and a 7-point nonuniform mesh finite-difference scheme is introduced to approximate the second-derivative operator. The scheme is applied using the method of lines. The necessary interface conditions for the TE and TM fields at an index discontinuity are appropriately included in the derivation. This scheme can model lossy dielectrics as well as metallic layers in a unified way. Numerical results are given for the fundamental TE and TM modes of a high-contrast waveguide and for a metal/dielectric single interface TM surface-plasmon mode showing excellent convergence behavior to the analytical results.

  • 25.
    Jamid, H. A.
    et al.
    Department of Electrical Engineering, King Fahd University of Petroleum and Minerals, Saudi Arabia.
    Akram, Nadeem
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Analysis of deep waveguide gratings: an efficient cascading and doubling algorithm in the method of lines framework2002In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 20, no 7, p. 1204-1209Article in journal (Refereed)
    Abstract [en]

    In this work, a computationally fast, numerically stable, and memory-efficient cascading and doubling algorithm is proposed within the method of lines framework to model long planar waveguide gratings having thousands of periods in the propagation direction. This algorithm can model 2(n) grating periods in n calculational steps and needs N-2 matrices for N sample points in the problem space. It can model periodic, quasi-periodic, symmetric, and asymmetric, gratings efficiently. Different deep waveguide gratings are modeled using this scheme and results for the fundamental TE mode spectral reflectivity are compared with published results showing excellent agreement.

  • 26. Jia, Shi
    et al.
    Pang, Xiaodan
    KTH, School of Information and Communication Technology (ICT). RISE Acreo AB, NETLAB, SE-16425 Kista, Sweden.
    Ozolins, Oskars
    Yu, Xianbin
    Hu, Hao
    Yu, Jinlong
    Guan, Pengyu
    Da Ros, Francesco
    Popov, Sergei
    KTH, School of Information and Communication Technology (ICT).
    Jacobsen, Gunnar
    Galili, Michael
    Morioka, Toshio
    Zibar, Darko
    Oxenlowe, Leif K.
    0.4 THz Photonic-Wireless Link With 106 Gb/s Single Channel Bitrate2018In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 36, no 2, p. 610-616Article in journal (Refereed)
    Abstract [en]

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

  • 27. Jiang, Wei
    et al.
    Shen, Linfang
    Chen, Daru
    KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Chi, Hao
    An extended FDTD method with inclusion of material dispersion for the full-vectorial analysis of photonic crystal fibers2006In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 24, no 11, p. 4417-4423Article in journal (Refereed)
    Abstract [en]

    An extended finite-difference time-domain (FDTD) method with inclusion of material dispersion for the full-vectorial analysis of photonic crystal fibers (PCFs) is presented in this paper. In order for this extended FDTD method to obtain a fast convergence and high accuracy, a constitutive-parameter averaging technique is employed. Numerical results for a typical PCF verify the validity of the extended FDTD method. With this FDTD mode solver, a new birefringent PCF is also investigated, and interesting results are obtained in this paper.

  • 28.
    Jänes, Peter
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Tidström, Jonas
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Thylén, Lars
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Limits on optical pulse compression and delay bandwidth product in electromagnetically induced transparency media2005In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 23, no 11, p. 3893-3899Article in journal (Refereed)
    Abstract [en]

    Delay bandwidth products (DBPs) and physical pulselengths obtainable in media exhibiting electromagnetically induced transparency (EIT) are analyzed. The study is performed in stationary media as well as for dynamic storing of light pulses in such media. In the latter case; the dispersion inherent in storage and readout of the pulses is analyzed. It is shown that absorption and the group velocity dispersion (GVD) are limiting factors. Analytical expressions for the minimum compressed 'pulselength and DBP are derived, and these expressions show good agreement with simulations of pulse propagation in EIT media.

  • 29.
    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.

  • 30. Kjellberg, T.
    et al.
    Nilsson, S.
    Klinga, T.
    Broberg, B.
    Schatz, Richard
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP. KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Investigation on the spectral characteristics of DFB lasers with different grating configurations made by electron-beam lithography1993In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 11, p. 1405-1415Article in journal (Refereed)
    Abstract [en]

    The single-mode stability for distributed-feedback (DFB) lasers with various electron-beam-written grating configurations has been investigated theoretically and experimentally, for both as-cleaved and AR-coated lasers. Other laser properties interesting for coherent and multichannel communications systems, such as linewidth and tunability, have also briefly been investigated. Lasers with more sophisticated grating structures, such as an optimized multiple phase-shifted or a corrugation-pitch-modulated grating, did not exhibit performance significantly superior to that of lambda;/4-shifted DFB lasers with an appropriate coupling coefficient. Antireflection (AR)-coating of the end facets proved indispensable for obtaining a high yield for lasers with single-mode operation at high output power and for reducing the large chip-to-chip variation seen for the as-cleaved lasers. A theoretical investigation of the effect of end reflections on the stopband and of the problem of determining the coupling coefficient was also made

  • 31. Kjellberg, T.
    et al.
    Schatz, Richard
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP. KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    The effect of stitching errors on the spectral characteristics of DFB lasers fabricated using electron beam lithography1992In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 10, p. 1256-1266Article in journal (Refereed)
    Abstract [en]

    Field stitching errors and their effect on the single-mode characteristics of distributed feedback (DFB) lasers fabricated using electron beam lithography were investigated. The stitching errors are associated with small-area, high-resolution electron beam exposure, which has the potential advantage of high-speed writing of laser gratings. Measurements show that the errors are composed of a systematic and a stochastic part. Their effect on the gain margin was simulated both for lambda;/4 phase-shifted and optimized multiple-phase-shifted DFB lasers. Simulations show that the lasers are insensitive to the systematic part of the stitching errors if the number of errors is large enough. The stochastic part was found to give rise to a variation in gain margin of the DFB lasers. It is concluded that the field stitching accuracy in the high-resolution mode of a commercial system for electron beam lithography is sufficient to provide a high yield of single-mode lasers. However, it is essential that certain precautions be taken considering exposure conditions and that a fault tolerant laser design be used

  • 32.
    Laurell, Fredrik
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Arvidsson, G.
    Webjörn, J.
    Fabricationof periodically domain-inverted lithium niobate channel waveguides for secondharmonic generation1989In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213Article in journal (Refereed)
  • 33.
    Laurell, Fredrik
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Helmfrid, S.
    Arvidsson, G.
    Opticalparametric amplification of a 1.54 µm single mode DFB laser in a Ti:LiNbO3waveguide1993In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213Article in journal (Refereed)
  • 34.
    Laurell, Fredrik
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Webjörn, J.
    Arvidsson, G.
    Holmberg, J.
    Wetetching of proton-exchanged lithium niobate - A novel processing technique1993In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213Article in journal (Refereed)
  • 35.
    Leong, Miu Yoong
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Larsen, Knud J.
    Jacobsen, Gunnar
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Popov, Sergei
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Zibar, Darko
    Sergeyev, Sergey
    Dimensioning BCH Codes for Coherent DQPSK Systems With Laser Phase Noise and Cycle Slips2014In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 32, no 21, p. 4048-4052Article in journal (Refereed)
    Abstract [en]

    Forward error correction (FEC) plays a vital role in coherent optical systems employing multi-level modulation. However, much of coding theory assumes that additive white Gaussian noise (AWGN) is dominant, whereas coherent optical systems have significant phase noise (PN) in addition to AWGN. This changes the error statistics and impacts FEC performance. In this paper, we propose a novel semianalytical method for dimensioning binary Bose-Chaudhuri-Hocquenghem (BCH) codes for systems with PN. Our method involves extracting statistics from pre-FEC bit error rate (BER) simulations. We use these statistics to parameterize a bivariate binomial model that describes the distribution of bit errors. In this way, we relate pre-FEC statistics to post-FEC BER and BCHcodes. Our method is applicable to pre-FEC BER around 10(-3) and any post-FEC BER. Using numerical simulations, we evaluate the accuracy of our approach for a target post-FEC BER of 10(-5). Codes dimensioned with our bivariate binomial model meet the target within 0.2-dB signal-to-noise ratio.

  • 36. Lewen, R.
    et al.
    Westergren, Urban
    KTH, Superseded Departments, Electronics. KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Schatz, Richard
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Berglind, Eilert
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Design of inductive p-i-n diode matching for optical receivers with increased bit-rate operation2001In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 19, no 12, p. 1956-1963Article in journal (Refereed)
    Abstract [en]

    We have studied matching of a p-i-n photodiode (PD) with a single serial inductive element for broadband operation. The bit rate and rise time may be significantly improved, compared to a device without inductor for nonreturn-to-zero (NRZ) modulation. The matched device offers improved pulse equalization leading to increased receiver sensitivity, and reduces the need for an additional pulse-equalizing filter. The material is presented so that it can serve as a guideline of how the inductor can be included when choosing the thickness of the absorption layer and/or area for a p-i-n PD design, and ends with typical design examples.

  • 37.
    Lewén, Robert
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Irmscher, Stefan
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Westergren, Urban
    KTH, Superseded Departments, Electronics.
    Thylén, Lars
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Eriksson, U.
    Segmented transmission-line electroabsorption modulators2004In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 22, no 1, p. 172-179Article in journal (Refereed)
    Abstract [en]

    We present segmented transmission-line (TML) electroabsorption modulators (EAMs) with characteristic impedance close to 50 M The segmented TML approach allows us to design a traveling-wave EAM with 50 Omega impedance and very high band width. The devices show low return loss (< -15 dB) and excellent frequency response up to 50 GHz, and exhibit a maximum model extrapolated 3 dBe bandwidth (BW) of 9,0 GHz. An effective modeling tool based on Bloch-wave analysis is derived. Design considerations and TML properties for periodic TML-EAMs are discussed.

  • 38. Li, Qiang
    et al.
    Liu, Fangfei
    Zhang, Ziyang
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Qiu, Min
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Su, Yikai
    System Performances of On-Chip Silicon Microring Delay Line for RZ, CSRZ, RZ-DB and RZ-AMI Signals2008In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 26, no 21-24, p. 3744-3751Article in journal (Refereed)
    Abstract [en]

    We theoretically study the group-delay characteristics of a silicon microring resonator based on the coupled mode theory, and experimentally demonstrate error-free operations of an on-chip delay line using a silicon-on-insulator (SOI) microring resonator with a 20-mu m radius. Four signals of different modulation formats are examined at 5 Gb/s, including return-to-zero (RZ), carrier-suppressed return-to-zero (CSRZ), return-to-zero duobinary (RZ-DB), and return-to-zero alternate-mark-inversion (RZ-AMI). Bit error rate (BER) measurements show that the maximal delay times with error-free operations are 80,95, 110, and 65 ps, respectively, corresponding to a fractional group delay of similar to 0.4, similar to 0.5, similar to 0.55, and similar to 0.35. The differences in delay and signal degradations have been investigated based on the signal spectra and pattern dependences. Although the delays are demonstrated in a single ring resonator, the analysis is applicable in slow-light resonance structures such as all-pass filters (APF) and coupled resonator optical waveguides (CROW).

  • 39. Li, Qiang
    et al.
    Zhang, Weichun
    Zhao, Hang
    Qiu, Min
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Two-Dimensional Analysis Photothermal Properties in Nanoscale Plasmonic Waveguides for Optical Interconnect2013In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 31, no 24, p. 4051-4056Article in journal (Refereed)
    Abstract [en]

    The inevitable light absorption in plasmonic waveguides (PWs) gives rise to heating of waveguides themselves. Here the photothermal effects in nanowire PWs, slot PWs, channel PWs, dielectric-loaded PWs and hybrid PWs are investigated in the cross section. The resistive heating is significant for all waveguides. The thermal feature sizes of the PWs are the main factors limiting the integration density. The copper PWs show the largest temperature rise compared with the gold PWs, the silver PWs and the aluminum PWs. These findings unveil the physical properties of PWs from the photothermal perspective and provide insights into the underlying factors influencing the adoption of PWs in optical interconnect.

  • 40. Liu, Chin-Pang
    et al.
    Polo, Valentin
    Van Dijk, Frederic
    Pfrommer, Holger
    Piqueras, Miguel Angel
    Herrera, Javier
    Martinez, Alejandro
    Karlsson, Stefan
    Kjebon, Olle
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics.
    Schatz, Richard
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics.
    Enard, Alain
    Yu, Yichuan
    Tsegaye, Tedros
    Chuang, Chin-Hsiu
    Seeds, Alwyn J.
    Marti, Javier
    Full-duplex DOCSIS/wirelessDOCSIS fiber-radio network employing packaged AFPMs as optical/electrical transducers2007In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 25, no 3, p. 673-684Article in journal (Refereed)
    Abstract [en]

    A hybrid fiber-radio access network architecture for simultaneous wireline and wireless transmissions of Data-Over-Cable Service Interface Specification (DOCSIS) signals is presented. An all-optical harmonic up-conversion technique using a dual-drive Mach-Zehnder modulator provides the downstream optical signal modulated not only at the intermediate frequency in the 600- to 900-MHz band for wireline transmission but also at the up-converted frequency in the 5.45- to 5.75-GHz band for wireless transmission. An InGaAsP/InGaAsP multiple-quantum-well asymmetric Fabry-Perot modulator/detector has been designed, fabricated, and packaged and has been employed in the base station (BS) as an optical/electrical transducer, simultaneously providing the functions of optical intensity modulation and photodetection. At the BS, the DOCSIS signals are recovered at the wireline and wireless frequencies for the respective feeding of a cable access network or a fixed wireless access network in a highly flexible approach. Full-duplex operation has been demonstrated for both access types in an indoor laboratory environment. In a subsequent small-scale field trial, real-life Internet traffic provided by a local community antenna television system operator has been transported over the present hybrid fiber-radio access network architecture, and simultaneous transmission of both DOCSIS and digital television signals has also been performed.

  • 41. Liu, W. S.
    et al.
    Jiang, M.
    Chen, D. R.
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Dual-Wavelength Single-Longitudinal-Mode Polarization-Maintaining Fiber Laser and Its Application in Microwave Generation2009In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 27, no 20, p. 4455-4459Article in journal (Refereed)
    Abstract [en]

    A novel approach for generating high-frequency microwave signals is proposed and experimentally demonstrated. With a pair of wavelength matched fiber Bragg gratings written directly in a polarization-maintaining erbium-doped fiber, a stable short cavity dual-wavelength single-longitudinal-mode (DW-SLM) distributed-Bragg-reflector fiber laser with orthogonal oscillation modes is realized at room temperature. The wavelength spacing between the two lasing modes is 0.374 nm. By heterodyning the two wavelengths of the DW-SLM fiber laser at a photodetector, microwave signal at over 46 GHz is achieved.

  • 42.
    Lundqvist, Henrik
    et al.
    KTH, School of Electrical Engineering (EES).
    Karlsson, Gunnar
    KTH, School of Electrical Engineering (EES).
    On Error-Correction Coding for CDMA PON2005In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 23, no 8, p. 2342-2351Article in journal (Refereed)
    Abstract [en]

    Optical-code-division multiple access (OCDMA) has been investigated as a multiple-access technique for a long time, but so far, it has not reached any practical success. We investigate the performance of low-complexity OCDMA systems with a realistic model of noise and interference; the main limitation of the system is beat noise. To improve the performance, we consider forward-error correction (FEC) and soft decoding using standard error-correcting codes. The achievable error rates are evaluated using simulations and show significant improvement when FEC is used. The results also show that frequency-hopping systems perform better than temporally coded systems when beat noise is taken into account.

  • 43. Matsui, Yasuhiro
    et al.
    Schatz, Richard
    KTH, School of Information and Communication Technology (ICT), Electronics.
    Pham, Thang
    Ling, William A.
    Carey, Glen
    Daghighian, Henry M.
    Adams, David
    Sudo, Tsurugi
    Roxlo, Charles
    55 GHz Bandwidth Distributed Reflector Laser2017In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 35, no 3, p. 397-403Article in journal (Refereed)
    Abstract [en]

    We have demonstrated a 1300-nm short-cavity distributed reflector (DR) laser having 55 GHz bandwidth (BW), and successful 112-Gb/s transmission using four-level pulse-amplitude-modulation (PAM-4), without any pre-equalization for the transmitter. Two effects were realized in the design and operation of the DR laser: photon-photon (P-P) resonance and detuned-loading. The P-P resonance effect was realized between the DFB and distributed Bragg reflector (DBR) modes that coexisted in the cavity of the DR laser. The detuned-loading effect was used to effectively enhance the differential gain through the dynamic change in the mirror reflectivity that occurs on the flank of the DBR mirror due to the frequency chirp under modulation. Despite a limited RC cutoff frequency of 22 GHz, a wide modulation BW of 55 GHz was achieved. It is shown that the RC limitation was counteracted by the combined effects of the detuned-loading, which reduces the damping of relaxation oscillations, and an in-cavity FM-AM conversion effect that created a high-pass filter effect in the modulation response. This will be discussed by way of simulations and experimentally observed eye diagrams for 10 Gb/s NRZ and 28 Gbd PAM-4. The short-cavity DR laser achieved 112-Gb/s PAM-4 transmission over links having a range of dispersions from -28 to +7 ps/nm without precompensation on the transmitter.

  • 44. 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.

  • 45. Nilsson, S.
    et al.
    Kjellberg, T.
    Klinga, T.
    Schatz, Richard
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP. KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Wallin, J.
    Streubel, K.
    Improved spectral characteristics of MQW-DFB lasers by incorporation of multiple phase-shifts1995In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 13, p. 434-441Article in journal (Refereed)
    Abstract [en]

    The single-mode stability of strained-layer MQW-DFB lasers with electron-beam written gratings containing zero, one and three phase-shifts, and with a relatively large coupling strength, has been investigated theoretically and experimentally. The fabricated lasers with the multiple phase-shifted (MPS) structure exhibited a higher degree of stability than the lambda;/4-shifted lasers, and a considerably improved stability for both categories with phase-shifts compared to the nonshifted lasers was obtained. These results were in good agreement with our simulations. An investigation of the linewidths of the phase-shifted lasers is also presented. The MPS lasers had a significantly lower linewidth floor (down to 600 kHz) than those with one phase-shift. There was no degradation of the side-mode suppression-ratio correlated to the linewidth floor or rebroadening. A possible explanation for the lower linewidth floors obtained for the MPS lasers is that this structure is less sensitive to inhomogeneous carrier fluctuations. Longitudinal fluctuations in the shape of the photon density distribution will thereby be suppressed

  • 46. 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.

  • 47. Pandi, Zsolt
    et al.
    Tacca, Marco
    Fumagalli, Andrea
    Wosinska, Lena
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics.
    Dynamic provisioning of availability-constrained optical circuits in the presence of optical node failures2006In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 24, no 9, p. 3268-3279Article in journal (Refereed)
    Abstract [en]

    This paper investigates what impact optical node failures may have on wavelength-division-multiplexed networks, in which reliable end-to-end optical circuits are provisioned dynamically. At the node level, the optical cross-connect (OXC) equipment availability measure is estimated using proven component level availability models. At the network level, end-to-end optical circuits are provisioned only when the level of connection availability required by the application can be guaranteed. With the objective of yielding efficient utilization of the network resources, i.e., fibers and OXCs, circuit redundancy is achieved by means of shared path protection (SPP) switching, in combination with. differentiated reliability (DiR). The resulting optimal routing and wavelength assignment problem is proven to be NP-complete. To produce suboptimal solutions in polynomial time, a heuristic technique is presented, which makes use of a time-efficient method to estimate the end-to-end circuit availability in the presence of multiple (link and node) failures. Using the proposed heuristic, a selection of representative OXC architectures and optical switching technologies is examined to assess the influence of the node equipment choice on the overall network performance.

  • 48.
    Pang, Xiaodan
    et al.
    Technical University of Denmark, Denmark.
    Lebedev, Alexander
    Olmos, JJ Vegas
    Monroy, Idelfonso Tafur
    Multigigabit W-band (75–110 GHz) bidirectional hybrid fiber-wireless systems in access networks2014In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Journal of Lightwave Technology, Vol. 32, no 23, p. 3983-3990, article id 6918365Article in journal (Refereed)
    Abstract [en]

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

  • 49.
    Petermann, Ingemar
    et al.
    ACREO AB, Kista.
    Skaar, Johannes
    Norwegian Univ. of Sci. and Technol., Trondheim.
    Sahlgren, Bengt
    ACREO AB, Kista.
    Stubbe, Raoul
    ACREO AB, Kista.
    Friberg, Ari
    KTH, Superseded Departments, Physics.
    Characterization of Fiber Bragg Gratings by Use of Optical Coherence-Domain Reflectometry1999In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 17, no 11, p. 2371-2378Article in journal (Refereed)
    Abstract [en]

    A method based on optical low coherence reflectometry for complete characterization of fiber Bragg gratings (FBG's) is presented. It is shown that the measured signal corresponds to the impulse response of the grating filter, and the measurement therefore. yields all information about the device, Experiments have been carried out with a novel dual-channel interferometer, The results are in excellent agreement with the theory, demonstrating the versatility of the method for characterization of fiber gratings.

  • 50. Pham Van, Dung
    et al.
    Rimal, B. P.
    Andreev, S.
    Tirronen, T.
    Maier, M.
    Machine-to-machine communications over FiWi enhanced LTE networks: A power-saving framework and end-to-end performance2016In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 34, no 4, p. 1062-1071, article id 7360869Article in journal (Refereed)
    Abstract [en]

    To cope with the unprecedented acceleration of machine-to-machine (M2M) services over cellular networks, this paper envisions a highly converged network architecture based on the integration of high-capacity and reliable Ethernet fiber-wireless (FiWi) access networks with flexible and cost-effective 4G long term evolution (LTE) technology to support M2M connectivity in an end-to-end fashion, i.e., from air interface to transport (backhaul) network. In such emerging architecture, energy efficiency must be addressed in a comprehensive way, in which both wireless front-end and optical backhaul segments are considered at the same time to maximize the battery life of battery-constrained M2M devices as well as reduce operational expenditures for network operators, while maintaining acceptable network performance. Toward this end, an end-to-end power-saving framework is introduced in this paper that devises a timeout driven discontinuous reception (DRX) mechanism for LTE-enabled M2M devices and a polling-based power-saving mechanism for optical network units (ONUs) to improve the overall energy efficiency. End-to-end performance in terms of energy saving and packet delay is analytically modeled based on a semi-Markov process for the front-end and an M/G/1 queue for the backhaul. The obtained results indicate that the device battery life is significantly prolonged by extending the DRX cycle, whereas the backhaul energy consumption is minimized by incorporating the ONU power-saving modes into the dynamic bandwidth allocation process of the optical backhaul.

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