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Lightwave Technology, Journal of

Issue 5 • Date March1, 2011

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Displaying Results 1 - 25 of 33
  • [Front cover]

    Page(s): C1
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    Freely Available from IEEE
  • Journal of Lightwave Technology publication information

    Page(s): C2
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    Freely Available from IEEE
  • Table of contents

    Page(s): 633 - 634
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    Freely Available from IEEE
  • Remotely Pumped Long-Reach Hybrid PON With Wavelength Reuse in RSOA-Based ONUs

    Page(s): 635 - 641
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1190 KB) |  | HTML iconHTML  

    Symmetrical full-duplex transmission in a Passive Optical Network (PON) is demonstrated over a 100 km dual-fiber ring with 1:16 split trees. The customer premises equipment is based on a Reflective Semiconductor Optical Amplifier (RSOA), which reuses the wavelength of the intensity modulated downstream signal for upstream data transmission. A commercial RSOA was used together with optical offset filtering at the upstream receiver to operate at data rates of 5 and 10 Gb/s. Margins of >; 8 dB are left at a data rate of 5 Gb/s, proving that the utilized downstream suppression scheme and therefore the intensity modulation format for both, down- and upstream, is suitable for its application in long-reach hybrid access networks. The signal degradation along the PON and the transmitted pump that features means of remote amplification in its conjunction points between the metro ring and the local trees are discussed and further possibilities for an improvement of the transmission performance are proposed. View full abstract»

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  • Unified Treatment of Forward and Backward Propagating Polarized Lightwaves

    Page(s): 642 - 655
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (338 KB) |  | HTML iconHTML  

    The implications of time symmetry on the relation between forward and backward propagation of polarized optical fields are discussed making use of a newly developed formalism. The constraints imposed by spatial symmetries to the effect of static fields on a medium birefringence are elucidated. Special cases are the Faraday effect and the Cotton-Mouton effect. Compensation of round-trip birefringence is finally investigated. View full abstract»

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  • Modeling Study of Nonreciprocal Phase Shift in Magnetooptic Asymmetric Slot Waveguides

    Page(s): 656 - 660
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (386 KB) |  | HTML iconHTML  

    Asymmetric slot waveguides with a magnetooptic material filling the slot are studied for their nonreciprocal phase shift properties. General properties and performance are first evaluated by a one-dimensional silicon slot waveguide model, to find optimal asymmetric waveguide profiles. The results are verified with a two-dimensional calculation for a realistic optimal waveguide structure. The achieved ratio of the waveguide nonreciprocal phase shift to the specific Faraday rotation of the magnetooptic material is at a level comparable with semiconductor waveguides having a garnet cladding. The geometry may be applied to silicon-based vertical slot waveguides for quasi-TE polarization, which provides integration potential with active components in Si photonic circuits. View full abstract»

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  • Improving Photodetector Performance by Means of Microoptics Concentrators

    Page(s): 661 - 665
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1788 KB) |  | HTML iconHTML  

    We discuss the benefits of using microoptics concentration arrays in connection with image (or pixellated) photodetectors, in terms of: 1) recovery of area fill-factor; 2) reduction of equivalent dark-current; 3) mitigate dead-time issues; and 4) improved dynamic range. As an example of application, we describe the fill-factor recovery in connection to an array of 32 × 32 6-μm diameter, 50-μm pitch, single photon avalanche detector (SPAD). We use a 32 × 32 array of microlenses, fabricated by polymer casting in a photoresist replica mold. We demonstrate, for the first time to the best of our knowledge, an increase by a factor × 25 of the effective spectral sensitivity of the final device. The lens array itself allows a × 35 recovery, and projected improvements in excess of × 50 appear feasible. View full abstract»

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  • Picosecond Optical Switching Using RF Nonlinear Transmission Lines

    Page(s): 666 - 669
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (165 KB) |  | HTML iconHTML  

    We propose a novel sub-ps optical switch composed of an interferometer in which the phase difference between the arms is controlled by a pair of electrooptic modulators (EOMs) driven by integrated nonlinear transmission lines (NLTLs). As a proof-of-concept we demonstrate 70 ps switching using discrete LiNbO3 traveling wave EOMs and commercially available NLTLs capable of delivering a 35 ps falling edge. This technique is simple and robust, and can potentially be extended to sub-ps switching by integrating the NLTL into the EOM waveguide. This fast switch can be used to implement an Optical Time Division Multiplexing (OTDM) network architecture. View full abstract»

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  • A Polarizer Using Thin Metallic-Film Subwavelength Grating for Infrared to Terahertz Region

    Page(s): 670 - 676
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (857 KB) |  | HTML iconHTML  

    A polarizer using a sinusoidal or triangular thin metallic-film subwavelength grating is proposed. The dependence of polarizer transmission characteristics on structural parameters of the grating was obtained numerically, and its potential for high performance was confirmed experimentally. The measured transmission loss for the TE-waves with a 25 nm-thick gold-film grating with a triangular profile was higher than 50 dB while the corresponding transmission loss for the TM-waves was lower than 1 dB in the frequency range of 1.0-2.5 THz. The metallic subwavelength grating structure has demonstrated its potential as a low-loss, high-extinction ratio, wide-aperture, and robust polarizer for the infrared and terahertz regions. View full abstract»

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  • Multi-Channel 40 Gbit/s NRZ-DPSK Demodulation Using a Single Silicon Microring Resonator

    Page(s): 677 - 684
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (770 KB) |  | HTML iconHTML  

    We comprehensively analyze the demodulation of wavelength division multiplexed (WDM) non return-to-zero differential phase-shift keying (NRZ-DPSK) signals by a single microring resonator. Simultaneous demodulation of multiple 40 Gbit/s WDM NRZ-DPSK channels is demonstrated using a single silicon microring resonator with free spectral range (FSR) of 100 GHz. Bit error measurements show very good performance for both through and drop port demodulations for all channels, and the drop port demodulation exhibits better wavelength detuning tolerance than for demodulation using a Mach-Zehnder delay interferometer (MZDI). View full abstract»

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  • Provisioning of Survivable Multicast Sessions in Wavelength-Routed Optical Networks With Scheduled Traffic

    Page(s): 685 - 690
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (794 KB) |  | HTML iconHTML  

    Provisioning survivable multicast sessions in wavelength-routed optical networks has already been studied under static or dynamic traffic. However, in many practical cases, customers tend to require a large bandwidth at a specified time interval. Scheduled traffic model, in which the setup and teardown times are known in advance or vary in a specified larger time window, is more appropriate to characterize this kind of traffic. In this paper, two scheduled traffic models are formulated and investigated for multicast protection in wavelength-routed optical networks, namely, Fixed Scheduled Traffic Model (FSTM) and Sliding Scheduled Traffic Model (SSTM). With the guaranteed 100% restorability against any single link failure, the FSTM formulation can achieve a global minimum cost for establishing all multicast sessions. A two-step optimization approach is further proposed to deal with the survivable multicast provisioning problem under SSTM. By optimizing the network resources jointly in space and time, survivable multicast sessions can be provisioned at much lower costs. View full abstract»

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  • Finite-Difference Mode Solver for Curved Waveguides With Angled and Curved Dielectric Interfaces

    Page(s): 691 - 699
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (390 KB) |  | HTML iconHTML  

    A finite-difference scheme for accurately analyzing step-index dielectric waveguides with angled and curved dielectric interfaces has been proposed by Chiang Here, this formulation is generalized to take into account a possible curvature of the entire waveguide along the propagation direction, and it is shown how Perfectly Matched Layers can be incorporated in order to accurately compute the bending or curvature loss of dielectric waveguides with step-index profiles of arbitrary shape. Furthermore, the formulation of the interface equations that relate the fields and their derivatives on both sides of a dielectric interface has been simplified, so that their implementation no longer requires any further explicit conversions between coordinate systems. View full abstract»

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  • Improvements to Long-Duration Low-Power Gain-Switching Diode Laser Pulses Using a Highly Nonlinear Optical Loop Mirror: Theory and Experiment

    Page(s): 700 - 707
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (760 KB) |  | HTML iconHTML  

    This work presents an experimental and theoretical study on the improvements to pulsed diode laser gain-switched (GS) optical sources. Simultaneous compression and reshaping of the limited quality pulses obtained with this technique are reported using a highly nonlinear optical loop mirror (HNOLM) directly coupled to the diode laser source, without any previous pulse conditioning. The HNOLM is based on the use of a microstructured optical fiber and a highly nonlinear semiconductor optical amplifier; it is compact and offers benefits in terms of reduced system complexity. The experimental observations are compared to a theoretical model of the system, and excellent agreement is observed. View full abstract»

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  • Extraordinary Coupling Into One-Way Magneto-Optical Photonic Crystal Waveguide

    Page(s): 708 - 713
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (708 KB) |  | HTML iconHTML  

    We present a two-dimensional magneto-optical photonic crystal waveguide, in which TM mode with proper frequency can propagate only in one direction. The photonic crystal is composed of square-lattice yttrium-iron-garnet (YIG) rods, with static magnetic field applied on it. In a special frequency range, this waveguide possesses only forward mode, while in another special frequency range, only backward mode. We also study the coupling of electromagnetic wave into it from air as well as from conductor waveguides. Numerical results show that the magneto-optical PhCs (MPC) waveguides have special transmitting performance, and can show high efficiency when electromagnetic wave is coupled into this waveguide. View full abstract»

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  • Metal–Insulator–Metal Surface Plasmon Polariton Waveguide Filters With Cascaded Transverse Cavities

    Page(s): 714 - 720
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (967 KB) |  | HTML iconHTML  

    In this work we propose a new approach for the design of resonant structures aiming at wavelength filtering applications. The structure consists of a subwavelength metal-insulator-metal (MIM) waveguide presenting cascaded cavities transversely arranged in the midpoint between the input and output ports. An extra degree of freedom added to this design consists in tilting the cavities around their midpoints which, besides effectively increasing the quality factor of the cavity, helps extending its range of applications by tuning multiple wavelengths. View full abstract»

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  • PDM-QPSK Modulator With a Hybrid Configuration of Silica PLCs and LiNbO _{3} Phase Modulators

    Page(s): 721 - 727
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (568 KB) |  | HTML iconHTML  

    We discuss detailed characteristics of a polarization-division-multiplexed quadrature-phase-shift-keying (PDM-QPSK) modulator with a hybrid configuration of silica planar lightwave circuits (PLCs) and LiNbO3 (LN) phase modulators. With a polarization multiplexing circuit consisting of a half-wavelength plate (HWP) and a Mach-Zehnder-type polarization beam combiner (PBC) in a PLC, the modulator outputs a PDM-QPSK signal with a inter-polarization-channel crosstalk smaller than -40 dB. The modulator also has a small insertion loss of 5.0 dB (7.7 and 8.4 dB for each polarization), and successfully operates at 100 Gb/s. View full abstract»

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  • Far Field of Bragg Reflection Waveguides: Characteristics and Closed-Form Approximation

    Page(s): 728 - 735
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (758 KB) |  | HTML iconHTML  

    A comprehensive study of the far-field diffraction pattern of Bragg reflection waveguides is presented. Using a Gaussian approximation of the near-field profile, an analytical formula for the far-field pattern of the fundamental Bragg mode is obtained. The proposed closed-form representation offers a powerful technique for examining the far-field characteristics, which provides insight into the design optimization of Bragg reflection waveguides. View full abstract»

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  • On the Effectiveness of Coupled Mode Theory in the Analysis of Photonic Crystal Coupled Resonator Devices

    Page(s): 736 - 743
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    Coupled resonator photonic crystal devices may find important applications in future integrated nanophotonic circuits. These devices are well suited for coupling of mode analysis, which usually requires much less computational resources compared with finite-difference time domain (FDTD) schemes. Coupled mode models also provide a useful physical insight in the device operation. In this paper, we present a general coupled mode theoretic model for the treatment of coupled cavity devices incorporating various phenomena such as dispersion, frequency variation of the coupling coefficients, nonadjacent cavity coupling, and waveguide mode self coupling. The model is validated comparing its results against the FDTD method and the strength of the underlying assumptions is highlighted. Various approximations that can lead to further simplification of the coupled mode model are also discussed. It is shown that, unless the device transfer function possesses very sharp resonances, coupled mode analysis can provide an accurate device description. View full abstract»

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  • Experimental Characterization of Roughness Induced Scattering Losses in PECVD SiC Waveguides

    Page(s): 744 - 749
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (521 KB) |  | HTML iconHTML  

    An atomic force microscope is used to directly measure the sidewall roughness of silicon carbide waveguides. In order to make the vertical walls accessible, the chip containing the rib waveguides was fixed on a 15 steel wedge and loaded onto an AFM scanner stage; this fitting ensures enough probe contact area on one of the sidewalls. The data was processed using a fully automated algorithm to extract the roughness in the direction of light propagation. This technique allows the investigation of devices at chip level without damaging the structures. The method was calibrated using a well-known smoothing process based on thermal oxidation of silicon waveguides to achieve low transmission loss and applied to PECVD silicon carbide waveguides. A very low loss behavior at 1.3 m ( dB/cm) is reported. View full abstract»

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  • Characterization of a Linearly Chirped FBG Under Local Temperature Variations for Spectral Shaping Applications

    Page(s): 750 - 755
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (877 KB) |  | HTML iconHTML  

    We develop and experimentally validate a method to characterize linearly chirped fiber Bragg gratings (CFBGs) under local temperature perturbations for tunable spectral shaping. The heat distribution along the FBG is modeled by a Gaussian-Lorentzian function. The phase and apodization profiles of the CFBG are characterized by measuring the complex reflection spectrum and subsequently using inverse scattering. Finally, coupled mode theory is used to predict the transmittivity of the CFBG under the local temperature perturbations. As an application, we use our model to spectrally shape the spectrum of a gain-switched laser (GSL) and generate ultra-short, optimally designed pulses for high speed wireless data distribution in indoor environments. View full abstract»

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  • Optimal Resource Provisioning for Dynamic Wavelength Services With Access Port Constraints

    Page(s): 756 - 769
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1030 KB) |  | HTML iconHTML  

    With increasing demands for dynamic high data-rate private line services from large customers, network carriers have begun to provide flexible on-demand connections to construct these customers' networks. Advances in optical devices have greatly improved the reconfigurability of the optical layer, which makes it possible to provide optical on-demand services at wavelength granularity (10 Gbps to 40 Gbps per channel). This new dynamic wavelength service model allows a customer owning or leasing a few terminal ports in the network to connect these ports on demand. The network must be pre-dimensioned with enough resources to support any possible connection configuration between the pre allocated ports of a dynamic wavelength customer. In this paper, we introduce a resource optimization problem for dynamic wave length services and propose a few efficient techniques to tackle this challenging problem. A heuristic optimizer based on a combination of simulated annealing and genetic algorithms is developed to solve the problem efficiently for large networks. We show that our solver can produce optimization solutions within 7% overhead of a lower bound with a small amount of computation. View full abstract»

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  • Fiber-Core-Matched Three-Dimensional Adiabatic Tapered Couplers for Integrated Photonic Devices

    Page(s): 770 - 774
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (772 KB) |  | HTML iconHTML  

    A three-dimensional (3-D) adiabatic tapered coupler is demonstrated to improve light coupling between single-mode fibers (SMF) and an integrated photonic chip. This 3-D taper, made by polymer via a fabrication process using mode extrusion in combination with photolithography, can have a large coupling area matching with a fiber core. For a silicon oxynitride waveguide coupling to a SMF, the measured coupler loss was 3 dB. The fiber misalignment tolerance is 3.5 m and 3 to 5 m for the lateral and vertical offset, respectively, according to a 3-dB loss window. View full abstract»

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  • Optical Single-Sideband Modulation With Tunable Optical Carrier to Sideband Ratio in Radio Over Fiber Systems

    Page(s): 775 - 781
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1069 KB) |  | HTML iconHTML  

    We show that an optical modulator that consists of an integrated dual parallel Mach-Zehnder modulator (dMZM) can be used for obtaining not only optical single-side band modulation but also tunability of optical carrier to sideband ratio (OCSR) simultaneously. Such a modulator will be vital for optimizing the performance of radio over fiber links by improving modulation efficiency and receiver sensitivity and by removing fiber chromatic dispersion induced RF power fading. It is shown that a wide range of OCSR tunability can be obtained by altering bias voltage of dMZM, and optimum OCSR, to maximize the output RF power, depends on RF modulation index and extinction ratio of the integrated dMZM. Good agreement between theory, simulation, and experiment is obtained. For typical extinction ratio and low modulation index, it is found that an OCSR of 0 dB is optimum to maximize RF carrier power. However, for multiband orthogonal frequency-division multiplexing (MB-OFDM) ultra-wideband (UWB) radio, the best error vector magnitude (EVM) of -21.8 dB is obtained experimentally at an OCSR of ~5.4 dB due to avoidance of clipping induced nonlinear distortion. View full abstract»

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  • Intra-Cavity Spectroscopy Using Amplified Spontaneous Emission in Fiber Lasers

    Page(s): 782 - 788
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (854 KB) |  | HTML iconHTML  

    Fiber laser sources offer interesting possibilities for gas sensors since they can operate over an extended wavelength range, encompassing the near-IR absorption lines of a number of important gases but a major problem is that overtone absorption lines of gases in the near-IR are relatively weak. In order to enhance sensitivity, we present here a simple method of intra-cavity absorption spectroscopy (ICAS) which makes use of the amplified spontaneous emission (ASE) already present within a fiber laser cavity. The ASE also provides a convenient broadband source for the simultaneous interrogation of several gases within the gain-bandwidth of the fiber laser. The key principle is based on adjusting the cavity attenuation to select an appropriate inversion level where the fiber gain curve is flat. Under this condition, the ASE undergoes multiple circulations within the fiber laser cavity, enhancing the effective path-length of a gas cell placed within the laser cavity. A theoretical model of system operation is given and we have experimentally demonstrated the principle of operation with acetylene and carbon dioxide using a simple erbium fiber laser system containing a 6 cm path-length, fiber coupled, intra-cavity, micro-optic gas cell. We have experimentally simultaneously observed 16 absorption lines for 1% acetylene gas in the 1530 nm region and detected the very weak carbon dioxide lines in this same wavelength region. A path length enhancement of in the linear regime has been demonstrated transforming the 6 cm micro-optic cell into an effective path length of m. We also demonstrate how the enhancement factor may be calibrated by use of a simple fiber-optic interferometer. Apart from the OSA, all components are inexpensive and the system is very simple to construct and operate. View full abstract»

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  • Complete Characterization of an Optical Pulse Based on Temporal Interferometry Using an Unbalanced Temporal Pulse Shaping System

    Page(s): 789 - 800
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1043 KB) |  | HTML iconHTML  

    We propose and demonstrate a simple method for the full characterization of an ultrashort optical pulse based on temporal interferometry, using an unbalanced temporal pulse shaping (UB-TPS) system. The UB-TPS system consists of a Mach-Zehnder modulator and two dispersive elements (DEs) having opposite dispersion, but nonidentical in magnitude. The entire system can be considered as a typical balanced TPS system for a real-time Fourier transformation to generate two time-delayed replicas of the input optical pulse, followed by a residual DE to perform a second real-time Fourier transformation to convert the two time-delayed pulse replicas to two frequency-sheared optical spectra. The spectral interferometry is performed in the time domain. The spectral magnitude and phase information of the input optical pulse is accurately and unambiguously reconstructed from the recorded temporal interference pattern based on a Fourier transform algorithm. Compared with a conventional pulse characterization system based on linear interferometric measurement using an optical interferometer implemented by using discrete components, the proposed system features better stability, higher adaptability, and single-shot measurement. The use of the proposed system for the characterization of a femtosecond pulse before and after passing through a 60-m-long single-mode fiber is experimentally demonstrated. View full abstract»

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Aims & Scope

The Journal of Lightwave Technology contains articles on current research, applications and methods used in lightwave technology and fiber optics.

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
Peter J. Winzer
Alcatel-Lucent Bell Labs