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Lightwave Technology, Journal of

Issue 4 • Date Apr 2001

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Displaying Results 1 - 17 of 17
  • Transmission performance of 10-Gb/s optical duobinary transmission systems considering adjustable chirp of nonideal LiNbO3 Mach-Zehnder modulators due to applied voltage ratio and filter bandwidth

    Page(s): 465 - 470
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (140 KB)  

    We investigate interplay between the residual and applied chirp of optical duobinary modulated signals in order to improve transmission performance. To find the best performance for 10-Gb/s optical duobinary transmission systems, we consider the residual chirp accompanying from the finite extinction ratio, the applied chirp adjusted by the applied voltage ratio (the chirp parameter) between two electrodes of LiNbO3 modulators, and the bandwidth of electrical low-pass filters used in duobinary transmitters. The simulation results suggest that nearly zero chirp during the mark (`1') period and large peak chirp at the middle of the space (`0') provide the best transmission performance. This zero chirp around marks and high peak chirp at the middle of each space can be controlled by the applied voltage ratio between two electrodes of modulator and the filter bandwidth, respectively View full abstract»

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  • Polarization and dispersive properties of elliptical-hole photonic crystal fibers

    Page(s): 495 - 503
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (228 KB)  

    We survey the properties of photonic crystal fibers with elliptical air holes, examining mode shapes, birefringence, group velocity walkoff and dispersion, and cutoff conditions. We find new types of behavior for each quantity and demonstrate the possibility achieving large birefringence with zero walkoff in the single-mode regime. We show that the dispersive properties of the vector modes are closely tied to those of the so-called fundamental space filling modes, and that at long wavelengths, the fibers exhibit a single-polarization single-mode regime of propagation without the presence of material anisotropy View full abstract»

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  • Analysis of signal degree of polarization degradation used as control signal for optical polarization mode dispersion compensation

    Page(s): 480 - 486
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (164 KB)  

    The basic property of degree of polarization (DOP) degradation of optical signal induced by polarization mode dispersion (PMD) in high-speed optical fiber transmission is investigated in detail. The DOP of the optical signal reflects the degree of waveform degradation caused by PMD, therefore, it is proposed to be used as the control signal judging the best compensation point for the optical adaptive PMD compensation techniques. However, the signal DOP is not only affected by PMD, but also by various factors, such as the modulation format, modulator chirp, fiber nonlinearity, amplified spontaneous emission (ASE), and so on. We use numerical simulations and experiments to explore the basic DOP property to detect PMD with these factors. We also show that using the signal DOP as control signal is especially useful for the optical duo-binary modulation because of its high sensitivity and wide PMD detection range View full abstract»

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  • Traffic adaptive WDM networks: a study of reconfiguration issues

    Page(s): 433 - 455
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (400 KB)  

    This paper studies the issues arising in the reconfiguration phase of broadcast optical networks. Although the ability to dynamically optimize the network under changing traffic conditions has been recognized as one of the key features of multi-wavelength optical networks, this is the first in-depth study of the tradeoffs involved in carrying out the reconfiguration process. We develop and compare reconfiguration policies to determine when to reconfigure the network, and we present an approach to carry out the network transition by describing a class of strategies that determine how to retune the optical transceivers. We identify the degree of load balancing and the number of retunings as two important, albeit conflicting, objectives in the design of reconfiguration policies, naturally leading to a formulation of the problem as a Markovian decision process. Consequently, we develop a systematic and flexible framework in which to view and contrast reconfiguration policies. We show how an appropriate selection of reward and cost functions can be used to achieve the desired balance among various performance criteria of interest. We conduct a comprehensive evaluation of reconfiguration policies and retuning strategies and demonstrate the benefits of reconfiguration through both analytical and simulation results. The result of our work is a set of practical techniques for managing the network transition phase that can be directly applied to networks of large size. Although our work is in the context of broadcast networks, the results can be applied to any wavelength-division multiplexing network where it is necessary to multiplex traffic from a large user population into a number of wavelengths View full abstract»

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  • Polarization mode dispersion in radio-frequency interferometric embedded fiber-optic sensors

    Page(s): 504 - 511
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (164 KB)  

    The effect of fiber birefringence on the propagation delay in an embedded fiber-optic strain sensor is studied. The polarization characteristics of the sensor are described in terms of polarization mode dispersion through the principal states of polarization and their differential group delay. Using these descriptors, an analytical expression for the response of the sensor for an arbitrary input state of polarization is given and experimentally verified. It is found that the differential group delay, as well as the input and output principal states of polarization, vary when the embedded fiber is strained, leading to fluctuations in the sensor output. The use of high birefringence fibers and different embedding geometries is examined as a means for reducing the polarization dependency of the sensor View full abstract»

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  • Simple star multihop optical network

    Page(s): 425 - 432
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (204 KB)  

    A new multihop wavelength division multiplexed (WDM) optical network with two wavelengths per node that can give the maximum throughput and minimum delay is proposed. It is called a “simple star” multihop network. This network has good characteristics in traffic balance and minimum average number of hops. Furthermore, unlike most existing networks, it does not impose an upper limit to the number of nodes View full abstract»

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  • Calculation of penalties due to polarization effects in a long-haul WDM system using a Stokes parameter model

    Page(s): 487 - 494
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (160 KB)  

    We derive a Stokes parameter model to calculate the penalties due to the combination of polarization mode dispersion (PMD), polarization dependent loss (PDL), and polarization dependent gain (PDG) in long-haul, dense wavelength division multiplexed (WDM) systems. In this model, we follow the Stokes parameters for the signal and the noise in each channel instead of following the full time domain behavior of each channel. This approach allows us to determine the statistical distribution of penalties with up to 105 fiber realizations and 40 channels. We validate this model to the extent possible by comparison to full numerical simulations. Using this model, we find that the interaction of PMD and PDL is the major source of penalties and that the effect of PDG is negligible in WDM systems with more than ten channels View full abstract»

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  • Comparison of temperature dependence in C-band and L-band EDFAs

    Page(s): 527 - 535
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (260 KB)  

    Temperature-dependent gain and noise characteristics of conventional band and long wavelength band erbium-doped fiber amplifiers are compared. Gain variations and noise figure penalties are shown for 980- and 1480-nm pump wavelength bands at different average inversion levels when the erbium coil temperature is cycled from -10°C to 80°C. Experimental results demonstrate that the L-band exhibits greater temperature-dependent gain and noise figure excursions compared to the C-band. Furthermore, it is shown that the impact of erbium coil temperature in the L-band is comparatively less dependent upon pump wavelength View full abstract»

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  • Monolithically integrated low-power phototransceivers for optoelectronic parallel sensing and processing applications

    Page(s): 546 - 552
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (124 KB)  

    A low-power GaAs-based monolithically integrated phototransceiver, consisting of a high-gain heterojunction phototransistor (WPT) and a microcavity light-emitting diode (MCLED) or a low-threshold vertical-cavity surface-emitting laser (VCSEL), is demonstrated. The HPT and MCLED/VCSEL are grown by molecular-beam epitaxy in a single step. The phototransistor exhibits a responsivity of 60 A/W at an input power of 1 μW. The input and output wavelengths are 850 and 980 nm, respectively. The MCLED-based phototransceiver exhibits an optical gain of 7 dB and power dissipation of 400 μW for an input power of 1.5 μW. The small signal modulation bandwidth is 80 MHz. On the other hand, the VCSEL-based phototransceiver exhibits an optical gain of 10 dB and power dissipation of 760 μW for an input power of 2.5 μW View full abstract»

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  • A simple broad-band coherence multiplexed optical access network and its scalability

    Page(s): 456 - 464
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (220 KB)  

    This paper proposes a novel and simply configured broad-band optical access network that uses coherence multiplexing (CM) and half-duplex bidirectional transmission. It allows the on-demand use of broad bandwidth on existing fiber-to-the-home (FTTH) access lines. The design of the proposed CM network considers degradation factors in CM systems. This paper introduces two analyses. The first one is a numerical simulation to optimize the tradeoff between available user number and fiber dispersion degradation, and the second estimates acceptable access-line loss in the network. These analyses show that 16 users×100 Mb/s (or 12 users×155 Mb/s) bandwidth Is possible on a standard single-mode fiber access line whose loss and length are under 9 dB and 10 km (and 7 km), respectively. The feasibility and scalability of the proposed network are verified by an experiment in which eight-channel 155-Mb/s half-duplex optical packet transmission is successfully demonstrated on a 7-km standard fiber access line with bit error rates better than 1×10-9. This study shows that the capacity of existing FTTH access lines that employ star couplers can be significantly enhanced View full abstract»

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  • Electrical measurements of multipath interference in distributed Raman amplifiers

    Page(s): 536 - 545
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (208 KB)  

    Measurements of multipath interference (MPI) using an electrical technique have shown that the use of distributed Raman amplification can significantly increase the amount of MPI in a system. The MPI is primarily attributed to double-Rayleigh scattering along the length of the transmission fiber. Analytical expressions for MPI have been developed that give good agreement with measurements and numerical simulations. These can be used to predict the buildup of MPI in a lightwave transmission system. Poor connectors will cause a further increase in MPI by causing back-reflections into the Raman gain cavity View full abstract»

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  • Single-polarization generation in fiber Fabry-Perot laser by self-injection locking in short feedback cavity

    Page(s): 520 - 526
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (156 KB)  

    Single-frequency and single-polarization lasing can be generated in a compact self-injection locked fiber Fabry-Perot laser with a short fiber Bragg grating feedback cavity. No discrete polarization control components are required. Different wavelengths actress the laser gain bandwidth can be generated by an appropriate combination of cavity designs and feedback fiber Bragg gratings. A 10-Gb/s nonreturn-to-zero transmission test demonstrates the laser's applicability for optical fiber communications View full abstract»

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  • Determination of bend mode characteristics in dielectric waveguides

    Page(s): 571 - 577
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (152 KB)  

    A new and effective method for the electromagnetic analysis of generic bent dielectric waveguides is presented. The method is based on the expansion of the bend mode in modes of the straight waveguide and permits determination of the shape and the phase constant of the fundamental mode of the bend waveguide with great accuracy at a very low computational cost. Simple analytical expressions of the phase constant, coupling losses, and bending-induced birefringence are derived under very general conditions. The proposed method is useful for the design and optimization of each bent section of integrated optics components View full abstract»

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  • Design and characterization of compact single-section passive polarization rotator

    Page(s): 512 - 519
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (184 KB)  

    In this paper an improved design for a short and low-loss polarization rotator is proposed, consisting of a single-section asymmetrical waveguide butt-coupled between two standard rib waveguides. At a wavelength of 1.55 μm, nearly 100% polarization conversion ratio is obtained, with a relatively short (320 μm) device length and an extremely low 0.5 dB total insertion loss. The simulation results are obtained using the full vectorial finite-element-based beam propagation, the junction analysis, and the modal solution approaches View full abstract»

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  • An evolutionary algorithm for the synthesis of multilayer coatings at oblique light incidence

    Page(s): 559 - 570
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (292 KB)  

    A robust evolutionary approach is proposed for the synthesis of multilayer coatings at oblique light incidence. The proposed approach consists of global and local strategies by integrating decreasing mutations and self-adaptive mutations via family competition and adaptive rules. Numerical results calculated at normal and oblique angles of incidence indicate that the proposed approach performs very robustly and is very competitive with other approaches. Our approach, although somewhat slower, is very flexible and can easily be adapted to other application domains. This approach is able to generate binary-type solutions based on two materials and to generate inhomogeneous solutions with continuous refractive-index variations View full abstract»

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  • Multiwavelength fiber laser sources with Bragg-grating sensor multiplexing capability

    Page(s): 553 - 558
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (128 KB)  

    Two erbium-doped fiber ring lasers (EDFRLs) wvith simultaneous emission at four different wavelengths are demonstrated. Both systems employ fiber Bragg gratings (FBGs) to select the operation wavelengths within the ring. The sensing capability of the FBGs has been taken advantage of, allowing for the sources to be used as sensor multiplexing schemes. The first system employs four FBGs in a tree filter topology, achieving four output channels with -5 dBm power each. The second system comprises an in-line filtering topology with active fiber segments within the filter. This second source yields 2-dBm output signals and allows for a higher number of lines to be easily added to the system. A comparison between both topologies is carried out, and their capability for sensor multiplexing is demonstrated View full abstract»

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  • Ultralong lightwave systems with incomplete dispersion compensations

    Page(s): 471 - 479
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (196 KB)  

    Ultralong nonreturn-to-zero optical transmission systems with incomplete dispersion compensations are studied. The dispersion of transmission fiber is periodically under- or overcompensated. Postdispersion compensation (PDC) at the receiver is used to compensate for the residual dispersion caused by incomplete compensation and to tailor the signal pulse shape. Formulas estimating the change of pulse width in the absence of amplifier noise during signal transmission and after PDC are given. During signal transmission, pulse width may be compressed or broadened by the combined effect of the dispersion and self-phase modulation (SPM). The change of pulse width nearly increases with the square of the distance during signal transmission. With amplifier noise, system performance evaluated by Q factor is studied. Several types of transmission fibers are considered. The Q factor can be significantly improved by proper PDC. Signal pulse is compressed when PDC is optimized. The characteristics of the maximum Q factor and the residual dispersion are studied, in which PDC is optimized. The results show that to achieve the best system performance, fiber dispersion should be undercompensated for positive dispersion parameter and overcompensated for negative dispersion parameter. The optimal fiber dispersion lies in the range from 4 to 10 ps/km/nm for the considered systems, and the optimal ratio of residual dispersion and fiber dispersion is about 1% 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.

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Meet Our Editors

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