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Lightwave Technology, Journal of

Issue 7 • Date April1, 2011

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Displaying Results 1 - 25 of 26
  • [Front cover]

    Page(s): C1
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  • Journal of Lightwave Technology publication information

    Page(s): C2
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  • Table of contents

    Page(s): 941 - 942
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  • Side-Hole Photonic Crystal Fiber With Ultrahigh Polarimetric Pressure Sensitivity

    Page(s): 943 - 948
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (540 KB) |  | HTML iconHTML  

    We propose a side-hole polarization-maintaining photonic crystal fiber (PM-PCF) with ultrahigh polarimetric sensitivity to hydrostatic pressure. The proposed fiber has a very simple structure with a core surrounded by a double row of large air holes and a central row of small air holes. A pair of ultralarge side holes was symmetrically introduced into the silica cladding of the fiber to enhance the polarimetric response to hydrostatic pressure. Modal birefringence B as large as 2.34 × 10-3 and polarimetric pressure sensitivity dB/dp as high as -2.30 × 10-5 MPa-1 were achieved at 1.55 μm for the proposed fiber. Combining the advantages of both side-hole fibers and PM-PCFs, it is believed to be an excellent candidate for future applications of hydrostatic pressure measurement. View full abstract»

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  • A Novel Boundary Element Method Using Surface Conductive Absorbers for Full-Wave Analysis of 3-D Nanophotonics

    Page(s): 949 - 959
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (783 KB) |  | HTML iconHTML  

    Fast surface integral equation (SIE) methods seem to be ideal for simulating 3-D nanophotonic devices, as such devices generate fields in both the interior device volume and in the infinite exterior domain. SIE methods were originally developed for computing scattering from structures with finite surfaces, and since SIE methods automatically represent the infinite extent of the exterior scattered field, there was no need to develop numerical absorbers. Numerical absorbers are needed when SIE methods are used to simulate nanophotonic devices that process or couple light, to provide nonreflecting termination at the optical ports of such devices. In this paper, we focus on the problem of developing an approach to absorbers that are suitable for port termination, yet preserve the surface-only discretization and the geometry-independent Green's function properties of the SIE methods. Preserving these properties allows the absorber approach to be easily incorporated in commonly used fast solvers. We describe our solution to the absorber problem, that of using a gradually increasing surface conductivity, and show how to include surface conductivity in SIE methods. We also analyze numerical results using our absorber approach to terminate a finite-length rectangular cross section dielectric waveguide. The numerical results demonstrate that our surface-conductivity absorber can easily achieve a reflected power of less than 10-7, and that the magnitude of the transition reflection is proportional to 1/L2d+2, where L is the absorber length and d is the order of the differentiability of the surface conductivity function. View full abstract»

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  • Spectral Anomalies of Polychromatic DHGB and Its Applications in FSO

    Page(s): 960 - 966
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    This paper contains some interesting experimental results of the study carried out on anomalous spectral behavior due to coherence and polarization change on polychromatic focused dark hollow Gaussian beam (DHGB). On the basis of experimental and numerical analysis, the possibility and significance of DHGB based free-space optical (FSO) links for indoor and outdoor optical communications are explored. View full abstract»

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  • Brillouin Gain Reduction Via B _{2} O _{3} Doping

    Page(s): 967 - 973
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    We present both modeling results and experimental data demonstrating that B2O3 (boric oxide) can be used as an effective SBS-suppressive optical fiber codopant due to a very large acoustic damping coefficient. A Ge-containing fiber with ~6 wt% B2O3 at room temperature has a Brillouin gain coefficient more than 4 dB lower than that of standard Ge-doped SMF. These B-doped fibers, unlike standard Ge-doped SMF, have Brillouin spectra that broaden with increasing fiber temperature. Modeling parameters (acoustic velocity, spectral width, etc.) for bulk B2O3 based on a fit-to-data are provided. Modeling results for the B-Ge-Si oxide system indicate that the bulk material gain falls below 0.5×10-11 m/W at 1534 nm near the 1B2O3:4SiO2 molar composition. View full abstract»

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  • Simple Fiber Model for Determination of XPM Effects

    Page(s): 974 - 986
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (745 KB) |  | HTML iconHTML  

    Previous investigations have revealed that the impairments of the cross-phase modulation (XPM) in dense wavelength-division multiplexing (DWDM) systems include two aspects: the XPM-induced phase noise and the XPM-induced polarization scattering. Such XPM phenomena are strongly dependent on the transmission system configurations and are nonintuitive. In this paper, a simple fiber model is proposed to facilitate the determination of XPM effects. By employing this model, the phase noise and polarization scattering are calculated based on the system configurations and the time-consuming computation by the split step Fourier method is avoided. The proposed model is verified by the dual polarization quadrature phase-shift keying coherent DWDM experiments and simulations in terms of the variance and autocorrelations of phase noise and polarization crosstalk as well as their dependence on relative polarization states and the overall Q-impairment. The proposed model helps deeper analysis of XPM phenomena, and eventually, leads to development of various XPM mitigation methods through transmission system design and coherent receiver DSP. View full abstract»

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  • Recovery of Absolute Gas Absorption Line Shapes Using Tunable Diode Laser Spectroscopy With Wavelength Modulation—Part 2: Experimental Investigation

    Page(s): 987 - 996
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (250 KB) |  | HTML iconHTML  

    Recovery of absolute gas absorption line shapes from first harmonic residual AM (RAM) signals in tunable diode laser spectroscopy with wavelength modulation (TDLS-WM) offers significant advantages in terms of measurement accuracy (for gas concentration and pressure), freedom from the need for calibration and resilience to errors, or drift in system parameters/scaling factors. However, the signal strength and SNR are compromised somewhat relative to conventional WM spectroscopy (WMS) by the signal dependence on the laser's intensity modulation amplitude rather than on the direct intensity, and by the need to operate at low modulation index, 0.75 in the previously reported study. In part 1 of this two-part publication, we report a more universal approach to the analysis of recovered RAM signals and absolute absorption line shapes. This new approach extends the use of RAM techniques to arbitrary m values up to 2.2. In addition, it provides the basis for a comparison of signal strength between the RAM signals recovered by the phasor decomposition approach and conventional first and second harmonic TDLS-WM signals. The experimental study reported here validates the new model and demonstrates the use of the RAM techniques for accurate recovery of absolute gas absorption line shapes to 2.2 and above. Furthermore, it demonstrates that the RAM signal strengths can be increased significantly by increasing the modulation frequency and defines regimes of operation such that the directly recovered RAM signals are comparable to or even greater than the widely used conventional second harmonic TDLS-WM signal. Finally, a critique of the RAM techniques relative to the conventional approaches is given. View full abstract»

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  • Analytical Expressions for Radiation Effects on Guided Mode Propagation in Long Period Gratings

    Page(s): 997 - 1002
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    Simple analytical expressions for guided power transmission through a periodic long-period grating with consideration of the significant radiation loss are derived from the complex coupled-mode theory. Under nearly phase-matching condition, the full coupled-mode equations are reduced to a set of two-mode equations for which close-form analytical solutions are readily obtained. For the long period grating with a high refractive index outer cladding, the effect of the radiation field on the guided mode can be well represented and explained by a decay factor for the envelope of the power profile along the waveguide. For the long period grating with infinite cladding, an approximate solution is proposed and shown to be in good agreement with the exact numerical solution. View full abstract»

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  • Time-Domain Modeling of Nonlinear Optical Structures With Extended Stability FDTD Schemes

    Page(s): 1003 - 1010
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (756 KB) |  | HTML iconHTML  

    Two numerical methodologies based on the finite-difference time-domain (FDTD) technique are formulated and applied to model optical structures with Raman and Kerr type nonlinearities. The first scheme is based on the alternating-direction implicit finite-difference time-domain (ADI-FDTD), while the second one is based on a recently introduced spatially filtered FDTD method. Both methods are able to extend FDTD time steps beyond the conventional Courant-Friedrichs-Lewy stability limit. It is demonstrated that both methods are significantly faster than the standard nonlinear FDTD, while maintaining its level of accuracy. Their potential as design and analysis tools for nonlinear periodic structures is demonstrated with the study of a 1-D problem involving a nonlinear Bragg reflector. View full abstract»

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  • Chirp Characteristics of Silicon Mach–Zehnder Modulator Under Small-Signal Modulation

    Page(s): 1011 - 1017
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (570 KB) |  | HTML iconHTML  

    Chirp characteristics of Silicon Mach-Zehnder Interferometer (MZI) modulators with forward-biased p-i-n and reverse-biased p-n structures are investigated by performing small-signal simulation, respectively. Simulation result shows that the chirp parameter is negative and influenced by the carrier absorption effect, the amplitude, and the frequency of applied sinusoidal modulating signals. Chirp performance at 10 GHz modulation frequency can be obtained by utilizing p-n depletion mode structure. Finally, a way to further lower the absolute value of the chirp parameter is provided by operating the MZI in a push-pull configuration. View full abstract»

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  • Tellurite Photonic Nanostructured Fiber

    Page(s): 1018 - 1025
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    In this paper, we address the challenges faced in the fabrication process of nanostructured fiber. We show that a slight nonuniformity of holes of the preform results in a difference in the added pressure in the holes of the fiber during the fabrication process. It may not be a notable problem for the microstructured fiber, but it can result in serious deformation or even collapse for nanostructured fiber. By using a model, we propose a distortion factor that indicates the distortion degree of the geometry of fiber compared with the geometry of preform. The hole size of preform is the most important variable to the distortion factor. A large hole size in the preform is of great significance in decreasing the distortion. We also show that when the temperature is increased, the surface tension is decreased, but the viscosity is decreased much more quickly, so the distortion becomes severe. For minimum distortion in the nanostructured fibers we demonstrate, preforms with comparatively large and uniform inner holes are fabricated by inflating with inert gas. By using such preforms, we fabricate hexagonal core and triangular core nanostructured fibers with the smallest size recorded. Supercontinuum generation from the nanostructured fiber is demonstrated. In this paper, the glass we use for the demonstration is a soft glass. By using polymer or silica glass, which is more suitable for nanostructure fabrication, and by controlling the uniformity of holes in the original cane more accurately, various nanostructured fibers with even smaller size and more complex structure, or nanowire array, should be able to be fabricated by the inflation method. View full abstract»

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  • Performance of an Integrated Coherent Receiver Module for up to 160G DP-QPSK Transmission Systems

    Page(s): 1026 - 1032
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    A coherent receiver module is presented, comprising two optical 90° hybrids monolithically integrated with eight waveguide p-i-n photodiodes in balanced configuration and two dual-channel linear transimpedance amplifiers. Its performance is demonstrated by transmitting up to 160 Gb/s dual-polarization quadrature phase-shift keying signals over 610 km standard single-mode fiber. View full abstract»

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  • Nitride-Based LEDs With High-Reflectance and Wide-Angle Ag Mirror {+} SiO _{2} /TiO _{2} DBR Backside Reflector

    Page(s): 1033 - 1038
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (825 KB) |  | HTML iconHTML  

    Nitride-based light-emitting diodes (LEDs) with a backside reflector combining a SiO2/TiO2 distributed Bragg reflector (DBR) and an Ag mirror were simulated and fabricated. With combining the three-pair SiO2/TiO2 DBR and an Ag mirror, it was found that we can significantly enhance the 96% reflectance of Ag mirror to 99.1% with an incident angle of 0°. Furthermore, reflectance of the proposed reflector depends slightly on incident light wavelength and the incident angle. With 350-mA current injection, it was found that the output powers were 122, 138, 153, 156, and 162 mW for the LEDs without reflector, with an Al mirror, with Al +3DBR mirror, with an Ag mirror, and with Ag+3DBR mirror, respectively. View full abstract»

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  • Intensity Noise Characteristics of Multimode VCSELs

    Page(s): 1039 - 1045
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    The intensity noise spectra of several multi-transverse mode 1550-nm vertical-cavity surface-emitting lasers (VCSELs) have been experimentally investigated. For a VCSEL emitting in two parallel polarized transverse modes the noise spectra of the individual modes and total power show two resonance peaks. The frequencies at which both peaks appear have been measured as a function of the bias current. Our experimental results confirm the theoretical predictions of Valle Differences in the noise spectra are experimentally observed when considering a VCSEL emitting in three transverse modes with polarization instabilities. We show that additional peaks appear in the noise spectra of the total power as the bias current is increased. View full abstract»

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  • Fictive Temperature of Larger Diameter Silica Optical Fibers

    Page(s): 1046 - 1050
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (140 KB) |  | HTML iconHTML  

    Fictive temperature (Tf) of pure silica cores was determined for a series of polymer-clad optical fibers via reflectance FTIR spectroscopy. The core diameters of the studied fibers were in the range 125-1500 μm. The fictive temperature was found to decrease gradually with increasing core diameter, which correlates with the anticipated fiber cooling rate. For a 1500 μm fiber, the radial distribution of the fictive temperature was examined. No dependence of Tf was observed upon the distance from the fiber axis, indicating that the heat conduction inside the silica fiber was much faster than the heat convection away from its surface, even for fibers with diameters greater than 125 μm. View full abstract»

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  • Effect of Aberrations on the Self-Imaging Phenomenon

    Page(s): 1051 - 1057
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (4300 KB) |  | HTML iconHTML  

    Diffraction gratings are used in measurement devices for scientific and industrial applications. As it is well known, self-images appear in the near field when diffraction gratings are illuminated with a coherent beam, such as a plane wave. This effect has been analyzed in depth and its behavior is well known under ideal grating and illumination conditions. Usually, the illumination beam is not perfectly collimated but it presents a certain degree of aberration. In this work we analyze the behavior of the self-images of an ideal amplitude grating when it is illuminated by an aberrated beam. As it is expected the contrast of the self-images decrease when the order of them increases and also when the aberration degree increases. In some cases, contrast inversion is also produced for high degree aberrations. View full abstract»

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  • Cooperative FSO Systems: Performance Analysis and Optimal Power Allocation

    Page(s): 1058 - 1065
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (654 KB) |  | HTML iconHTML  

    In this paper, we investigate the cooperative diversity technique as a candidate solution for combating turbulence-induced fading over free-space optical (FSO) links. In particular, we propose a novel cooperation strategy that is suitable for quantum-limited FSO systems with any number of relays and we derive closed-form expressions for the error performance of this strategy. In scenarios where the channel-state-information (CSI) is available at the different nodes, we propose an optimal power allocation strategy that satisfies the Karush-Kuhn-Tucker (KKT) conditions and that further boosts the performance of FSO networks. It turned out that this closed-form optimal solution corresponds to transmitting the entire optical power along the “strongest link” between the source and the destination nodes. A simple procedure is proposed for selecting this link and for distributing the power among its different hops. View full abstract»

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  • Blank page

    Page(s): 1066
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  • 37th IEEE Photovoltaic Specialists Conference (PVSC)

    Page(s): 1067
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    Freely Available from IEEE
  • 2011 EDS J.J. Ebers Award call for nominations

    Page(s): 1068
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    Freely Available from IEEE
  • 23rd IEEE International Symposium on Power Semiconductors and ICs

    Page(s): 1069
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    Freely Available from IEEE
  • Photonics for environmental sensing

    Page(s): 1070
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    Freely Available from IEEE
  • Journal of Lightwave Technology Information for authors

    Page(s): C3
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    Freely Available from IEEE

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