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Lightwave Technology, Journal of

Issue 4 • Date Feb.15, 2008

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Displaying Results 1 - 16 of 16
  • Table of contents

    Page(s): 389
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  • Cost Evaluation of Optical Packet Switches Equipped With Limited-Range and Full-Range Converters for Contention Resolution

    Page(s): 390 - 407
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1963 KB) |  | HTML iconHTML  

    Two architectures are proposed for a wavelength-division multiplexed optical packet switch equipped with both limited-range wavelength converters (LRWCs) and shared full-range wavelength converters (FRWCs). The FRWCs are used to overcome the performance degradation in terms of packet loss probability due to the use of LRWCs only. Two different sharing strategies of the FRWCs are considered. In the first architecture, a pool of FRWCs is shared among the arriving packets. In the second one, the sharing is only partial and the packets directed to the same output share a same pool of FRWCs. A probabilistic model is proposed to dimension the number of shared FRWCs so that the same packet loss probability of a switch equipped with only shared FRWCs is guaranteed. After introducing a cost model of the converters depending on the conversion range, we show that the architectures may allow a conversion cost savings on the order of 90%. View full abstract»

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  • High-Current Photodetectors as Efficient, Linear, and High-Power RF Output Stages

    Page(s): 408 - 416
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (620 KB) |  | HTML iconHTML  

    Recent progress in high-current photodiodes now makes it possible to efficiently generate over 26 dBm of RF power directly from the output of a photodiode. This paper describes two photodetector designs which demonstrate excellent large- and small-signal behavior. Maximum small-signal compression currents have increased to over 700 mA at 300 MHz. Output RF power amplifier stage efficiencies of over 45% (class AB operation) and 35% (class A) have been achieved from 0.3 to 6 GHz with RF power outputs over 26 dBm. The linearity figure of merit (LFOM) is also shown to be greater than 50, leading to the possibility of implementing very high linearity RF power amplifiers in the future. View full abstract»

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  • Detection Sensitivity of Brillouin Scattering Near Fresnel Reflection in BOTDR Measurement

    Page(s): 417 - 424
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (632 KB) |  | HTML iconHTML  

    We discuss the effect of Fresnel reflection on BOTDR measurement. We show that the theoretical detection sensitivity with respect to Brillouin scattering is limited by the pulse modulation effect and phase noise of the light source that is incorporated into the Brillouin spectrum by way of the Fresnel reflection, when the Brillouin sensor is located near the Fresnel reflection point. We describe the detection sensitivity in the presence of Fresnel reflection in terms of the minimum detectable sensor length. In regard to the pulse modulation effect, we find that when the pulsewidth is short, the noise in the Brillouin spectrum is large and the detection sensitivity deteriorates. We derive quantitative equations and confirm the equations experimentally. When the pulsewidth is 10 ns with a 1-MHz linewidth laser, the boundary Fresnel reflection determining whether or not we can measure a 1-m sensor fiber near the Fresnel reflection is about 30 dB lower than that for a 100 ns pulsewidth. A 1-m sensor fiber near the Fresnel reflection could be measured with a 10-ns pulse only when the Fresnel reflection was very low at about . Moreover, the effect of the laser linewidth is also discussed analytically. The analysis suggests that a laser with a narrower linewidth will provide better sensitivity. View full abstract»

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  • An Enhanced SOA-Based Double-Loop Optical Buffer for Storage of Variable-Length Packet

    Page(s): 425 - 431
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (951 KB) |  | HTML iconHTML  

    To extend the buffer depth of a fiber loop optical buffer, we have experimentally demonstrated an enhanced semiconductor optical amplifier (SOA)-based dual-loop optical buffer (DLOB) for storing variable-length optical packets. We have theoretically derived constraints governing the buffer depth of the DLOB, in which the SOA not only provides a nonlinear phase shift in the loop to implement the buffer function but also compensates for the fiber loop attenuation during long-time storage. It is found that the maximum allowable length of a stored packet to avoid the counter-propagation packet collision inside the SOA depends on the SOA bias position as well as the length of the fiber loop. To demonstrate the effectiveness of the proposed enhanced configuration, we have successfully demonstrated the storage of 2.5-Gbps variable-length packets even when the length of the input packet exceeds the corresponding length of the fiber loop. Another unique advantage of the proposed enhanced DLOB configuration is that it can also overcome the problem of power leakage of the stored packet due to a directional gain difference of single SOA and gain saturation. Index View full abstract»

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  • Tunable Diode Laser Spectroscopy With Wavelength Modulation: A Phasor Decomposition Method for Calibration-Free Measurements of Gas Concentration and Pressure

    Page(s): 432 - 440
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    The principles and implementation of a phasor decomposition method for analyzing signals in tunable diode laser spectroscopy with wavelength modulation are described. This new technique enables recovery of the isolated and normalized residual amplitude modulation (RAM) signal from measured first harmonic signals at any chosen fundamental modulation frequency. Like the previously reported RAM technique, this new approach is absolute, yielding gas absorption line shape functions, concentrations and pressures without the need for calibration, under certain defined operating conditions. It represents an advancement of the RAM technique in that it obviates the need to operate at a specific high frequency to achieve phase quadrature between the RAM and derivative signals: the signals may be recovered at their maximum levels at any frequency. Measurements of the 1650.96 nm and the 1666.2 nm rotation/vibration absorption line shape functions for 1% and 10% methane in nitrogen at various pressures are compared to theoretical predictions derived from HITRAN data. The excellent agreement confirms the validity of the new technique. Further measurements of concentration and pressure confirm the efficacy of the technique for determining concentration in industrial process environments where the pressure may be unknown and changing. With the above features this new method is particularly suited to stand alone instrumentation for on-line deployment in industrial processes where the calibration factors in the conventional approach would present significant difficulties. View full abstract»

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  • Highly Birefringent Photonic Crystal Fibers With Ultralow Chromatic Dispersion and Low Confinement Losses

    Page(s): 441 - 448
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (813 KB) |  | HTML iconHTML  

    Highly birefringent photonic crystal fibers (PCFs) with low confinement loss with ultralow and ultraflattened chromatic dispersions at wide wavelength band are presented. The transverse electric field vector distributions of two linearly polarized fundamental modes, their effective indices, modal birefringence, confinement losses and chromatic dispersion of the proposed PCFs are reported by using full-vector finite-element method (FEM). Significant improvements of PCFs in terms of the birefringence, chromatic dispersion and confinement losses are demonstrated by careful investigation of all air holes in each ring, air holes diameters and hole-to-hole spacing. In addition to this, the polarization beat length results of the proposed PCFs are also reported and discussed thoroughly. View full abstract»

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  • Analytical Model for Cross-Gain Modulation and Crosstalk in Quantum-Well Semiconductor Optical Amplifiers

    Page(s): 449 - 456
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (536 KB) |  | HTML iconHTML  

    An analytical model of the dynamic characteristics of a quantum-well (QW) semiconductor optical amplifier (SOA) is developed. Closed-form expressions for the optical gain and cross-gain modulation (XGM) for arbitrary input pulses are derived. The model takes into account the carrier capture and escape transitions between the QW and the continuum states. This model is also used to derive a closed-from expression for interchannel XGM crosstalk in multichannel SOA systems. The model/analysis provides insight into the effect of the SOA parameters on the performance of a wavelength-division multiplexed system. We found that crosstalk in a multichannel SOA system can be reduced by reducing the escape lifetime. View full abstract»

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  • Comments on “Study of the Complex Atomic Susceptibility of Erbium-Doped Fiber Amplifiers”

    Page(s): 457 - 459
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  • Slow light and its applications

    Page(s): 460 - 461
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  • Have you visited lately? www.ieee.org [advertisement]

    Page(s): 462
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  • IEEE copyright form

    Page(s): 463 - 464
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  • Journal of Lightwave Technology Information for authors

    Page(s): 465
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  • Blank page

    Page(s): 466
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  • [Front cover]

    Page(s): 467
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  • Journal of Lightwave Technology publication information

    Page(s): 468
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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