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Lightwave Technology, Journal of

Issue 4 • Date April 2006

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Displaying Results 1 - 25 of 41
  • [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): 1625 - 1627
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    Freely Available from IEEE
  • Code-based all optical routing using two-level coding

    Page(s): 1627 - 1637
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    Code-based all optical routing employing a two-level-coding scheme is proposed. The first level of coding is employed to establish connections between users within a local area network; a second level of coding provides routing/interconnectivity between networks. The limitations due to physical-layer impairments, such as relative intensity noise (RIN) of the optical source, the signal-dependent shot noise, optical beat interference (OBI), and thermal noise at the receiver, which are some of the fundamental issues in the design of practical optical code division multiple access (CDMA) systems, are analyzed for the two-level scheme. The throughput in terms of "packets/time slot" offered by the scheme is also compared with that of the wavelength division multiple access (WDMA) system. The system capacity in WDMA is limited by the number of available wavelengths; optical CDMA, on the other hand, has many codes (user addresses), but the throughput is limited by multiple user interference, OBI, and RIN. System designs that overcome these effects and thereby improve the throughput are suggested. View full abstract»

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  • From IP over WDM to all-optical packet switching: economical view

    Page(s): 1638 - 1645
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    In this paper, a technoeconomical study of several (optical) packet-switching node architectures is described. Therefore, different architectures proposed in IST-WASPNET and IST-LASAGNE projects as well as a standard optical circuit switching approach are considered, and their economical impact is estimated by means of cost comparisons between the different technologies. The switching architectures all use optical fiber as a transport medium, but each of them uses a different technology to process switching. Their cost is evaluated as a function of most characteristic parameters for each technology. In the all-optical approaches, the main cost is that related to the fiber assembly, whereas for electronic processing, the most expensive cost is related to the optical-electronic-optical (OEO) conversions. The results show that the integration of optical components is crucial to make all-optical packet-switching nodes feasible. View full abstract»

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  • A new family of 2-D optical orthogonal codes and analysis of its performance in optical CDMA access networks

    Page(s): 1646 - 1653
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    A new family of two-dimensional optical orthogonal code (2-D OOC), one-coincidence frequency hop code (OCFHC)/OOC, which employs OCFHC and OOC as wavelength hopping and time-spreading patterns, respectively, is proposed in this paper. In contrary to previously constructed 2-D OOCs, OCFHC/OOC provides more choices on the number of available wavelengths and its cardinality achieves the upper bound in theory without sacrificing good auto-and-cross correlation properties, i.e., the correlation properties of the code is still ideal. Meanwhile, we utilize a new method, called effective normalized throughput, to compare the performance of diverse codes applicable to optical code division multiple access (OCDMA) systems besides conventional measure bit error rate, and the results indicate that our code performs better than obtained OCDMA codes and is truly applicable to OCDMA networks as multiaccess codes and will greatly facilitate the implementation of OCDMA access networks. View full abstract»

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  • OCDMA over WDM PON-solution path to gigabit-symmetric FTTH

    Page(s): 1654 - 1662
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    It will be revealed that a myth of deploying low bit-rate uplink fiber-to-the-home (FTTH) services while providing a high bit-rate downlink is wrong. Therefore, for the future broadband FTTH services, the focus should be on the capability to provide gigabit- or even multigigabits-per-second both in up- and downlinks, namely gigabit symmetric systems. Optical code-division multiple access (OCDMA) now deserves a revisit as a powerful alternative to time-division multiple access and wavelength-division multiple (WDM) access in FTTH systems. In this paper, the authors will first highlight the OCDMA systems. The system architecture and its operation principle, code design, optical en/decoding, using a long superstructured fiber Bragg grating (SSFBG) en/decoder, and its system performance will be described. Next, an OCDMA over WDM passive optical network (PON) as a solution for the gigabit-symmetric FTTH systems will be proposed. The system architecture and the WDM interchannel crosstalk will be studied. It will be shown that by taking advantage of reflection spectrum notches of the SSFBG en/decoder, the WDM interchannel crosstalk can be suppressed and can enable OCDMA over WDM PON to simultaneously provide multigigabit-per-second up- and downlinks to a large number of users. View full abstract»

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  • Performance analysis of modified accelerative preallocation MAC protocol for passive star-coupled WDMA networks

    Page(s): 1663 - 1673
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1000 KB) |  | HTML iconHTML  

    For the passive star-coupled wavelength-division multiple-access (WDMA) network, a modified accelerative preallocation WDMA (MAP-WDMA) media access control (MAC) protocol is proposed, which is based on AP-WDMA. To show the advantages of MAP-WDMA as an adequate MAC protocol for the network over AP-WDMA, the channel utilization, the channel-access delay, and the latency of MAP-WDMA are investigated and compared with those of AP-WDMA under various data traffic patterns, including uniform, quasi-uniform type, disconnected type, mesh type, and ring type data traffics, as well as the assumption that a given number of network stations is equal to that of channels, in other words, without channel sharing. As a result, the channel utilization of MAP-WDMA can be competitive with respect to that of AP-WDMA at the expense of insignificantly higher latency. Namely, if the number of network stations is small, MAP-WDMA provides better channel utilization for uniform, quasi-uniform-type, and disconnected-type data traffics at all data traffic loads, as well as for mesh and ring-type data traffics at low data traffic loads. Otherwise, MAP-WDMA only outperforms AP-WDMA for the first three data traffics at higher data traffic loads. In the aspect of channel-access delay, MAP-WDMA gives better performance than AP-WDMA, regardless of data traffic patterns and the number of network stations. View full abstract»

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  • Design and performance of a reconfigurable liquid-crystal-based optical add/drop multiplexer

    Page(s): 1674 - 1680
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    The authors describe a reconfigurable optical add-drop multiplexer designed for 50-GHz channel spacing over either the C- or L-bands. The system may also function as a variable optical attenuator. The design features a reflective liquid-crystal modulator, a compact free-space spectrometer, polarization diversity, and fine-scale attenuation control. View full abstract»

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  • Distributed measurement of the chromatic dispersion of an optical fiber using a wavelength-tunable OTDR

    Page(s): 1681 - 1688
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    In this paper, a distributed measurement of the chromatic dispersion (CD) of an optical fiber is presented. The measurement is based on the analysis of a set of bidirectional optical time domain reflectometer traces collected over the wavelength range of interest. To calculate the distributed CD of the fiber, several approximations are required. The validity of these approximations is verified via a numerical simulation for both step-index and dispersion-shifted fibers (DSFs). These simulations allow the placement of an upper bound on the error of the measurement. Experimentally, measurements of both step-index and DSFs are reported. View full abstract»

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  • Choice of MUX/DEMUX filter characteristics for NRZ, RZ, and CSRZ DWDM systems

    Page(s): 1689 - 1696
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (392 KB) |  | HTML iconHTML  

    This paper investigates the influence of filter bandwidth and flank steepness of both multiplexing and demultiplexing filters in dense wavelength division multiplexed systems (spectral efficiency 0.8 b/s/Hz) in the presence of coherent wavelength division multiplexing (WDM) crosstalk. Using a recently introduced technique for the statistically reliable performance prediction of systems impaired by coherent WDM crosstalk, this paper presents numerical results for nonreturn-to-zero (NRZ), 33% duty-cycle return-to-zero (RZ), and 67% duty-cycle carrier-suppressed return-to-zero signals. This paper confirms that steep filter flanks are generally preferable, both in terms of optical signal-to-noise ratio penalty and in terms of filter bandwidth tolerance. View full abstract»

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  • Optical return loss measurements and simulation of an arbitrary array of concatenated reflective elements on field-installed optical links

    Page(s): 1697 - 1702
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    A new simple model, based on the zigzag diagram of transmission-line theory, is used to predict the optical return loss (ORL) for an arbitrary array of concatenated reflective elements on a typical optical network. A very good agreement to ORL measurements performed on different types of optical fiber plant is found. View full abstract»

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  • Extending optical transmission distance in fiber wireless links using passive filtering in conjunction with optimized modulation

    Page(s): 1703 - 1709
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    The authors demonstrate a simple passive technique for increasing the transmission distance in fiber wireless links through the application of a narrowband fiber Bragg grating (FBG) with high reflectivity (90-99%). They are applied in a conventional downstream link and also for the upstream in a wavelength-reused scheme. In the conventional nonwavelength-reused system, the grating is used to optimize the optical modulation depth and, hence, the receiver sensitivity in the downstream transmitted signal by reducing the power of the optical carrier before fiber transmission. In the wavelength-reused systems, the highly reflective FBGs can be effectively used at the base stations to recover a major portion of the optical carrier (as high as 99% of the downlink carrier) for uplink transmission from a weakly modulated downstream signal. In the latter case, the penalty in the downstream signal due to the large extraction of carrier power is partially offset by the sensitivity enhancement obtained in the filtering process. The authors present experimental results for the increased transmission performance for both the nonwavelength-reused and wavelength-reused scenarios. The increase in the sensitivity (at biterrorrate=10-9) in the nonwavelength-reused scheme for a given launch channel power that facilitates the increased transmission distance can be as large as 7 dB. The relative increase in the power margin for the upstream signal can be up to 4 dB in the wavelength-reused scheme. This would more than double the currently demonstrated transmission distances in such wavelength-reused systems without any optical amplification. The scheme is applicable to a wide range of radio frequencies and modulation depths. View full abstract»

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  • Limitations to and solutions for optical loss in optical backplanes

    Page(s): 1710 - 1724
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    In this paper, recent literature on the discussion on high-speed backplanes with optical, electrical, and mixed solutions, as well as on polymer-waveguide systems suitable for implementation on printed circuit boards (PCBs), is reviewed from the point of view of their optical losses. The reevaluation of the optical power budget for realistic high-speed optical polymer-waveguide links on backplanes showed that signal amplification is necessary to boost the signal, which resulted in an additional literature review on advances in optical amplifiers based on silicon bench technology available. Finally, a concept study of an active optical waveguide amplifier device, based on planar optical waveguide amplifiers and semiconductor optical amplifiers, was performed. The amplification device can be flip-chip mounted on the backplane to compensate for optical losses due to signal routing, which increases the overall degree of freedom in waveguide routing on high-density interconnects for backplanes. The hybrid concept design guarantees compatibility with the processes of the PCB industry. View full abstract»

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  • 10-Gb/s millimeter-wave signal generation using photodiode bias modulation

    Page(s): 1725 - 1731
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    We present a simple 120-GHz-band millimeter-wave (MMW) modulation method that uses the bias-voltage dependence of unitraveling-carrier-photodiode output power, which we call photodiode (PD) bias modulation. We investigated the dependence of the output-power-saturation mechanisms on the bias voltage. We used a lowpass filter in the bias circuit to increase the modulation bandwidth, and the 3-dB modulation bandwidth was over 7 GHz. We demonstrated the modulation of 120-GHz MMW signals at a data rate of 10 Gb/s using PD bias modulation. View full abstract»

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  • Broadband parametric amplification in photonic crystal fibers with two zero-dispersion wavelengths

    Page(s): 1732 - 1738
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    In this paper, the fourfold parametric enhancement over Raman gain of the total optical fiber-amplifier gain is analyzed. Such fiber-amplifier gain may be obtained with a relatively flat profile over a bandwidth in excess of 70 nm by using a microstructure or photonic crystal fiber with two zero-dispersion wavelengths. Optimal fiber-amplifier gain enhancement occurs whenever the pump wavelength is slightly shorter than the second zero-dispersion wavelength of a microstructure optical fiber. View full abstract»

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  • Characterization of fiber Bragg gratings using spectral interferometry based on minimum-phase functions

    Page(s): 1739 - 1757
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    The focus of this paper is on interferometric systems that utilize spectral interferometry based on minimum-phase functions (MPFs) to fully characterize any fiber-Bragg-grating (FBG) spectra without exceptions. The approach presented involves sending a broadband light source (e.g., a short laser pulse) into the FBG of interest and using an optical spectrum analyzer (OSA) to record the spectrum of the interference between the reflected pulse from the grating and the time-delayed version(s) of the original short pulse. The square root of this measured spectrum, which yields the Fourier-transform (FT) magnitude of the input-pulse-sequence electric-field envelope, is then processed to uniquely recover both the phase and the amplitude of the FBG spectrum. The underlying principle for this unique recovery is that by construction, the input pulse sequence sent to the OSA is close to an MPF; thus, it is possible to recover its FT phase spectrum using only the measurement of its FT magnitude spectrum. This is an important result since, by merely measuring the FT magnitude, the entire complex spectrum of the grating can be recovered. Furthermore, this technique can conveniently be used to simultaneously characterize more than one FBG, using a single FT magnitude measurement. This technique has important advantages over existing techniques: a higher resolution and the ability to use longer duration laser pulses. View full abstract»

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  • Analysis of fiber fabry-Pe´rot interferometric sensors using low-coherence light sources

    Page(s): 1758 - 1767
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    Sensitivity, fringe contrast, and dynamic range are the three most important parameters in the theoretical performance evaluation of fiber Fabry-Pe´rot (F-P) interferometric sensors. This paper theoretically models the effect that the cavity length, the F-P finesse, the source bandwidth, mirror misalignments and symmetry play in the sensitivity, fringe contrast, and dynamic range of a fiber F-P interferometer interrogated with a low-coherence light source. The developed systematic fiber F-P interferometer analysis approach and the numerical analysis results on both guided and unguided fiber F-P interferometer (FFPI) sensors may provide useful guidance for sensor design optimization. View full abstract»

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  • Doppler effect in flexible and expandable light waveguide and development of new fiber-optic vibration/acoustic sensor

    Page(s): 1768 - 1775
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    New principle and a geometrical arrangement of an optical fiber for a vibration/acoustic measurement are proposed in the present paper. The sensor is based on a new finding that a frequency of light wave transmitted through a bent optical fiber is shifted by vibration at the bent region. The phenomenon can be explained as Doppler's effect in flexible and expandable light waveguide. Several configurations of the sensor have been designed, and very high sensitivity is achieved in the extremely wide frequency range. Principle, sensor configuration and theoretical sensitivity, measurement system, and some experimental consideration are described in the present paper. The sensor sensitivity was examined experimentally in the low and middle frequency range, and the detectability was confirmed experimentally in the frequency range of acoustic emission signals. View full abstract»

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  • Coated long-period fiber gratings as high-sensitivity optochemical sensors

    Page(s): 1776 - 1786
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (368 KB) |  | HTML iconHTML  

    In this paper, the numerical and the experimental analyses of coated long-period fiber gratings (LPFGs) as a high-sensitivity optochemical sensor are presented. The proposed structure relies on LPFGs coated with nanoscale high refractive index chemical-sensitive overlays. The deposition of overlays with refractive index higher than the cladding one leads to a modification of the cladding-mode distribution. If the overlay features are properly chosen, a strong field enhancement within the overlay occurs, leading to an excellent sensitivity of the cladding-mode distribution to the coating properties. The effects of overlay thickness and cladding-mode order on sensor performances have been numerically and experimentally investigated. In order to provide a high-sensitivity and species-specific optochemical sensor, this mechanism has been proved with nanoscale overlays of syndiotactic polystyrene (sPS) in the nanoporous crystalline δ form. The sensitive material has been chosen in light of its selectivity and high sorption properties towards chlorinated and aromatic compounds. Sensor probes were prepared by using dip-coating technique and an adequate procedure to obtain the δ-form sPS. Experimental demonstration of the sensor capability to perform subparts-per-million detection of chloroform in water at room temperature is also reported. View full abstract»

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  • Polarization properties of interferometrically interrogated fiber Bragg grating and tandem-interferometer strain sensors

    Page(s): 1787 - 1795
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    Lead sensitivity in low-coherence interferometric fiber-optic sensors is a well-known problem. It can lead to a severe degradation in the sensor resolution and accuracy through its effect on the fringe visibility and interferometric phase. These sensitivities have been attributed to birefringence in the various components. In the current work, an analysis of the polarization properties of fiber Bragg grating and tandem-interferometer strain sensors, using Stokes calculus and the Poincare´ sphere, is presented. The responses of these sensors as a function of the birefringence properties of the various components under different illuminating conditions are derived. The predicted responses demonstrate very good agreement with experimentally measured responses. These models provide a clear insight into the evolution of the polarization states through the sensor networks. Methods to overcome the lead sensitivity are discussed and demonstrated, which yield a differential strain measurement accuracy of 18 nε·rms for a fiber Bragg grating sensor. View full abstract»

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  • Monolithic 3-D silicon photonics

    Page(s): 1796 - 1804
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    A monolithic CMOS compatible process has been developed to realize vertically integrated devices in silicon. The method involves the implantation of an oxygen into a patterned silicon substrate to form buried guiding structures. These buried devices are separated from a surface silicon layer by an intervening layer of silicon dioxide formed through the implantation process. Photolithography and etching is used to define devices on the surface silicon layer. The method has been utilized to realize the vertically coupled microdisk resonators and a variety of microresonator-based integrated optical elements. A new method for extraction of the unloaded Q of a cavity from its measured spectrum is also described. View full abstract»

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  • Tunable multiwavelength fiber laser employing a comb filter based on a polarization-diversity loop configuration

    Page(s): 1805 - 1811
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    A tunable multiwavelength fiber laser based on a semiconductor optical amplifier (SOA) is newly proposed. The proposed fiber laser employs a fiber comb filter based on a polarization-diversity loop configuration (PDLC) for the multiwavelength selection. The spectral characteristic of the comb filter is graphically explained by tracing the state of polarization (SOP) of the light propagating through the filter on the Poincare sphere. Particularly, the method of adjusting the filter characteristics is established with the help of the Poincare-sphere representation. The experimental results show that 18 laser lines oscillate with the signal to amplified spontaneous emission noise ratio over 25 dB. Particularly, all of the laser lines with a fixed channel spacing of ∼ 0.8 nm can be continuously shifted by adjusting only a wave plate contained within the filter. View full abstract»

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  • Characterization of wavelength-tunable single-frequency fiber laser employing acoustooptic tunable filter

    Page(s): 1812 - 1823
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    This paper demonstrates and characterizes a novel wavelength-tunable single-frequency erbium-doped fiber ring laser incorporating an all-fiber acoustooptic tunable bandpass filter and a self-constructed saturable absorption grating (SAG). Stable single-longitudinal-mode operation was achieved over the wavelength range of 48 nm with a sidemode suppression ratio higher than 50 dB. The wavelength tuning characteristics, and the laser dynamics in wavelength switching and sweeping are analyzed in detail. A theoretical analysis on the effect of the SAG is also described. View full abstract»

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  • Amplified-spontaneous-emission spectrum of the radiation field in surface-emitting DFB lasers

    Page(s): 1824 - 1833
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    In this paper, the authors calculate the amplified-spontaneous-emission spectrum of the radiation field in surface-emitting distributed feedback (DFB) lasers. The response of the laser cavity to the Langevin noise source in the frequency domain is obtained using the newly developed Green's functions for the slowly varying amplitudes of the guided waves. The authors show that the power spectra from the surface and the edge are different, and this discrepancy is due to excitation of the radiation field by the interference between the counter-propagating waves inside the cavity. This feature can be properly exploited in the design of surface-emitting DFB lasers for optical communications. 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