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Lightwave Technology, Journal of

Issue 10 • Date Oct 2002

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Displaying Results 1 - 12 of 12
  • Noise characteristics of a single-mode laser diode subject to strong optical feedback

    Page(s): 1847 - 1850
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (251 KB) |  | HTML iconHTML  

    An experimental study has been performed of the relative intensity noise (RIN) of a semiconductor laser in optical feedback regimes I to V. At low bias current, a low RIN is observed with low feedback ratio, the RIN increased in the coherence collapse regime (regime IV) and decreased in regime V. The RIN in regime V is lower than that of the solitary laser. For higher bias current, a higher feedback ratio is needed for the semiconductor laser to transit from regime IV to V. The measurements are found to be in good qualitative and quantitative agreement with theoretical predictions. View full abstract»

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  • Optimization of microwave properties for ultrahigh-speed etched and unetched lithium niobate electrooptic modulators

    Page(s): 1856 - 1863
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (683 KB) |  | HTML iconHTML  

    Simultaneous phase velocity and characteristic impedance matching of the ultrahigh-speed electrooptic modulators is presented by using the finite-element method (FEM). It is also shown that the dielectric loss in the silica buffer layer is larger than that in the lithium niobate substrate and when these dielectric losses are included, the resulting bandwidth is reduced significantly. It is also shown that for an etched LN structure, it is relatively easier to match both Nm and Zc simultaneously and the resulting optical bandwidth is also greater. View full abstract»

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  • A fast algorithm for the simulation of propagation in large-area 2-D photonic crystal devices

    Page(s): 1869 - 1875
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (573 KB) |  | HTML iconHTML  

    A fast numerical method for the simulation of propagation of light beams in large-area photonic crystal devices is presented. It is shown that if the propagation of a localized field is considered, a numerical code that does not require implementation of any boundary condition may be realized, with a computational complexity that scales almost linearly with the device length. View full abstract»

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  • System outage probability due to the combined effect of PMD and PDL

    Page(s): 1805 - 1808
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (291 KB)  

    The system outage probability induced by polarization mode dispersion (PMD) and polarization dependent loss (PDL) is studied by Monte Carlo simulations using a new waveplate model. The previous waveplate model gives zero PMD and PDL probability densities when PMD and PDL exceed certain values, while our new model does not have such a limitation. It is shown that the system outage probability strongly depends on the interaction of PMD and PDL and the acceptable PMD limit drops significantly with the increase of PDL. View full abstract»

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  • 1.49-μm-band gain-shifted thulium-doped fiber amplifier for WDM transmission systems

    Page(s): 1826 - 1838
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (607 KB) |  | HTML iconHTML  

    This paper describes in detail the amplification characteristics of gain-shifted thulium-doped fiber amplifiers (GS-TDFAs) operating in the 1480to 1510-nm wavelength region (1.49-μm S-band) for use in wavelength-division-multiplexing (WDM) systems. Gain shifting of a TDFA, which normally has a gain band at 1.47 μm (S+-band), is achieved by two types of dual-wavelength pumping: (1) 1.05 and 1.56 μm or (2) 1.4 and 1.56 μm. The main pump source at 1.05 or 1.4 μm creates population inversion between 3F4 (upper laser level) and 3H4 (lower laser level), while the auxiliary pump source at 1.56 μm reduces the average fractional inversion down to approximately 0.4, which is a desired level for gain shifting. We show experimentally that the former provides a low internal noise figure (<4 dB) due to high fractional inversion at the input end of a thulium fiber, while the latter provides a very high optical efficiency but a higher internal noise figure (∼5 dB) due to the lower fractional inversion at the input end. These characteristics were verified by numerical simulation based on a comprehensive rate equation modeling. We demonstrated a 1.4- and 1.56-μm laser-diode-pumped GS-TDFA with an optical efficiency of 29.3% and high output power of +21.5 dBm. Gain flatness and tilt control were also investigated. These results strongly confirm the feasibility of using GS-TDFAs in practical ultralarge-capacity WDM networks. View full abstract»

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  • Full-vector finite-element beam propagation method for three-dimensional nonlinear optical waveguides

    Page(s): 1876 - 1884
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (723 KB)  

    A full-vector finite-element beam propagation method (VFE-BPM) in terms of all the components of slowly varying electric fields is described for the analysis of three-dimensional (3-D) nonlinear optical waveguides. Electric fields obtained with this approach can be directly utilized for evaluating nonlinear refractive index distributions. To eliminate nonphysical, spurious solutions, hybrid edge/nodal elements are introduced. Furthermore, to avoid spurious reflections from the computational window edges, anisotropic perfectly matched layer boundary conditions are implemented, and to reduce computational effort for the nonlinear optical waveguide analysis, an iterative algorithm is also introduced. The effectiveness of the present approach is verified by way of numerical examples: nonlinear directional couplers, spatial soliton emission phenomena, and soliton couplers. View full abstract»

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  • Graded-index polymer optical fiber with high temperature and high humidity stability

    Page(s): 1818 - 1825
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (857 KB) |  | HTML iconHTML  

    It was clarified for the first time that the slight attenuation increment observed in the previous poly methyl methacrylate (PMMA)-dopant system graded-index polymer optical fiber (GI POF) we reported originated in the excess scattering loss induced by the aggregation of absorbed water into the POF. Although the PMMA material generally absorbs two weight% of water at maximum, the low attenuation of the conventional step-index (SI) POF whose core material is PMMA can be maintained at 70°C, 80% relative humidity (RH) atmosphere because the absorbed water might be homogeneously dispersed without any aggregation in the core of POF. On the other hand, addition of dopant material having higher refractive index than that of PMMA is required to form the refractive index distribution in the GI POF, which decreases the amount of water absorption into polymer, because the dopant material is more hydrophobic than PMMA. Therefore, in spite of the small amount of absorbed water such as 0.5 wt.%, the absorbed water molecules can not be uniformly dispersed but must be aggregated to form heterogeneities in the refractive index of the polymer matrix. It was clarified that a dopant material that is as hydrophilic as PMMA was required to maintain the attenuation of the PMMA-dopant system GI POF under high temperature and high humidity atmosphere, and such a suitable dopant system GI POF was proposed. View full abstract»

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  • 2R regeneration based on dispersion-imbalanced loop mirror and its applications in WDM systems

    Page(s): 1809 - 1817
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (768 KB) |  | HTML iconHTML  

    2R regeneration based on dispersion-imbalanced loop mirror is investigated including the characteristics of transfer function, output extinction ratio, initial chirp, predispersion, and WDM signals transfer functions. Theoretical results show that the input peak power is a critical parameter for the dispersion-imbalanced loop mirror (DILM) and furthermore, to guarantee the multiwavelength operation of the DILM, limitations due to accumulated dispersion and dispersion slope have to be considered. Our experiment demonstrates that 6×10 Gb/s WDM signals can be successfully regenerated by a novel 2R regenerator based on a DILM consisting of a single mode fiber (SMF) and a highly nonlinear dispersion-shifted fiber (DSF) after WDM transmission over 40 km SMF of the WDM signals. View full abstract»

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  • All-fiber wavelength-tunable acoustooptic switches based on intermodal coupling in fibers

    Page(s): 1864 - 1868
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (311 KB) |  | HTML iconHTML  

    In this paper, we demonstrate a novel all-fiber wavelength-tunable acoustooptic switch utilizing intermodal coupling in a two-mode fiber (TMF). Its all-fiber configuration consisting of a fiber acoustooptic tunable filter and a mode-selective coupler results in the low loss (<2 dB) operation. The operating bandwidth >50 nm, the switching time of 40 μsec, and the crosstalk of 20 dB were achieved. By controlling the design parameters of the two-mode fiber, the 3-dB bandwidth of the switched signal was varied from 2.5 nm to >35 nm. A novel all-fiber dynamic optical add-drop multiplexer is also demonstrated using two acoustooptic switches in series. View full abstract»

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  • Single-mode condition for silicon rib waveguides

    Page(s): 1851 - 1855
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (474 KB) |  | HTML iconHTML  

    The geometrical conditions required for single-mode propagation in large cross-section silicon-on-insulator (SOI) waveguides were investigated using the beam propagation method (BPM). The cases of both vertical-walled and sloping-walled (trapezoidal) rib structures were considered. In the trapezoidal case some approximate methods were compared with the simulated results. Expressions for the single-mode condition for both types of waveguide were defined. View full abstract»

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  • Performance of optical bit rate limiters with pre- or post-optical amplification

    Page(s): 1797 - 1804
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (634 KB) |  | HTML iconHTML  

    A communication system incorporating a bit rate limiter (BRL) device is analyzed using recently proposed statistical models for power splitters and combiners. We also consider the possible optical attenuation and amplification before and after BRL device. We obtain the total output moment generating function (MGF) of the number of photoelectrons at the receiver end for two possible synchronization procedures. Furthermore, we use saddle-point approximation method to evaluate the system performance considering the effects of shot-noise, thermal noise, and source extinction ratio. View full abstract»

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  • Comparison of gain clamped and conventional semiconductor optical amplifiers for fast all-optical switching

    Page(s): 1839 - 1846
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (519 KB)  

    This paper reports computer simulation results to compare a Mach-Zehnder interferometer (MZI) when the two arms of it operate with gain-clamped and conventional semiconductor optical amplifiers (gcSOA and convSOA, respectively) for fast all-optical switching. The comparison is for demultiplexing optical pulses from 160 Gb/s to the base rate of 10 Gb/s or 40 Gb/s. The gain dynamics of the gcSOA is presented, the switching windows at the drop port of the MZI for both cases that were referred before and finally an evaluation of them is discussed. 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