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Lightwave Technology, Journal of

Issue 11 • Date Nov 1998

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Displaying Results 1 - 14 of 14
  • A femtosecond code-division multiple-access communication system test bed

    Publication Year: 1998 , Page(s): 1953 - 1964
    Cited by:  Papers (88)  |  Patents (16)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (216 KB)  

    This paper reports comprehensive experimental results on a femtosecond code-division multiple-access (CDMA) communication system test bed operating over optical fiber in the 1.5 μm communication band. Our test bed integrates together several novel subsystems, including low-loss fiber-pigtailed pulse shapers for encoding-decoding, use of dispersion equalizing fibers in dispersion compensated links for femtosecond pulse transmission and also in femtosecond chirped pulse amplification (CPA) erbium doped fiber amplifiers (EDFAs), and high-contrast nonlinear fiber-optic thresholders. The individual subsystems are described, and single-user system level experimental results demonstrating the ability to transmit spectrally encoded femtosecond pulses over a 2.5-km dispersion compensated fiber link followed by decoding and high contrast nonlinear thresholding are presented View full abstract»

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  • Improved receivers for coherent FSK systems

    Publication Year: 1998 , Page(s): 1973 - 1980
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (380 KB)  

    There has been considerable interest over the last decade in the detection of digital coherent lightwave signals corrupted by phase noise. However, the majority of the work has been in the performance analysis of various modulation schemes. In addition, the receivers studied have, in general, been zero-phase noise optimal or ad hoc modifications of these. In this paper, we consider the design problem of constructing optimal receivers for systems using frequency shift keying (FSK). Using the innovations approach, we show the format of the optimal receiver and use a small phase noise approximation to derive suboptimal receivers. Also, receivers based on optimum linear filters are also derived. Both receivers are analyzed by simulation and performance improvements over the standard receivers are shown. Furthermore, the receivers developed can equally well be used to further improve the performance of other detection schemes such as postdetection filtering and time diversity. The methodology is also used to derive equivalent receivers for systems using on-off keying (OOK) View full abstract»

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  • Calculation of the wavelength filter properties of the fiber-slab waveguide structure using vector mode expansion

    Publication Year: 1998 , Page(s): 2034 - 2039
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (188 KB)  

    A vectorial solution technique is applied to investigate the dispersion characteristics of the ridge modes of a waveguide structure comprising a slab and optical fiber. The power transmission characteristics of the device with respect to wavelength are calculated under various device parameters, such as slab index and fiber-slab separation. We discuss the effects of such parameters on the bandwidth and rejection of the notch filter produced by this structure View full abstract»

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  • Heterodyne autocorrelation method for characterizing 1.55 μm optical pulse train and for measuring dispersion and nonlinearity in optical fibers

    Publication Year: 1998 , Page(s): 1981 - 1989
    Cited by:  Papers (2)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (288 KB)  

    Heterodyne autocorrelation measurement of 1.55 μm optical pulses from an actively mode-locked external cavity diode laser is performed before and after transmission through an optical fiber. In heterodyne autocorrelation, optical spectrum is resolved electronically. This method is suitable for measurement of optical pulses with a spectral width of less than 100 GHz, and it gives not only the pulse width and chirp of the pulses, but also it is useful for determining the dispersion and optical Kerr constant of an optical fiber. Analytical formalism for deducing these quantities is given for Gaussian pulses. Principal measurement is performed using a mode-locked diode laser. Dispersion is measured for a conventional-dispersion fiber of 35 km. Also, self-phase modulation (SPM) is measured for a dispersion-shifted fiber of 15.83 km View full abstract»

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  • Combination of beam propagation method and mode expansion propagation method for bidirectional optical beam propagation analysis

    Publication Year: 1998 , Page(s): 2040 - 2045
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (300 KB)  

    A combined method of the beam propagation method (BPM) and the mode expansion propagation method (MEPM) is proposed for the analysis of reflections of both transverse electric (TE) and transverse magnetic (TM) polarized waves in waveguiding structures containing longitudinal discontinuities. BPM based on the finite-element method (FEM) is applied to slowly varying regions and MEPM is applied only to regions including abrupt discontinuities. FEM is also utilized for evaluating the eigenmodes necessary for the MEPM analysis. To show the validity and usefulness of the present approach, numerical examples for a semiconductor laser facet with antireflection coating and an optical directional coupler are presented View full abstract»

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  • Impact of transmission performance on path routing in all-optical transport networks

    Publication Year: 1998 , Page(s): 1965 - 1972
    Cited by:  Papers (29)  |  Patents (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (132 KB)  

    The impact of transmission related issues on the routing strategies for transparent all-optical wavelength division multiplexed (WDM) transport networks is analyzed in this paper. Three different categories of routing algorithms are analyzed: algorithms based on the wavelength path (WP) strategy, based on the virtual wavelength path (VWP) strategy and requiring only a limited number of wavelength converters in the network partial virtual wavelength path (PVWP). It results that the PVWP allows a saving in network devices with respect to the WP similar those permitted by the VWP also attaining transmission performances near those attained by the WP that are quite better that those attained by the VWP View full abstract»

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  • Crosstalk of passive directional couplers

    Publication Year: 1998 , Page(s): 2020 - 2027
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (292 KB)  

    Crosstalk in directional couplers (DC's) is an important parameter for device and system performance. Although various crosstalk mechanisms have been studied through the course of integrated optics, the fundamental lower limit for crosstalk is still uncertain. In this paper, crosstalk mechanisms are reviewed and fundamental limits are discussed. A new model for optical scattering is presented, and the effect of bending loss variation between the two propagating modes in the taper region on the crosstalk is discussed View full abstract»

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  • Pressure-dependent Sellmeier coefficients and material dispersions for silica fiber glass

    Publication Year: 1998 , Page(s): 2002 - 2005
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (104 KB)  

    The pressure-dependent Sellmeier coefficients are essential to characterize the optical design parameters for the optical fiber communication systems under deep sea environmental conditions. These coefficients are calculated for densified silica glass for the first time to compute the pressure dependence of material dispersion at any wavelength from the ultraviolet (UV) to 1.71 μm. The zero dispersion wavelength λ0 (1.2725 μm at 0.1 106 N m -2) varies linearly with pressure, and dλ0/dP is 0.0027 nm/(106 N m-2). The calculated value is approximately one-third of the experimental value of 0.0076 nm/(106 N m-2) for a germanium-doped dispersion shifted fiber having λ0=1.5484 μm and -0.0070 nm/(106 N m-2) for a pure silica-core fiber cable having λ0 =1.2860 μm. Since, the refractive indexes are increased with pressure, the negative value of shift of the zero-dispersion wavelength is erroneous. The explanations are due to Ge-doping in silica glass, a possible temperature fluctuation of 0.16°C in the pressure-dependent measurement system of the zero dispersion wavelength and different experimental conditions of the silica glass and the optical fibers. This anomaly can also be attributed to the internal strain development at the core-cladding and fiber-jacketing boundaries due to pressure, which shows a larger experimental value. It accounts for the experimental values satisfactorily View full abstract»

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  • Acoustically scanned low-coherence interrogated simultaneous measurement of absolute strain and temperature using highly birefringent fibers

    Publication Year: 1998 , Page(s): 2010 - 2015
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (148 KB)  

    We have utilized a traveling acoustic pulse in a two-mode optical fiber to create a moving beam splitter coupling light from LP01 to LP11 mode. As these optical modes have different group velocities, a variable intermodal delay is generated as a function of acoustic pulse position in the fiber. The device can be used as a receiving interferometer in low-coherence interferometry to scan time delay for carrying out fast extended range absolute measurement using simple analog electronic circuits. With this scanning technique we demonstrate measurement of absolute strain over 1600 με in the temperature range from 20 to 60°C with resolutions of the order of 40 με and 0.7°C, respectively, employing highly birefringent fibers as sensing elements View full abstract»

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  • 100% efficient narrow-band acoustooptic tunable reflector using fiber Bragg grating

    Publication Year: 1998 , Page(s): 2006 - 2009
    Cited by:  Papers (21)  |  Patents (15)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (88 KB)  

    This paper reports a 100% efficient Bragg-grating-based acoustooptic superlattice modulator in a fiber whose diameter is reduced by HF etching. The acoustically induced reflections, which appear on both sides of the Bragg stop-band, are tunable by altering the acoustic frequency, and have bandwidths corresponding to weak versions of the permanent Bragg grating. These unique properties may lead to important applications in, e.g., reconfigurable wavelength division multiplexing, Q-switching, amplitude modulation, and frequency shifting View full abstract»

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  • Multimode power divider using radiation from tight bending waveguide

    Publication Year: 1998 , Page(s): 2028 - 2033
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (156 KB)  

    By using a large-core and high-Δ polymeric optical waveguide, we developed the mode-division power divider which enables wide-angle power dividing, and compared it with a conventional Y-junction power divider. The core size and Δ were 100×100 μm2 and 5.4%, respectively. At the conditions of 25° branching angle and 50/50 splitting ratio, the excess loss of the mode-division and Y-junction were estimated to be 2.5 and 9.5 dB, respectively. These values were including 1.2 dB fiber-connecting loss. Furthermore, we observed that both the mode-division type outputs have almost the same modal power distribution as the input View full abstract»

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  • Volterra series approach for optimizing fiber-optic communications system designs

    Publication Year: 1998 , Page(s): 2046 - 2055
    Cited by:  Papers (22)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (300 KB)  

    A new methodology for designing long-haul fiber-optic communication systems is presented. We derive the overall Volterra series transfer function of the system including linear dispersion, fiber nonlinearities, amplified spontaneous emission (ASE) noise from the fiber amplifiers, and the square-law nature of the direct detection (DD) system. Since analytical expressions for the probability of error are difficult to derive for the complex systems being used, we derive analytical expressions for an upper bound on probability of error for integrate-and-threshold detection at the receiver. Using this bound as a performance criterion, we determine the optimal dispersion parameters of each fiber segment required to minimize the effects of linear dispersion, fiber nonlinearities and ASE noise from the amplifiers. We study the dependence of optimal dispersion parameters on the average power levels in the fiber by varying the peak input power levels and the amplifier gains. Analytical expressions give us the freedom to choose system parameters in a practical manner, while providing optimum system performance. Using a simple system as an example, we demonstrate the power of the Volterra series approach to design optimal optical communication systems. The analysis and the design procedure presented in this work can be extended to the design of more complex wavelength division multiplexed (WDM) systems View full abstract»

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  • A novel optical phase modulator design suitable for phased arrays

    Publication Year: 1998 , Page(s): 2016 - 2019
    Cited by:  Papers (9)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (112 KB)  

    A new design of optical phase modulator in SIMOX has been demonstrated, which allows duplication of active waveguides with a minimum requirement for external contacts and metallization. The device is based on a common cathode configuration and requires 56.5 mA at 1.65 V to produce a π-phase shift. To confirm the experimental results, the same device structure has been modeled, and provided good agreement, with Vπ calculated to 1.70 V and 52.6 mA View full abstract»

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  • Fabrication and characterization of Yb3+:Er3+ phosphosilicate fibers for lasers

    Publication Year: 1998 , Page(s): 1990 - 2001
    Cited by:  Papers (33)  |  Patents (15)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (264 KB)  

    Fabrication process of efficient Yb3+,Er3+ codoped phosphosilicate fibers by modified chemical vapor deposition (MCVD) combined with the solution doping technique is studied in detail. We show that the process can be adapted to incorporate low viscosity phosphate glass and some important issues in the fabrication process are discussed. These include the sensitive presintering pass. We also report on the fabrication of a low loss all-glass double clad Yb3+:Er3+ codoped fiber. We explain how we evaluate the fibers and discuss the effect of the ytterbium to erbium concentration ratio on the laser characteristics. Finally, we present results of some investigations into the mechanisms which can affect the efficiency of the lasers, and show that the detrimental up-conversion from the metastable level of the erbium ions is dramatically reduced by the presence of the ytterbium ions 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