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Lightwave Technology, Journal of

Issue 2 • Date Feb 1992

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Displaying Results 1 - 23 of 23
  • 1.5-μm wavelength tunable phase-shift-controlled distributed feedback laser

    Page(s): 199 - 205
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    A 1.5 μm wavelength tunable phase-shift-controlled distributed feedback laser diode is studied. This wavelength tunable laser controls the light output power and the oscillation wavelength independently by current injection. During wavelength tuning, the submode suppression ratio is large and an almost constant spectral linewidth from 24 to 29 MHz is achieved over a wavelength tuning range as wide as 113 GHz (9.0 Å). The threshold gain change and the loss change are small during wavelength tuning and as a result an almost constant light output power is achieved View full abstract»

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  • Optical power limiting amplifier and its applications in an SONET self-healing ring network

    Page(s): 206 - 214
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    The authors demonstrate an erbium-doped optical power limiting amplifier (OLA), study its noise characteristics, and discuss its application in the protection rings of a four-fiber, SONET self-healing interoffice ring network. System and network considerations are also presented. The feasibility of the network was tested by a system experiment using an OLA for up to 200-km conventional single-mode fiber transmission at a bit rate of 1.244 Gb/s (OC-24 line rate) View full abstract»

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  • Transmission characteristics of wide-aperture optical fiber taper

    Page(s): 135 - 141
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    The transmission characteristics of the wide-aperture optical fiber taper (OFT) have been determined experimentally under diffuse and parallel light excitation. Power transmission efficiency versus the normalized radius of the excited input aperture of the OFT has been obtained in both cases. The OFT forms a specific output intensity distribution provided that a uniform excitation of all the OFT modes is ensured. Power transmission efficiency of more than 50% can be obtained at an appropriate normalized radius of the incident laser beam. The wide-aperture OFT is, independent of or within the cavity-taper output laser (CTOL) concept, a suitable element for launching power laser emission into optical fibers View full abstract»

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  • Pulse response of avalanche photodiodes

    Page(s): 169 - 181
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    A study has been made of the time response of heterostructure avalanche photodiodes for InGaAs and InP/InGaAs material systems. A transfer/scattering matrix method, where the matrix parameters are related to the ionization coefficients, has been used. A time domain study has been carried out to find the time variation of electron and hole number densities and currents View full abstract»

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  • Observation of nonbiased degradation recovery in GaInAsP/InP laser diodes

    Page(s): 194 - 198
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    Conventional accelerated lifetests of laser diodes generally involve operating the devices continuously at either constant drive current or power output with periodic recording of their characteristics. In this work, a new observation of degradation recovery from a noncontinuous lifetest performed on 1.3-μm GaInAsP/InP double-heterostructure (DH) laser diodes of the inverted-rib structure is reported. This nonconventional lifetest method involves constant 5-mW/facet biasing at 50°C followed by a period of no bias at room temperature. On average, the threshold current and current for 5-mW/facet output reduced by 6.7 and 8.4%, respectively, during the unbiased period. Redistribution of mobile defects in the cladding layer is postulated to be the mechanism responsible for the degradation recovery View full abstract»

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  • Circular core polarization-maintaining optical fibers with elliptical stress-induced cladding

    Page(s): 118 - 124
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    The reproducible technology for producing high-birefringence fibers with stress-induced elliptical cladding and circular core is described. The authors have obtained fibers that have a birefringence of about (1-3) 10-4, a mode coupling parameter of about (2-7) 10 -5 m-1, and loss of less than 0.5 dB/km at 1.6 μm. The authors have found effects restricting the capability of test fibers to maintain the state of linear polarization View full abstract»

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  • Mode coupling in angled facet semiconductor optical amplifiers and superluminescent diodes

    Page(s): 215 - 219
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    The modal reflectivity of an angled facet has been calculated for index-guided devices when the fundamental mode excites various higher order modes at the facet. The calculations were carried out for waveguide widths ranging from 2 to 20 μm for various lateral index steps and at wavelengths of 834, 1300, and 1550 nm. Plots from these calculations can be used to determine the appropriate facet angles to obtain a given modal reflectivity and optimize the design of optical amplifiers and superluminescent diodes View full abstract»

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  • A planar InP/InGaAs avalanche photodiode with floating guard ring and double diffused junction

    Page(s): 182 - 193
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    The authors discuss the fabrication, performance, and design of a novel, planar In0.53Ga0.47 As/InP separate absorption and multiplication region avalanche photodiode (SAM-APD) with floating guard rings and a double Zn diffused junction. The APD, grown by both vapor phase epitaxy and metalorganic vapor phase epitaxy, is observed to have a uniform gain of 85, a minimum primary dark current density of 5×10-6 A/cm2 at 90% of breakdown, and a capacitance of 0.4 pF for a front-side illuminated device. Both experimental and analytical results show that the double-diffused floating guard ring structure prevents edge breakdown, and also greatly reduces the electric field along the semiconductor/insulator surface. The operation mechanisms and the optimum design of the planar APD based on a two-dimensional device model are discussed View full abstract»

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  • An optical multiaccessor designed for a fiber-optic star-ring LAN

    Page(s): 250 - 254
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    An optical waveguide-type multiaccessor for physically star and logically ring local area networks (star-ring LANs) has been manufactured. The multiaccessor has sufficient low optical transmission loss to bypass some failure nodes without an optical repeater. As the multiaccessor (eight-node-connection type) features are small size, 5 cm square by 0.5 cm thick, a smaller cable concentrator can be applied. The design method used for the multiaccessor to minimize total optical transmission loss caused by both signal interference loss and bypassing loss when failure nodes are bypassed in the star-ring LAN is described. The experimental results for the 32 Mb/s single-mode fiber-optic star-ring system show that at least three nodes can be continuously bypassed by using the multiaccessor with a coupling ratio of 0.5 and a bypass loss of 3 dB. As a result, highly reliable and inexpensive star-ring LANs can be designed with the multiaccessor View full abstract»

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  • Effects of dispersion and birefringence on the performance of quantum well mode converters

    Page(s): 227 - 234
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    The device characteristics of GaAs multiple quantum well (MQW) polarization modulators, designed for operation at wavelengths of 865 and 870 nm, respectively, are investigated and shown to depend strongly on the dispersive and anisotropic optical properties of the quantum well medium. Results indicate that the observed decrease in spectral bandwidth and conversion efficiency at wavelengths detuned from the excitonic bandgap by ~250 Å can be accounted for, theoretically, if electroabsorptive loss terms are included in the coupled-mode analysis of polarization conversion in MQW waveguides. Device design considerations and applications of MQW polarization modulators to integrated optic filtering, wavelength division multiplexing/demultiplexing, and the frequency tuning of semiconductor lasers are presented View full abstract»

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  • Vector circuit method applied for chiral slab waveguides

    Page(s): 150 - 155
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    Eigenvalue equations for the propagation constants of lightwaves in open chiral slab waveguides are derived. The analysis makes use of vector circuit modeling of a chiral slab, the method which has been previously applied for calculating reflection and transmission of electromagnetic waves in chiral multilayer structures. The general eigenvalue equation for the guide which is valid for arbitrary boundary impedance conditions on the slab interfaces is derived, and three special cases are analyzed in detail: an open chiral dielectric slab with dielectric half spaces of the opposite sides of the slab, a chiral slab on an ideally conducting surface, and a chiral slab on an ideal magnetic surface. The theory is visualized by calculated dispersion curves indicating the chirality effect on the wave propagation characteristics View full abstract»

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  • Nonmetallic 1000-fiber cable

    Page(s): 130 - 134
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    A nonmetallic high-fiber-count cable that contains fiber ribbons inserted tightly into slots and has tensile force applied to the central and slotted-rod unit strength members is described. The cable bending flexibility, tensile strain, and cable diameter, which are important for its economical and efficient construction, were theoretically and experimentally evaluated and an optimum combination of diameters for the strength members was obtained. Based on the results, a nonmetallic 1000-fiber cable was manufactured and its transmission, mechanical, and water-blocking performances were confirmed to be excellent View full abstract»

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  • The transverse electrooptic modulator (TEOM): fabrication, properties, and applications in the assessment of waveguide electrooptic characteristics

    Page(s): 163 - 168
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    The fabrication of a novel electrooptic modulator with a transverse electrode geometry, formed by parallel electrodes on opposite faces of a thinned lithium niobate substrate straddling a strip waveguide, is reported. The device, referred to as a transverse electrooptic modulator (TEOM), has several advantages over standard electrooptic waveguide modulators using a coplanar electrode geometry. It is shown that it is possible to achieve a 30% reduction in the operating voltage for a given electrode spacing and a substantial reduction in the figure of merit, the power required per unit bandwidth, for electrooptic modulators with either lumped or traveling wave electrode structures. Moreover, a more accurate estimate of the electrooptic coefficients is possible than with modulators using strip waveguides and coplanar electrodes View full abstract»

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  • Relaxation oscillations in waveguide distributed feedback lasers

    Page(s): 220 - 226
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    The authors present an analysis of relaxation oscillation in planar and fiber distributed feedback lasers taking into account end reflectivity. The laser characteristics obtained as a function of the system parameter show competition between two different resonators (Fabry-Perot and distributed) as well as the influence of the gain saturation on the parameters describing relaxation oscillations View full abstract»

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  • All-optical CDMA using `quasi-prime' codes

    Page(s): 279 - 286
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    The use of fiber-optic lattices for the generation of quasi-prime codes is described, and their application to CDMA communications is discussed. Theoretical and experimental results (including typical autocorrelation and crosscorrelation performance) are presented for the programmable all-optical generation and decoding of such codes using electrooptically switchable lattices View full abstract»

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  • Influence of intensity modulation produced by LD direct modulation on transmission characteristics of CPFSK differential detection system

    Page(s): 255 - 264
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    Transmission characteristics of a CPFSK differential detection system with LD direct modulation are studied by computer simulation. Simulation results show that the optimum wavelength for LD direct modulation CPFSK transmission shifts to a wavelength longer than zero dispersion wavelength because of the phase difference between the intensity and frequency modulation components. A precise investigation of the dependence of optimum total dispersion on several parameters reveals the essential role of the phase difference between intensity and frequency modulation induced by LD direct modulation. The transmission distance allowing a 1-dB power penalty at 10 Gb/s is 117 km for a wavelength 30 nm shorter than the zero dispersion wavelength, while the distance is 183 km for a wavelength 30 nm longer. This indicates that the zero dispersion wavelength shift is 11 nm for 100-km transmission View full abstract»

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  • Fundamental second-order nonlinear distortions in analog AM CATV transport systems based on single frequency semiconductor lasers

    Page(s): 235 - 243
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    The author analyzes the fundamental second-order nonlinearities and their composite distortions in lightwave analog AM CATV transport systems based on single frequency semiconductor lasers. The nonlinear interaction between the photons and the electrons in the laser, the nonlinear dynamics of laser spatial hole burning, and the nonlinear interaction of fiber chromatic dispersion and laser frequency chirping are strongly dependent on the CATV carrier frequencies. The author found that the overall distortions increase for higher carrier frequencies and longer fiber spans. The distortion levels, however, are within the critical requirements for current and future CATV transport systems View full abstract»

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  • A coupled-mode analysis of modulation instability in optical fibers

    Page(s): 156 - 162
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    A coupled-mode formulation in the frequency domain has been developed and applied to the analysis of the modulation instability (MI) due to the self- and cross-phase modulations (SPM and XPM) in optical fibers. The modulation instability of two copropagating beams with the same polarization at different carrier frequencies is examined in detail. It is demonstrated that, by identifying the phase-matching conditions among different sideband components, the modulation instability due to the SPM and the XPM may be described by a set of reduced coupled-mode equations. Simple analytical expressions for the gain are derived under this condition. The approximate formulas are compared with the full wave solutions and their scopes of validity are discussed View full abstract»

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  • Explanation of launch condition choice for GRIN multimode fiber attenuation and bandwidth measurements

    Page(s): 125 - 129
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    In order to predict the attenuation and bandwidth of a graded index (GRIN) multimode fiber system accurately, the fiber composing the system is best characterized by a restricted launch attenuation measurement and an over-filled-launch (OFL) bandwidth measurement of the fibers. The rationale for these launches is provided in terms of the power evolution in the fiber and its impact on system performance, and the basic physics of GRIN multimode fiber. Experimental results are shown that demonstrate the results View full abstract»

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  • An alternative derivation of the Gordon-Haus effect

    Page(s): 273 - 278
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    One of the limitations on the achievable data rate of soliton lightwave systems at fixed distance, or on the achievable distance at a fixed data rate, is a timing jitter that is caused by the interaction of the soliton pulses with spontaneous emission noise. An elementary derivation of the Gordon-Haus effect that does not require prior knowledge of any of the more advanced concepts used in the original derivation is presented View full abstract»

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  • Photorefractive effects in proton exchanged LiTaO3 optical waveguides

    Page(s): 142 - 149
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    A circuit model is proposed to describe photorefractive effects in LiNbO3/LiTaO3 channel waveguides at any intensity level. Capacitive charge storage at the waveguide boundaries is assumed to be provided by trapping states associated with photoconductivity. A consequence of this model is that photoconductive transients are independent of optical intensity at low intensity levels. Photovoltaic and photoconductive effects in proton exchange LiTaO3 channel waveguides were experimentally investigated. Dark conductivities of 2×10-15 to 2 ×10-14(Ω-cm)-1 were extrapolated from photoconductivities up to 2×10-13 (Ω-cm)-1 for power levels of 0.1 to 3 mW. Large DC voltage dependent effects on the conductivity were observed. Straight channel waveguides were observed to be free of photovoltaic effects for output power levels below 35-75 mW View full abstract»

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  • Ultrafast photonic ATM switch with optical output buffers

    Page(s): 265 - 272
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    An ultrafast photonic asynchronous transfer mode (ATM) (ULPHA) switch based on a time-division broadcast-and-select network with optical output buffers is presented. The ULPHA switch has an ultra-high throughput and excellent traffic characteristics, since it utilizes ultrashort optical pulses for cell signals and avoids cell contentions by novel optical output buffers. Feasibility studies show that an 80×80 ULPHA switch with 1-Gb/s input/output is possible by applying the present technology, and that more than 1 Tb/s is possible by making a three-stage network using such switches. As an experimental demonstration, 4-bit 40-Gb/s optical cells were generated and certain cells were selected at an output on a self-routing basis. With its high throughput and excellent traffic considerations, the ULPHA switch is a strong candidate for a future large-capacity optical switching node View full abstract»

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  • DC-1 Gb/s burst-mode compatible receiver for optical bus applications

    Page(s): 244 - 249
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    The characteristics and performance of a high-speed, burst-mode compatible receiver for optical bus or packet communications are described. It employs an Si bipolar differential transimpedance amplifier, an auto-threshold tracking level control circuit, and a DC-coupled decision circuit (ECL compatible quantizer). To cope with intermittent data packets, the threshold control circuit can capture data amplitude and set the logic threshold in about 1 ns. Using an avalanche photodiode, the typical receiver sensitivity is -37.5 dBm (10 -9 BER) at bit rates up to 900 Mb/s, with a dynamic range of 23 dB for both pseudorandom and burst-mode signals. At 1 Gb/s, the sensitivity is -35 dBm. With a worst-case reset time <100 ns for the threshold control circuit, this receiver can be used for optical bus applications where data signals with varying optical power are employed 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