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Lightwave Technology, Journal of

Issue 7 • Date July 1997

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Displaying Results 1 - 23 of 23
  • Modulation instability and its impact in multispan optical amplified IMDD systems: theory and experiments

    Publication Year: 1997 , Page(s): 1071 - 1082
    Cited by:  Papers (33)  |  Patents (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (497 KB)  

    The nonlinear interaction between amplified spontaneous emission noise and copropagating signal in a dispersive optical fiber is investigated both theoretically and experimentally. A transfer matrix formulation is used to solve the nonlinear propagation equation. A continuous wave (CW) input optical signal format isolates the effect of modulation instability (MI) from the signal self-phase modulation. The change of the relative intensity noise (RIN) spectrum at an optical receiver caused by MI has been analyzed extensively in multispan optical amplified systems, and thus the impact of MI in the performance of intensity modulation and direct detection (IMDD) systems is evaluated. Performance of systems with distributed dispersion compensation (DC) and a lumped DC at the receiver are compared in terms of the effect of MI, the results show that the highest efficiency of DC to reduce the effect of MI can be achieved by putting a lumped DC module at the receiver side. Excellent agreement between theory and experiment demonstrates a good understanding of the mechanism of MI and its impact in the performance of terrestrial optical transmission systems. View full abstract»

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  • Correction To "Extended Baseline Architecture For Nonblocking Photonic Switching"

    Publication Year: 1997 , Page(s): 1253
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (15 KB)  

    First Page of the Article
    View full abstract»

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  • Coherent optical frequency domain reflectometry using phase-decorrelated reflected and reference lightwaves

    Publication Year: 1997 , Page(s): 1102 - 1109
    Cited by:  Papers (9)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (200 KB)  

    We report a new scheme for coherent optical frequency domain reflectometry (C-OFDR) where the coherence length of the lightwaves does not limit the measureable fiber length. In this scheme, we use the beat spectrum which results when we mix reflected and reference lightwaves whose phases are not correlated. We demonstrated this scheme using a narrow-linewidth-lightwave source and an external electro-optical phase modulator. We measured Rayleigh backscattering and Fresnel reflections from a 30-Ion optical fiber, and achieved a spatial resolution of 5 m for two neighboring Fresnel reflectors located at the far end of the fiber. We estimated the expected spatial resolution and single-way dynamic range for our new scheme and show that it is capable of measuring long optical fibers with high-spatial resolution View full abstract»

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  • Control of Bragg grating resonant wavelength through its dependence on the effective index of a waveguide

    Publication Year: 1997 , Page(s): 1156 - 1164
    Cited by:  Papers (1)  |  Patents (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (220 KB)  

    Fabrication tolerances for control of the Bragg wavelength of gratings in waveguides are studied. Techniques are demonstrated to hold the period of the grating constant to ±0.04 nm over the majority of the exposed wafer area, and ridge waveguides fabricated with standard thin film process equipment are found to have Bragg wavelengths constant to within ±0.2 nm. Additionally, adjacent ridges with differing widths are written in a single photomask/etch process step and found to controllably shift the Bragg wavelength over a 10-20-nm band suitable for a distributed Bragg reflector (DBR) laser array or a monolithic comb filter for wavelength division multiplexing (WDM) filtering/routing arrays View full abstract»

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  • Brillouin/erbium fiber lasers

    Publication Year: 1997 , Page(s): 1198 - 1204
    Cited by:  Papers (35)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (140 KB)  

    Brillouin/erbium fiber lasers (BEFLs) have been recently demonstrated as a novel mode of operation of a fiber laser. In a hybrid Brillouin/erbium fiber laser, the combination of two gain media, the gain from the erbium-doped fiber (EDF) and Brillouin gain in single-mode optical fibers allows a resonator to be constructed which supports a laser comb with ~10 GHz or ~0.1 nm line spacing at room temperature. In this paper, we present a detailed discussion of the operation of BEFLs. Single and multiple wavelength generation is discussed, and modeling of single wavelength operation is described View full abstract»

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  • Polarizer-and analyzer-induced noise in fiber-optic polarization-sensitive intermodal interferometers

    Publication Year: 1997 , Page(s): 1110 - 1119
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (304 KB)  

    A theoretical and experimental study on the influence of imperfect polarizer/analyzer and their nonideal orientation along fiber axes on the generation of noise in bimodal polarization-sensitive interference is presented in this paper. It is shown that the polarimetric responses of each mode, the intermodal response of the orthogonal polarization as well as the crossed terms are superimposed upon the intermodal response considered to be the useful signal. The theoretical analysis is based on the use of spatial interferometric Stokes parameters and the Muller matrix method. Exact analytical expressions for the noise contributions are derived. Experimental data confirms the basic theoretical results and shows that the greatest noise contribution for a polarization-sensitive intermodal interferometer comes from the polarimetric and the crossed term View full abstract»

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  • Polarization splitting in lossy/gainy MQW directional couplers

    Publication Year: 1997 , Page(s): 1233 - 1240
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (352 KB)  

    We analyze polarization splitting of light in directional-coupler polarizers by using a transverse modal transmission-line representation. Because it is based on rigorous modal solutions, this approach provides very accurate results and can be applied to situations involving either lossy or gainy materials. By considering a polarizer in which multiquantum-well layers act as one of the two waveguides forming the coupling region, we find that maximum polarization discrimination is achieved at an optimal distance that is different from the polarization length predicted by conventional coupled-mode methods. We derive a novel criterion for determining that optimal length, examine the effect of material loss or gain, and obtain the far-field intensity of the light at the output of the coupler View full abstract»

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  • Vector normal modes on two-core optical fibers. I. The normal mode solutions

    Publication Year: 1997 , Page(s): 1213 - 1224
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (556 KB)  

    A vector theory based on the circular harmonics expansion method combined with the finite-element method is formulated to solve the guided normal modes on the two-core fiber with radially inhomogeneous core index profiles. Numerical examples are given for the two-identical-core cases with power-law core index profiles. Polarization patterns for the vector modes on the strongly guiding two-core fiber structure, such as that of a fused coupler made with biconical tapering technology under weakly fusing condition, are presented View full abstract»

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  • Optical phase conjugation of multiwavelength signals in a dispersion-shifted fiber

    Publication Year: 1997 , Page(s): 1061 - 1070
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (340 KB)  

    Optical phase conjugation (OPC) of multiwavelength signals in a dispersion-shifted fiber (DSF), which can be used for dispersion compensation in the wavelength division multiplexing communication system, is theoretically studied. The multiwavelength phase-conjugate signals are generated by four-wave mixing (FWM) in the dispersion-shifted fiber. There are the pulse-shape distortion and the induced frequency chirping in the phase-conjugate signals owing to pump depletion and the cross-phase modulation among the signals and phase-conjugate signals, respectively. The FWM among the pump wave, signals, and phase-conjugate signals causes unequal conversion efficiencies for the multiwavelength signals and enhances the induced frequency chirping in the phase-conjugate signals. The induced frequency chirping may deteriorate the restoration of the pulse shape. Both the pulse-shape distortion and induced frequency chirping increase with the signal and pump powers. The formula for the induced frequency chirping that is only caused by the signals through cross-phase modulation is derived. The requirement of the signal power in the dispersion-shifted fiber for the restoration of the pulse shape by the optical phase conjugation is estimated and numerically verified View full abstract»

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  • Wavelength conversion using semiconductor optical amplifiers

    Publication Year: 1997 , Page(s): 1181 - 1190
    Cited by:  Papers (85)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (220 KB)  

    This paper reports a detailed theoretical study of the dynamics of wavelength conversion using cross-gain and cross-phase modulation in semiconductor optical amplifiers (SOA's) involving a large signal, multisection rate equation model. Using this model, recently reported experimental results have been correctly predicted and the effects of electrical and optical pumping on the conversion speed, modulation index, and phase variation of the converted signal have been considered. The model predicts, in agreement with experimental data, that recovery rates as low as 12 ps are possible if signal and pump powers in excess of 14 dBm are used. It also indicates that conversion speeds up to 40 Gb/s may be achieved with less than 3 dB dynamic penalty. The employment of cross-phase modulation increases the speed allowing, for example, an improvement to 60 Gb/s with an excess loss penalty less than 1 dB View full abstract»

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  • AC characteristics of optically controlled MESFET (OPFET)

    Publication Year: 1997 , Page(s): 1205 - 1212
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (332 KB)  

    A perturbation technique is used to develop a more accurate model of the time varying characteristics of the optically illuminated ion-implanted metal semiconductor field-effect transistor (MESFET) OPFET. In this model, the carrier life time is considered as a function of the carrier concentration in the channel. The carrier concentration in the active channel is altered due to the absorption of the incident light, which affects the carrier life time. The influences of this effect on the device parameters and characteristics is studied and analyzed. Based on this model the current voltage characteristics, the gate-source capacitance, and the threshold voltage of the OPFET have been evaluated for different incident light power intensities. This model shows comparable results to other reported models View full abstract»

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  • High-efficiency focusing waveguide grating coupler with parallelogramic groove profiles

    Publication Year: 1997 , Page(s): 1142 - 1148
    Cited by:  Papers (3)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (184 KB)  

    A high-efficiency focusing waveguide grating coupler (FWGC) using parallelogramic group profiles is proposed, designed and fabricated. A new waveguide grating structure has been employed which consists of bilayered grating with one grating etched into the guiding layer and the other into a high-index cladding layer. Computer simulation shows that both high directionality and large radiation decay factor are obtainable with this structure. Fabrication of this FWGC by electron beam lithography is described. A coupling efficiency of 86% and focusing spot size full-width at half maximum (FWHM) of around 10 μm have been achieved View full abstract»

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  • Properties of loss-coupled distributed feedback laser arrays for wavelength division multiplexing systems

    Publication Year: 1997 , Page(s): 1191 - 1197
    Cited by:  Papers (9)  |  Patents (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (180 KB)  

    The characteristics of loss-coupled distributed feedback (DFB) semiconductor laser arrays are investigated both theoretically and experimentally. Using simulations based on a transfer matrix method, the strong influence of the residual facet reflectivity on the singlemode yield and the statistical fluctuation of the emission wavelength for as-cleaved and AR/HR coated loss-coupled DFB lasers is pointed out and compared to purely index-coupled λ/4 phase-shifted devices. Experimental results and the fabrication techniques are given for loss-coupled 1.55 μm InGaAs/InGaAlAs/InP DFB laser arrays with four channels and integrated striped thin-film heaters, which were successfully used for fine tuning the channel spacings View full abstract»

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  • Time dependent perturbation theory and tones in cascaded erbium-doped fiber amplifier systems

    Publication Year: 1997 , Page(s): 1083 - 1087
    Cited by:  Papers (18)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (124 KB)  

    The time dependent perturbation theory of the gain dynamics of erbium-doped fiber amplifiers (EDFAs) is presented in this paper. The perturbed output is expressed explicitly in terms of the input perturbation. The general theory is then applied to sinusoidal tones; the results agree well with the experiment View full abstract»

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  • Filter synthesis for coupled waveguides

    Publication Year: 1997 , Page(s): 1149 - 1155
    Cited by:  Papers (10)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (268 KB)  

    The synthesis of realistic coupled waveguide filters is considered. The emphasis is on the synthesis of physical devices, rather than on the approximate coupled-mode representations. For this purpose, variational optimization is combined with the normal-mode analysis of interacting waveguides. Physical effects such as the change in coupling strength with waveguide or material dispersion are naturally taken into account. The beam propagation method (BPM) is used to verify the effectiveness of the designs and thus lends a measure of confidence of the applicability of the method to realistic devices View full abstract»

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  • ARROW-B type polarization splitter with asymmetric Y-branch fabricated by a self-alignment process

    Publication Year: 1997 , Page(s): 1165 - 1170
    Cited by:  Papers (11)  |  Patents (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (252 KB)  

    We have proposed and demonstrated a polarization splitter based on an ARROW-B type waveguide. This device has an asymmetric Y-branch configuration, connecting a waveguide with a large modal birefringence to a low-birefringent waveguide which is channeled by a stripe lateral confinement structure. The device can achieve a high extinction ratio without precise mask alignment, since these two waveguides are connected by a self-alignment process. In addition, a low insertion loss is achieved because of adiabatic Y-branching. We designed this device at the wavelength of 1.55 μm and fabricated it using RF sputtering. As a result, high extinction ratios of -19.4 dB for TE mode and -19.0 dB for TM mode were achieved View full abstract»

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  • Chromatic dispersion distribution measurement along a single-mode optical fiber

    Publication Year: 1997 , Page(s): 1095 - 1101
    Cited by:  Papers (12)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (200 KB)  

    A nondestructive measurement technique, which uses a four-wavelength bidirectional optical time domain reflectometer (OTDR) to measure the chromatic dispersion distribution along a single-mode fiber, is compared with the destructive interferometric technique. The experimental results obtained by this technique are in good agreement with those obtained by the interferometric technique. In addition, a measurement procedure is proposed for a transmission line composed of different types of single-mode fiber. These results show that this technique is extremely useful for the design of wavelength division multiplexer (WDM) and finite difference multiplexer (FDM) optical communication systems View full abstract»

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  • Active harmonic modelocking of an erbium fiber laser with intracavity Fabry-Perot filters

    Publication Year: 1997 , Page(s): 1171 - 1180
    Cited by:  Papers (16)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (356 KB)  

    We present both experimental and theoretical investigations of the operation of a harmonically modelocked erbium fiber ring laser stabilized by an intracavity bit-rate etalon. Our model analyzes the effects of cavity components and operating parameters on laser stability and output pulse characteristics. The model predicts the output pulsewidth variation with laser cavity parameters such as cavity length, dispersion, and finesse of intracavity Fabry-Perot etalons. If the laser cavity length is not optimized, a maximum 50% increase in pulsewidth can occur at 5 Gb/s pulse rate. A repetition rate etalon with a finesse of 50 is sufficient to provide a side-mode suppression ratio of over 50 dB in the laser output. We also discuss how detuning from the optimal modulation frequency increases the excess noise that affects the laser stability. The theory predicts a maximum detuning range of ±100 kHz, which agrees with the experimental observations. These theoretical results can guide the design of similar lasers over a wide range of operating parameters View full abstract»

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  • Vector normal modes on two-core optical fibers. II. The modal cutoffs

    Publication Year: 1997 , Page(s): 1225 - 1232
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (488 KB)  

    For pt.I see ibid., vol.15, no.7, p.1213-24 (1997). A vector theory based on generalization of the circular harmonics expansion method combined with the finite-element method is formulated to determine cutoff values for higher-order normal modes on the two-core fiber with radially inhomogeneous core index profiles. The method is developed under the transverse magnetic field formulation in order to avoid the spurious solutions. Numerical examples are given for the two-identical-core cases with power-law core index profiles View full abstract»

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  • Characterization of a ferroelectric liquid crystal-based time delay unit for phased array antenna applications

    Publication Year: 1997 , Page(s): 1088 - 1094
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (104 KB)  

    An experimental demonstration of a photonic time delay unit (PTDU) based on ferroelectric liquid crystal devices and Thompson polarization beamsplitters (TBSs) is presented. High signal-to-noise ratios (SNRs) (>96 dB) and optical polarization extinction ratios (ER,~40 dB) are demonstrated for the PTDU using an active noise filter technique. Using a 5 V peak square wave switch drive signal, a 70 μs switching speed is demonstrated for this PTDU that can be used in fast (e.g., 5000 beam/s) beam scanning phased array systems. A shorter switching speed of 35 μs is also observed using a high 15 V peak transitional voltage driving signal View full abstract»

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  • A spanning bus connected hypercube: a new scalable optical interconnection network for multiprocessors and massively parallel systems

    Publication Year: 1997 , Page(s): 1241 - 1253
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (344 KB)  

    A new scalable interconnection topology suitable for massively parallel systems called the spanning bus connected hypercube (SBCH) is proposed. The SBCH uses the hypercube topology as a basic building block and connects such building blocks using multidimensional spanning buses. In doing so, the SBCH combines positive features of both the hypercube (small diameter, high connectivity, symmetry, simple routing, and fault tolerance) and the spanning bus hypercube (SBH) (constant node degree, scalability, and ease of physical implementation), while at the same time circumventing their disadvantages. The SBCH topology permits the efficient support of many communication patterns found in different classes of computation such as bus-based, mesh-based, tree-based problems as well as hypercube-based problems. A very attractive feature of the SBCH network is its ability to support a large number of processors while maintaining a constant degree and constant diameter. Other positive features include symmetry, incremental scalability, and fault-tolerance. An optical implementation methodology is proposed for SBCH. The implementation methodology combines both the advantages of free space optics with those of wavelength division multiplexing techniques. A detailed analysis of the feasibility of the proposed network is also presented View full abstract»

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  • On the characterization of optical fiber network components with optical frequency domain reflectometry

    Publication Year: 1997 , Page(s): 1131 - 1141
    Cited by:  Papers (31)  |  Patents (79)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (200 KB)  

    The basic features of coherent optical frequency domain reflectometry are presented. The ultimate limits of range and sensitivity were discussed, as well as polarization effects. It is shown that this technique is very suitable for optical network components characterization, and accurate measurements of a number of such components are presented View full abstract»

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  • Simple low-frequency optical fiber accelerometer with large rotating machine monitoring applications

    Publication Year: 1997 , Page(s): 1120 - 1130
    Cited by:  Papers (23)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (196 KB)  

    A simple fiber optic accelerometer with large rotating equipment monitoring applications is presented. The sensor is optimized for detection of mechanical vibrations in the frequency range 0.2-140 Hz. The minimum detectable acceleration is 0.025 m/s2 root mean square (rms), and it has low transverse sensitivity. The transducer operating principle, based on a fiber optic cantilever beam without any selamic mass on it, is simple and easy to construct, and the intensity-modulation and compensation techniques developed require simple electronic processing and provide very good stability and accuracy. Other advantages of the system are its robustness, compact size, and cost-effectiveness, which make it appropriate for industrial applications, specially for those where harsh environments are involved. The complete process of research and development of the sensor has been carried out, from the theoretical study of its operation principles, through the design, fabrication, experimental characterization and enhancement, to its starting up in a high-power electric station for hydrogenerator monitoring 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