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Lightwave Technology, Journal of

Issue 3 • Date March 2000

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Displaying Results 1 - 23 of 23
  • A photonic front-end processor in a WDM ATM multicast switch

    Publication Year: 2000 , Page(s): 273 - 285
    Cited by:  Papers (9)  |  Patents (11)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (926 KB)  

    Dense wavelength-division multiplexing (DWDM) technology has provided tremendous transmission capacity in optical fiber communications. However, switching and routing capacity is still far behind transmission capacity. This is because most of today's packet switches and routers are implemented using electronic technologies. Optical packet switches are the potential candidate to boost switching capacity to be comparable with transmission capacity. In this paper, we present a photonic asynchronous transfer mode (ATM) front-end processor that has been implemented and is to be used in an optically transparent WDM ATM multicast (3M) switch. We have successfully demonstrate the front-end processor in two different experiments. One performs cell delineation based on ITU standards and overwrites VCI/VPI optically at 2.5 Gb/s. The other performs cell synchronization, where cells from different input ports running at 2.5 Gb/s are phase-aligned in the optical domain before they are routed in the switch fabric. The resolution of alignment is achieved to the extent of 100 ps (or 1/4 bit). An integrated 1/spl times/2 Y-junction semiconductor optical amplifier (SOA) switch has been developed to facilitate the cell synchronizer. View full abstract»

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  • Allowable received OTDR light power for in-service measurement in lightwave SCM systems

    Publication Year: 2000 , Page(s): 286 - 294
    Cited by:  Papers (4)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (405 KB)  

    To measure in-service optical transmission lines in optical video distribution systems using subcarrier multiplexing (SCM) techniques, we clarify how measurement light from an optical time domain reflectometer (OTDR) affects the signal transmission performance when the light enters an optical network unit (ONU). We describe the additional noises induced when OTDR light is injected into the ONU and analyze the relationship between received OTDR light power and carrier-to-noise ratio. Moreover, we use the analysis to provide a technique for estimating the allowable received light power in lightwave SCM systems and show the dominant factors determining this allowable power. Finally, by using the estimation technique, we clarify the required rejection ratio for a filter designed to prevent OTDR light from entering ONU's in wavelength division multiplexing systems. View full abstract»

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  • Modeling of penalties on chains of optical amplifiers with equalizing filters

    Publication Year: 2000 , Page(s): 295 - 300
    Cited by:  Papers (2)  |  Patents (15)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (161 KB)  

    A mathematical model for the calculation of optical signal-to-noise ratio (SNR) on cascades of erbium doped fiber amplifiers (EDFA's) with interposed equalizing filters in the fiber spans is presented. The model enables to simulate different types of cascade, whether the filters are placed after each amplifier or after any group of amplifiers. Criteria for the design of the optimal filter are presented for a typical configuration. The relation between preemphasis and penalty on SNR is studied, and for the first time to our knowledge it is shown that some asymmetry may arise when using in line optical filters. A study of the sensitivity of penalty at receiver toward preemphasis at transmitter based on the model is presented. View full abstract»

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  • Phase shift keying using optical delay modulation for millimeter-wave fiber-optic radio links

    Publication Year: 2000 , Page(s): 301 - 307
    Cited by:  Papers (7)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (284 KB)  

    We propose a novel phase shift keying technique that uses optical delay modulation for fiber optic radio links. Using only a 2/spl times/1 switch and a delay line, this technique enables modulation of a millimeter-wave carrier at bit rates of several gigabits per second or higher, where high-speed devices are not needed. Binary phase shift keying (BPSK) was experimentally demonstrated, 2-Gb/s data signal on a 40-GHz carrier was transmitted over a 5-km optical fiber without any error. The coherent crosstalk noise, due to insufficient extinction ratio of optical switches, was evaluated. The BPSK modulation technique can he extended to multiphase shift-keying modulation. View full abstract»

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  • Gain stabilization in gain clamped EDFA cascades fed by WDM burst-mode packet traffic

    Publication Year: 2000 , Page(s): 308 - 313
    Cited by:  Papers (18)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (129 KB)  

    This paper studies via simulation the stabilizing effect of all-optical gain-clamping (AOGC) in a chain of erbium-doped fiber amplifiers (EDFA) fed by wavelength-division multiplexing (WDM) burst-mode packet traffic. AOGC is necessary to suppress swings of output power and optical signal-to-noise ratio (OSNR). A case study is selected, in which only the first EDFA in a cascade of six amplifiers is clamped using a ring laser configuration. A numerical model which solves the transcendental equation for the average inversion at each EDFA is used for the analysis. The traffic is generated on the eight WDM channels by ON-OFF time-slotted sources, with statistically independent ON and OFF durations, randomly generated by a truncated Pareto distribution with infinite variance. The simulation model includes the generation of amplified spontaneous emission within each amplifier and the propagation of the lasing power generated in the AOGC EDFA through the cascade. It is shown that the sizable power and OSNR swings arising in an unclamped cascade of EDFA's can be effectively suppressed when a lasing signal a few decibels above the aggregate signal power develops in the AOGC EDFA and propagates along the cascade. View full abstract»

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  • Optical fiber design for field mountable connectors

    Publication Year: 2000 , Page(s): 314 - 319
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (103 KB)  

    This paper presents a study on optical fiber and connector ferrule assembly design optimization aimed at minimizing modal interference in field-mountable single-mode fiber connectors that utilize a ferrule mounted short fiber stubs and integrated splices. A theoretical model for analyzing the modal interference is proposed and verified experimentally. It is shown that modal interference can be reduced by optimizing both the fiber design and its surrounding material. View full abstract»

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  • Distributed beat length measurement in single-mode optical fibers using stimulated Brillouin-scattering and frequency-domain analysis

    Publication Year: 2000 , Page(s): 320 - 328
    Cited by:  Papers (7)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (276 KB)  

    We present a method for distributed measurement of beat length, differential group delay, strain, and temperature in long length single-mode optical fibers. Toward this aim, we employ the polarization state sensitive effect of stimulated Brillouin scattering (SBS). The distributed measurement is realized by applying frequency-domain analysis. We present the analytical relationships between the Brillouin interaction of two counterpropagating waves in the fiber and the polarization states. Experimental results confirm the ability of the method to measure distributed beat length. View full abstract»

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  • Nonlinear pulse switching using long-period fiber gratings

    Publication Year: 2000 , Page(s): 329 - 333
    Cited by:  Papers (11)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (86 KB)  

    We show that the intensity required to achieve all-optical switching in long-period fiber gratings can be reduced by orders of magnitude through the use of uniform phase-shifting regions between gratings. Predicted switching intensities are of the order 100 MW/cm/sup 2/ compared to 10 GW/cm/sup 2/ for normal device configuration. View full abstract»

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  • Propagation of the fundamental mode in curved graded index multimode fiber and its application in sensor systems

    Publication Year: 2000 , Page(s): 334 - 342
    Cited by:  Papers (21)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (239 KB)  

    A novel principle of light transmission through very small radius bend in optical fibers is presented. The potential applications of the proposed structure are fiber optic sensors and other fiber optic systems. The design makes use of graded index multimode fiber as transmission medium. However, the feed to the multimode fiber is through a single mode fiber to ensure that only the lowest order spatial mode is launched. Similarly the receiver is also coupled to the sensing element through a single mode fiber. The fundamental mode within graded index multimode fiber proves to be very insensitive to macrobends if bend radius is larger than certain critical value. If bend radius is reduced below critical value the loss increases very rapidly and this allows for construction of relatively sensitive macrobend fiber optic sensor. This work presents a quantitative theoretical model of the proposed structure and a detailed experimental investigation of structure with possibilities for its practical applications. View full abstract»

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  • The Er/sup 3+/-fiber gain coefficient derived from a dynamic gain tilt technique

    Publication Year: 2000 , Page(s): 343 - 347
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (94 KB)  

    We describe a new method to determine the Er/sup 3+/-fiber gain coefficient using a dynamic gain tilt technique. The method is based on attenuation measurement, gain measurements and crossover optimization of dynamic gain tilt. Results demonstrate that this method is very simple, highly accurate and especially useful for extended band erbium doped fiber amplifiers (EDFAs) design. View full abstract»

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  • System design and optimization of optically amplified WDM-TDM hybrid polarization-insensitive fiber-optic Michelson interferometric sensor

    Publication Year: 2000 , Page(s): 348 - 359
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (292 KB)  

    We investigate the optically amplified time-division-multiplexed (TDM) polarization-insensitive fiber-optic Michelson interferometric sensor (PIFOMIS) system using erbium-doped fiber amplifier (EDFA). The EDFA was named preamplifier, in-line amplifier or postamplifier; by the position it was located. We find that the preamplifier EDFA has limited usefulness because of its unstable amplification of the optical pulse trains. Both post- and in-line cases can work successfully in the TDM-PIFOMIS system. The amplitudes of the optical pulse trains are stable after amplified by the in-line EDFA, this is a significantly advantage of the optically amplified TDM-PIFOMIS system. The MPDS of the unamplified TDM-PIPOMIS system with an extinction ratio (ER) of 33 dB of the output pulse of the optical guide wave (OGW) modulator was 2.4/spl times/10/sup -5/ rad/(Hz)/sup 1/2/ at 1 kHz. For maintaining MPDS better than 3.4/spl times/10/sup -5/ rad/(Hz)/sup 1/2/ at 1 kHz, the allowable worst ER for the post- and in-line amplified system are 20 and 17.8 dB, respectively, and the corresponding input signal peak power should be larger than -20 and -25 dBm. While employing such two post- and two in-line EDFAs in the TDM-PIFOMIS system, the allowable loss of the sensor array is 47 dB. We analyze the phase-induced intensity noise (PIIN) of the optically amplified TDM-PIFOMIS system in detail and propose methods to reduce the PIIN. The output optical pulse of an intensity modulator with high ER is a key issue to minimize the PIIN and sensor crosstalk in the system. In order to reduce the system PIIN, complexity and cost, we suggest an optimum optically amplified WDM (wavelength-division multiplexing)-TDM hybrid PIFOMIS system with four wavelengths and four eight-sensor subarrays. View full abstract»

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  • High-speed InGaAlAs-InAlAs MQW directional coupler waveguide switch modules integrated with a spotsize converter having a lateral taper, thin-film core, and ridge

    Publication Year: 2000 , Page(s): 360 - 369
    Cited by:  Papers (6)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (414 KB)  

    Fully packaged 2/spl times/2 and 4/spl times/4 semiconductor optical switch modules are successfully developed by integrating spotsize converters (SSCs) consisting of lateral tapers, thin-film cores, and ridges in InGaAlAs-InAlAs multiple quantum-well (MQW) directional coupler waveguide switches in the 1.55-/spl mu/m wavelength region. Good reproducibility is obtained for the perfect coupling length of the directional coupler by appropriately designing the ridge width and gap of strip-loaded optical waveguides and by making use of the Cl/sub 2/ reactive-ion-beam-etching and successive wet-etching. Since the switching time is sufficiently short (<70 ps, which is limited by the driver speed) for the 4/spl times/4 switch module, no bits are lost during a 10-Gb/s switching experiment at a wavelength of 1.55 /spl mu/m. View full abstract»

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  • Scanning near-field optical microscope for the characterization of optical integrated waveguides

    Publication Year: 2000 , Page(s): 370 - 374
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (431 KB)  

    A scanning near-field optical microscope for the characterization of optical integrated devices has been developed. Compatible with a normal optical characterization setup the experimental setup allows a tapered uncoated optical fiber to scan the optical device with constant height by means of a shear force control using a tuning fork, and to obtain the evanescent field emerging from it. In this way, images showing simultaneously the topography with lateral resolution better than 10 nm and vertical resolution of 1 nm, and the optical field distribution have been obtained. Images obtained over rib waveguides show the guided mode intensity distribution, allowing characterization of the propagation of the light in the device for up to 1 mm. Identification of the guided mode propagation has been achieved by comparing the images with computer simulations. Measurement of the experimental decay lengths of the evanescent field obtained by the microscope allows a determination of the effective refractive index of the structure to be made. View full abstract»

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  • Stable lightwave synthesized frequency sweeper using Fabry-Perot cavity composed of Faraday rotator mirrors

    Publication Year: 2000 , Page(s): 375 - 383
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (226 KB)  

    We describe a stable lightwave synthesized frequency sweeper (LSFS) using a Fabry-Perot (FP) cavity composed of two Faraday rotator mirrors (FRMs). In the former half of this paper, we numerically simulate the behavior of amplified spontaneous emission (ASE) noise accumulations, and show that angular deviations of the FRMs can cause instability in the frequency sweep span. We also show that the span is stabilized by placing a polarizer in one of the FRMs because the FP cavity then works as a single-polarization cavity with a small transmittance fluctuation. Experimental results confirming the stability of this LSFS are provided in the latter half of this paper. View full abstract»

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  • High-efficiency unitraveling-carrier photodiode with an integrated total-reflection mirror

    Publication Year: 2000 , Page(s): 384 - 387
    Cited by:  Papers (3)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (125 KB)  

    A novel photodiode (PD) structure with an integrated total-reflection mirror which can enhance the quantum efficiency in back-illuminated geometry is proposed. Due to the diagonal propagation of the reflected light at the total-reflection mirror through the absorption layer, the efficiency is improved by about 50% from that of the normally irradiated case. By employing a unitraveling-carrier structure together with a thick absorption layer of 4700 A, the fabricated PD exhibits a high responsivity of 0.65 A/W, a high 3-dB bandwidth of 50 GHz, and a high-output voltage of 5 V, simultaneously. View full abstract»

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  • Forces on a Rayleigh particle in the cover region of a planar waveguide

    Publication Year: 2000 , Page(s): 388 - 400
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (415 KB)  

    We report on the optimization of a waveguide structure for the maximization of the radiation forces exerted on a Rayleigh particle in the cover region. The two main radiation forces involved are the transverse gradient force which attracts a particle into the waveguide and the combined scattering and dissipative forces which drive the particle forward along the channel. The dependence of these forces on parameters including the incident wavelength, the surrounding medium embedding the particles, and the polarizability of the particles is discussed. Both dielectric and metallic gold spheres of radius 10 nm are considered in the model. Special emphasis is devoted to the maximization of the transverse gradient force due to the optical intensity gradient at the waveguide surface, and the wavelength dependence of the polarizability of gold nanoparticles. View full abstract»

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  • Simple and accurate procedure for modeling erbium-doped waveguide amplifiers with high concentration

    Publication Year: 2000 , Page(s): 401 - 408
    Cited by:  Papers (9)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (204 KB)  

    We present an accurate, fast, and easily implemented procedure for modeling erbium-doped waveguide amplifiers (EDWAs) with high concentration doping level. The model is shown to be in a very good agreement when compared with experimental results, and is used in a detailed analysis of a waveguide amplifier with 980-nm pumping. View full abstract»

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  • New full-vectorial numerically efficient propagation algorithm based on the finite element method

    Publication Year: 2000 , Page(s): 409 - 415
    Cited by:  Papers (45)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (148 KB)  

    A new full-vectorial beam propagation algorithm based on the versatile finite element method, in order to accurately characterize three-dimensional (3-D) optical guided-wave devices, is presented. The computationally efficient formulation is based on the two transverse components of the magnetic field without destroying the sparsity of the matrix equation. The robust perfectly matched layer (PML) boundary condition is incorporated into the formulation so as to effectively absorb the unwanted radiation out of the computational domain. The efficiency and precision of the proposed full-vectorial propagation approach is demonstrated through the analysis of single optical waveguide, directional couplers, and electrooptic modulator. View full abstract»

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  • Dynamic stimulated Brillouin scattering analysis

    Publication Year: 2000 , Page(s): 416 - 424
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (162 KB)  

    We present a new simple analysis-including the effect of spontaneous emission-of the (dynamic) influence of stimulated Brillouin scattering (SBS) on the detected receiver eye diagram. It applies in principle for general types of modulation formats such as the digital formats of amplitude shift keying (ASK), frequency shift keying (FSK), and phase shift keying (PSK). The analysis is formulated for a determination of the signal power depiction and intersymbol interference (ISI) caused by the combined effect of fiber dispersion, fiber attenuation and nonlinear fiber effects such as the effect of self-phase modulation (SPM) and SBS. The analysis allows a quantification of the dithering influence on the SBS threshold. Representative numerical examples are presented for two single-channel ON-OFF modulated 10-Gh/s systems utilizing Franz-Keldysh and Mach-Zehnder-type modulators. View full abstract»

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  • Design equations for the reflectivity of deep-etch distributed Bragg reflector gratings

    Publication Year: 2000 , Page(s): 425 - 429
    Cited by:  Papers (11)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (85 KB)  

    This paper reports a computationally efficient, grid-independent method for calculating the reflectivity of deep-etch distributed Bragg reflector (DBR) gratings. The method employs Gaussian beam propagation in conjunction with a Fabry-Perot model that includes the effects of multiple reflections in multiple cavities. We include both, grating pitch and number of Bragg pairs in our analysis. We obtain very good agreement with results generated by a Helmholtz equation solver. View full abstract»

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  • Analysis of a microwave time delay line based on a perturbed uniform fiber Bragg grating operating at constant wavelength

    Publication Year: 2000 , Page(s): 430 - 436
    Cited by:  Papers (21)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (167 KB)  

    This paper presents the modeling of a new microwave time delay line based on a uniform fiber Bragg grating (FBG) with a section which period has been perturbed. The time delay can be modified by changing the position of the perturbation along the grating. Theoretical results are presented for a 5-cm long uniform grating and optical signal is modulated up to 18 GHz. Experimental setup used magnetic fields to change the period locally along the grating and a 330 ps maximum time delay is shown. Comparison between calculations and measurements show a perfect agreement. Such a delay line offers many advantages for beamforming applications in phased array antennas where the operation at a fixed wavelength is required in order to simplify the architecture of these systems. View full abstract»

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  • Efficient time-domain finite-difference beam propagation methods for the analysis of slab and circularly symmetric waveguides

    Publication Year: 2000 , Page(s): 437 - 442
    Cited by:  Papers (19)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (180 KB)  

    The generalized Douglas scheme is applied to the time-domain finite difference beam propagation methods (TD-BPMs) in rectangular and cylindrical coordinates. High accuracy and efficiency are demonstrated through the analysis of optical pulse propagation in slab and circularly symmetric waveguides. As an example of a reflection problem, the TD-BPM in cylindrical coordinates is applied to the analysis of a fiber Bragg grating with a sinusoidal index change. Effectiveness of the present scheme is discussed in comparison with the conventional TD-BPM and the finite-difference time-domain method. View full abstract»

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  • Improving the response of optical phase modulators in SOI by computer simulation

    Publication Year: 2000 , Page(s): 443 - 450
    Cited by:  Papers (15)  |  Patents (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (150 KB)  

    This paper reports on the simulation of a low-loss single-mode optical phase modulator fabricated in silicon-on-insulator (SOI) material. The device operates by injecting free carriers to change the refractive index in the guiding region, and has been modeled using the two-dimensional (2-D) device simulation package SILVACO. SILVACO has been employed to optimize the overlap between the injected free carriers in the intrinsic region and the propagating optical mode. Attention has been paid to both the steady state and transient properties of the device. In order to produce quantitative results, a particular p-i-n device geometry has been employed in the optimization, but the trends in the results are general enough to be of help in the design of many modulator geometries. The specific example device we have used is designed to support a single optical guided mode and is of multimicrometer dimensions thus simplifying fabrication and allowing efficient coupling to-from single-mode fibers (SMF's) or other single-mode devices. The modeling indicates that increased dc device performance results from an increase in the doping concentrations and the contact diffusions of the p/sup +/ and n/sup +/ regions. The transient performance of the device in terms of switching times depends on the separation of the p/sup +/ and n/sup +/ regions. The optimizations are applicable to large (multimicrometer size) modulators. Phase modulators with low driving currents (<8 mA) and modulators with transient rise times of 39 ns and fall times of 6 ns are predicted. 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