By Topic

Proceedings of the IEEE

Issue 10 • Date Oct. 1970

Filter Results

Displaying Results 1 - 25 of 51
  • [Front cover and table of contents]

    Page(s): c1
    Save to Project icon | Request Permissions | PDF file iconPDF (1258 KB)  
    Freely Available from IEEE
  • Scanning the issue

    Page(s): 1407 - 1409
    Save to Project icon | Request Permissions | PDF file iconPDF (283 KB)  
    Freely Available from IEEE
  • Optical communications—A decade of preparations

    Page(s): 1410 - 1418
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1179 KB)  

    This paper, an introduction to this first Special Issue on Optical Communications, follows some of the arguments that have prevailed for and against optics as a viable communications medium for terrestrial and space applications, and assesses the present state of the art of optics devices, systems, and theory, based on discussions with scientists and engineers who have been specializing in the optical field. It also attempts in a small way to give some appreciation of the special problems the traditional communications engineer faces in readjusting his thinking and his "physical intuition" in going from the world of electrons to the world of photons. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Coherent optical sources for communications

    Page(s): 1419 - 1439
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (5239 KB)  

    The development of coherent optical sources, producing usable amounts of power, has provided a stimulus for communications research. Coherent sources in the form of lasers and parametric oscillators are available at wavelengths which span the entire optical spectrum. This paper reviews the state of the art of coherent optical sources with major emphasis on the most highly developed sources. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Modulators for optical communications

    Page(s): 1440 - 1457
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1918 KB)  

    This paper reviews the field of high-speed small-aperture modulators for applications in optical communications, with emphasis on electrooptic modulation. The capabilities and limitations of electrooptic modulators are discussed based on a review of the physical origin of the electrooptic effect. Thermal and photoconduction phenomena, which may severely limit the operation of practical devices, are emphasized. The modulation power and bandwidth limitations using various schemes of electrooptic interaction are derived and compared. It is shown that lumped modulators are capable of efficient modulation for bandwidths up to about 1 GHz for visible wavelengths and are also attractive for their simplicity. For broader bandwidth capability the traveling wave or zigzag types of interaction become more efficient but with added complexity. Finally, acoustooptic and magnatooptic modulators are briefly discussed and compared with electrooptic modulators. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Direct modulation of semiconductor lasers

    Page(s): 1457 - 1465
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1091 KB)  

    Methods for direct modulation of semiconductor lasers are reviewed with the objective of indicating the advantages and limitations of each method. Techniques for producing amplitude, pulse, and frequency modulation of the optical wave are included. The modulation capabilities of present pulsed lasers are analyzed with special attention given to their operation at room temperature. In addition, several ways of producing analog position or width modulation of microwave-rate optical pulses are described, and the capabilities of optical frequency modulation by acoustic waves are reviewed. A new way of obtaining mode-locked optical pulses with a semiconductor laser is also suggested. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Photodetectors for optical communication systems

    Page(s): 1466 - 1486
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2368 KB)  

    The characteristics of high-sensitivity photodetectors suitable for wide bandwidth optical communication systems are summarized. Photodiodes, photomultipliers, and photoconductive detectors for wavelengths from 0.3 µm to 10.6 µm are covered. The use of internal current gain by means of avalanche and electron multiplication and by means of optical heterodyne detection to increase sensitivity of high speed photodetectors is discussed. The application to visible and infrared laser communication systems is reviewed. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Subnanosecond gating properties of the dynamic cross-field photomultiplier

    Page(s): 1487 - 1490
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1754 KB)  

    Experimentally measured characteristics of the sampling function in the dynamic cross-field photomultiplier are presented. A self-mode-locked He-Ne laser with a pulse-repetition rate nearly equal to the photomultiplier sampling rate is used to determine the sampling characteristics of this device. Experiments with a device with two regions in which different dc fields can be established are also reported. With this device, sampling intervals of less than 10 percent of the RF electric field period can be obtained with very little reduction in gain compared to conditions yielding-broader sampling intervals. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Optical components and technology in laser space communications systems

    Page(s): 1491 - 1503
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1919 KB)  

    Passive linear optical components play a primary role in an optical communications system for use in space applications. The important functions of acquisition, tracking, transmit-beam off-set, and background-noise discrimination may be efficiently implemented using passive optical elements. These specific system functions are discussed with reference to a representative system in order to identify the required features of particular optical components. This is followed by a detailed discussion of the optical components including: a 1/2-Å Fabry-Perot filter; a transfer-lens/optical-image-divider combination capable of 0.1-second of arc tracking accuracy; variable deviation wedges for transmit-beam offset; dichroic beamsplitters for isolation between the transmit and receive beams; and an axicon for redistributing the Gaussian energy profile from a TEM00-mode laser to match the obscured circular aperture of a conventional Cassegrainian telescope. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Integrated optical circuits

    Page(s): 1504 - 1512
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1722 KB)  

    Research on optical communication systems indicates the future need for a compact, rugged, and economical medium for circuit realization. Encapsulated planar arrays of rectangular dielectric waveguides are attractive for this purpose. The individual guides would have dimensions on the order of a few micrometers while the planar arrays might cover an area of a few square centimeters. Integrated circuit technology appears adaptable to batch processing such circuits. Recent theoretical and experimental results are surveyed which support this viewpoint. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Optical waveguide transmission

    Page(s): 1513 - 1522
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2322 KB)  

    As optical communication systems are being studied in more detail, the need for many different types of optical waveguides becomes apparent. The applications range from miniature optical circuit connections to long-distance high-capacity transmission links. The requirements with respect to cost, attenuation, dispersion, or flexibility are vastly different. As different as the specifications are the guides evolving for various purposes. We describe the state of the art and give a survey of those guides which show the greatest future potential. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A survey of clear-air propagation effects relevant to optical communications

    Page(s): 1523 - 1545
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2349 KB)  

    The theory and observations of the optical propagation effects of the clear turbulent atmosphere are reviewed, with particular attention to those characteristics most important to the designer of an optical communication system. Among the phenomena considered are the variance, probability distribution, spatial covariance, aperture smoothing, and temporal power spectrum of intensity fluctuations, and similar quantities for phase fluctuations and angle of arrival. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Measurement of the average structural characteristic of the atmospheric refractive index

    Page(s): 1546 - 1547
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (145 KB)  

    Measurements of the square of the structure constant of the atmospheric refractive index averaged over a 25-km propagation path are presented. The daily behavior of this parameter Cn2for 4 days in July, 1969, are shown. The measured values are in the range from 0.5 to 4×10-17cm-2/3. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • The optical scatter channel

    Page(s): 1547 - 1563
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2370 KB)  

    The scatter fields experimentally observable at the image plane of an optical receiver are modeled in a way that is consistent with the concepts and notations of both radiative transfer theory and the probability-computing receiver. Transient response and Doppler effect are considered. Single-particle scattering and its relationship to multiple scatter as treated by radiative transfer theory are reviewed. The statuses of experimental data and a variety of approximate methods for predicting the channel are also discussed. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Some experiments on the propagation of light pulses through clouds

    Page(s): 1564 - 1567
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1317 KB)  

    This paper describes a facility for measuring the spatial and temporal impulse response of a cloud to a pulse of light from a Q-switched ruby laser, and presents some experimental results. No single simple model adequately describes the transient response of real clouds in the variety of situations observed. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Laser-Raman radar for air pollution probe

    Page(s): 1568 - 1571
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (685 KB)  

    As an experimental verification of a novel application of the laser-Raman radar, frequency-shifted Raman components of a Q-switched ruby-laser pulse from atmospheric molecular gases and from chemicals in an oil plume, such as CO2, CO, SO2, O2, and N2, were analyzed selectively. These results demonstrate the practical usefulness of this new optical system as a real-time air pollution probe. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Background noise in optical communication systems

    Page(s): 1571 - 1577
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1712 KB)  

    The origin and magnitude of the several kinds of background noise that perturb optical communication receivers are discussed, including background radiation sources viewed directly, radiation reflected from background objects, and radiation scattered by the atmosphere into the receiver field of view. An extensive bibliography on this topic is presented. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Quantum-mechanical communication theory

    Page(s): 1578 - 1598
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2453 KB)  

    This paper is concerned with the problem of finding the structure and performance of the receiver that yields the best performance in the reception of signals that are described quantum-mechanically. The principles of statistical detection and estimation theory are discussed, with the laws of quantum mechanics taken into account. Several specific communication systems of practical interest are studied as examples of applying these principles. Basic concepts in quantum mechanics that are needed in these discussions are briefly reviewed. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Steady-state quantum analysis of linear systems

    Page(s): 1599 - 1611
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1278 KB)  

    A rigorous basis for the quantum analysis of the steady state of linear distributed systems is established. The analysis of a distributed system of finite length requires, for self-consistency, that excitations be stated at the boundaries of the system even in the absence of externally applied excitations. The commutators of the amplitudes at the boundaries are stated and a useful analogy with thermal noise of classical systems is established. The use of these boundary conditions enables one to formulate the theory of the steady state for distributed quantum systems. When the system under consideration is coupled to a dissipation mechanism, operator-noise sources have to be assigned to the dissipative elements. The commutation relations that must be obeyed by these noise sources are derived. This formalism enables one to analyze the steady-state operation of an attenuator and of a maser amplifier. Finally, properties of multiterminal-pair networks are discussed using the steady-state quantum approach. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Communication theory for the free-space optical channel

    Page(s): 1611 - 1626
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1562 KB)  

    The current understanding of quantum detectors, the noise mechanisms which limit (are basic to) their operation, and their application to optical communications (theory) is summarized. In this context, we are considering channels in which the electromagnetic field is not subjected to any propagation effects other than a geometric loss. (Such a channel would exist between satellites.) Consequently, we will concentrate on optimum time processing using the tools of statistical communication theory. Fundamental to the study of a detection process is the need to develop a good mathematical model to describe it [1]-[6]. Therefore, approximately one-fifth of the paper is devoted to establishing, in a semi-classical analysis, the quantum detector output electron number as a conditional Poisson process with the conditioning variable being the modulus of the electromagnetic field. Once this has been established, these results are used to derive various limiting probability densities related to actual practice. Although the mathematical details are omitted, these results will be presented from the viewpoint of orthogonal function expansions and interpreted in terms of an eigenspace. The resulting current flow is analyzed next as a shot noise process, and the power density spectrum is calculated. Attention is focused on isolating the signal components from the noise in terms of both the current probability density and the power density spectrum. Examples are given where appropriate. At this point, an understanding of the underlying noise processes will have been presented and attention will shift to analog and digital communications. The analog communication will be presented primarily in terms of the signal-to-noise ratio. The S/N ratio in direct detection will be presented both as a ratio of the integrals of two separate portions of the spectrum and as a ratio of two moments of the probability density describing the current. These calculations will be extended to include heterodyne detection. Digital communications will be discussed in the context of detection theory. It will be shown that the likelihood ratio is often a monotonic function of the random variable representing the number of electrons flowing. Hence optimum processing will consist of a weighted count of e- lectrons from various counting modes. Digital design will be presented in terms of M-ary signaling, error probabilities, and information rates. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Communication theory for the turbulent atmosphere

    Page(s): 1626 - 1650
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2746 KB)  

    This paper is concerned with an examination of how statistical communication theory can be used to combat the effects of atmospheric turbulence in optical communication systems. The objective is to provide a framework to be used in discussing and relating the analytical results presently available in the literature as well as some new, or at least not widely known, results and in motivating and guiding future work. Both digital communication and parameter and waveform estimation are considered, with the greater emphasis on the former. As necessary mathematical preliminaries, the relevant statistical channel model, the problems of spatial representation, quantum field models, and the output statistics of optical detectors are considered. For digital-communication systems, the structure and performance of optimum quantum receivers and of structured receivers, e.g., direct-and heterodyne-detection receivers with either a single detector or a detector array, are discussed and related. The simplifying approximations and assumptions required to obtain these results are emphasized. Estimation theory is considered primarily from a classical (nonquantum) viewpoint. The quadratic functional structure of the processors that result from certain approximations to the likelihood functional are emphasized. Cramer-Rao bounds on the estimation performance are considered and applied to several examples. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Communication through optical scattering channels: An introduction

    Page(s): 1651 - 1665
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3576 KB)  

    The theoretical possibilities of communicating through scattering channels are considered in the context of digital communication. Direct-detection, heterodyne, and optimum receivers are discussed and the near optimality of direct-detection systems is noted. It is found that the error probability depends only upon the total received signal energy if certain noise thresholds are exceeded; below these thresholds the performance deteriorates rapidly. It is often difficult to exceed the thresholds with present-day technology, but it should become possible to do so as the technology evolves. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Wide-band optical communication systems: Part I—Time division multiplexing

    Page(s): 1666 - 1683
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1941 KB)  

    The purpose of this paper is to consider the theoretical error performance of several digital formats suitable for use with a mode-locked laser source, to discuss the problems of implementing these formats, and to consider the design of an illustrative system. Several techniques for time multiplexing are also described. It is assumed that the transmission medium introduces only additive noise and that the detection process is signal shot noise limited. Among the formats examined the practical choices which can achieve highest information rates with lowest probabilities of error are binary, differential phase shift keying, and binary pulse position modulation. For purposes of illustrating state-of-the-art performance the design of a 4000-mile repeatered binary pulse code modulation intensity modulated system is outlined. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Wide-band optical communication systems: Part II—Frequency-division multiplexing

    Page(s): 1683 - 1690
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (801 KB)  

    Frequency-division multiplexing techniques offer means for circumventing the bandwidth limitations of optical modulators and detector. Practical broad-band long-distance optical communication system of this type appear feasible and some possible embodiments are described. Calculations are made to determine the approximate information capacity and other characteristics of several 4000-mile repeaterad systems. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Atmospheric optical communications systems

    Page(s): 1691 - 1709
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2032 KB)  

    The increasing sophistication of optical (and infrared) components and techniques, combined with rapidly expanding communication requirements, suggests that optical systems operating partly or entirely within the atmosphere may soon represent desirable solutions to real communications problems. The design of such systems will be strongly influenced by considerations of atmospheric turbulence, molecular absorption, and aerosol scattering. The most promising alternatives are heterodyne systems operating at the 10.6 µ wavelength, and direct-detection systems at near-infrared or visible wavelengths. Feasible links include horizontal, ground-to-satellite, and satellite-to-ground (or aircraft) geometries. System requirements and atmospheric effects are reviewed. Components, signaling, and diversity techniques which will partially overcome atmospheric limitations are discussed. Specific representative systems designs are presented. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.

Aims & Scope

The most highly-cited general interest journal in electrical engineering and computer science, the Proceedings is the best way to stay informed on an exemplary range of topics.

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
H. Joel Trussell
North Carolina State University