Showing papers on "Optical communication published in 1978"
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TL;DR: In this paper, an analytical model for GaAs-AlGaAs double heterostructure high-radiance LED's intended for use in optical communication systems is presented, which takes all the important device and material parameters, such as self absorption, heterointerfacial recombination, doping concentration, active-layer width, injection carrier density, and carrier confinement into account.
Abstract: We present an analytical model for GaAs-AlGaAs double heterostructure high-radiance LED's intended for use in optical communication systems. This model takes all the important device and material parameters, such as self absorption, heterointerfacial recombination, doping concentration, active-layer width, injection carrier density, and carrier confinement into account. A theoretical discussion of the effect of these parameters on LED output power and modulation bandwidth is given along with experimental results which are in good agreement with the model. The best high-output 50-μm LED's (biased near saturation) emitted 15 mW into the air with a radiance of 200 W/cm2. sr (highest ever reported for a surface emitter LED) and a modulation bandwidth of 17 MHz; the highest bandwidth obtained was 170 MHz at 2-mW output.
78 citations
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46 citations
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TL;DR: In this paper an exact analysis of probability of error for optical fiber communication systems is described using the Gauss quadrature rule (GQR) and the moments of the decision circuit input signal.
Abstract: In this paper an exact analysis of probability of error for optical fiber communication systems is described using the Gauss quadrature rule (GQR) and the moments of the decision circuit input signal. As an example of the analysis, two line codes for a system with 280 Mbits/s, the binary code and the bi-phase code, are compared.
46 citations
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28 Aug 1978TL;DR: A thin plate of III-V direct-bandgap semiconductor, preferably with anti-reflective coatings, operates as superior optical filter for light having a wavelength which exceeds a given wavelength in the visible or infra-red spectrum.
Abstract: A thin plate of III-V direct-bandgap semiconductor, preferably with anti-reflective coatings, operates as superior optical filter for light having a wavelength which exceeds a given wavelength in the visible or infra-red spectrum. Such a filter is particularly suitable for use in a duplex optical communication system employing a fiber-optic transmission line.
45 citations
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TL;DR: The use of guided wave optical components for performing logic and computation is proposed, using switches and intensity modulators fabricated on an electrooptic substrate for serial-parallel binary adder.
Abstract: The use of guided wave optical components for performing logic and computation is proposed. The basic logic gates are switches and intensity modulators fabricated on an electrooptic substrate. The states of the switches and modulators are determined by electrical signal voltages. The output signal from each of the gates is intensity-modulated light, while inputs can be electrical signals or a combination of electrical and optical signals. Individual gates can be interconnected on a substrate by dielectric waveguides, so that sequential operations are possible. This is illustrated by a configuration for a serial-parallel binary adder. The propagation delay, as determined by the optical pathlength, is calculated to be of the order of 20–40 psec/gate, assuming that the substrate material is lithium niobate, and the logic voltage level is 5 V.
39 citations
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TL;DR: It is shown that the authors can realize a more economical, high-performance, half-duplex data transmission system by using an LED-DET scheme.
Abstract: Half-duplex transmission over a single optical fiber using an LED source–detector (LED-DET) scheme, that is, LED's being used both as light sources and as photodetectors, has been demonstrated. The effective quantum efficiency in the detector mode, including optical power coupling from the fiber, was measured to be 18%, which is compared with the furcation loss in the conventional duplex transmission system using optical directional couplers. It is shown that we can realize a more economical, high-performance, half-duplex data transmission system by using an LED-DET scheme.
23 citations
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21 Dec 1978TL;DR: In this paper, the microwave, low-noise GaAs-metal-semiconductor, field effect transistor (MESFET) photodetector operates at a low bias voltage, normally, below 6 V.
Abstract: The microwave, low-noise GaAs-metal-semiconductor, field-effect transistor (MESFET) has a cutoff frequency higher than 80 GHz and possesses a good optical responsiveness over a very wide spectral range, from visible to near-infrared wavelengths. The drain-current variation of the MESFET is proportional to the input optic intensity. If the light is modulated, MESFET detects the high-speed subcarrier. Besides the low-noise and amplification-gain advantages, the MESFET photodetector operates at a low bias voltage, normally, below 6 V. The common-gate configuration at zero drain voltage also can function in a photocapacitive mode in which the capacitance changes with the change in polarized light intensity. The S-parameter of the device has been characterized up to Ku-band. The high-frequency optical receiver is ready to be designed and optimized using this charaterization. For high-speed fiber-optic communications, the monolithic receiver, the ILD driver, and the low-cost repeater all can be fabricated by using the MESFET's.
20 citations
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TL;DR: In this paper, a model for Burrus-type high-radiance double-heterostructure LED's is described, which makes it possible to calculate the maximum optical power emitted from a diode chip, the equilibrium optical power coupled into an optical fiber of a given numerical aperture and core diameter, and the transient response of the spontaneous emission of the LED, and afford criteria for optimization of these devices.
Abstract: Phenomenological models for Burrus-type high-radiance double-heterostructure LED's are described which make it possible to calculate the maximum optical power emitted from a diode chip, the equilibrium optical power coupled into an optical fiber of a given numerical aperture NA and core diameter, and the transient response of the spontaneous emission of the LED, and afford criteria for optimization of these devices. Measured values of power and rise time are found to agree with theory to a useful degree of approximation. Reliability data for optimized LED's are presented.
19 citations
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01 Oct 1978
TL;DR: In this article, the authors investigated short-haul non-line-of-sight optical scatter communication links in the middle ultraviolet (UV) wavelength region, where the absence of solar background radiation makes wide-angle receivers practical.
Abstract: : This report discusses the work performed in the second year of a two year program to investigate short-haul non-line-of-sight optical scatter communication links. The wavelength region considered for this study is the middle ultraviolet (uv) (2000 A - 3000 A). This region is attractive for communication purposes because the absence of solar background radiation makes wide-angle receivers practical. Furthermore, the short wavelengths result in significant scatter from molecular atmospheric constituents (Rayleigh scatter), so that the availability of a non-line-of-sight link is extended into clear weather. The goal of the investigation has been to obtain a fundamental understanding of scatter propagation in low visibility atmospheric environments. In particular, the work has focused on the determination of parameters needed for optical communication system design, such as angular spread and multipath time spread.
19 citations
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10 Jan 1978TL;DR: Optical access and duplex couplers for multimode, fiber, and data transmission are discussed in this article, where a single fiber can be used for data transmission in both directions and a number of different depths and widths are etched into silicon along natural crystal planes to position fibers of different diameters and provide reflective silvered surfaces.
Abstract: Optical access and duplex couplers for multimode, fiber, data transmissionines Access couplers are for use with multiterminal communication systems whereas duplex couplers allow a single fiber to be used for data transmission in both directions Grooves of different depths and widths are etched into silicon along natural crystal planes to position fibers of different diameters and to provide reflective silvered surfaces Optical communication signals pass through smaller-diameter transmission lines to larger lines Light surrounding the smaller-diameter line from the larger line is reflected by the reflective surfaces Thus, information may be received and added as desired
18 citations
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TL;DR: The performance of a phase-locked loop driven by the photodetector current in an optical receiver is analyzed and the variance of the phase-errors of the loop is found as a function of the relevant system parameters.
Abstract: This paper analyzes the performance of a phase-locked loop driven by the photodetector current in an optical receiver. The variance of the phase-errors of the loop is found as a function of the relevant system parameters. The results are in good agreement with experimental data obtained via computer simulation.
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14 Jun 1978TL;DR: In this paper, a duplex optical communication system employing the same electrooptic device alternately as a source and as a detector of optical wave energy, and using a single optical fiber to connect pairs of locations, interference produced by reverse Rayleigh scattering along the fiber is minimized by means of R-C equalizers.
Abstract: In a duplex optical communication system employing, at each location, the same electrooptic device alternately as a source and as a detector of optical wave energy, and using a single optical fiber to connect pairs of locations, interference produced by reverse Rayleigh scattering along the fiber is minimized by means of R-C equalizers. The modulation signal applied to the electrooptic device (11) during its transmitting period is simultaneously applied to the equalizer (20). During the receiving period, the signal stored in the equalizer is coupled to the local receiver (18), along with the signal from the electrooptic device, wherein it combines destructively with the reverse Rayleigh scattered signal produced along the fiber by the original transmission.
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TL;DR: In this paper, a 1.1 Gb/s InGaAsP/InP d.h. injection laser at a room-temperature environment has been demonstrated and the operating wavelength was 1.27 μm.
Abstract: Pulse-code modulation of InGaAsP/InP d.h. injection lasers at a 1.1. Gb/s rate in a room-temperature environment has been demonstrated. The operating wavelength was 1.27 μm. Fabrication and characteristics of the lasers, design of the 1.1 Gb/s circuitry, and performance of the experimental transmitter are described briefly.
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TL;DR: In this article, the possibilities of optical communication at 4 μm wavelength are discussed and a novel heterojunction system is described for making the necessary detectors and high-radiance sources, with the possibility of room-temperature operation.
Abstract: The possibilities of optical communication at 4 μm wavelength are discussed. New materials are proposed for optical fibres capable of very low loss at this wavelength. The possibility of fabricating not only glass but single-crystal optical fibres at acceptable growth rates is suggested. A novel heterojunction system is described for making the necessary detectors and high-radiance sources, with the possibility of room-temperature operation. Advantages of optical communication at 4 μm rather than at 1 μm include relaxed demands on the precision of optical alignment (particularly important for single-mode operation), greater tolerance of transition metal impurities in the fibre as well as reduced scattering loss, and, therefore, the promise of much lower fibre loss if the required purity can be achieved. Extremely long stage lengths, e.g. 1000 km, should be possible if, as seems likely, fibre losses approaching 10−3 dB/dm can be achieved. Other possible wavelengths for optical communications are also discussed.
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TL;DR: The receiver sensitivity of a moderate bit rate optical fiber communication link is investigated and the effect of both power conversion among the guided modes of the fiber and power loss to the radiation field from theguided modes is examined.
Abstract: The receiver sensitivity of a moderate bit rate optical fiber communication link is investigated. The effect of both power conversion among the guided modes of the fiber and power loss to the radiation field from the guided modes is examined. Three different receiver filter designs are considered; a zero-forcing equalization procedure and two filters which do not compensate for the pulse dispersion introduced by the optical fiber channel. The degree of sophistication required in the detection process is a function of the mode coupling and attenuation parameters and the numerical results provide useful quantitative information for this aspect of system design. In particular, the channel parameter values for which processing techniques are required to compensate for pulse dispersion can be obtained from the results.
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TL;DR: The construction of a working prototype data bus using mirror terminals demonstrates the feasibility of such systems for use in optical communications at the present state of the art.
Abstract: A prototype fail-safe optical data bus utilizing active LiTaO3 electrooptic mirror terminals has been constructed and tested. Features of the system include (1) a single optical source; (2) an optical insertion loss of less than 6 dB and a tapoff ratio of 13 dB for the mirror terminals in the fail-safe mode; (3) compatibility with commercially available LED sources, P-I-N photodiode detectors, and step-index multimode monofibers; (4) remote terminal modulation depth approaching 50% for 100 V applied; and (5) the use of a pulse transformer technique which allows the required electrooptic modulation voltages to be obtained from a 5-V electrical supply. The construction of a working prototype data bus using mirror terminals demonstrates the feasibility of such systems for use in optical communications at the present state of the art.
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21 Dec 1978
TL;DR: In this paper, three classes of optical communications systems are addressed: OCULT (Optical Communications Using Laser Transceivers), ELOS (Extended Line-of-Sight) optical communications, and satellite to subsurface optical communications.
Abstract: Optical communication in the atmosphere, space, the marine boundary layer, and underwater are being investigated for a variety of applications. Three classes of optical communications systems will be addressed: OCULT (Optical Communications Using Laser Transceivers), ELOS (Extended Line-of-Sight) optical communications, and satellite to subsurface optical communications. OCULT is a 10.5µ high rate reciprocal tracking heterodyne laser communications system designed for nearly all-weather duplex video bandwidth communications to horizon limited ranges. Of special interest are effects of coherent propagation through fogs and turbulence. The ELOS system is a 1.06μ optical aeorsol scatter communications system for ranges of 30 to 300 miles. Scattering measurement at 40 to 80 miles through the marine boundary layer will be presented. The satellite to subsurface communication efforts deal with blue/green transmission from a satellite, through the atmosphere (including clouds) to a submerged receiver, exploiting the blue/green "window" in ocean water. The multiple forward scattered and diffusion transport of semi-plane waves through clouds and ocean waters will be discussed.
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26 Jul 1978
TL;DR: In this article, the condition of power supply of the processor for the gate between the optical detector and the optical source was controlled to eliminate the condition that the power supply is always applied and to economize the power consumption.
Abstract: PURPOSE:To eliminate the condition that the power supply of the processor is always applied and to economize the power consumption, by controlling the condition of power supply of the processor for the gate between the optical detector and the optical source.
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15 Dec 1978
TL;DR: In this paper, the authors proposed a scheme to secure a signal transmission without increasing the transmission band for the main signal by giving AM to the signal row with the monitor/order signal.
Abstract: PURPOSE:To secure a signal transmission without increasing the transmission band for the main signal by giving AM to the main signal row with the monitor/order signal.
01 Jun 1978
TL;DR: In this article, the authors present an inexorable growth in the electronic handling of information, and optical-fibre communication systems will make a large contribution to this growth, but just where will optical communication systems make their impact in society given their present physical limitations and performance?
Abstract: We are witnessing an inexorable growth in the electronic handling of information, and optical-fibre communication systems will make a large contribution to this growth. But just where will optical communication systems make their impact in society given their present physical limitations and performance?
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TL;DR: In this article, the smoke-signaler's blanket is replaced by an acoustoor electro-optic modulator, and the modulator functions much as the blanket does, stopping or passing a pulse of light rather than a puff of smoke.
Abstract: Integrated optics was born out of the needs of optical communications. Communication by light waves is not a new idea. To understand its requirements, consider the early example shown in Figure 1. Simple as this system is, it has the essential elements of the most modern digital communications system. First, a source of the light wave, or carrier wave, is needed. For the smoke-signaler, this was a bonfire. In a modern system the bonfire is replaced by a laser or light-emitting diode (LED). The next step is modulation, putting the message on the light beam. Currently the smoke-signaler's blanket is likely to be replaced by an acoustoor electro optic modulator. Alternatively the laser may be internally modulated, as we shall discuss later. In a digital system the modulator functions much as the blanket does, stopping or passing a pulse of light (rather than a puff of smoke) . The message is sent in a prearranged code, ours being much more sophisticated than that used by the smoke-signaler, of course. The next requirement of the system is a transmission medium. The smoke signaler used the air, but it was, particularly over large distances, un reliable. Recently it is being replaced as an optical-communication medium by thin, highly transparent glass fibers. Finally, a detector is required at the receiving end, an eye in the case of the smoke-signaler, plus a decoder, the attached brain. One modern kind of detector is the photodiode, probably feeding into an electronic decoder connected ulti mately perhaps to a telephone receiver or TV display.
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22 Jun 1978
TL;DR: In this paper, a double heterostructure semiconductor laser has been used as a light source for an optical communications system, where the spatial distribution of the lasing filament changes from that occuring at the start of the LAS regime, so that the optical flux emitted by the laser has self-saturating properties.
Abstract: A double heterostructure semiconductor laser having the configuration of its optical cavity arranged to impose a constraint on the lasing filament as the spatial distribution of the lasing filament changes from that occuring at the start of the lasing regime, so that the optical flux emitted by the laser has self-saturating properties. This protects the laser from catastrophic facet erosion and enables a simpler control circuit to be used to drive this laser when it is used as a light source for an optical communications system.
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TL;DR: In this paper, a silicon device with an optical threshold, which can operate as a digital optical switch, is presented, and a good correlation between theory and the experimental results is obtained.
Abstract: This paper presents a silicon device (m.i.s.t.), with an optical threshold, which can operate as a digital optical switch. Its operation and characteristics are presented. A good correlation between theory and the experimental results is obtained. The responsivity and sensitivity of 0.9 AW?1 and 3.9 × 10?4 mA/?V are obtained, respectively. Possible applications in fast optical digital isolation and in optical communication systems are envisaged.
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TL;DR: A combined pulse-amplitude/pulse-position modulation tachnique is proposed for digital optical communication systems and evaluations of its behaviour in terms of coding efficiency, spectral density, timing information content, and error probability are summarised.
Abstract: A combined pulse-amplitude/pulse-position modulation tachnique is proposed for digital optical communication systems. Evaluations of its behaviour in terms of coding efficiency, spectral density, timing information content, and error probability are summarised. Alternative receiving schemes are devised to improve system performance.
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02 Oct 1978
TL;DR: In this article, a light communication unit of small size hardly being affected of mechanical vibration and environment, through the use of composite refractive substance FKB for multiplication, separation, and synthesis of signal light.
Abstract: PURPOSE:To enable the communication of signal having large capacity and less noise, by forming the light communication unit of small size hardly being affected of mechanical vibration and environment, through the use of composite refractive substance FKB for multiplication, separation, and synthesis of signal light.
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TL;DR: It is shown that a multilevel signal can significantly increase the information rate and/or the repeater spacing and at the same time equaliser design can be simplified.
Abstract: The theory for multilevel signal applications in digital optical-fibre communications is derived for systems with avalanche and nonavalanche photodetectors. It is shown that a multilevel signal can significantly increase the information rate and/or the repeater spacing. At the same time equaliser design can be simplified.
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TL;DR: In this paper, the authors present an inexorable growth in the electronic handling of information, and optical-fibre communication systems will make a large contribution to this growth, but just where will optical communication systems make their impact in society given their present physical limitations and performance?
Abstract: We are witnessing an inexorable growth in the electronic handling of information, and optical-fibre communication systems will make a large contribution to this growth. But just where will optical communication systems make their impact in society given their present physical limitations and performance?