Showing papers on "Optical communication published in 1980"
TL;DR: In this paper, an a.f.c. (automatic frequency control) experiment using a Peltier cooling element is described, where the frequency fluctuation can be reduced to below 10 MHz.
Abstract: In the somewhat distant future, heterodyne-type optical communications will appear, increasing channel capacity and repeater separation. At present, the greatest difficulty is the frequency drift of lasers. The letter describes an a.f.c. (automatic frequency control) experiment using a Peltier cooling element; it is shown that the frequency fluctuation can be reduced to below 10 MHz.
101 citations
TL;DR: In this paper, the transmission characteristics of optical fiber connectors are analyzed in detail in order to calculate nonlinear distortions and noise due to instable speckle patterns, and the fluctuation amplitude of the transmission loss and its sensitivity, with respect to a wavelength shift of the laser source, are determined for coherent and partially coherent laser sources.
Abstract: The transmission characteristics of optical fiber connectors are analyzed in detail in order to calculate nonlinear distortions and noise due to instable speckle patterns. The fluctuation amplitude of the transmission loss and its sensitivity, with respect to a wavelength shift of the laser source, are determined for coherent and partially coherent laser sources. Nonlinear distortions due to fiber connectors yield a second-order harmonic distortion of typically -36 dB for a single-longitudinal mode injection laser, and typically -65 dB for a multimode laser. The noise performance has also been estimated for both low frequency and high frequency fluctuations.
88 citations
01 Jun 1980
TL;DR: Results of research in areas of potential interest for optical communications are surveyed: novel fiber-optic components, integrated optics (sources and modulators/switches), novel device fabrication methods, and integration of optical components.
Abstract: Current trends in research and development of components for optical communication are reviewed. Emphasis is placed on active components for fiber-optic systems which have undergone recent major advances. Basic properties of optical fibers and recent technological improvements in splices, connectors, and source/detector-fiber couplers are presented first. This background information serves as a basis for describing recent developments in optical sources (e.g., device reliability, LED's and laser diodes) and photodetectors. Developments in both the 0.8-0.9-µm and 1.0-1.7-µm wavelength regions are covered. Also surveyed are results of research in areas of potential interest for optical communications: novel fiber-optic components, integrated optics (sources and modulators/switches), novel device fabrication methods, and integration of optical components.
77 citations
Patent•
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05 Sep 1980
TL;DR: In this paper, a full-duplex, high-data rate optical communications between geographically separate data processing facilities by means of identical optical transceivers is described. But the authors do not specify the level of optical attenuation.
Abstract: The disclosed optical data link provides full-duplex, high-data rate optical communications between geographically separate data processing facilities by means of identical optical transceivers. Transmitter optics include an LED and a collimating Fresnel lens for providing a collimated, modulated light beam. Receiver optics include a focusing Fresnel lens and a photoreceptor for converting the impinging modulated light beam into corresponding electrical signals, which are amplified by a gain-controlled amplifier. The LED is selectively translatable along its optical axis to provide focal length correction for temperature-induced focal length distortion, while the photoreceptor is selectively translatable along its optical axis to provide, in addition to focal length correction, a preselected amount of optical energy attenuation. To control the output signal level from the gain-controlled amplifier, a microprocessor in the gain control loop is responsive to a signal level code to selectively enable successive levels of electronic attenuation in the gain-controlled amplifier, and, if the dynamic range of electronic attenuation is exhausted without achieving an optimum output signal level, to selectively adjust the level of optical attenuation by incrementally translating the photoreceptor. To control transmitted signal power, the microprocessor is responsive to a temperature indication code to translate the light emitting diode to the actual focal length of the associated Fresnel lens, thereby correcting temperature-induced focal length distortion and optimizing transmitted signal power.
62 citations
TL;DR: This four-fiber optical reversing switch has a simple structure, a low insertion loss, and a low operating voltage and should find a wide range of applications in fiber-optic communication systems.
Abstract: A liquid-crystal switch capable of switching nearly 100% of unpolarized light from one multimode fiber to another had been conceived and demonstrated experimentally. The switch uses a double interaction with a single layer of nematic liquid crystal in which the liquid alignment is initially in plane at 90° to the light propagation. This four-fiber optical reversing switch has a simple structure, a low insertion loss, and a low operating voltage. It should find a wide range of applications in fiber-optic communication systems.
51 citations
TL;DR: The cutoff rate is derived for a digital communication system employing an optical carrier and direct detection and the coordinated design of the encoder, optical modulator, and demodulator is studied using the cutoff rate as a performance measure rather than the more commonly employed error probability.
Abstract: The cutoff rate is derived for a digital communication system employing an optical carrier and direct detection. The coordinated design of the encoder, optical modulator, and demodulator is then studied using the cutoff rate as a performance measure rather than the more commonly employed error probability. Modulator design is studied when transmitted optical signals are subject simultaneously to average-energy and peak-value constraints. Pulse-position modulation is shown to maximize the cutoff rate when the average-energy constraint predominates, and the best signals when the peak-value constraint predominates are identified in terms of Hadamard matrices. A time-sharing of these signals maximizes the cutoff rate when neither constraint dominates the other. Problems of efficient energy utilization, choice of input and output alphabet dimension, and the effect of random detector gain are addressed.
45 citations
TL;DR: A multipurpose directional coupler based on integrated optics technology that operates as a gate that can open and close in <0.1 psec and can be used to generate, modulate, time-multiplex, or demultiplex subpicosecond pulses at any optical wavelength is described.
Abstract: A multipurpose directional coupler based on integrated optics technology is described. The coupling characteristics of the device is controlled by a narrowband microwave biasing signal that travels in synchronism with the light in the guides. This velocity-matched coupler operates as a gate that can open and close in <0.1 psec and can be used to generate, modulate, time-multiplex, or demultiplex subpicosecond pulses at any optical wavelength. Such a device seems to be a promising tool for extending current frontiers in such fields as optical communication, time-domain spectroscopy, metrology, and computer logic where extremely short pulses are useful.
39 citations
Patent•
26 Mar 1980
TL;DR: In this paper, an improved compact form for switching unpolarized optical signals from one multimode fiber guide to selected ones of a plurality of such fiber guides is presented. But this form is not suitable for single-input single-output (SISO) systems.
Abstract: Magnetooptical switches for application in optical communication and data processing systems for switching, multiplexing, and demultiplexing take improved compact forms for switching unpolarized optical signals from one multimode fiber guide to selected ones of a plurality of such fiber guides. Reflection and transmission switches are provided, as well as devices for simultaneous switching of both upstream and downstream light waves.
39 citations
TL;DR: In this paper, the authors presented the Semiconductor Devices for Optical Communications (SDE) for optical communications, which is a family of semiconductor devices designed for optical communication.
Abstract: (1980). Semiconductor Devices for Optical Communications. Optica Acta: International Journal of Optics: Vol. 27, No. 10, pp. 1398-1399.
32 citations
TL;DR: In this article, the first GaInAs p-i-n/f hybrid optical receiver for longer-wavelength optical communication systems was reported, which has a capacitance of 0.3 pF and quantum efficiency of 25%, and gives a receiver sensitivity for a 140 Mbit/s n.r.z.t.
Abstract: Preliminary results are reported on the first GaInAs p-i-n/f.e.t. hybrid optical receiver for longer-wavelength optical communication systems. The GaInAs photodiode has a capacitance of 0.3 pF and quantum efficiency of 25%, and gives a receiver sensitivity for a 140 Mbit/s n.r.z. system at 1.24 μm of −40.7 dBm for a 10−9 error rate.
31 citations
Patent•
28 May 1980
TL;DR: In this article, the operational reliability of a light source in an optical communication system has been increased by an improved redundant arrangement of light sources and the switching arrangement of the same, and the present light source arrangement comprises a plurality of light source each of which provides a different wavelength from one another.
Abstract: The operational reliability of a light source in an optical communication system has been increased by an improved redundant arrangement of light sources and the switching arrangement of the same. The present light source arrangement comprises a plurality of light sources each of which provides a different wavelength from one another, an electrical switch for actuating the selected one of the light sources, said electrical switch being arranged to replace the actuated light source when there is something wrong with the light source in operation, and an optical multiplexer the input of which is coupled to the outputs of the light sources, and the output of the optical multiplexer is connected to an optical fiber cable.
TL;DR: In this paper, the fabrication of low capacitance v.p.t. InGaAs/InP p-i-n photodiodes having a high responsivity up to 1.6 μm wavelength is described.
Abstract: The fabrication of low capacitance v.p.e. InGaAs/InP p-i-n photodiodes having a high responsivity up to 1.6 μm wavelength is described. The receiver sensitivities of the p-i-n f.e.t. hybrid receiver for a 280 Mbit/s system, measured at 1.3μm and 1.5 μm are -38.9 dBm and -39.4 dBm,respectively.
01 Oct 1980
TL;DR: Two types of semiconductor devices are available for use as light sources in fiber transmission systems: light-emitting diode (LED) and semiconductor laser (SRL).
Abstract: Two types of semiconductor devices are available for use as light sources in fiber transmission systems. The simpler device, the light-emitting diode (LED), emits light in many directions and is useful with large core diameter, multimode fibers. The more complicated semiconductor laser emits more collimated light and can couple 10-100 times more power into a multimode fiber and can also be efficiently coupled to small-core single-mode fibers. LED's will be adequate for use in the more numerous data bus and low-to-medium capacity transmission systems, and will be used whenever possible because of their simpler driving circuit requirements, lower temperature sensitivity. and lower cost. Semiconductor laser with their higher power and narrower emission spectrum will be required for high-capacity and long-span transmission systems.
TL;DR: In this article, an integrated optical cutoff modulator is fed back electrically to an electrooptical oscillator, which can be used as an optical clock generator or electrical switchable oscillator for optical communication systems.
TL;DR: The most critical interferences in optical broadband communication systems at 0.85 μm are the modal noise in a graded-index fiber and the feedback problems in d.h. semiconductor lasers as discussed by the authors.
Abstract: The most critical interferences in optical broadband communication systems at 0.85 μm are the modal noise in a graded-index fibre and the feedback problems in d.h. semiconductor lasers. Experiments with these two phenomena in a high-speed digital transmission system are described.
Book•
06 May 1980
TL;DR: In this article, the authors present contributions by a group of specialists working as a team, covering most aspects of fiber optic communication since its inception, including theory, technology, design and practical applications.
Abstract: Presents contributions by a group of specialists working as a team, covering most aspects of fibre optic communication since its inception. Numerical examples help the reader perform calculations associated with fibre optics experiments. Examples show how a representative optical communication system is designed. Material covers theory, technology, design and practical applications.
Patent•
19 May 1980
TL;DR: In this paper, a direction sensor is formed with several units of photo detectors distributed at the circumference of disk 4, and thus the arrival direction of light 3 can be detected by the difference of the output among detectors 5.
Abstract: PURPOSE:To realize the optical transmission while the directions change relatively and without lowering the transmission efficiency by detecting the arrival direction of the light from the 2nd station via the direction sensor of the 1st station and then turning the directivity of the 1st station toward the 2nd station based on the detected direction. CONSTITUTION:Stations 1 and 2 are installed for the optical communication. And in case station 2 tracks light 3 emitted from station 1, the arrival direction is detected for light 3 via the direction sensor provided to station 2. The direction sensor is formed with several units of photo detectors 5 distributed at the circumference of disk 4, and thus the arrival direction of light 3 can be detected by the difference of the output among detectors 5. Then based on the information detected by the direction sensor, the directional characteristics of the sensor of the self-station is altered to the direction of light 3 sent from station 1.
TL;DR: In this paper, a new type of multi/demultiplexer using an interference filter and a single graded-refractive-index (g.r.i.n.) rod lens is described.
Abstract: Wavelength division multiplexing (w.d.m.) techniques, which transmit light signals with different wavelengths through a single optical fibre, are required to increase transmission capacity. The letter describes a new type of multi/demultiplexer using an interference filter and a single graded-refractive-index (g.r.i.n.) rod lens. It has a simple structure and a low near-end crosstalk (less than −50 dB).
13 Nov 1980
TL;DR: In this paper, an incoherent optical system that performs the product of an input vector and a stored matrix is described, where the input vector is suitably biased and entered into the system on an array of infrared light emitting diodes.
Abstract: An incoherent optical system that performs the product of an input vector and a stored matrix is described. The input vector is suitably biased and entered into the system on an array of infrared light emitting diodes. The output vector is measured on parallel elements of a PIN photodiode array. With proper data encoding, vectors and matrices with complex elements can be achieved. An experimental system designed to perform discrete Fourier transforms is described. While the throughput rate of the current system is 108 data samples per second, systems with throughput rates of 1010 can be envisioned.© (1980) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
TL;DR: In this paper, a Monte Carlo simulation technique is applied to obtain the space-time response of the channel when an optical receiver with a specified field of view is located at a specified distance below the cloud.
Abstract: An optical signal,an impulse in space and step in time,is incident on a plane,parallel fixed,homogeneous cloud. The incident signal is modelled as a stream of photons, each of them executing a random walk. A Monte Carlo simulation technique is applied to obtain the space-time response of the channel when an optical receiver with a specified field of view is located at a specified distance below the cloud. The response is obtained as angular, spatial and temporal dispersions. Various simulation steps are described. For thin clouds two variance reduction techniques, i.e. Russian roulette and forced collision, are used. It is shown that the bottom of the cloud tends to diffuse uniformly and the 3 dB exit beam width saturates. The rise time in this channel is found to be of the order of several nanoseconds.
TL;DR: Optimum and certain suboptimum adaptive processors are developed for receivers that synchronously demodulate the IF signal and those that use envelope demodulation and a simple expression is developed for the optimum aperture size of an optical heterodyne receiver.
Abstract: The performance of an optical heterodyne receiver for communication through the clear-air turbulent atmosphere is considered. Optimum and certain suboptimum adaptive processors are developed for receivers that synchronously demodulate the IF signal and those that use envelope demodulation. Error probabilities are presented demonstrating the effects of turbulence level, signal strength, and spatial diversity on binary orthogonal communication systems. In addition, a simple expression is developed for the optimum aperture size of an optical heterodyne receiver.
TL;DR: In this paper, the authors proposed a new modulation technique to reduce speckle noise in multimode optical fiber analogue transmission systems using semiconductor laser diodes, and the feasibility of analogue video transmission system using the proposed modulation technique has been confirmed.
Abstract: The letter proposes a new modulation technique to reduce speckle noise in multimode optical fibre analogue transmission systems using semiconductor laser diodes. The feasibility of analogue video transmission systems using the proposed modulation technique has been confirmed.
TL;DR: In this paper, experimental data are used to demonstrate that the 1-1.6 μ wavelength range is potentially useful for wide-band fiber-optic telecommunications, and the authors propose a wideband wideband fiberoptic communication system.
Abstract: Experimental data are used to demonstrate that the 1–1.6 μ wavelength range is potentially useful for wide-band fiber-optic telecommunications.
Patent•
18 Nov 1980
TL;DR: In this article, the light signal with the data field in the frame constitution, which is transmitted through the optical fiber cable, defined as a electric power source control bit is output through photo.
Abstract: PURPOSE:To make the composite cable using copper wires needless, by using frame information dependent upon the light signal, which is transmitted through the optical fiber cable, to control power-on and-off. CONSTITUTION:The light signal with the data field in the frame constitution, which is transmitted through the optical fiber cable, defined as a electric power source control bit is output through photo.electric conversion part 11 and serial. parallel conversion part 7. Remote unit 2 controlled by the center unit utilizes a proper bit on the data field to turn on contact SW2 of switch 15 through power switch control part 14, and the main power from power source 13 is supplied to respective conversion parts 11 and 7. Consequently, since information of light is used to supply power, the composite cable using copper wires and so on are needless.
Patent•
10 Jul 1980
TL;DR: In this paper, the branch line was provided to the optical fiber itself to reduce the general loss of the branch circuit as well as simplify the structure by providing a branch line to the fiber itself.
Abstract: PURPOSE:To reduce the general loss of the branch circuit as well as to simplify the structure by providing the branch line to the optical fiber itself CONSTITUTION:Two-way optical communication circuit 21 comprises optical fiber 22 and 23, luminius element 24, photo detector 25 plus evaporation film 27 each Film 27 is formed by cutting obliquely the optical fiber and polishing the cut surface into the flat surface, featuring the semitransparent mirror Thus the optical signals transmit through or are reflected on film 27 to be turned into the transmission and reception signals
15 Mar 1980
TL;DR: In this paper, the feasibility of using optical communication systems for data telemetry from deep space vehicles to Earth-based receivers is evaluated, and the effects of background interference and weather on receiver performance are evaluated.
Abstract: The feasibility of using optical communication systems for data telemetry from deep space vehicles to Earth based receivers is evaluated. Performance analysis shows that practical, photon counting optical systems can transmit data reliably at 30 to 40 dB high rates than existing RF systems, or can be used to extend the communication range by 15 to 20 dB. The advantages of pulse-position modulation (PPM) formats are discussed, and photon counting receiver structures designed for PPM decoding are described. The effects of background interference and weather on receiver performance are evaluated. Some consideration is given to tracking and beam pointing operations, since system performance ultimately depends on the accuracy to which these operations can be carried out. An example of a tracking and pointing system utilizing an optical uplink beacon is presented, and it is shown that microradian beam pointing is within the capabilities of state-of-the-art technology. Recommendations for future theoretical studies and component development programs are presented.