Optical waveguide intelligence transmission systems will expand rapidly over the 1975 to 1990 interval. From US system production usage of less than $2 million in 1975, production will accelerate to an annual rate of $61 million in 1980 and $833 million in 1990. No single technology in fiber or other components will monopolize the market; different components will be chosen, depending upon application. R and D expenditures will continue at a high level. Although military applications received the greatest early publicity, commercial telecommunications will be the leading market from the start. Computer systems, office electronics and process controls will also be strong growth areas.
This paper reviews the technical aspects and summarizes the technology status of fiber optical communications. The most promising fiber types are evaluated based upon their dispersion, loss, and cost characteristics. The status of fiber cabling is summarized. An evaluation and status of optical sources are reported, and the state-of-the-art receiver sensitivity is summarized.
In order to develop optical communications we are supposed to study each part of the transmission network: optical fibres with cabling and coating, connection, sources and codes, detectors together with the electronics needed in equalization and peripheral components. The French government tends to harmonize the industrial studies to those of the state laboratories. This leads us to describe the fibre optic research in FRANCE as: the structure and relations between government and private laboratories or factories; the effort on materials, cabling and splicing; the effort on sources and detectors; a short review of system realization.
Many waveguide devices have been developed to perform optical logic functions in thin films, such as transmitting, receiving, switching, multiplexing, and modulating. (1) They are essential to the realization of high-data-rate (gigabits per second) single-mode optical fiber communication systems. The state of art of this development is reviewed in this paper.
GaAs is the material of greatest interest for active integrated optical devices or circuits which include light source as well as other optical circuit elements. In this paper we shall review the current status of integrated optics in GaAs, discussing both the technology of integration and development of devices.
The manufacture of fiberoptics has undergone profound changes in the past few years, a phenomenon which has resulted in optical fibers possessing important new properties. This paper will describe several of the recent developments in fiberoptic manufacturing processes, the impact of these developments on fiber properties, the implications of improved fiber properties on potential uses, and a brief analysis of the kinds of improvements that might be expected in the near future.
Within the last few years GaAs/GaAlAs heterostructure laser diodes have been developed which are capable of continuous operation at 300°K and above for prolonged periods of time.(1-5) These lasers are suitable for a variety of uses including fiber optic communication, optical scanning, and writing of high density optical memories. However, in order to take full advantage of the small size and increase the utility of the devices in complex systems, it is desirable to be able to integrate these lasers into a monolithic optical circuit. The distributed feedback, a (DFB) laser presents just such an opportunity.
Two methods for measuring the dispersion associated with propagation of different modes in guiding structures are presented. While the usual measurements are based on the direct observation of the distortion under gone by propagating pulses, in the first method one obtains information on the delays among the different modes by observing the changes of the coherence properties of a continuous signal. In the second method, one observes the temporal variation of the output intensity once the input signal has been frequency modulated. These methods allow one to appreciate time differences of the order of some picoseconds, so that sufficient delays can be obtained over short fiber lengths. Experiments are illustrated in which delays of this order of magnitude have been actually measured.
A new relatively simple way of calculating bend radiation is developed. As is often done in propagation over gently curved surfaces, the fiber curvature is accounted for by placing a straight fiber in a fictitious medium which is inhomogeneous in the plane of the bend. For a gently curved fiber, the medium is slowly varying and the WKB method is used to approximate the radial field dependence. This solution is related to the unperturbed straight fiber solution through an ansatz which is consistant with the WKB solution. The propagating modes in this approximation remain orthogonal allowing an immediate generalization to the multimoded case. The radiation loss per unit length is calculated two ways and is consistent with results in the literature.
The strength of optical waveguide fibers is characterized by the presence of flaws distributed randomly over their surface in a way determined by the material and its past history. Fast fracture and time dependent strength measurements on waveguide fibers are presented and interpreted within the framework of Weibull statistics and fracture mechanics theory. A method of determining a complete set of time-to-failure parameters from short gauge length strength measurements is developed and applied to stress corrosion data obtained on fibers held at constant load in a high humidity environment. The effect of fiber strength on optical cable design, manufacture and installation is analyzed using simple cable structures to illustrate the general principles involved.
Digital fiber optic data link terminal modules are being developed in a number of laboratories, and often the modules take the form of black boxes without convenient access to internal signals. This paper discusses types of measurements which can be made using only the digital terminals of the link. Bit-error-rate (BER) vs signal power data can, of course, provide a means for proving overall link performance, but it can also be used to determine certain internal parameters of the receiver. The theoretical dependence of the BER vs light signal power curve shape on receiver input noise equivalent power and comparator slicing level is discussed. BER vs light signal power measurements obtained with an experimental link are presented and interpreted with the aid of the theoretical curves. The effect of other problems, such as hum or oscillation on the BER data, are mentioned. Sensitivity of the system BER to bit rate is also discussed, with application to determining system operating limits. Since BER measurements are simple to make and can easily be automated, they may prove to be a useful means for either laboratory evaluation or production-line acceptance testing of sealed terminal modules.
A glass fiber-waveguide dosimeter is described which is particularly well adapted to monitoring radiation over large areas such as cargo holds, waste storage facilities and around reactor and accelerators. The useful range extends below 10 mR to above 10 4R, providing a 10 fold sensitivity increase over conventional glass-block dosimeters. The sensitivity of a lead flint fiber-optic sensing element is discussed and its response due to γ-ray exposure, exposure rate, photon energy, fading and temperature is presented. The response to fast neutrons is compared with that to v rays - Sn/Sγ ~ 0.1 (in rads(tissue)).
The use of optical fibers for illumination and imaging of internal organs and tissue in conventional and transcutaneous endoscopy is described. The fabrication of flexible and rigid multifibers and of optical fibers with graded refractive index for imaging is discussed. Low-loss optical fibers for medical application are described in conjunction with the transmission of white laser light for illumination and in the application of high-power lasers in surgery. References to published work on the development and use of fiberscopes in medicine are given.
Today's mass spectrometers provide data to the researcher in two modes: (1) in the form of a photographic plate where line densities provide integrated ion abundances, and (2) in the form of a strip chart recording where peak intensities provide ion abundances during a mass versus time scan. Both types of data suffer from low sensitivity - the former due to the insensitivity of photographic emulsions to positive ions (104 ions required for a detectable line) and the latter from a low duty cycle due to spectral scanning (typically 10-2 - 10-4). This paper describes the development of an electro-optical ion detector combining the best features of photographic and electrical ion detection (i.e., wide mass range coverage and low ion detection threshold respectively). A nineteen fold fiber optic image dissector is discussed which reformats the 1 mm x 361 mm mass spectrometer focal plane format to a 19 mm x 19 mm format suitable for vidicon imaging and electronic display of the data.
The application of the optical fiber waveguides to laser gyroscopes is divided into two sections: 1) The ring interferometer and 2) The ring laser. Experiments show that a well defined, stable interference pattern can be obtained using a single mode fiber. This together with the experimentally obtained coupling efficiency of laser radiation into the fiber (-50%) indicate that in addition to a sensitive ring interferometer gyroscope a ring laser gyroscope can be built using a single mode fiber waveguide as the passive part of the laser cavity.
A wide range of potential applications for fiber optic cables is under consideration for Army communication systems. Two current US Army Electronics Command cable development programs (one for long haul TDM systems and the other for local distribution systems) are described in this paper. Design details are discussed at some length, and evaluation of theoretical, mechanical, and environmental characteristics of several constructions are given.
This paper examines potential applications of optical fiber for both civil and military application. Examples of prototype systems are given as a basis for the examination of future links. Cable cross section, bandwidth, and transmission distance tradeoffs are compared with those of coaxial cable, to reveal the relative merits of the two media.
The A-7 Airborne Light Optical Fiber Technology (ALOFT) Demonstration was established by the Navy to confirm that fiber-optic technology is sufficiently practical and mature to be used in internal aircraft data-signal transmissions and to demonstrate the feasibility of a full system application. A description of the ALOFT system design is presented, including explanations of the design trade-offs that led to the components selected by the system development contractor, IBM, Federal Systems Division, Owego, NY. A description of the tests being conducted on the ALOFT system is provided with a summary of the most significant results to date. The objectives and approach of the economic analysis, recently initiated as a part of the ALOFT project, is briefly described.
The transmission of analog video signals is one of the many promising applications of fiber optics technology. With the advent of high power, high radiance GaAlAs double heterostructure light emitting diodes which have adequate linearity, and low loss optical fiber cables the design of point-to-point baseband video bandwidth systems has become straightforward. This paper discusses LED characteristics, including linearity and its effect on differential gain, receiver design and signal to noise ratio, and overall link performance. It is shown that transmission links of up to 2 km at 56 dB S/N are possible without the use of intermediate line amplifiers. The performance of a 10 MHz bandwidth demonstration link containing one line amplifier is better than 0.1 dB differential gain and 0.2Ã° differential phase at a S/N of 53 dB.