FIBER OPTICS STANDARD DICTIONARY
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MARTIN H. WEIK
SPRINGER-SCIENCE+BUSINESS MEDIA, B.v. JOIN US ON THE INTERNET WWW: http://www.thomson.com EMAIL: [email protected] thomson.com is the on-line portal for the products, services and resources available from International Thomson Publishing (ITP). This Internet kiosk gives users immediate access to more than 34 ITP publishers and over 20,000 products. Through thomson.com Internet users can search catalogs, examine subject• specific resource centers and subscribe to electronic discussion lists. You can purchase ITP products from your local bookseller, or directly through thomson.com.
Cover Design: Said Sayrafiezadeh, Emdash Inc. Copyright © 1997 Springer Science+Business Media Dordrecht Originally published by Chapman & Hali in 1997 Softcover reprint ofthe hardcover 3rd edition 1997
Ali rights reserved. No part of this work covered by the copyright hereon may be reproduced or used in any form or by any means-graphic, electronic, or mechanical, including photocopying, recording, taping, or information storage and retrieval systems-without the written permission of the publisher. I 23456789 10 XXX 0100 99 98 97 Library of Congress Cataioging-in-Publication nata Weik, Martin H. Fiber optics standard dictionary / Martin H. Weik. - 3rd ed. p. cm. Includes bibiiographicai references. ISBN 978-1-4613-7760-3 ISBN 978-1-4615-6023-4 (eBook) DOI 10.1007/978-1-4615-6023-4 1. Optional communications - Dictionaries. 2. Fiber optics• Dictionaries. 1. Title. TK5102.w45 1997 621.36'92-dc21 97-6013 CIP British Library Cataloguing in Publication nata available
"Fiber Optics Standard Dictionary, 3rd edition," is intended to present technically accurate and authoritative information from highly regarded sources. The publisher, editors, authors, advisors and contributors have made every reasonable effort to ensure the accuracy of the information, but cannot assume responsibility for the accuracy of ali information or for the con• sequences of its use. To my wife, Helen, for the love and encouragement she has given me during the preparation of this and prior editions And God said, Let there be light; And there was light. And God saw the light, That it was good; and God divided the light from the darkness. Genesis 1:3-4
Now the whole Earth had one language and few words. And the Lord said, "Behold, they are one people; And they have all one language; And this is only the beginning of what they will do; And nothing that they propose to do Will now be impossible for them." Genesis 11: 1,6
In the beginning was the Word, and the Word was with God, and the Word was God. John 1:1 Contents
Preface IX Introduction xvii
Appendices A. Abbreviations and Acronyms 1127 B. Tables 1204 Table 1: Frequency Ranges and Designators Table 2: Higher Frequency Ranges and Extension Designators Table 3: The Metric System of Units Table 4: Prefixes Used with Metric Units Table 5: Radiometric Terms Table 6: T-Carrier Hierarchy for North America Table 7: T -Carrier Hierarchy for Japan Table 8: T -Carrier Hierarchy for Europe (CEPT) Table 9: Near, Intermediate, and Far Field Characteristics Table 10: T -Carrier Characteristics C. Bibliography 1210 Preface
Fiber Optics Vocabulary Development In 1979, the National Communications System published Technical InfonnationBulle• tin TB 79-1, Vocabulary for Fiber Optics and Lightwave Communications, written by this author. Based on a draft prepared by this author, the National Communications System published Federal Standard FED-STD-1037, Glossary of Telecommunications Terms, in 1980 with no fiber optics tenns. In 1981, the first edition of this dictionary was published under the title Fiber Optics and Lightwave Communications Standard Dictionary. In 1982, the then National Bureau of Standards, now the National Institute of Standards and Technology, published NBS Handbook 140, Optical Waveguide Communications Glossary, which was also published by the General Services Admin• istration as PB82-166257 under the same title. Also in 1982, Dynamic Systems, Inc., published the Fiberoptic Sensor Technology Handbook, co-authored and edited by this author, with an extensive Fiberoptic Sensors Glossary. In 1989, the handbook was republished by Optical Technologies, Inc. It contained the same glossary. In 1984, the Institute of Electrical and Electronic Engineers published IEEE Standard 812-1984, Definitions of Terms Relating to Fiber Optics. In 1986, with the assistance of this author, the National Communications System published FED-STD-1037A, Glossary of Telecommunications Terms, with a few fiber optics tenns. In 1988, the Electronics Industries Association issued EIA-440A, Fiber Optic Terminology, based primarily on PB82-166257. The International Electrotechnical Commission then pub• lished IEC 731, Optical Communications, Terms and Definitions. In 1989, the second edition of this dictionary was published. Also in 1989, the Department of Defense published MIL-STD 2196(SH), Glossary: Fiber Optics. The original draft was pre• pared by this author while he was serving as a consultant to the Naval Sea Systems Command's Fiber Optics Program Office. In 1991 the National Communications System, again with the assistance of this author, published Federal Standard FED• STD-1037B, Glossary of Telecommunications Terms, with considerably more fiber optics tenns than were in the FED-STD 1037 A of 1986. In 1996 the National Commu• nications System published Federal Standard FED-STD-1037C, Glossary ofTelecom• munications Terms, with a very much larger number of fiber optics tenns and defini• tions than were in FED-STD 1037B, particularly in the area of lightwave communications. Hundreds of tenns and definitions were taken from or directly based on the definitions in the second edition of this dictionary. This author actively participated in all of these standards efforts aimed at producing fiber optics vocabula• ries, sometimes by being a member of the standards body responsible for the publica• tion, sometimes by chairing the committee responsible for the publication, and some• times by editing or submitting comments on drafts of the publications.
ix Preface x
This Edition This third edition of the Fiber Optics Standard Dictionary is based not only on these publications, but also on the enonnous volume of scientific and technical literature in the area of fiber optics published by technical societies, research institutions, technical magazines, book publishers, and manufacturers of fiber optic systems and components.
Limitations of Current Fiber Optics Glossaries and Vocabularies The Shortfall: Each of the aforementioned glossaries or vocabularies, and others, was designed to (a) cover a specific fiber optic application area, such as communications, sensing, or illumination, (b) reach or appeal to a specific audience, or (c) cover the tenns used in a specific publication or series of publications. Thus, none of these individual works constitutes a comprehensive coverage of the fields of optical systems, fiber optics, lightwave communications, optical sensing, and illumination. Each was prepared by a group of professional people representing a specific interest group. Usually the definitions within a given standard, and among standards, were not always consistent. Each standard had a different fonnat for the definitions. Each standard had a specific purpose and was designed for a specific audience, such as scientists, engineers, technicians, contractors, government employees, or corporate employees. Very little attempt was made to correlate tenns and definitions among the various standards. Thus, a truly comprehensive dictionary has a requirement to serve as an umbrella that covers all related areas and interests even if it becomes necessary to resort to multiple definitions of the same tenn. For example, to communications systems operating personnel, an open circuit is a circuit available for use, i.e., an available line. To systems installation and maintenance personnel, an open circuit is one that has an optical or electrical discontinuity. The Need: By their very nature, standards are devoted primarily to fundamental principles and theory, rather than changing state-of-the-art and advanced technology, the very areas in which persons in a field are currently engaged and have a need for a current dictionary. Technical and scientific papers, technical specifications of products, work statements for contracts, and technical books are being prepared that require up-to-the-moment definitions. Proper tenns and definitions are needed now in order that workers in the field can communicate effectively at all levels. The tenns that technicians use to describe splicing and installing fiber optic cables are as important as the tenns that engineers use that relate to how lightwaves propagate in the fiber optic cables. When both technicians and engineers use the same language, cables will be installed so they work properly. In addition, administrators, managers, and supervisors must speak to both groups in a common language. Overcoming the Shortfall and Meeting the Need: This comprehensive dictionary, with precise, technically accurate, and clearly written definitions, along with examples, illustrations, explanations, and cross references, (a) is designed to overcome all the shortcomings of existing glossaries and vocabularies by meeting the needs of all persons engaged in, or in anyway related to, the field of optical systems, particularly fiber optic and lightwave communications systems, (b) is designed to be as consistent as possible with the published standards, and (c) is designed to embrace not only all the areas covered by the standards but also, with sufficient depth, the related areas that optical systems must interface with. xi Preface
Trends in Fiber Optic Technology
There is no doubt that in the areas of communications, control, data processing, illumination, and sensing, the photon is rapidly replacing the electron. In the last five years, huge advances have been made in optical systems component manufacturing technology, particularly in fiber optics and lightwave communications components. Phase-shift mask technology promises to improve the fabrication of optical integrated circuits. Spin coating procedures are being used on prebaked wafers to produce integrated circuits. Fiber optic pressure sensors have a resolution of lOPa (pascals) over a pressure range of ±5 kPa (kilopascals). Advances in deep submicron technology resulted in components of the order of 0.35 ~m (micron) to 0.5 ~m. Image compression ratios between 5 and 20 have become commonplace for handling the medical images encountered in tomographic, echocardiographic, and X-ray procedures. In laser pro• duction, spectral line-width· power products of 16 MHz· mW (megahertz· milli• watts) have been reached. The new quantum well laser has considerably reduced tum-on time, allowing higher signaling rates. Fiber optic couplers use embedded mirrors to couple light into and out of optical fibers. New laser-amplifier gates with low insertion loss, high on-off extinction ratios, and low crosstalk levels are being used to boost optical power. Great strides have been made in the development and use of optical fiber amplifiers, eliminating the requirement to amplify signals by first converting them to electronic signals. Advances in polarization multiplexing has resulted in a 1-Tb • S-1 (terabit per second) data signaling rate transmitted through a nonzero-dispersion shift optical fiber. A 200-km (kilometer) transoceanic repeater span at a data signaling rate of 20 Gb • S-1 (gigabits per second) has been achieved using soliton transmission. Quantum laser boxes of coherent islands of highly trained epitaxy with a lateral size of 10 nm (nanometers) to 20 nm and heights of between 1 nm and 6 nm. Vertical cavity amplifying photonic switches are being operated at a wavelength of 1.55 ~m (microns) with a 14-dB gain and a lO-ps (picosecond) switching (transition or commutation) time. Fiber optic blood oximeters measure the amount of oxygen in blood in situ and thus eliminate the need to extract blood samples. Transenvironmental fiber optic feedthroughs are operating at a pressure differential of 15,000 psi (pounds per square inch) and a temperature range of -40° to 325°F. In 1993, Bell Laboratories, now a part of Lucent Technologies, produced the world's fastest and smallest silicon transistor, a O.I-~m (micron) device that operates at room temperature. In 1994, they transmitted 40 Gb· S-1 (gigabits per second) over a single optical fiber. This is equivalent to 2.5 million simultaneous phone calls or their equivalent of a mix of voice, data, and video signals. Bell Laboratories have produced arrays of lasers such that 10,000 of the lasers could fit on the head of a pin and each could handle a pulse repetition rate of 350 Gp . S-1 (gigapulses per second). They have produced lasers that can be tailored to emit light at nearly any wavelength over a very wide wavelength spectrum, introducing practical wavelength division multiplexing. The light-carrying capacity of optical fibers is being doubled every year. The per unit cost of data transmission and storage is being reduced at an exponential rate. Lucent Technologies has developed a dense wavelength division multiplexer (DWDM) that is used at the receiving end of a fiber optic link to sort and route lightwave signals carried on eight channels, i.e., wavelengths, on a single optical fiber. Each channel carries 2.5 Gp • S-1 (gigabits per second), or a total of 20 Gp • S-1 on the single optical fiber. This is equivalent to transmitting 5000 novels in one second. The DWDM, the first commercial application-specific integrated optical circuit (O-ASIC) produced by Lucent Technologies, uses optical waveguides Preface XlI etched onto a silicon substrate in much the same way as electronic components are integrated onto computer chips. The Lawrence Livermore National Laboratory has achieved a reduction of feature sizes on chips from 0.35 !lm (microns) to 0.1 !lm and below. Using extreme ultraviolet (EUV) lithographic techniques, chips are pro• duced ten times faster with 1000 times more memory capacity than current chips. A 300,000-fold reduction in the number of defects for the multilayer, coated reflective masks used to transfer the circuit patterns onto the silicon wafers has been achieved. Instruments are now available that are capable of measuring surface shapes at l/50th and l/20th the width of visible lightwaves. Instruments called phase-shifting diffraction interferometers have the precision of l/1000th of the wavelength of visible lightwaves. Additional breakthroughs are occurring at an ever-increasing rate. In essence, the role of the electron is being systematically reduced to that of developing power, producing force, and producing lightwaves, while the role of the photon is being expanded to embrace the areas of information transfer, computing, and control.
Applications of Fiber Optics Replacement: The use of optical systems, particularly fiber optic systems, is expanding at an ever-increasing rate. During the last 10 years, fiber optic cables have replaced coaxial and twisted pair cables in long-distance trunks. Fiber optic cables are easier to install, are lighter, and are smaller than their electronic counterparts. Thus, fiber optic cables are easier to pull through existing ducts and cable raceways. Their higher transmission rates, immunity to electromagnetic interference, longer repeater distances, lower power requirements, and higher flexibility make them particularly attractive and cost-effective. Beyond trunking, fiber optic cables are being installed in fiber optic cable-to-the-curb, cable-to-the desk, and cable-to-the home systems. Their wide bandwidth provides more capacity than is required to meet all voice, data, and video requirements of any end-user set of instruments. For example, the new Phoenix, Arizona library users can look through windows in interior walls of the William Bruder library building and see the mechanical systems as well as the fiber optic "wiring." Expansion: In addition to information transfer systems, fiber optic applications are expanding rapidly in such areas as medicine, illumination, optical power, sensing, endoscopy, and control. The advent of optical fiber amplifiers has greatly simplified the transmission of optical signals over long distances without the cumbersome and energy-consuming task of conversion to electronic signals, amplification, and reconversion to optical signals in a repeater. Advances in optical fiber technology are increasing the repeaterless transmission distances and the pulse repetition rate at the same time, as exemplified by the 200-km 20-Gb • S-1 fiber optic link cited above. Switching: Continued progress in the installation of fiber optic communications systems has resulted in a widespread interest in the use of optical components to perform the required switching functions that are being performed by electronic components. Optical switching provides a quantum leap in transmission capacity. For example, a typical exchange handles 100,000 private lines, i.e., subscribers, each with a 64 kb • S-1 (kilobits per second) channel. This requires a total aggregate data signaling rate of about 10 Gb • S-1 (gigabits per second). If a 10 Tb • S-1 (terabits per second) optical switch is used, the same number of users could each have a 100-Mb. S-1 (megabits per second) private line, i.e. loop. The wide band channels would enable voice, data, and video transmission in each loop. The bandwidth is virtually unlimited. The optical carrier frequency is approximately 230 THz (terahertz). Considering the xiii Preface width of the available wavelength window, about 0.5 x 109 voice channels, or about 300,000 high-definition television channels, become available. In short, the rapid advance in optical switching is a direct result of the emerging dominance of the optical fiber in point-to-point and network transmission systems. Transmission: One reason for the success of the optical fiber as a propagation medium is the low level of interaction of the information carriers-the photons• compared to the high level of interaction exhibited by electrons. Thus, optical circuits can be crossed in a common plane without interaction among the circuits, i.e., without short circuits. However, some crosstalk does occur and has to be eliminated. At the present time, controlling light with light is problematic. Thus, electronic circuits are used to control the optical circuits. In essence, the switching fabric may be optical but control still rests with electronic circuits. However, 100 Gb • S-1 (gigabits per second) and higher streams may soon be handled universally in commercial systems using an all-optical technology. The wide bandwidth of optical systems, combined with the use of space division multiplexing (SDM), wavelength (frequency) division multiplexing (WDM), and time division multiplexing (TDM) allows for an increased number of channels each with wide bandwidths. For example, optical cross-connects and optical add-drop multiplexers can be used with an optical, i.e., a photonic, switching fabric for asynchronous transfer mode (ATM) and synchronous transfer mode (STM) in future systems. This being the case, the distinction between transmis• sion and switching may well disappear. The transmission layer and the switching layer may become one and the same. Eventually, perhaps after a long-term research effort, a fully optical transmission and switching system will evolve in which optical signals are used both for control and for data representation. Some obstacles to the all-optical system are (a) the development of higher optical power generation and distribution systems, (b) the development of a faster all-optical switching capability, and (c) the basic limitations imposed by the fundamentals of the physics of lightwaves used to control lightwaves, limitations that do not occur when electrons are used to control photons. One significant impetus for the development of the all-optical network is the code and format independence, i.e., the transparency, afforded by the optical system. Compatibility: The rate of widespread implementation of the all-optical system is somewhat impeded by the necessity for maintaining compatibility with the legacy imposed by the existing electronic systems. Currently, fiber optic links or trunks can be inserted into electronic systems because the fiber optic links are electronic at both ends. All-electronic links and trunks can continue to be used or retired as dictated by economic considerations. A direct buried fiber optic cable requires less maintenance than an overhead paired cable. The fiber optic station/generator section at a switching center drives the fiber optic cables. All else at the switching center is electronic. When the electronic switch is replaced with an optical switch, the fiber optic cables may terminate directly on the switch terminals and a step increase in flexibility, capacity, and reliability in networking will be achieved. Problems: Some problems must be overcome before the all-optical system is realized. Optical fiber amplifiers are somewhat noisy, perhaps because of the weak interaction between the data-carrying photons and the controlling photons. Nonlinear• ity is a limitation to be overcome. In addition to being noisy, the circuits are subject to crosstalk. Optical signals are difficult to process, i.e., to amplify, shape, and time compared to electronic signals. Measured from the advent of the early telegraph experiments, electrical or electronic signaling is close to a century and a half old. Optical signaling has been around for only a few decades. Optical components need Preface XIV to be made available in the quantity and variety as electronic components. Only then can the transition to all-optical systems be complete and the requirement that optical systems be driven by electronic devices can be eliminated. Future Tradeoffs: Further research and development is required before it can be said that all-optical systems will be more cost-effective than all-electronic systems or than optoelectronic systems. It is not yet possible to cite with precision the tradeoffs between the systems, at least not until optical components become more plentiful and varied. However, the aforementioned problems are not insurmountable. The field of optical networking, transmission, and switching is a dynamic and rapidly progressing one. For example, optical fiber amplifiers are now available commercially that operate at 1.31 Ilm (microns) and at 1.55 Ilm. Optical amplification is sufficient to overcome the attenuation that occurs in optical fibers, such as the 0.35 dB • km-l (decibels per kilometer) that occurs at 1.31 Ilm and the 0.2 dB • km-l that occurs at 1.55 Ilm. The all-optical network offers great promise, leading to the higher perfor• mance systems that are required to meet the challenges of the information age. When the problems encountered in optical switching are overcome, it is expected that the optical fiber amplifier will play an increasing role toward the further development of the global information highway. It seems only logical that apparently massless photons, lightwaves, and radio waves that do not require a return path should provide a more effective carrier of information to the remotest of places than the comparatively cumbersome weighty electron that eventually must find its way back to its source.
The Information Superhighway Increasing Demands: The demands for increased data transmission rates, wider band• widths, lower error rates, higher reliability, and lower cost are driving fiber optic systems into the communications, computer, data processing, and control systems markets at the expense of the all-electronic systems. The electromagnetic spectrum used for radio and video transmission is becoming overcrowded. The radio spectrum appears limited to about 109 Hz (hertz) for lack of components responsive to higher frequencies. The optical spectrum is of the order of 1014 Hz, a spectrum in which there are responsive components. Each order of magnitude is about as large as the sum of all the lower orders. To meet the ever-growing demand for increased volumes of information transfer at increased data rates, resort to optical systems seems to be an inevitable necessity. In addition, optical systems have a considerable edge over electronic systems in the race for superminiaturization and reduction of power require• ments. Trends: The current trend of networking faster computers inherently will require the faster data rates afforded by fiber optic systems. Computers need higher computer• to-computer transmission rates and wider bandwidths. Modem communications sys• tems require higher traffic capacities. Initially there was no real amalgamation of communications, computer, data processing, and control systems. Only during the last decade has meaningful integration occurred, giving rise to the modem mix of communications concepts, such as multimedia, cyberspace, the information superhigh• way, Internet, servers, World Wide Web®, clients, B-ISDN, SONET, cellular tele• phones, personal communications, open systems architecture, the OSI-RM, and E-mail, to name but a few. All of these fast moving and accelerated developments and applications of communications systems occurred with equal rapidity in the military, civilian, and commercial sectors. Integration of computer and communica• tions systems has become commonplace. As electronic components continue to be xv Preface replaced by optical components, the era of the all-optical integrated communications, computer, data processing, and control systems appears to be close at hand.
Real Time Modem communications systems enable real time (a) acquisition and distribution of information, (b) remote control of systems and devices, (c) telemetering of data from any remote place to any other place, (d) search of remote databases, (e) conversational operation of geographically widely separated personal computers, (f) remote job entry and access into computers from and to nearly anywhere around the world, and (g) worldwide rapid message and packet transmission. Fiber optic transmission systems perform these real time functions without the band-limitation and interference that occurs in electronic transmission systems, including radio and video transmission. News reaches homes and offices as it occurs. House-to-house street fighting in civil and national wars, the devastating effects of earthquake, flood, and fire, and the investigations of legislative, judicial, and law enforcement authorities may be wit• nessed in billions of homes and offices around the world in the same moment they occur. Communications has in fact tied the elements of the world together, though these very same elements may be far from united in purpose. Fiber optic systems provide for real time operation by allowing error-free, secure, simultaneous transmis• sion of voice, data, and video transmission on a single optical fiber.
Security The establishment of Internet, cyberspace, the information superhighway, and the global information highway has given rise to a generation of predator hackers and larcenists who invade privacy, violate copyright laws, break security codes, steal trade and industrial secrets, illegally manipulate financial accounts, illegally obtain information for private profit, distribute pornographic literature, promote drug transac• tions, and entice unsuspecting citizens into illegal activities. Cyberspace is difficult to police, though many traps have been set and many predators have been caught, arrested, and charged. With little precedence for such cases, courts are ill prepared to handle them. In many cases, legal procedures are not clear. Identification of exactly what is considered criminal is difficult. Shortly after arrest and conviction, most hackers are given small fines, suspended sentences, and the freedom to continue their illegal and illicit operations. Much needs to be done in the area of secure communications systems to provide adequate protection against the criminal hacker before the enormous benefits of the superhighway are further jeopardized. The situa• tion is similar to that of the early days of the telephone when everyone was concerned about wiretapping. However, the current situation goes beyond wiretapping. It includes illegal tapping of information resources. Further enhancement of secure systems is becoming more and more essential. Fiber optic cables are difficult to tap. Highly sophisticated advanced technology equipment is required. Also, penetration is easily detected because the drain of optical power required during tapping is easily detected. In addition, current techniques in reflectometry allow the exact location of the tap to be determined.
The Changing Face of Computers and Communications Gradually, the electronic computer changed the face of communications systems. Computer-to-computer, database-to-database, and terminal-to-terminal communica- Preface xvi tions capabilities were added to the conventional person-to-person, multicast, and broadcast communications systems. Up until the 1990s, the communications commu• nity considered computers as just another end instrument on their communications lines. The computer community considered communications lines simply as links between computers and work stations. Multimedia interconnection became essential. Homes and offices with personal computers required video and graphic capabilities. Broader bandwidths, higher data signaling rates, and more channels were required. The communications community began to use computers to control their communications systems and the communications systems were used to interconnect computers. Fi• nally, with remote job entry, computer networking, and database interconnection, the boundary between the two communities began to disappear. Current trends indicate that electronic computers will be replaced with optical computers and electronic transmission systems will be replaced with fiber optic transmission systems. As integration continues, the interfaces between computers and their interconnecting networks should gradually, if not rapidly, disappear. If current trends continue, eventu• ally the lightwave, or the photon, will supercede the electron.
MARTIN H. WEIK, DSc. Introduction
This Edition This Fiber Optics Standard Dictionary, Third Edition, is an eightfold increase in content over that of the second edition, from about 2000 entries to about 16,000 entries. Practically every definition carried over from the second edition has not only been recast with improved clarity, style, format, accuracy, and precision, but has also been augmented and updated to reflect changes in technology and the many new applications being made in the area of optical systems. New and old definitions reflect the latest trends in the design, development, manufacture, installation, operation, application, and maintenance of optical systems and components. Close alignment is maintained with the latest international, national, Federal, military, technical society, and industrial standards. Though particular emphasis is placed on fiber optic communi• cations systems, extensive coverage is given to other optical systems, such as laser beam transmission systems, optical switches, optical integrated circuits, optical sen• sors, optical control devices, interfaces with electronic systems, illumination systems, optical power generators and transmitters, imaging systems, and medical instruments. Coverage in all areas bordering on and related to fiber optic systems and components has been expanded to enable users of this dictionary to bridge any existing gap that may occur between optical systems and electronic, acoustic, or mechanical systems, particularly in the bordering areas of communications, computer, data processing, and control systems hardware, software, and firmware.
Scope This dictionary covers all aspects of optical systems in general and fiber optic technol• ogy in particular, not only those areas in which fiber optic applications are widespread, such as local and long-distance communications, but also in the up and coming new areas into which fiber optic technology is being extended, such as computing, sensing, illumination, control, data processing, data storage, telemetering, and imaging. Exten• sive coverage is devoted to communications applications, such as computer network• ing, data exchange, multicasting, broadcasting, point-to-point communications, tele• phone, telegraph, radio, television, facsimile, wirephoto, radar, spread spectrum, navigation, military, and related systems and components. For comparative purposes, and to help bridge the gap between existing legacy systems and fiber optic systems, some coverage is devoted to other transmission media, such as open wire, twisted pair, paired cable, microwave, satellite, coaxial cable, and visual systems. Of course, coverage is devoted to cradle-to-the-grave system lifecycles, such as design, develop• ment, testing, fabrication, installation, operation, application, maintenance, and sal• vage of optical communications, computer, data processing, and control systems networks, equipment, and components. Extensive coverage is given to the software
XVll Introduction XVlll aspects of optical systems, such as the codes, protocols, procedures, computer pro• grams, and arrangements associated with optical systems. Specifically, this dictionary covers, among many other related areas, the following topics: absorption error control active systems facilities analog systems facsimile antennas fiber optic components asynchronous systems fiber optics attenuation fixed communications battlefield surveillance frequency broadcasting gating buffering graphics cabling illumination carriers imaging checking systems information management circuitry information retrieval circuits information storage codes information systems coding information theory command guidance installation communications devices interactive systems communications engineering interfacing communications security interference communications systems jamming communication theory key communications traffic keying compaction lasers configuration management layered systems connectors lightwave communications control systems local area networks coupling logic cybernetics medical instrumentation cyberspace message switching database management microwave communications data conversion military communications data integrity modulation data processing multiplexing data transmission network architecture detection network management digital systems networking display systems network topology distortion noise documentation open systems electromagnetic theory optical communications electronic warfare optical fibers electro-optical systems optical power emanation security optics enciphering optoelectronics encryption packet switching xix Introduction passive systems service personal computers service features photodetectors signal processing photonics signaling polarization sources program management spread spectrum systems propagation media standards propagation modes storage protocols strategic communications pulsed systems surveillance radar switching radiation control switching systems radio synchronization receivers synchronous systems reception tactical communications reflection telegraphy repeaters telephony routing timing satellite communications transceivers scattering transmission secure systems transmitters security video systems sensing systems virtual systems sensors wave propagation servers
Application of this Dictionary Defined and referenced in this dictionary are the terms that (a) are written and spoken by designers, developers, manufacturers, vendors, users, managers, administrators, operators, and maintainers of optical systems, particularly fiber optic communications systems, subsystems, and components, including related and interconnected systems and components, (b) are used by educators, students, members of standards organiza• tions, and government personnel, (c) are used by individuals to communicate with each other, particularly in written and spoken form in seminars, letters, conversations, calls, and messages, and (d) are used by systems personnel, such as administration, operation, and maintenance personnel.
Sources Sources of material for this dictionary are many. This edition subsumes the entire second edition, which, of course, subsumed the first edition. The basis for calling this the "standard" dictionary is that the definitions are based on international, national, Federal, military, technical society, industrial, communications carrier, and technical society standards. The author served on vocabulary standards bodies at the interna• tional, national, Federal, defense, military, and technical society levels. In order to overcome delays in standards development, the latest literature in optical, fiber optic, and lightwave communications, computer, data processing, and control systems was screened for new terms, for which definitions were written, until diminishing returns precluded further search for new terms. Many definitions from various sources had Introduction xx to be edited to ensure technical accuracy, precise wording, consistency in format, and compatibility with existing standards. In thousands of cases, examples, explana• tions, and clarifications were added. In many of the entries, several definitions for the same term had to be included, not only because usage of the same term is different in different fields, but also because different sources used a different approach to describe the concept represented by the term, such as (a) the use of a verbal definition in comparison to a mathematical expression or (b) the use of a description of functions of an entity rather than its composition. The reader has the benefit of all of these varia• tions.
Organization of Entries Ordering Entries are arranged in natural spoken English alphabetical word order. Punctuation and special signs and symbols, such as spaces, hyphens, slashes, and ampersands, are ignored in ordering. No attempt is made to embed Greek letters and Arabic numerals among Roman, i.e., English, letters. Therefore, if a word contains a Greek letter or an Arabic numeral, it is treated as if the Greek letter comes after "z" and the numeral comes after a Greek letter. If the entry starts with a Greek letter or an Arabic numeral, it is placed at the very end of the entire alphabet on a special page entitled "/1." Of course, if a numeral is spelled out, such as four-color theorem, the term is placed in its normal alphabetical position, i.e., under "F."
Cross Referencing Every significant word in a multiple-word entry is also entered in the main listing along with a reference to the fully expressed entry. For example, near field diffraction pattern is defined. Following the definition is Synonym Fresnel diffraction pattern. There is an entry diffraction pattern with a definition. Following the definition is the entry See near-field diffraction pattern, along with the names of other types of diffraction patterns. Also, there is an entry pattern: See near-field diffraction pat• tern, along with the names of other types of patterns. This makes all significant words in a multi word entry accessible. There also is an entry Fresnel diffraction pattern: Synonym: near field diffraction pattern. The definition will always be found at the preferred term as recommended by standards bodies, rather than at its synonym. The practice of arbitrarily cross referencing all significant words in a multi word entry creates a useful tool. Quite often readers will seek a multi word entry without knowing the exact words in the entry but the correct entry will be recognized when seen. For example, assume the name and definition of a specific type of network is being sought. Under the entry network all the types of networks that are defined in this dictionary are listed. Scanning the list usually brings to mind the sought name from which the definition can be found.
Format Usually each entry consists of a set of parts presented in a fixed sequence. The parts are (a) the term being defined, i.e., the term name, (b) one or more defining phrases that are the generally accepted standard definitions of the term, (c) one or more notes, following the word Note, usually devoted to units, examples, equations, and explanations, (d) one or more synonyms, following the word Synonym(s), and (e) cross references to other entries. See is used to refer the reader to various types of the entity being defined. See also is used to refer the reader to the definitions of xxi Introduction closely related or contrasting concepts to enable a more complete understanding of the definition. Refer to Fig.(s) is used to refer to the figure or figures that directly illustrate the definition and that are placed adjacent to the entry. Refer also to Fig.(s) is used to refer to figures elsewhere in the dictionary that also helps understand the definition. The boldfaced word in each figure caption corresponds to the relevant entry. Finally, Refer to Appendix B, Table(s) refers the reader to one or more tables in Appendix B that also contribute to the definition. Restructuring of Terms Except where absolutely required by published standards, prepositional phrases are reduced to modified nouns. For example, index of refraction is reduced to refractive index, angle of incidence to incidence angle, angle of reflection to reflection angle, and period of performance measurement to performance measurement period. The reader is also cautioned in the use of abbreviations of international organizations. For example ISO is the official abbreviation for the International Organization for Standardization and BIU is the official abbreviation for the International Time Bureau. Most of these variances occur because international standards bodies some• times adopted the French titles, thus making the letters, their sequencing, or both, different in English. However, in the vast majority of cases, most international stan• dards bodies by international agreement draft and approve vocabulary definitions in American English. These may then be translated into other languages. Optical versus Fiber Optic versus Optical Fiber The standards organizations have taken different positions in regard to these three terms. One international standards organization defines optical cable as consisting of optical fibers and other components surrounded by a jacket. Other standards organizations define fiber optic cable in the same way optical cable is defined. Then, there are different words for the same thing, such as optical coupler, optical fiber coupler, fiber optic coupler, and fiber coupler, further contributing to the difficulty of preparing definitions and indexing terms. One international standards body uses optical regenerator section because optical pulses are generated and dispatched by the section. Another standards body uses fiber optic regenerator section because optical fibers are used instead of wires or coaxial cables. This author has adopted a kind of compromise. Optical is generic. Thus, "optical system" is not synonymous with "fiber optic system," even in the restricted area of communications. A system of mirrors and lenses, such as is found in a microscope or telescope, is an optical system rather than a fiber optic system. Thus, a fiber optic system is an optical system, but not vice versa. "Fiber optic" is more specific than "optical." If the optical fiber itself is addressed, "optical fiber" is used, as in "optical fiber core" and "optical fiber cladding." Thus, "fiber optic core" would be inappropriate. If an optical fiber is combined with other components to create a device, the device is a fiber optic device, such as a fiber optic cable, fiber optic coupler, and fiber optic data link. This is consistent with most standards. Finally, "optical" is always used to modify terms that are not hardware, such as optical signal, optical pulse, and optical power. If a term being sought is not found under one of these terms, the reader should check the others. In this dictionary, most cases of the various forms have been cross referenced. Communication versus Communications Finally, among the standards and the technical literature, the author was unable to find consistency in the use of "s" on the end of many terms, such as "communications," "telecommunications," and "systems," particularly when used as a modifier. For Introduction XXll example, in the same standard, one can find "communications system" and "communi• cation system" used in the same sense, and often in the same entry of a given standard. Even the names of bodies responsible for communications standards are not consistent in this regard. For example, there is the International Telecommunication Union and the National Communications System. Except in rare instances, such as communica• tion theory, the author has elected to use the more prevalent final "s" when communi• cations, telecommunications, and systems are used as modifiers. If uniformity in this regard is not maintained, alphabetization becomes erratic. Terms containing "communications" become widely separated from those containing "communication." Look-up becomes difficult. The reader is placed in the position of having to guess which word to search for and then possibly having to search for both in two different areas of the alphabetic sequencing. Cross referencing all of these would create exces• sive redundancy.
Encyclopedia This dictionary may be used as an encyclopedia and therefore as a handy reference manual. The See, See also, Refer to Fig., Refer also to Fig., Refer to Table, and Refer also to Table references serve as linkages to related entries enabling the reader to develop complete concepts in specialized areas without having to guess which concepts relate to the definition being sought. The cross references are also a hint to which terms used in a definition are also defined in this dictionary. Finally, the technical terms that are used in definitions are defined whether or not they are cross referenced. There is little value in a dictionary in which the definitions themselves contain complex, unknown, and undefined terms. As a final note, the technical terms used in the Preface, this introduction, the captions of figures, the definitions, and the appendices are defined in this dictionary.
MARTIN H. WEIK, DSc. Acknowledgments
The author extends his appreciation and gratitude to the many persons he has worked with during the years since the printing of the Second Edition. Much of their expertise has found its way into the pages of this edition. In particular, special thanks go to Mr. James H. Davis, Fiber Optics Program Office, Naval Sea Systems Command; Mr. Lonnie Benson, Dynamic Systems, Incorporated; Mr. Thomas F. Blizzard, Log• icon Eagle Technology Corporation; and Ms. Evelyn Gray, Institute for Telecommuni• cation Sciences, U.S. Department of Commerce.