Fiber Optics Illustrated Dictionary - Part 6 pptx

Fiber Optics Illustrated Dictionary network transmissions protocols with addresses assigned in the . ampr.org domain. The sharing ofpacket radio communications among amateur radio buffs began with packet bulletin board systems (PBBSs) similar to the BBSs popular with computer hobbyists in the early and mid-1980s. The main differences between the two were that computer BBSs were primarily interconnected by land-based telephone lines and modems, whereas packet radio BBSs were interconnected by wireless radio frequency communications through terminal node con- trollers (TNCs) with abroadcast distance of about 20 miles or so. Relays were still necessary for long-distance packet communications. When the Internet and rCP/IF became well established, many computer buffs shut down their BBSs and migrated to the Internet. Packet radio followed suit, forming the AmprNet to utilize low-cost global aiIwaves and simultaneous two-way communications. AmateurRadio Emergency Service ARES. A public service organization of licen,sed Amateur Radio Operators of the American Radio Relay League (ARRL) who voluntarily provide emergency communications for public service events. ARES cooperates with state and local governments and the American Red Cross. http://www.ares.org! Amateur Radio International Space Station ARISS. An organization established to research and support the use of amateur radio in space; ARISS evolved out of the Space Shuttle Amateur Radio Ex- periment (SAREX). It serves as an educational out- reach tool and experimental communications testbed. It also provides backup for emergency s~ace communications and a medium for "off-duty' communication with friends and family members. A Memorandum ofUnderstanding was signed between ARISS and various national radio organizations in 1996 along with agreements with NASA and the Russian Energia. NASA liaises with the public through its Division ofEducation programs and Web site. Leadership and consultation are provided by the ARRL and AMSAT. ARISS designs, builds, and op- erates amateur radio equipment in cooperation with International Space Station programs. It established ISS Ham as atechnical team to support hardware development, training, and operations while in orbit. While the initial communications of SAREX and ARISS were audio only, video is also an important aspect ofradio communications and slow scan television (SSTV) is included in ARISS projections. See Space Shuttle Amateur Radio Experiment. http://ariss.gsfc.nasa.gov/ amateurradio operator, ham radio operatorA radio broadcasting hobbyist permitted to transmit ra- AMSAT-OSCAR Satellite Projects - Selected Overview Phase II Satellites - developmental, low-orbit, operational, longer lifespan. See OSCAR. Phase III Satellites - operational, high elliptical orbit, longer lifespan. Phase IV Satellites - operational, high geostationary or drifting geostationary orbit, long lifespan. Satellite Launch Notes AMSAT-OSCAR 1 12 Dec. 1961 Phase-4A. 10 lb., beacon, 22-day orbit. Initiated by a U.S. west coast group. Nonrechargeable batteries. Elliptical orbit at 421 kilometers. Quarter-wave monopole antenna. Morse code telemetry. U.S. Air Force launched. AMSAT-OSCAR 4 21 Dec. 1965 TRW Radio Club construction. Elliptical orbit at 34,000 kilometers (intended for circular orbit). No telemetry. Sleeve dipole and monopole antennas. AMSAT-OSCAR 8 5 Mar. 1978 Phase-2D. Circular LEO at 910 kilometers. Several antennas. Battery failed June 1983. AMSAT-OSCAR 10 16 Jun. 1983 NASAINORAD #14129. Phase-3B. Similar to OSCAR I, with some improvements. Coatings provided better temperature control. On-board propulsion. High-altitude, elliptical, synchronous-transfer Molniya orbit at 35,449 kilometers. AMSAT-OSCAR 13 15 Jun. 1988 NASAINORAD #19216. Phase-3C. Linear analog transponder. Magnetorquer stabilization. Elliptical orbit at 38,000 kilometers, Molniya. Carried RUDAK-l, which failed. AMSAT-OSCAR 16 22 Jan. 1990 NASAINORAD #20439. PACSAT. Sun-synchronous near-polar LEO at 800 kilometers. Store-and-forward file server and AX.25 protocol. Digital repeater. 42 © 2003 by CRC Press LLC dio signals over specific frequencies. Most licenses that permit amateur transmissions require that the operator be licensed and fulfill certain requirements. In the U.S., also often called ham radio operator. amateur satellite service A radio communication service using space stations or Earth-orbiting satellites for the purposes of the amateur radio- communications service. See amateur service, AMSAT, OSCAR. See AMSAT-OSCAR Satellite Projects Chart. amateur senice Radio communications services for the purpose of self-training, intercommunication, and technical investigations carried out by amateurs, that is, licensed or otherwise authorized persons interested in radio technique solely with personal, educational, or nonpecuniary aims. See American Radio Relay League. amateurtelevision AmTV, ATV. Black and white or color image broadcasts through amateur radio frequencies, with or without accompanying sound broadcast. Some amateur enthusiasts prefer to use ATV to mean fast scan TV over amateur bands, and SSTV for slow scan image transmission. With ad- vancements in television technology, advanced television has begun to be identified with the ATV ab- breviation, occasionally causing confusion. In the future it may be advisable to use AmTV to designate amateur television. See slow scan television. amberA very light, transparent or semitransparent, warm golden substance from fossilization tree resin from pine trees that have been extinct for millions of years. Amber floats in water and occasionally washes up on the coasts of Europe after storms, intermingled with kelp and other natural debris. Sometimes insects can be found imbedded in the amber, preserved for centuries. Amber can be highly polished and has been used for jewelry for thousands of years. The chief importance of amber to telecommunica- tions is its static electrical properties, which can be observed by rubbing amber with a cloth (or on your hair) and using it to attract small fragments of tissue paper. In fact, the Greeks observed this property, and Plato recorded" the wonderful attracting power of amber " in his Timaeus dialog. The Greek word for amber is elektron. ambient n. Environment, atmosphere, mood, sur- roundings. ambient light The light existing in an environment around and in addition to any deliberately established lights associated with a system. Ambient light may come from sunlight, reflective surfaces, phosphores- cent materials, etc. and is typically composed of a variety of wavelengths. Ambient light conditions affect mood and visibility and may be critically important to optical applications using precision instruments, those sensitive to light and those dependent upon specific types or levels of light for specialized applications (darkroom devices, microscopes, lasers, telescopes, etc.). The visibility and size of laser spots, for example, is affected by the amount and color of ambient light in addition to the distance traveled before the beam hits a reflecting surface. ambient noise, room noise The general acoustic noise level of an environment, usually measured in decibels. The ambient noise in terminal rooms with printers or other equipment may be sufficient to cause hearing loss over time. Technicians who work long hours with high speed printers should wear ear protection. ambient temperature The temperature in the environment around an object or system. Ambient temperatures may affect the durability, stability, and per- formance of many types of components, especially conducting materials that conduct not only transmission signals but also ambient temperature. For components that are especially sensitive to temperature extremes or fluctuations, the housings may be designed to control or mediate ambient temperatures. AMDM ATM multiplexer/demultiplexer. America Online AOL. A large, commercial Internet Services Provider (ISP) that provides access to the Internet, AOL-specific forums, news, email, and other features. AOL evolved from Quantum Com- puter Services, conceived by S. Case and J. Kimsey as a computer BBS providing online information and consumer services through modems. In 1989 Quan- tum was renamed to America Online and was launched with realtime chat, email, and special interest forums. Case became President of the company in 1990 and CEO in 1993. AOL became a publicly traded company in 1996. In 1998, it acquired Compu- serve and ICQ, two well-known network services, as well as MapQuest, in 2000. In 2001, AOL completed a merger with Time Warner. America's CarriersTelecommunicationsAssocia- tion ACTA. A U.S based trade organization, representing commercial long-distance vendors (nondominant interexchange vendors). Of signifi- cance is the fact that ACTA has lobbied the Federal Communications Commission (FCC) to bar long-distance digital telephony over the Internet. The focus of ACTA is providing representation for its members to various legislative and regulatory bodies, and to further business activities of its members. American Association for Artificial Intelligence AAAI. A nonprofit organization founded in 1979 to advance education in and scientific understanding of thought and intelligent behavior and their embodi- ment in machines. http://www.aaaLorg/ American Association for the Advancement of Science AAAS. Descended from the Association of American Geologists and Naturalists, the AAAS was formed with a broader mission in 1848 to promote the development of science and engineering in the United States. http://www.aaas.org/ American Association of Physics Teachers AAPT. The AAPT supports professional and research physics and physics education through activities and publications, including the American Journal of Phys- ics, Physics Today, and The Physics Teacher. Phys- ics and engineering (applied physics) are at the heart of the understanding and development of all communications systems. http://www.aapt.org/ 43 © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary American Bell Telephone Company In 1875, the Bell Patent Association was formed by Alexander Graham Bell with investors willing to finance his telegraphy research. Two years later, in 1877, The Bell Telephone Company was formed by Bell, who included his associate, Thomas Watson. The company was formally incorporated in Massachusetts in 1878. Theodore N. Vail was hired as the general manager and had a long association with the company and its successors. In 1878, the Bell Telephone Company and the New England Telephone Company were consoli- dated into the National Bell Telephone Company. Then, in 1880, American Bell Telephone Company was incorporated. In 1881, American Bell purchased Western Electric Manufacturing Company and developed it into Western Electric Company, the equipment manufacturing arm of American Bell. American Bell was the parent of the American Tele- phone and Telegraphy Company (AT&T). AT&T was established in New York as a subsidiary in 1885 for handling long-distance calls. These two were then merged into AT&T in 1899. See AT&T; Vail, Theo- dore N.; Western Electric Company. American Civil Liberties Union ACLU. A prominent, nonprofit, nonpartisan, civil liberties organization founded in 1920 which now has more than a quarter million members. The ACLU monitors and protects freedom and takes action against violations of civil liberties wherever they may occur. The ACLU has a strong presence on the Web in light of the fact that many new freedom-related legislative actions have been taken as a result of the growth of the In- ternet. The ACLU publishes ACLU Online and the biweekly Cyber-Liberties Update electronic maga- zine. The ACLU deals with many telecommunica- tions issues including Web censorship, online privacy, encryption, and more. http://www.aclu.org/ American Communication Association ACA. A not-for-profit association founded to promote aca- demic and professional research, theory, criticism, and debate on human communications. ACA publishes The American Communication Journal, a professional, peer-reviewed, online publication. http://www.americancomm.org/ American Engineering Association AEA. A national nonprofit professional association supporting and promoting American leadership in engineering. http://www.aea.orgl American Electronics Association AeA. A Wash- ington, D.C based professional association with of- fices in the U.S. and abroad, founded in 1943. AeA is dedicated to helping member companies excel in a global competitive market. AeANET is AeA's means of communicating industry news, surveys, and public policy issues to its membership. In 200 I, the AeA presented a public policy report to the 107th U.S. Congress asserting the importance of adapting to a new global Information Age. As its Pub- lic Policy priorities, the AeA listed expansion of science and math education, protection of privacy, sim- plification ofInternet taxation, export controls, res- toration of Presidential fast-track trade negotiating 44 authority, monitoring of China's conformance with World Trade Organization (WTO) agreements, and broadband deployment through forbearance in regu- lation and the promotion ofcompetition. The report further lists statistics for the high-technology industry in the Quick Facts Appendix 3 section. http://www.aeanet.org/ American Institute ofElectrical Engineers AlEE. Formed as aresult of growing electrical development in the 1800s and the International Electrical Exhibi- tion in 1884, to represent the profession and develop standards for the industry. Norvin Green, president of Western Union Telegraph Company, was the first president. Alexander Graham Bell and Thomas A. Edison were among the first six vice-presidents. AIEE was presented The Clark Collection in 190 I by Schuyler Skaats Wheeler. The Clark Collection was one of the world's great libraries of electrical technology. Andrew Carnegie further donated $1.5 million for AlEE premises. AlEE was merged with the Institute of Radio Engineers (IRE) in 1963 to form the IEEE. See IEEE, Institute of Radio Engineers. American Library Association ALA. Agoverning body and support group for American librarians. The ALA provides member services, workshops, conferences, and administrative support. The organization has a long history of service to the public and its members. The ALA Code ofEthics goes back to a Sug- gested Code ofEthics proposed in 1930. The author acknowledges the generous help received from many librarians in the creation of this dictionary. http://www.ala.org/ American Mathematical Society AMS. A large professional society dedicated to promoting mathematical research and education, founded in 1888. Head- quartered in Providence, R.I., the AMS sponsors conferences, member services, online resources (e.g., MathSciNet) and a large number ofmathematical publications. http://www.ams.orgl American Mobile Satellite Corporation AMSC. A commercial provider ofseamless mobile communications services across North America under the SkyCell trademark. Hughes Communications is the largest shareholder,joined by AT&T Wireless, Singa- pore Telecom, and Mitel Corporation. A variety of services are marketed to govemment agencies, emergency organizations, and major corporations. AMSC is permitted to provide domestic mobile satellite services (MSS) in the upper L-band. American Morse Code, Railroad Morse Asystem of dots and dashes used to represent characters for distance communications, quite possibly developed by Alfred Vail, while working with Samuel Morse. Due to the fact that American Morse includes some characters with internal spaces, which can be confus- ing to some, it is not often used, International Morse code is preferred. See Morse code. American National Standards Institute ANSI. A significant U.S. private sector, nonprofit, standards- promoting body based in New York. ANSI was founded in 1918 by a group ofengineering societies and government agencies. The ANSI Federation © 2003 by CRC Press LLC contributes the enhancement of global competitive- ness of U.S. businesses by promoting the development and support of consensus standards and con- formity assessment systems. Information on the many important ANSI standards is available online in the ANSI searchable database. http://www.ansi.org/ American Optical AO. A long-standing American optical finn known for its eyeglasses, lenses, and scientific instrument components. AO began producing spectacles ( eyeglasses) in 1833 after having originally been established as ajewelry shop. In 1838, Charles Spencer began marketing microscopes, setting up business as Spencer and Sons, in 1865. In 1869, American Optical Company was established by G. W. Wells. In 1843, William Beecher, AO's founder, produced steel eyeglasses on equipment of his own invention. Five years later, the product line was extended to gold frames. By 1898, AO was establishing industry standards for certain lenses. A research laboratory was established in 1909, one that was to attract a significant pool of talent, and AO was awarded a number of patents in the optics industry. In the early 1920s, the Spencer company in- troduced optical spectrometers, goniometers, and re- fractometers. In 1935,American Optical acquired the Spencer Lens Company, which operated as AO's In- strument Division as of 1945. By the 1920s, the company had expanded from consumer eyeglasses into industrial safety products and expanded further into military optics in the early years of World War II. Many renowned scientists in the optical community have worked at one time or another for American Optical. While AO didn't express much interest in fiber optics in the 1950s, W. Hicks, arecentAO em- ployee who left to fonn another company, succeeded in fabricating a fiber filament, through fiber pulling, that could transmit light as a single-mode waveguide, in 1959. The potential of the single-mode waveguide was recognized by Elias Snitzer and described by him in a paper written in 1961. During the 1960s and 1970s, many pioneering optical medical instrument components were produced by AO. In 1999 - 2000, American Optical was acquired by SOLA, an Australian lens company. American Public Power Association APPA. A national American service organization representing local or publicly owned electric utility companies. http://www.appanet.org/ American Public Radio See Public Radio Interna- tional. American Radio MuseumA diverse, well-selected collection of over a hundred years history of antique radio and electrical technologies, including a Tesla coil, Nipkow disc, Leyden jars, static generators, pho- nographs, and significant makes and models of crystal detectors and historic radios. Descended from the Bellingham Radio Museum, ARM was founded in the Pacific Northwest by Jonathan Winter. http://www.antique-radio.org/radio.html AmericanRadioRelay League ARRL. Founded in 1914 by Hiram Percy Maxim, with assistance from Clarence D. Tuska and a number of their colleagues, the ARRL is now a worldwide organization with almost 200,000 members, headquartered in the United States. Tuska was a youthful tinkerer and radio hobbyist when he met Maxim. The ARRL name is derived from the way in which amateur radio operators, constrained to certain power levels and frequencies, would cooperate by relaying messages from one per- son to another in order to send over greater distances or difficult terrain. The ARRL cooperates with various radio groups and governing authorities such as the International Tele- communications Union (ITU) and the Federal Com- munications Commission (FCC). Its members have contributed to many of the technological milestones in communications history, including the pioneering of frequencies that were originally thought to be use- less (and hence were assigned to amateurs). More recently, amateur radio enthusiasts have cooperated in satellite communications projects with AMSAT. The ARRL monthly publication QSThas been available for more than 80 years. See AMSAT, International Amateur Radio Union. The ARRL's call letters are WIAW. http://www.arrl.org/ American Speaking Telepbone Company A historic telephone company, based upon the Edison transmitter, established by Western Union in 1877 to compete with the Bell Company. With hundreds of thousands of miles of telegraph lines already installed throughout North America that could be adapted for telephone transmissions, Western Union was seen as a real threat to the Bell empire. American Standard Code for Information Inter- change ASCII. An important, alphanumeric 7-bit (128-character) communications standard widely used around the world for the transmission of textual messages. ASCII is a simple system, used on telegraph systems and computers. It doesn't support for- matting attributes such as bold, italic or underline, and it is primarily useful for English and western Euro- pean languages. ASCII often functions as a lowest common denomi- nator for textual communications since it is supported by most electronic mail, word processing, text edit- ing, and desktop publishing programs, which may otherwise be incompatible. Differing formats are often resolved through ASCII translation and conversion. See ASCII for a chart showing the characters, control characters, and hex, decimal, and octal values for each. See ASCII and see Appendix for a chart, EBCDIC. American Telephone and Telegraph Company AT &T. See AT&T for an explanation of the company's origins, history, and technologies. American Voice Input/Output Society AVIOS. A not-for-profit organization dedicated to promoting and supporting speech applications research and technologies. Speech applications include voice recognition, speech recognition, and speech generation, all of which are now important input and output capabilities of computer systems and digital telephony networks. http://www.avios.com/ 45 © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary American Wire Gauge, Brown and Sharpe Wire Gauge AWG. Astandardized wire diameter system, exclusive of covering, for nonferrous conductors such as copper and aluminum. With a range from 1 to 40, lower numbers denote thicker wires, higher ones thin- ner wires. Generally, for a specific material, the current-carrying capability increases as the diameter of the wire increases and the AWG number decreases. AWG 1 corresponds to a diameter 00.35 mm with an amp rating of ca. 191, whileAWG 40 corresponds to 0.799 mm and an amp rating of ca. 0.02. With finer wires manufactured and used for finely detailed electronics circuits, some charts extend the gauge sizes down to 0000 (11.68 mm). Since heavier wires are usually more expensive, con- sumers tend to purchase the thinnest wire that will accomplish the task at hand. It's important to get wire that not only is adequate to carry the current desired, but that is strong enough to bend and stretch, especially around connectors, panels, punch-down blocks, etc. If the wire breaks at the connection point, it's not very useful. See Birmington Wire Gauge. Ames Research Center ARC. Aresearch organization dedicated to creating new knowledge and technologies within NASA's areas of interest. ARC was formed in 1939 by the U.S. National Advisory Com- mittee on Aeronautics (NACA), which became part of National Aeronautics and Space Administration (NASA) in 1958. AMHS See Automated Message Handling System. AMI 1. See Alternate Mark Inversion. Amiga Multimedia Personal Computer The first of the Amiga line of computers. the Amiga 1000 was released in August 1985. 1tfeatured preemptive multitasking, bllilt-in serial andparallelports, a Motorola MC68000 CPU with coprocessor chips, two mOllse/joystick ports, composite or RGB color graphics up to 640 x 400 pixels (more in overscan mode), and two-channel (16-voice) stereo sound. Amiga computer A remarkable personal computer system for its time, the Amiga was developed by Jay Miner (hardware), Carl Sassenrath, R.I. Mical, et al. in the early 1980s. The original Amiga team members were part of the Hi-Toro company, a small develop- 46 ment company whose members created the Lorraine, which was bought oul by Commodore Business Ma- chines in the fall of 1984 and became the Amiga. The Amiga was well equipped for 1985 with full serial, parallel, and joystick ports, full-color graphics, the ability to run multiple screens simultaneously in different resolutions, NTSC video compatibility, built-in 4-channel (16-voice) stereo sound, fast graphics display with coprocessing chips, and a Motorola MC68000 CPU chip running at 7.15909 MHz with 32/16-bit internaVexternal addressing. The Amiga had a fully preemptive multitasking operating system (working quite well in only 256 kilo- bytes of memory) which came with both a graphical user interface (GUI) and a text command line interface, both available for use at the same time. It helps to remember that in 1985 most personal computers lacked peripheral ports and employed single- tasking, monochrome graphics, and command line in- terfaces for prices ranging from $3,000 to $6,000. The Amiga 1000 offered everything built in, including monitor and sound, for under $2,000. The only other computer at the time significantly competitive with the Amiga was the Atari ST (the Apple IIgs never quite made the grade). Other Amiga models, including the 2000, 3000 and 4000, and updates to the as were released over the next several years, followed by a new type of product from Commodore, the CD32. The Amiga is historically significant not only for providing the first viable platform for desktop video, but for its many capabilities that have subsequently been incorporated into other systems (certain patented as- pects of the Amiga have been used by prominent computer companies in today's mainstream products), showing the prescience and desirability of its design and features. Even a decade after its release, most personal computers lacked many of the Amiga's early capabilities, despite faster CPUs and other advances in technology. In 1994 Commodore-Amiga folded due to problems in executive management and marketing. The Amiga product line was acquired by a German company, Escom, AG, (Amiga Technologies) and was later sold to Gateway, Inc., in 1997. Developers' conferences were reinstituted the same year. Gateway subsequently licensed use of the technology and trade iden- tifiers to Amino Development Corporation, later known as the Amiga Corporation. Amiga conferences were still being held as of March 2001. See Amiga CD32; Commodore Business Machines; Mindset computer; Miner, Jay. AMIS See Audio Messaging Interchange Specifi- cation. AML I. See Actual Measured Loss. 2. analog micro- wave link. 3. ARC Macro Language. A line-based in- terpreted programming language for the AtcInfo GIS, from ESRI. 4. Aurora Macro Language. An object- oriented, event-driven language for the Aurora Edi- tor, a text editor from nText Research. AMLCD active matrix liquid crystal display. See active matrix display. © 2003 by CRC Press LLC ammeter, ampere meterAn instrument for measuring the flow of electric current in alternating or di- rect current in ampere units. In communications circuits, where current may be very small (below one ampere), milliammeters and microammeters are used. When ustd as a measuring and diagnostic instrument, an ammeter is connected in series with a circuit to measure the current as it passes through. If the total current is above the range of the ammeter, or is such that it might cause damage to the sensitive instrumen- tation, part of it may be predirected through a shunt connected in parallel. See ampere, shunt. Historic Ammeter or Ampere Meter H Fig. 3 ~ B A ~ ~~~ Fig. 2 Ag.5 Historic drawings are often useful for describing basic mechanics and the forerunners to electronics as the essential components can be more easily visual- ized. The above diagram shows the basic stlUcture and components of a historic ammeter, which is tech- nologically descended from the galvanometer. [Popu- lar Mechanics, May 1907. J AMN See Abstract Machine Notation. AMP See advanced metal powder. ampacity The current-carrying capability, in amperes, of a circuit or cable. Typically ampacity is specified in product descriptions to indicate various types of cable assemblies, which may collectively consist of various combinations of wires and insu- lating materials. AMPAS See Academy of Motion Picture Arts and Sciences. ampere, amp (symb. - A) Aunit of measurement of flow of electric current, named after A. Ampere. It is a practical meter-kilogram-second unit of ~lectric current equivalent to a flow of one coulomb per second, or to the steady current produced by one volt when applied across a resistance of one ohm. The international ampere was traditionally expressed as the steady current that will deposit silver at the rate of 0.001118 grams per second when flowing through a neutral silver nitrate solution. The accepted scientific definition has since been re- placed by a SI unit of electric current defined as a constant current that, in two straight parallel infinite conductors of negligible cross section placed one meter apart in a vacuum, would produce a force between conductors of2 x 10· 7 N/m. See volt, watt. Ampere, Andre-Marie (1775-1836) A French physicist and mathematician who described and developed terminology for the nature of electricity. He also sought, in 1820, to formulate a combined theory of magnetism and electricity following some of the investigations ofH. C. 0rsted. In 1826, Ampere published an important paper, the "Memoir on the Mathematical Theory of Electrody- namic Phenomena, Uniquely Deduced from Experi- ence" in which he described electrodynamic forces in mathematical terms. Many later experimenters built on Ampere's ideas, and his discoveries led to the development of magnet-moving coil instruments. The ampere unit of measure of electric current is named after him. See ampere, galvanometer. Andre-Marie Ampere Andre-MarieAmpere was inspired by the discoveries of @rsted and worked with Arago to follow them up. Together they further investigated electrical and magneticforces from which Ampere sought to formulate a unified theory to explain these phenomena. Ampere's law In electromagnetism, the magnetic field associated with an electric current is propor- tional to the current. Ampere's law expresses this mathematical relationship and states that for a closed- loop path, the sum of the length elements times the magnetic field in the direction of the length element is equal to the permeability times the electric current within the loop. (Stating the rule in English is easier than calculating the integrals related to complex paths associated with irregular enclosed spaces.) Currents within these bounded spaces are positive or negative. Ampere's law has applications in assessing magnetic fields associated with conducting transmission wires and coils. Ampere's and Gauss's law together enable mathematical modeling of static magnetic fields. Ampere's law does not apply directly to a circuit with a charging capacitor. See Biot-Savart law, Gauss's law, Maxwell's equations. Ampere's rule Based upon his discoveries in electromagnetism, Andre-Marie Ampere described a 47 © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary Amplitude Modulation are methods that may significantly reduce output amplitude fading. See amplitude. The lOp amplill/de modularion (AM) diagram (A) shows an ul/modulated 'carrier' signal. The middle (B) shows the signal modulatedso that the amplitude varies through time. The bo[(om (C) shows the 'modulation envelope' which convE:Ys useJul inJonnatiol/, such as magI/iII/de oJthe modularion. amplitude modulation AM. A very common means of adding information to a carrier wave. A basic radio wave carries no information. By varying or modulating the amplitude in apredetermined way, signals can be created which can be reconstructed as data, sound, or images at the receiving end of the transmission. This system was adopted in the early telegraph systems and is familiar in the form of AM radio broadcasts. AM radio typically requires about 10 kilohertz of bandwidth and is more subject to noise than frequency modulated (FM) radio. Designations of AM radio frequencies are under the jurisdiction ofthe Federal Communications Commission (FCC), and they have changed from time to time. In 1993, the FCC increased the upper limit of the AM band from 1605 kHz to 1705 kHz. Once frequency modulation (FM) was developed by Armstrong, it was thought that its superiority would overshadow amplitude modulation, but AM radio stations are still common decades later. One of the simplest ways to modulate is to create in- tervals ofcurrent that are either on or off, as in Morse code telegraph communications and some types of binary computer signaling. Most computer modems use amplitude modulation and demodulation to A c B method for determining the direction in which a magnetic needle orients itself when in the vicinity of a current of electricity. See Biot-Savart law, left-hand rule, right-hand rule. ampere-second A unit of electric charge flowing past a point in a current-carrying wire per second with a constant current of one ampere. Thus, amperes times seconds equals coulombs. See coulomb. amplification See amplify. amplifier A device or system that increases the magnitude or intensity of a phenomenon such as sound. This is accomplished in electronics through an increase in power, voltage, or current. Amplifying a signal doesn't necessarily make it louder, bigger, brighter, etc. than the original. The effect ofamplifi- cation at the receiving end, or at atransfer point, may increase the signal that is received above its charac- teristics at the point it is received, but not necessarily above the original. Some systems are intended to increase the signal above the level of the original, as in public address systems and blow horns. Amplifi- cation systems seek to minimize the possible amplification or introduction of noise in the signal, while increasing the meaningful parts of the signal. See re- generative relay. amplify To electrically, mechanically, optically, or conceptually enlarge; to increase the power or signal strength of; to make louder; to exaggerate. Am- plification is a crucial process in many communications technologies that enables signals to be made effective, audible, or able to travel longer distances. amplitude I. The measure of the magnitude or ex- tent of some property, movement, or phenomenon. 2. The magnitude of variation in some changing quan- tity from an established value such as zero, or from its extents. See amplitude modulation. 3. In a dia- grammatic representation ofa wave, the measure of the magnitude from the highest point in the waveform, to the lowest. amplitude distortion Assuming a fundamental wave in a steady-state system, an undesirable condition in which the outgoing waveform differs from the incoming waveform sufficiently to affect the perception or informational content ofthe signal. amplitude equalizer Corrective electronics, usually passive, designed to compensate for less than desir- able amplitudes over a range of frequencies. Equal- izers are used in audio recording and playback. amplitude fading In an amplitude-modulated carrier wave, fading is the attenuation of the amplitude across frequencies, more or less uniformly. In passive laser communications links, atmospheric fluc- tuation is one factor contributing to amplitude fading and quadrature amplitude modulating (QAM) systems may be especially susceptible. Barbier et al. have described automatic gain control circuitry to help reduce fade. In multimode, multichannel, optical fiber interferom- eters, assessment and reduction ofamplitude fading are more complex. Kotov et al. have suggested that summing the signal magnitudes over various chan- nels or selecting a channel with the largest amplitude 48 © 2003 by CRC Press LLC convert from digital computer transmission signals to analog telephone transmission signals, and back again at the receiving modem. Various types of amplitude modulation have been developed, and other nonamplitude modulation tech- niques exist, such ·as frequency modulation, in which the frequency of the signal, rather than its amplitude, is varied. See absorption modulation, amplitude shift keying, frequency modulation, modem, modulation, quadrature phase shift keying. amplitude separation In television transmissions, the separation of the incoming signal into a video component and a synchronization signal component. amplitude shift keying, intensity modulation, on/offkeying ASK. Abasic type of modulation that employs a constant-frequency signal, with two different signal levels used to represent binary values. In its simplest form, one state is represented by the lack of presence of the carrier, and the other by the presence of the carrier at aconstant amplitude, hence onloffkeying (OOK). AmprNet See Amateur Packet Radio Network. AMPS See Advanced Mobile Phone System. AMR See anisotropic magneto resistance. AMS 1. Account Management System. 2. See Ameri- can Mathematical Society. 3. American Meteorologi- cal Society. 4. Attendant Management System. 5. automated management system. AMSAT The Radio Amateur Satellite Corporation. A global organization of amateur radio operators who share an active interest in building, launching, and communicating amateur radio technology through noncommercial satellites. AMSAT was founded in 1969 as a result of the 1961 Project OSCAR satellite launchings. AMSAT was established as a not-for- profit educational organization to foster amateur par- ticipation in space research and communication. Many early launchings have piggybacked as second- ary payloads on weather satellites. More recently, AMSAT satellites have shared launch vehicles with other commercial and scientific craft. In the mid-l 990s, AMSAT became associated with ARISS amateur radio experiments aboard the Inter- national Space Station. Soon after, it became involved in the international Phase 3D satellite project, also called AMSAT-OSCAR 40 (AO-40). This project supports cameras, sensors, transmitters and receiv- ers in several radio frequency bands, including S, K, U, V, L, and X bands. It is the fourth of AMSAT's high-altitude, global communications satellites, designed to replace earlier satellites that failed on launch or were no longer functional due to limited lifespans or technical failures. As ofApril 2001, efforts were underway to recover AO-40. In general, the satellite was in good condition, with some individual glitches that didn't impinge on overall health. However, since orbit 201, when it lost its solar lock, it was officially in a state of"hibernation" (unable to sense the Sun) with the magnetorque system off until solar lock could be reinstituted. AMSAT now consists ofa number ofloosely affili- ated organizations around the world, some bearing the AMSAT name with extensions, working together through cooperative rather than formal arrangements. AMSAT sponsors discussion lists and publishes a weekly online report on satellites, covering almost three dozen individual orbiting bodies, including space stations. Many AMSAT enthusiasts are highly skilled technicians, and their knowledge and expertise have contributed to developing new technologies, in cooperation with a number ofagencies, including the Eu- ropean Space Agency (ESA). See Amateur Radio In- ternational Space Station. See amateur satellite service and OSCAR for charts of the earlier satellite projects. http://www.amsat.org/ AMSC See American Mobile Satellite Corporation. AMSC-l Acommercial satellite, operating in the L- band frequencies, owned by American Mobile Sat- ellite Corporation. AMSC-I provides voice, data, fac- simile, paging, and other mobile communications services, particularly to commercial transport companies. Communication is through satellite phones or cellular/satellite hybrid phones. AMSS 1. See Aeronautical Mobile Satellite Service. 2. Airborne Multi-Spectral Scanner. An aircraft- mounted scanning spectrometer for acquiring high- resolution imagery. 3. See Asian Mobile Satellite System. AMTOR amateur teleprinting over radio. AMTS See Automated MaritimelMarine Telecom- munications System. analog 1. Relating to, similar to, linear, continuous with. 2. Circuits or devices in which the output or transmission varies as a continuous function of the input. Here are two examples commonly used to il- lustrate the distinction between analog and digital display and selection systems: TIme Piece Displays. Most analog watches have con- tinuously sweeping minute and hour hands that move through a 360 degree arc through the action ofinternal rotating gears. Contrast this to a digital watch which stays on a one-minute or one- second setting until the next has been reached, and then 'flips over' the display to the next minute in discrete units. Dials and Buttons. In older AM radios, the turning of an analog radio dial will move the station pointer in a continuous path through the various frequencies, and the transitions can be heard as the signals from various stations get stronger and weaker. In newer car radios, a push-button digital system is often used (sometimes in conjunc- tion with an analog dial) to store the locations of preferred radio stations. Pushing the buttons 'jumps' to the desired stations without passing through the intervening frequencies. Traditionally, phone conversations were processed as analog transmissions over copper wires. Gradually, digital switches and optical backbones were intro- duced, but the link to the customers' premises re- mained analog. When computers were first remotely accessed over analog phone lines through modems, 49 ;."! , i:\:.r • d © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary it was necessary to convert the digital signals from the computer to analog signals through modulation. With the growing availability of mobile phones, ISDN, etc., end-to-end digital transmissions are possible and conversion from analog to digital is less often necessary. See digital, ISDN, modem. anamorphic Capable of display in varying aspect ratios in the X and Y axes. Traditional television images are displayed at 4:3 aspect ratios and some mov- ies are anamorphed (modified as to their aspect ratios) to fit television displays. Display systems may be anamorphic but, more often, the media being displayed have been put through an anamorphic process before being stored and distributed (e.g., DVD mov- ies). Thus, these images are not so much anamorphic as they are anamorphed. It is entirely possible that image media may someday be truly anamorphic, stored in such a way that acomputerized display system could process the incoming data and display at the desired aspect ratio in realtime. See ananlorphing, letterboxing. anamorphing Altering the aspect ratio of an image, optical beam, or other directional entity. The tenn is most often applied in two-dimensional situations where one dimension or the other is altered, rather than both. In imaging systems, this is typically in the X and Yaxes. In fabrication processes, parts may be anamorphed in one or two out of three dimensions. In laser optics, anamorphing prisms are used to reduce, enlarge, or correct a beam size or shape. Thus, an elliptical beam from a laser diode, for example, may be corrected in one dimension by small anamorphing lenses to create a circular beam. anamux analog multiplexer. ANC All Number Calling. anchor I. Something that serves to steady or hold, such as a guy wire or stake. 2. In hypertext programming, an element enabling links to related information. The anchor delimits the two ends of the hyper- link, designated with a tag as follows: <A link tag="!ocation">link text</A> anchor frame 1. In HTML coding, a frame (a defined section of the display) that contains at least one anchor tag (e.g., <A HREF » pointing to addresses, data, or images to be associated with that frame. The TARGET tag can be used to specify that an anchor applies to a specific frame if there is more than one frame associated with a page. 2. In advanced television (ATV) technologies, a video frame used for pre- diction, most commonly an I-frame or P-frame. B- frames are not used as anchor frames. See ATSC Digi- tal Television Standard. Anchorage Accord An ATM Forum document com- prising Foundation Specifications needed to assemble an ATM network infrastructure. This important suite established criteria for maintaining interoperability of ATM products and services. There were five dozen specifications listed in the Anchorage Accord, including intercarrier specifications, LAN emulations, interface requirements, physical layer specifications, traffic management specifications, and testing suites. The approval of the Accord was announced by the 50 ATMForum Technical Committee in April 1996. The step was an important one in forging working rela- tions among theorists, specifications developers, and commercial implementers and was instrumental in furthering the acceptance and adoption of ATM as a networking technology. The Committee assured developers that specifications would be downwardly revised if interoperability problems were found in actual implementation. In August 1997, six additional specifications were announced, mainly to facilitate Internet connections and the transmission of converg- ing multimedia data over ATM (e.g., voice or video overATM). The Accord documents can be downloaded free of charge from the ATM Forum specifications archive on the Web. See asynchronous transfer mode. http://www.atmforum.com! ancillary charges Charges for optional or value- added services. AND See Automatic Network Dialing. Anderson bridge Adevice, usually employing a galvanometer, that measures reactance in order to de- termine capacitance or inductance by balancing against afrequency standard. Andreessen, Mark Andreessen developed the first version of Mosaic, the precursor to the Netscape Navigator browser, in early 1993 while at the Na- tional Center for Supercomputing Applications. He was working with the Software Development Group developing for Unix. In 1994, he joined forces with Mark Bina, some of his colleagues at the University ofIllinois, and developers from Silicon Graphics to fonn Mosaic Communications. They essentially re- wrote the code, as the new Mosaic company didn't have the rights to market the version developed at the University. The company also had to change its name, so as not to infringe on the University rights to "Mo- saic" as a tradename. The new company was called Netscape Communications and is now well-known for creating the Web browser known as Netscape Navigator. Andrew File System AFS. Adistributed file system named for Andrew Carnegie and Andrew Mellon. AFS grew out ofacollaboration between Carnegie- Mellon University and International Business Ma- chines (IBM). anechoic I. Not echoing or reflecting sound. 2. An environment without noise, or without significant noise. Sound recording rooms are designed to echo as little as possible, with thick, porous materials re- sembling foam egg crates absorbing the sound so it is prevented from reflecting back to the recording equipment. Speakerphones work better in anechoic environments. See acoustics. angle Within the context of the central point in a circular reference, the displacement between two lines or surfaces originating or passing through the same reference point relative to one another, usually expressed in degrees or radians. If the two lines or surfaces are equivalent, the angle is considered to be zero. The number used to express the magnitude of the angle increases as the angle increases through a © 2003 by CRC Press LLC regular arc in a selected plane until they are again equivalent, thus a 360 arc in degrees or 21t arc in radians. Basic Angle Designations 360 0 or 2u radians Angles are commonly designated with semicircles or squares (90°) are expressed in degrees or radians, based upon 360 degrees in a circle or 21C radians. The concept of angle is intrinsic to almost every aspect of optics. Because light is said to travel in straight lines unless it is reflected or refracted in measurable, predictable ways in its interaction with common optical components, the geometry of angles enables the calculation of distances which, in turn, makes it poossible to model, design, fabricate, and use thousands of optical components. angle of acceptance See acceptance angle. angle ofarrival The angle between the Earth's surface and the center ofa radiant beam from the antenna to which it is radiating. angle ofbeam The predominant range of direction of radiant energy from a directional transmit- ting antenna. angle of deflection See angle of divergence. angle of divergence In a cathode-ray tube (CRT), for example, the spread or divergence of an electron beam from an imaginary center posi- tion for that beam as it travels from the cathode to the coating on the inside surface of the front of the tube. A well-focused beam should spread as little as possible. Higher amplitudes tend to result in higher divergence. Aperfectly straight beam has an angle of divergence that equals zero. See spreading loss. angle of incidence The angle at which a radiant beam (or line) encounters an obstacle or theo- retical reference, calculated in relation to the perpendicular (normal) from the surface of the obstacle. See incidence angle for a fuller explanation and diagrams. angle of radiation The angle between the Earth's surface and the center ofa radiant beam from the antenna from which it is radiating. See normal, Brewster's angle, Snell's law. angle brackets < > Symbols very commonly used in programming code as delimiters or arithmetic operators. These are best known as greater than (» and less than «) symbols. In HTML, the angle brackets delimit markup tags, e.g., <p> signifies a paragraph opening. Angles - Degrees/Radians/Triangle This diagram illustrates how angles are derived relative to the center of an imaginary circle anda be- ginning referencepoint. Shown clockwisefrom the top are eqUivalent measurements on two common geomet- ric scales, degrees and radians. The Greek letter theta (6) is often used to designate an angle and the Greek letters alpha (a) and beta (/3) often refer to specific angles that are compared or mathematically summed (e.g., the combined angles of a triangle add up to 180~ which is a useful refer- encefor calculations, especially when combinedwith Pythagorean conceptsfor right triangles (a triangle with a 90°angle]). Angle of Incidence Example This simplified diagram of an electromagnetic in- cident wave encountering a dielectric with different refractiveproperties illustrates the angleofincidence (a) and the angle of refraction (f3) as well as normal which is established, by definition, as 90°perpendicular (at rightangles) to the plane upon which the inci- dent wave makes contact with the interveningdielec- tric. 51 © 2003 by CRC Press LLC . Overview Phase II Satellites - developmental, low-orbit, operational, longer lifespan. See OSCAR. Phase III Satellites - operational, high elliptical orbit, longer lifespan. Phase IV Satellites - operational, high geostationary or drifting geostationary orbit, long lifespan. Satellite Launch Notes AMSAT-OSCAR 1 12 Dec. 1 961 Phase-4A. 10 lb., beacon, 22-day orbit. Initiated by a U.S. west coast group. Nonrechargeable batteries. Elliptical orbit at 421 kilometers. Quarter-wave monopole antenna. Morse code telemetry. U.S. Air Force launched. AMSAT-OSCAR 4 21 Dec. 1 965 TRW Radio Club construction. Elliptical orbit at 34,000 kilometers (intended for circular orbit). No telemetry. Sleeve dipole and monopole antennas. AMSAT-OSCAR 8 5 Mar. 1978 Phase-2D. Circular LEO at 910 kilometers. Several antennas. Battery failed June 1983. AMSAT-OSCAR 10 16 Jun. 1983 NASAINORAD #14129. Phase-3B. Similar to OSCAR I, with some improvements. Coatings provided better temperature control. On-board propulsion. High-altitude, elliptical, synchronous-transfer Molniya orbit at 35,449 kilometers. AMSAT-OSCAR 13 15 Jun. 1988 NASAINORAD #192 16. Phase-3C. Linear analog transponder. Magnetorquer stabilization. Elliptical orbit at 38,000 kilometers, Molniya. Carried RUDAK-l, which failed. AMSAT-OSCAR 16 22 Jan. 1990 NASAINORAD #20439. PACSAT. Sun-synchronous near-polar LEO at 800 kilometers. Store-and-forward file server and AX.25 protocol. Digital repeater. 42 ©. Overview Phase II Satellites - developmental, low-orbit, operational, longer lifespan. See OSCAR. Phase III Satellites - operational, high elliptical orbit, longer lifespan. Phase IV Satellites - operational, high geostationary or drifting geostationary orbit, long lifespan. Satellite Launch Notes AMSAT-OSCAR 1 12 Dec. 1 961 Phase-4A. 10 lb., beacon, 22-day orbit. Initiated by a U.S. west coast group. Nonrechargeable batteries. Elliptical orbit at 421 kilometers. Quarter-wave monopole antenna. Morse code telemetry. U.S. Air Force launched. AMSAT-OSCAR 4 21 Dec. 1 965 TRW Radio Club construction. Elliptical orbit at 34,000 kilometers (intended for circular orbit). No telemetry. Sleeve dipole and monopole antennas. AMSAT-OSCAR 8 5 Mar. 1978 Phase-2D. Circular LEO at 910 kilometers. Several antennas. Battery failed June 1983. AMSAT-OSCAR 10 16 Jun. 1983 NASAINORAD #14129. Phase-3B. Similar to OSCAR I, with some improvements. Coatings provided better temperature control. On-board propulsion. High-altitude, elliptical, synchronous-transfer Molniya orbit at 35,449 kilometers. AMSAT-OSCAR 13 15 Jun. 1988 NASAINORAD #192 16. Phase-3C. Linear analog transponder. Magnetorquer stabilization. Elliptical orbit at 38,000 kilometers, Molniya. Carried RUDAK-l, which failed. AMSAT-OSCAR 16 22 Jan. 1990 NASAINORAD #20439. PACSAT. Sun-synchronous near-polar LEO at 800 kilometers. Store-and-forward file server and AX.25 protocol. Digital repeater. 42 ©. permitted to transmit ra- AMSAT-OSCAR Satellite Projects - Selected Overview Phase II Satellites - developmental, low-orbit, operational, longer lifespan. See OSCAR. Phase III Satellites - operational, high elliptical orbit, longer lifespan. Phase IV Satellites - operational, high geostationary or drifting geostationary orbit, long lifespan. Satellite Launch Notes AMSAT-OSCAR 1 12 Dec. 1 961 Phase-4A. 10 lb., beacon, 22-day orbit. Initiated by a U.S. west coast group. Nonrechargeable batteries. Elliptical orbit at 421 kilometers. Quarter-wave monopole antenna. Morse code telemetry. U.S. Air Force launched. AMSAT-OSCAR 4 21 Dec. 1 965 TRW Radio Club construction. Elliptical orbit at 34,000 kilometers (intended for circular orbit). No telemetry. Sleeve dipole and monopole antennas. AMSAT-OSCAR 8 5 Mar. 1978 Phase-2D. Circular LEO at 910 kilometers. Several antennas. Battery failed June 1983. AMSAT-OSCAR 10 16 Jun. 1983 NASAINORAD #14129. Phase-3B. Similar to OSCAR I, with some improvements. Coatings provided better temperature control. On-board propulsion. High-altitude, elliptical, synchronous-transfer Molniya orbit at 35,449 kilometers. AMSAT-OSCAR 13 15 Jun. 1988 NASAINORAD #192 16. Phase-3C. Linear analog transponder. Magnetorquer stabilization. Elliptical orbit at 38,000 kilometers, Molniya. Carried RUDAK-l, which failed. AMSAT-OSCAR 16 22 Jan. 1990 NASAINORAD #20439. PACSAT. Sun-synchronous near-polar LEO at 800 kilometers. Store-and-forward file server and AX.25 protocol. Digital repeater. 42 ©

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