Fiber Optics Illustrated Dictionary - Part 101 pps

Fiber Optics Illustrated Dictionary von Neumann, Janos (Jobann "Jobn") (1903- 1957) A Hungarian-born American mathematician who developed novel and influential theories in ad- vanced mathematics, game theory, and quantum me- chanics. He was fluent in several languages, gregari- ous, and considered brilliant even by the elite scien- tists he worked with on the Manhattan nuclear bomb project. Von Neumann produced a body of work in the mid- 1900s that significantly influenced the design and evolution of computing machinery, including practi- cal implementation ideas, conditional control, self- modifying code, program storage, and much more. Von Neumann collaborated with Mauchly and Eckert on the EDVAC computer project. See EDVAC. John von Neumann - Mathematician Many of von Neumann 50 contributions to game theory have applications and consequencesforprac- tical applications outside the realm of pure mathemat- ics. These can be applied in the design and operation of 'thinking' machines. von Neumann machineAclassification of comput- ing systems, based upon the work of John von Neumann, that includes single-instruction, single- data computation, which requires the repeated access and fetching of instructions and data. VoP See voice over packet. VOR VHF omnidirectional range. VP virtual path. A generic term to describe a logical connection consisting of combined virtual channels. In an ATM environment, it refers to the unidirectional transport of ATM cells belonging to virtual channels with the same endpoints, associated by a common identifier value. Related abbreviations include VPCI (Virtual Path Connection Identifier), VPI (Virtual Path identifier), VPL (Virtual Path Link), and VPT (Virtual Path Terminator). See virtual path connec- tion, virtual private network. VPC See virtual path connection. 992 VPN See virtual private network. VQ vector quantization. VRAM Video RAM. Memory chips designed to en- hance graphics display. Bisynchronous input/output. Related is SVRAM, Synchronous VRAM which reads only in or out at one time. See WRAM. VRML Virtual Reality Modeling Language. A pro- gramming language for developing 3D interactive image environments. This is apopular goal of video gaming and simulation developers. VRML allows you to create a sequence of images that can be pre- sented in a World Wide Web environment in combi- nation with a VRML clientlbrowser. There are stand- alone and Web browser-compatible VRML clients available from several vendors. See Virtual Reality Modeling Language for historical background. VRML Review Board VRB. Originally the VRML Architecture Group (VAG), founded in 1995, the VRML Review Board participates in and oversees Virtual Reality Modeling Language development, documentation, and formal specifications. http://vag. vrml. org/ VSAT See Very Small Aperture Terminal. VSC 1. See Vertical Service Code. 2. See Virtual Switch Controller. VSR See Very Short Reach. VSX Verification Suite for X/open. See X Windows System. VT-l 00 A data terminal, and terminal emulator, origi- nally developed by Digital Equipment Corporation (DEC), which has become an industry standard and is widely used in telecommunications. The VT-l 00 emulation setting in telecommunications programs works with almost any remote system and is prob- ably the one to select if you get strange characters or formatting in your software. Web browsers are quickly overtaking VT-I00 as a front-end to online sessions, but VT-l 00 is still a valuable standby when connecting to remote systems in text mode. For the most part, it has been superseded by VT-220 and other newer standards, but it is still a good fallback if com- patibility is a problem. VTAM Virtual Telecommunications Access Method. A data communications access method used in Inter- national Business Machines' (ffiM's) Systems Net- work Architecture (SNA). See Systems NetworkAr- chitecture. VTP See Virtual Trunking Protocol. VTS Vehicular Technology Society. Vulcan Street plant The historic location of the world's first hydroelectric central power supplier. It provided direct current, as did many of the early power stations. The use of direct current vs. alternat- ing current was a subject of hot debate in the early days of power stations, with Thomas Edison support- ing direct current against strong opposition by Nikola Tesla and Westinghouse, who felt alternating current was a better choice. Alternating current first gained a foothold in Europe, where the high cost ofbatter- ies spurred inventors to look for other solutions. See Mill Creek plant. © 2003 by CRC Press LLC W 1. abbrev. wait. In the Hayes modem command set, W is a dial string modifier that directs the se- quence of events to wait for the dial tone before con- tinuing with any further operations. 2. abbrev. watt. See watt. 3. The USOC FCC code for wall mount jack. 4. abbrev. white (as in B & W TV). 5. abbrev. wideband, which is now often used as a prefix with other telecommunications names and abbreviations. 6. abbrev. wide as in wide area network (WAN). 7. symb. work. 8. abbrev. World and Wide and Web (and other 'W' words) simultaneously when used with a number modifier, for example, W3. This short- hand format is areference to mathematical notation. W-CDMA abbrev. wideband Code Division Multiple Access. See Code Division Multiple Access. W-DCS See wideband digital cross-connect system. W2XBS The Radio Corporation of America's (RCA's) first television broadcasting station, located in New York city. W2XBS was established in 1928 and gave the popular cartoon character "Felix the Cat" the exposure that made him a 'star.' In F ebru- ary 1940, it became the first station to provide tele- vision coverage of ice hockey, basketball, and a num- ber of other athletic events. In March 1940, W2XBS broadcast the first opera presentation on TV. W3 See World Wide Web. W3C See World Wide Web Consortium. WAAS See Wide Area Augmentation System. WABI See Windows Application Binary Interface. WABlserver See Windows Application Binary In- terface server. WACK wait (with) acknowledgment. A signal sent by a transmissions receiving station indicating that there needs to be a wait or delay before transmitting a positive acknowledgment (ACK). For example, the receiver may acknowledge receipt of the last block of transmitted data but not be ready to receive more data, a common situation with network printing de- vices or data relays or routers. WACS See White Alice Communications System. waferA fine thin disk, usually cut from alarger piece of the substance. Many materials are cut into wafers including semiconductor materials, quartz crystals, and synthetic gems used in optical systems. Silicon is one of the most common materials used in semi- conductors. Many electronic chips are layers of wa- fers and photovoltaic panels are arrays of wafers. Since many wafers used in electronics and other in- dustries are extremely thin, production methods are very specialized. A traditional metal saw· is not ap- propriate, especially since the part cut away and lost by the saw blade, the keif, would be larger than the width of the wafer itself. See thin film WAG Wireless Application Group. See WAP Forum. WAIS See Wide Area Information Server. Wait on Busy U.K. term for a Call Waiting type of optional subscriber service in which a caller encoun- tering a busy signal can wait on the line until the call in progress is over and be automatically connected. walkaway An individual who leaves a process with- out completing it. This is an important concept in pro- gramming and many aspects of networks. Operators, software developers, and hardware manufacturers must anticipate possible walkaways and decide when to turn offa system or time out an abandoned process. • On ATMs, a user may walk off and forget to take the bank card. Some machines will beep loudly to alert the user before she or he is out of ear- shot. Some are programmed to recall and hold the card if it is not removed in a specified amount of time. On computing systems (especially shared net- work terminals) processes are often timed out and the user may be logged off after a certain period of inactivity. This is particularly impor- tant if there are limited logins available or lim- ited IP numbers assigned to Internet connections that must be shared among many users. • In telephone networks, auser might walk away without hanging up the line. In this case, the phone signaling systemmay detect the inactiv- ity and send the message "Ifyou'd like to make a call, please hang up " If this fails to get at- tention, it may be followed by a loud intermit- tent raucous buzzing sound. On information kiosks or computerized library card catalog systems, users often leave the in- formation system in various states that are con- fusing to a new user accessing the terminal. The software may be programmed to return to the main menu after aperiod of inactivity. 993 © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary waitstate In computer programming and processing, a time during which the processor waits. This may be explicitly established or may be dependent upon other events. Wait states are introduced for many rea- sons, for timing, synchronization, to reduce power de- mands, etc. They are especially prevalent in systems where there is a disparity between the processing or data transfer speeds ofvarious interconnected com- ponents. The wait state can help manage these dis- crepancies by 'slowing down' the faster components relative to others. Wake-on-LAN An mM system for enabling central- ized network systems to 'wake up' or power on re- mote workstations. This is useful for remotely updat- ing software, logging files, and uploading or down- loading messages or other files. walk time Propagation delay in a Token-Ring net- work. Walk time plus service time combines to form scan time, the mean interval between the arrival of tokens at any given station. walk-through Aprocess of being presented or go- ing through the basic physical, visual, or functional aspects of aproduct or process. Thus, a network ISP might walk auser through installation and setup ofa modem. (Use a hyphen when it's a noun, and a space when it's a verb.) walkingcode 1. Computer code that ''walks through" a region of memory, code, or file data unit by unit. Depending upon the function, data may be altered as it travels through the code. Examples include tree walking code for hierarchical data structures or stalk walking code for searching through a stack. 2. An in- telligence professional, code expert, or messenger who memorizes infonnation to be imparted at another time or location or who speaks in a code or natural language that can only be understood by a few people. 3. In computer simulations, code that enables the user to walk through a modeled environment such as plan- etary terrain. 4. In robotics, software algorithms or heuristic procedures that enable a robot to navigate terrain in a manner somewhat like legged creatures. wall outletAwall-based electrical or fiber connec- tion point for various devices designed for easy con- nections, often positioned above the baseboard or at shoulder height. Some devices are semipermanently wired into wall outlet (e.g., wall phone), but many wall outlets are designed for the modular, temporary installation of electrical cords, transmission cords (e.g., extension phone), and other connections. wall telephone Atelephone designed to mount on a wall at a comfortable height for the user. Wall phones were common until the 1960s when they began to be superseded by smaller, portable, plugin "extension" phones. Wall phones are still used in premises where theft might be a problem (restaurants, pay phone booths, etc.). Wall, Larry Software author ofm, a popular news- reading system, and Perl, a significant interpreted scripting language widely used on the Internet. Larry Wall has also authored several bestselling program- ming books, most notably books on the Perl program- ming language. See Perl. 994 Wollaston prism A unidirectional light-refracting component with a high spectral range. A Wallaston prism is constructed by combining two similar trian- gular prisms with their optical axes perpendicular to one another. Epoxy is commonly used as a bonding agent. In use, it is oriented with the optical axes of the two bonded prisms perpendicular to the incident light beam. A Wollaston prism can be made from a number of types of transparent crystal-like materials (e.g., quartz), but the use ofIceland spar helps maximize beam deviation. Iceland spar is also used for Nicol prisms. A Wallaston prism can be used to split a laser beam into two beams. The exiting beams will be oppositely polarized from one another, with the angle ofdevia- tion related to the wavelength of the beam. The two sections of the prism may be the same size or the wedge angle may be adjusted to further control beam divergence. See Iceland spar, Nicol prism. Wollaston Prism In a Wollaston prism, the incident light beam (I) is refracted into two oppositelypolarized beams (R J , R) when it encounters the bond between the two prisms. The primary difference between the Wallaston and Nicol prisms is that the Nicol prism laterally diverts one of the beams through the first blockwhile the other beam travels through the second block, whereas the Wallaston prism refracts the beams in almostsymmet- ric directions through the second block. Wollaston, William Hyde (1766-1828) A multi- talented English chemist and physiologist who estab- lished a lab at the Royal Society, in 1793, and im- proved upon the voltaic pile (the forerunner ofstor- age capacitors), in 1813. Wollaston made many con- tributions to the development of optical instruments and their application for studying optical properties in various materials. In 1802 he developed a refractometer to measure the refractive indexes of various materials and, in the same year, discussed his verification of the unique refractive properties of Iceland Spar to the Royal Society. In 1809, he devised a crystal goniometer to study crystal angles that was more effective than tra- ditional contact goniometers. Sometime around the late 1700s, Wollaston observed thin, dark lines in the solar spectrum when light was passed through a thin slit and a dispersing prism. J. Fraunhofer later made the connection between these lines and the spectral properties ofmaterials and © 2003 by CRC Press LLC they are now called Fraunhofer lines or the Fraunhofer spectrum. Wollaston also had an interest in crystallography and devised instruments to help him study and infer their atomic structure. See Wollaston prism. WAN See Wide Area Network. WANMC See Wide Area Network Management Center. wander Timing deviation or drift. In networking, especially high speed networks in which synchroni- zation is important, wander and jitter can contribute to signal degradation. Physical factors such as con- nectors, regenerators, or temperature variants can contribute to wander due to propagation delay. Over longer distances, this effect can become magnified, with the pulse position gradually shifting. In SONET networks, wander has a more specific meaning; it consists ofa phase variation tracked and passed on by a phase-locked loop. This is managed by tracking the incoming signal and passing it through a filter, to extract timing data. Wang Global A finn that fonned an alliance with Microsoft to provide local area network (LAN) ser- vices. Wang Global was merged into Getronics NV, a Netherlands information technology (IT) services firm, in 1999. WAP Wireless Application Protocol. See WAP Fo- rum, Wireless Application Protocol. WAP Forum, WAP Application Protocol Forum Ltd.An industry trade association representing mem- bers from all sectors of the mobile communications industry supporting the Wireless Access Protocol (WAP). The Forum is focused on developing and pro- moting interoperable, securable wireless network technologies and standards and in supporting their deployment and utilization. W AP pursues these goals through the establishment of Charters that are handled by Specification Working Groups (SWGs) and Expert WAP Subgroup WAP Forum Groups Summary Description WAP Architecture - chartered Aug. 2000 by the Specification Working Group The development of wireless architecture to provide a framework for specifications built around Wireless Application Protocol (W AP). This is an ongoing project requiring consistency, completeness, and conformance to WAP specifications. Open to all members. Wireless Application Group (WAG) - chartered Jan. 2001 by the Specification Working Group Responsible for specifying WAP application technologies, including application enablement features such as programming interfaces, content formats, and user agents (VAs) to enable data services on handheld devices. WAG will be active as long as specifications and their maintenance are required and is chartered to cooperate with various standards bodies and specification groups. Although one of the more recent Working Groups, much of the effort within the W AP Working Groups has concentrated on this group. Open to representatives of member companies. Wireless Protocols Group (WPG) - chartered Oct. 2001 by the Specification Working Group Responsible for defining protocols related to unreliable and reliable data transfer between network entities, provisioning ofWAP client devices, and supporting protocols and protocol services. Open to all members. Wireless Interoperability Group (WIG) - chartered Sept. 2001 by the Specification Working Group Ensure the continued development ofWAP certification, the continued review ofWAP conformance and specifications, and the development and validation of test suites for conformance. Open to individuals employed by member companies. Wireless Telephony Applications (WTA) - chartered Feb. 2001 by the Specification Working Group Responsible for defining a framework for making simple, secure, extensible mobile network services accessible through WAP services. It further assists the WAE group in defining a WAE architecture that enables a single WAP application-level architectural model. Open to member companies. Wireless Security Group (WSG) - chartered Feb. 2001 by the Specification Working Group Responsible for specifying WAP security protocols and services as well as interaction with entities that serve security purposes. Open to member companies. Multimedia Expert Group (MMEG) - chartered Mar. 2001 by the Technical Working Group A coordination and information-sharing group responsible for defining requirements, use cases, and/or recommendations focusing on mobile multimedia applications and services and for positioning WAP as the preferred platform for developing wireless multimedia services. Subgroups concentrate on specific technologies such as Smart Cards (SCEG), telematics, wireless developers, and others. Open to member company representatives and multimedia communications experts. 995 © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary Working Groups (EWGs). Groups are represented in the W AP Forum Groups Summary chart. The WAP Forum has also initiated a developer reg- istration and content verification program and aW AP certification program for manufacturers to apply for certification testing for compliance to the W AP pro- tocol suite. See Wireless Access Protocol. http://www.wapforum.org/ WAP Security Toolkit WST. A suite of security mechanisms to support security aspects of the Wire- less Applications Protocol developed by the W AP Forum for wireless portable devices. See WAP Fo- rum, Wireless Transport Layer Security. WAR See Wireless Application Reader. war dialerAn automated dialing system that sequen- tially dials a new number for each succeeding call, sometimes taken from a computer database. War di- alers are used by those dialing to a large number of phone-access BBS systems, by collection agencies, telemarketers, and teleresearchers. There are restric- tions in some areas on the use of war dialers for com- mercial solicitations. war room A strategy and decision-making facility, often related to critical big business or government activities. The war room may be a closed, secure en- vironment with no equipment other than perhaps tables and chairs, or it may include sophisticated elec- tronics for monitoring and communications. The u.s. Department of Defense opened a new war room in the Pentagon in 1969. It was equipped with a variety of high technology systems, including closed-circuit television, teletype communications, and various data processing systems and has since been updated to reflect the evolution in technology. War rooms are also common to specific command centers and are often interlinked. F or a lighthearted introduction to war rooms, the Hawk Films/Kubrick/Peter Sellers movie Dr. Strangelove is a classic parody of war room activi- ties. See skunkworks. warble tone Atone resembling abird's warble in that it fluctuates in tone periodically, sometimes quickly. Because people tend to notice fluctuating tones more readily than steady sounds, warble tones are often used as signal tones, as on public address systems. A warble tone is usually one of the options included with multitone generators, which also feature sirens, steady tones, and timed pulses for various public or employee alert needs. Warble tones are used diagnos- tically in conjunction with an integrating detector device to measure crosstalk in a transmissions line. WARe See World Administrative Radio Conference. warm boot Restarting a system without powering it off. On a computer, this is often accomplished by se- lecting a 'restart' menu item or using a designated combination of keyboard keys. On a computer, a warm boot typically resets most of the operating sys- tem and basic hardware configuration parameters, but may not go through the entire repertoire of hardware systems test sequences that may be stored in ROM. See reboot. warm image assessment WIA. Using video imaging 996 to assess a component during heat treatment. For ex- ample, in fiber filament splicing, an arc is sent across the splice area to melt together the fiber ends and the WIA system locates the core and processes infonna- tion as the fusion arc causes the light-conducting core to glow. See fusion splicing, profile alignment system. warranty A promise on the part ofa manufacturer, retailer, or service provider that the goods or services provided will meet stated tenns of manufacturing quality, use, or lifespan. Most warranties are limited to manufacturing defects, and refunds, replacements, or damages up to the original price or replacement price of the product. Terms ofwarranties in the com- puter industry tend to be about three months, although longer warranties on equipment are now beginning to be honored, ranging from one to five years. Few warranties will cover abuse, loss, or damage from natural disasters. Washington Internet Project A communications project with a portal on the Web providing news, views, discussion groups, an index of regulatory pro- ceedings, and other communications venues for the discussion of significant Internet issues related to fed- eral and state governments. It is also known as CyberTelecom. http://www.cybertelecom.org/ WASI Wide Area Service Identifier. watch, watchpointAmeans of monitoring program functioning, usually within a software debugger, while the application is being executed. Watch com- mands are often used in conjunction with trace and break commands and watchpoints are set much the same way as tracepoints. water bore A device that uses a highly pressurized jet of water to bore holes intended for the insertion of underground conduit and cabling. WATM Wireless ATM. A number of initiatives are under way to provide better support for wireless ser- vices over asynchronous transfer mode (ATM) net- works. One of the proposals is for a Radio Access Layer (RAL) by the Olivetti Research Laboratory, which has developed a prototype wireless ATM lo- cal area network (LAN). See Research in Advanced Communications in Europe. WATS Wide Area Telephony Service, Wide Area Telecommunications Service. A discounted long-dis- tance service. This service originated from AT &T, but the name became generic and is now broadly used. WATS services can be incoming, outgoing, or both; WATS lines can be installed with incoming and out- going services handled over the same line (al- though this may limit the service). As with many dis- count services, the savings are dependent upon the pattern of usage. IfWATS lines are used more often and longer, the savings may be negligible or nulli- fied. Watson, Thomas A. (1854-1934) A multitalented machinist and famed assistant to Alexander Graham Bell, Watson filed for a telephone patent for a two- bell ringer in 1878. He also designed the Watson board, a very early and not entirely practical, tele- phone switchboard. By 1901 he was operating the largest shipyard in the nation, but was replaced as © 2003 by CRC Press LLC head of the company and left the finn to pursue ge- ology. With encouragement by Bell, he subsequently studied voice (Bell was asuperior orator) and became an actor and playwright. Thomas Watson - Telephone Pioneer Thomas A. Watson, approximately 1914 or 1915. [Library of Congress American Memory Collection.] Watson, Thomas J., Sr. (1874-1956) Watson joined the Computing-Tabulating-Recording Company in 1914 and became President the following year. In 1924, the Computing-Tabulating-Recording Com- pany became International Business Machines (IBM), a significant firm in computing history. After four decades at the helm, he passed the position on to his son, Thomas J. Watson, Jr. (1914- ) who also "inherited" a number of coveted board positions in the business community. See Hollerith, Herman; In- ternational Business Machines. Watson, ThomasJ., Jr. (1914-1993) The son of bus i- ness magnet, Thomas J. Watson, Sr., Watson was granted a degree at Brown University. According to his biography, he was not very academically inclined and got his degree with help from scholarship dona- tions by his father. Watson, Jr., became a sales repre- sentative for IBM and then took time away from the company to serve in the U.S. Army Air Corps during World War II. He rejoined IBM in 1946 and became Vice President and a member of the Board. In 1956, he succeeded his father as Chief Executive Officer (CEO). Following a heart illness, Watson stepped down from the position of CEO in 1971, but remained as Chairman of the Executive Committee until he re- tired in 1985. Watson, Research Center Thomas J. The Thomas J. Watson Research Center is headquarters for the IBM Research Division, with eight laboratories worldwide. Historically, the lab is descended from the Watson Scientific Computing Laboratory that was opened in February 1945 by Thomas 1. Watson, Sr. and Nicolas Murray Butler, President ofColumbia University. The IBM/Columbia facility was expanded in 1953 and ceased operations in 1970. A new lab, also named after the longtime President of IBM, was established by IBM in 1961. This center focuses on physical, mathematical, and computer sciences; tech- nology; semiconductors; and information services. Watson, William (1715-1789) An English experi- menterwho demonstrated in 1746 that electrical cur- rent could be sent through a wire about 3 kilometers long, using the Earth as a return conductor, a tech- nique later applied in many technologies including early two-way telegraph systems. watt W. An absolute meter-kilogram-second (MKS) unit to describe electrical power that is equal to the amount of work done at the rate of one absolutejoule per second. Described a different way, a watt is the electrical power expended when 1 ampere ofdirect current (DC) passes through a resistance of 1 ohm. F or large units of power, the kilowatt (1000 watts) is typically used. See Ohm's law; power, electrical; Watt, James. Watt, James (1736-1819) A Scottish inventor who pioneered the steam engine, after whom the watt is named. WATTC See World Administrative Telegraph and Telephone Conference. wattmeter An instrument for measuring electrical power in watts. The wattmeter is similar to a dyna- mometer, which measures force or power in that it employs a moving coil and a field coil; however, the windings on the coils differ from the dynamometer. See dynamometer. wave Aperiodically oscillating or undulating process, or physical or electromagnetic phenomenon. The length of awave is related to its frequency. High-en- ergy waves such as X-rays are shorter than lower- energy waves such as light waves. WAVE A commercial product from MPR Teltech Ltd. which permits the simultaneous realtime connection of up to eight different sites through ATM switches for broadcast TV quality videoconferencing. wave audio See waveform audio. wave division multiplexing WDM. A means of us- ing separate channels grouped around distinct wave- lengths to increase the capacity of afiber optic trans- mission system. Proposed methods for multiple wave division are known as dense wave division multiplex- ing (DWDM). See wavelength division multiplexing. wave filter Adevice such as a transducer that sepa- rates waves on the basis of frequency. Some loss oc- curs during this process, depending upon the method used and the characteristics of the wave. See wave trap. wave length See wavelength. wave packet Ashort burst or pulse of waves. wave trap A device usually placed between the re- ceiver and the incoming waves that excludes un- wanted waves, especially undesired frequencies or interference waves. Like the receiver itself, a wave trap is often tunable to optimize control over incom- ing waves. See wave filter. 997 © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary waveform The shape, or spatial characteristics, of an electromagnetic wave. 2. A graphical representation of the spatial characteristics of an electromagnetic wave, as on a scope or 2D or 3D coordinate system illustration or modem. Waveforms are typically graphed according to amplitude across time. Wave- forms with certain recognizable shapes, when graphed, have been given names to distinguish them from one another. waveform audio A digital representation of sound waves, often created by sampling through a pulse code modulation (PCM) technique. Waveform edit- ing on microcomputers became well supported in the mid-1980s. The early Macintosh supported audio waveforms, and many pioneer computer musicians used Macintosh music sequencing and editing soft- ware to create electronic music compositions. The Atari ST was released with a basic midi device built in and the Amiga in 1985 came with built-in multiple channel 8-bit stereo sound. By the late 1980s, 16-bit third-party sound cards were available for most of these computers. Todd Rundgren, musician, com- poser, and multimedia designer, began using Macin- toshes and Amigas to create digital sound videos and CDs in the mid and late 1980s. There are many file formats for storing sound waves, and sound files can be played from Web pages on the Internet with browsers that support sound (assuming the computer has a sound card; most types of com- puters came with built-in sound cards by 1986). The .wav extension is commonly used to designate audio files ofaparticular format on the Internet. waveform editorAn applications program on a com- puter, or specialized electronic device, which allows the user to display, evaluate, and alter the character- istics of a wave. A computer display often uses a graphics system to represent the wave, as in tradi- tional oscilloscopes. The dials on the simulated com- puter scope are often represented as buttons on the screen or may be input from ajoystick or specialized peripheral. Waveform editors are used to alter the characteris- tics of music patches, voice, or speech files. Adjust- ments can alter the volume, tone, hannonics, echo, and other characteristics, and when converted to digi- tal form on the computer, the adjusted files can be stored and replayed later, or cut and pasted to create songs or speeches. Digital sound editing with a wave- form editor can be combined with digital video se- quences to synchronize the sound and video and to "put words into people's mouths." See waveform au- dio. waveform monitor An oscilloscope or oscilloscope- like computer applications program that surveys an input signal and displays its characteristics on a screen. Typically there are dials or graphical user in- terface gadgets and buttons to adjust the displayed wave. wavefront control, wavefront distortion compen- sation A type of image "sharpening" mechanism in which certain types ofdistortion (e.g., image sharp- ness or focus), which may be introduced as the wave 998 passes through an aperture, are corrected on the other side. It was historically called aperture tagging. The type and means ofcorrection depends upon the application, the character of the wave, and the preci- sion needed. In conjunction with awavefront detec- tor, correction may be applied by phase modulators, data processing algorithms, or micro-electromechan- ical systems (MEMs). Wavefront control to correct aperture distortion is applicable to a number of digi- tal imaging, laser, telescopic, and scintillating sys- tems. At supercooled temperatures, micro-machined mem- brane deformable mirrors (MMDMs) have been stud- ied as potential wavefront correctors. waveguide A device for confining and channeling the propagation of electromagnetic waves, often through a hollow round tube, hollow rectangular tube, coaxial cable, or fiber optic cable. The interior environment of the waveguide will vary with the type of wave be- ing channeled, since it must allow sufficient room relative to the characteristics of the wave so as not to change or diminish the signal. Thus, waveguides are more practical for high frequency waves such as mi- crowaves. waveguide dispersion The process by which an elec- tromagnetic wave becomes distorted as it passes through a waveguide. Since the dimensions and shape ofa waveguide interact with the phase and velocity characteristics of a wave, the waveguide's geomet- ric properties may cause dispersion of the guided sig- nal. waveguide laser A gas laser that incorporates a tube as a waveguide to channel the direction of the laser beam. waveguide lens A device used with microwaves, in which the waveguide elements act as lenses to pro- duce the required wave phase changes through refrac- tion. waveguide phase shifter A device that takes the phase of the incoming waves and adjusts them in terms oftheir output current or voltage. waveguide propagation A type of long-range com- munication that makes use of the atmospheric wave- guiding channels that arise between the ionospheric D region and the Earth's surface. See ionospheric sublayers. waveguide scattering Scattering of an electromag- netic wave that occurs due to the geometric charac- teristics of the waveguide structure, as in an antenna or fiber optic cable, not due to the materials of which the waveguide is constructed. WaveLAN A commercial IEEE 802.11-compliant wireless local area network (LAN) system. WaveLAN was originally introduced in North America by AT&T in 1990 and 1995 and in Austra- lia and New Zealand by Lucent Technologies in 1998. The system has been installed in more than 50 coun- tries overall. Without extension antennas, the system has· a range of up to about 400 meters. Early versions of WaveLAN used 915 MHz, while newer WaveLANs use 2.4 GHz direct sequence spread spectrum (DSSS) © 2003 by CRC Press LLC technology and are designed to co-exist with stan- dardized 10-MBps DSSS technologies. wavelength The distance, when measured from any point on a wave, to the corresponding point in the phase of the next wave in a related type or series of waves, stIch as sound or light waves. Awave's length is sometimes described in units of distance and some- times in tenns of the time it takes, from the phase of a wave to the corresponding phase of the next related wave, to travel through the same point. Waves can differ dramatically in length, as can be seen, for example, from the various categories of des- ignated radio bands, which range from a single mil- limeter (EHF band) to tens of kilometers (VLF band) when expressed in distance, or from 30 to 10 kHz when expressed in frequency or cycles per second. See band. Wavelength-Agile Optical Transport and Access Network See WOTAN. wavelength-shifting WLS. The property of a Basic Wave Concepts B '" 11\1\1\ ' 1\' f\J\ t',,;" '<;;' , ' • ". '.' " ;. A Wave motion in familiar objects can illustrate some of the basic concepts related to waves in general, including those that can t be seen, such as acoustic and electromagnetic waves. Imagine a string attached to a fIXed point (diagram A) that is given a shake to set it in motion. The kinetic enetgyfrom the pulse is transmitted to the string and moves towards the fIXed point in the direction away from which the wave was initiated. The stringvibrates in only one plane and is known as a traveling wave. Thus, a traveling wave moves perpendicular (normal) to the longitudinal axis of the medium, in this case, the string. If there were no friction or obstacles to impede its progress, the pulse would continue indefinitely. However, even if the wall were infinitelyfar away, the wave would eventually die out due to attenuation from the string 50 interaction with air, which serves to gradually dissipate the energy. Waves can move in otherways than the simplepulse in the string on the left. In the metal spring (diagram B) apulse initiated by pulling longitudinally on the spring results in a different type of motion. The kinetic energy alternately compresses and expands the elastic segments of the spring, pulsing the ene7gJ' longitudinally along the axis of the spring. Longitudinal wave compression in a medium is characteristic of sound waves. Without a medium in which the molecules can alternately move closer together andfarther away, there can be no sound. That swhy there is no sound in a vacuum. Complex waves can also be combinations ofbasic wave motions. For example, the ripples at the surface of apool of water are similar to the string above in that they move horizontally away from the source of the pulse, but they move in concentric circles outward rather than in one direction. Water waves also embody aspects of longitudinal waves, since the water alternately compresses and decompresses as the wave moves through it. If the waves hit an obstacle (e.g., a cliffside or the side of a boat), some of the waves will be reflected back across the incoming waves, causing interference patterns (right) that are similar to the patterns of light observed with interferometers. 999 © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary component that changes the wavelength of applied energy to re-emit it at another wavelength. For ex- ample, a scintillator can convert X -ray energy into light energy which, in turn, can be converted to elec- trical impulses to make practical use of the informa- tion. Fiber is sometimes used in a scintillating com- ponent to convert heat energy into light energy at a specific wavelength (e.g., blue light in a calorimeter) and may also be used to channel the light energy out of the wavelength-shifting component to other com- ponents. See scintillator. wavelength division multiple access WDMA. One of two common optical multiplexing techniques in which each transmitter transmits at different wave- lengths within a narrow spectrum, and the receiver extracts the desired wavelengths with a bandpass optical filter. See space-division multiple access. wavelength division multiplexing WDM. A means of multiplexing different wavelengths through the same strand of fiber to greatly increase the capacity of data transmission over fiber optic cables. Optical signals at different frequencies do not interfere with one another. The technology permits a substantial amount of data to travel over even one strand, and when the strands are bundled, it permits transmission in the terabits per second range, ample for high band- width applications like video, data, and simultaneous voice. WDM has become increasingly important to fiber optic communications, with improvements in both speed and distance making it practical for national backbones. In October 2001, Fujitsu announced hav- ing successfully tranmitted WDM signals over a dis- tance of 7400 Ian at 2.4 terabits/sec. Advances in re- peater configuration, exploiting Raman amplification technology, were also expected to increase power and reduce overall costs. See add! drop multiplexing, fre- quency division multiplexing. wavelength selector A mechanism for selecting a single channel from many channels in a multiplexed fiber optic transmission. Typically a coupler affixed to a fiber Bragg grating is used, though research in- dicates that adjacent long-period gratings may help reduce loss for selected and unselected channels. See fiber grating. wavelength shifterA device or process that takes an incoming series of waves and shifts their frequencies so the outgoing waves are related to the incoming waves, but in a different range. It is very common in satellite communications for the incoming signals to be shifted so they don't interfere with subsequent outgoing signals. In photocells, wavelengths may be shifted by means of compounds so that the length of the outgoing waves is related but greater. wavelet analysis Wavelet analysis involves looking at time and frequency. A prototype function (analyz- ing wavelet or mother wavelet) is used as a starting point for dilations and translations by creating a high- frequency reference and a low-frequency reference, which are analyzed, in turn, for aspects of time and frequency. See wavelet theory. wavelet fIlter compression An analysis low/high- 1000 pass filter technique used in wavelet compression by selective quantization in which images are decom- posed into frequency bands. Wavelet encoding com- bined with vector quantization (VQ) has been shown to be a good means of compressing image data, and several schemes for accomplishing this have been de- veloped. See wavelet. wavelet packets Calculated linear combinations of wavelets that retain many of the properties of the par- ent wavelets from which they are derived. wavelet theory A set of mathematical concepts and techniques related to the representation and manipu- lation ofoscillating wave forms according to scale. Wavelet analysis provides a means to use approxi- mating functions contained within finite domains and are well-suited to representing data with sharp dis- continuities. Wavelet theories and algorithms are being applied to audio and image compression with some practical and interesting results. When wavelet concepts are used in image compression, they share some characteris- tics with discrete cosine transform (DCT), although the functions used are more complex than cosines. Wavelet compression is sometimes used in conjunc- tion with other methods, such as vector quantization, to provide low-loss, high-compression ratios. They have also been used in turbulence studies, human vi- sion, radar systems, astronomy research, and fractal imaging. Wavelets are used in conjunction with, and sometimes instead of, Fourier transform methods, depending upon the application. Unlike Fourier trans- forms, wavelet transforms are not limited to sines and cosines, and can comprise an infinite set. See discrete cosine transform, Fourier transform, wavelet trans- form. wavelet transform, discrete wavelet transform D WT. A linear mathematical technique that is a sub- set of wavelet packet transform. DWT is used to gen- erate a data structure with segments of various lengths. In a sense, a transform is a means of rotat- ing a function so it can be visualized and analyzed with a different set of tools, those tools being not only mathematical algorithms, in this case localized fre- quency wavelet functions, but also conceptual mod- els. To simplify calculations, the DWT is factored into a product with a few sparse matrixes using self-simi- larity. Wavelet transforms differ from Fourier trans- forms in that they are localized in space, and an infi- nite possible number of basis functions can be applied to them, unlike Fourier transforms which use only sines and cosines, but they also share some common basic properties. See Fourier transform, wavelet, wavelet packets, wavelet theory. wavelet types Due to the variety of possible types of wavelet transforms, some wavelets have been grouped into families, on the basis of vanishing mo- ments, and subclasses, on the basis of the number of coefficients and level of iteration. Many more await development and discovery. The Daubechies wave- let family has a fractal structure. Others are Symmlet, Coiflet, and the simpler Haar family, often used to introduce wavelets in educational contexts. © 2003 by CRC Press LLC wax master An original physical master intended as a prototype for making one or more copies, usually with a more durable material. Since wax is easily shaped, stretched, changed, and otherwise manipu- lated, it is a good medium for creating prototypes of production parts. Wax is used to design jewelry, sculpture, certain types of audio recordings, proto- type components, and more. Once sufficient copies of the original are made, the wax is sometimes re- used for other proj ects. way station An intermediate office in a communica- tions line. An intermediate phone in a way circuit, one which is not the main console. way wire, way circuitAparty line circuit that con- nects a number of subsidiary stations to a main switching or relay station. See party line. WBC wideband channel. WBEM See Web-Based Enterprise Management. WCAV Web Clipping Application Viewer. See Web Clipping application. WCP 1. See Web Clipping proxy. 2. See Wireless Certificate Profile. 3. wireless communications plat- form/product. 4. See wireless communications pro- tocol. WDM See wave division multiplexing. WDMA See wavelength-division multiple access. WDP 1. See Wireless Datagram Protocol. 2. Work! Workforce Development Program. wearable public key infrastructure WPKl. A pub- lic key infrastructure and accompanying applications described by Muller and Smart in June 2000 for use with the Bristol University Cyberjacket. It is a low- computational-overhead system for providing au- thentic records of meetings and conversations and a password system where the user doesn't have to re- member passwords to facilitate wearable computing. Web colloq. See World Wide Web. Web address See Uniform Resource Locator. Web browserA display and hypertext client used as a front-end to Web-related services on the Internet. For a fuller explanation see browser, Web. Web Clipping application WCA. A software appli- cation technique used by Palm Computing to provide the capability to utilize a small Web site or related type of database on a wireless Palm PDA device. These have also been called Palm Query applications (PQAs). A WCA is a form of application partition- ing in the sense that part of the application is on the device and part of the information is presumably be- ing accessed from a remote proxy server that con- nects, for example, to a remote Web site on the Inter- net. This approach is intended to reduce download times and to provide a solution for Web access with appliances with limited resources (as with wireless handheld devices). A Web clipping application uses a subset of HTML (hence the tenn clipping) to create basic forms, graph- ics, and hyperlinks, which is then compiled with the Web Clipping/Query Application Builder (WCAB or QAB). The application runs inside the Web Clipping Application Viewer WCAV. Web Clipping can be used to implement a number of types of micro- browsers. See microbrowser, Web Clipping proxy. Web Clipping proxy WCP. Web clipping proxy serv- ers provide an environment for accessing Web-type information via Web Clipping applications. The ap- plication connects with the WCP through a wireless connection, makes a request that is handled through the Internet by the WCP and sent as a compressed product back to the wireless device and Web Clip- ping app. It may also be used for simulating and test- ing Palm as Web Clipping applications. See Web Clipping application. Web hostingA service in which Internet Service Pro- viders (ISPs) enable a business or individual to store Web pages on the ISP's computer system, instead of on the user's computer. Since an ISP's machines are typically connected to the Internet all the time and since a certain amount of Web server setup is needed to make a Web site function properly, it is very prac- tical to have the ISP manage the administration of the Web server. The design, management, aQd updates of the individual Web page are left up to the user or can be handled by the ISP for a fee. An ISP can also arrange for the registration ofa do- main name for the Web site, with the user paying the fee to the ISP, who passes it on to the registration au- thority, or with the user paying the registration au- thority directly and the ISP handling the setup of the necessary computer configuration. See domain name. Web master See Webmaster. Web search engine The World Wide Web is an enor- mous repository of information and it changes all the time, so there's no practical way to find a particular page without alittle help. Enterprising programmers quickly realized that tools were needed to make it easier to locate infonnation on the Web. As a result, they developed 'search engines,' which are applica- tion programs in Web format designed to facilitate the location and retrieval of information according to user-specified parameters or categories. Most search engines provide a text window for the user to type in a keyword, after which the user clicks a "Search" button, resulting in the display ofa listing ~~~~~!;~::i~!~~~h~=~~~¥~~:~:::. dreds, thousands, or even millions of 'hits,' that is, pages that include the specified keyword. It's obvi- ously not practical to try to visit several thousand sites, so most search engines allow the user to nar- row the search by adding more keywords and pro- viding operators such as AND and OR to focus the search. This can reduce the resulting hits to a more manageable number. Search engines also provide means for businesses and individuals to get their Web pages listed so others can find them. There is usually a button at the top or bot- tom of the page for this purpose. There are thousands of search engines on the Web. Many sites have their own local search facilities, but there are also a dozen or so very prominent Web search tools that are commonly used. The applications listed in the appendix all perform general searches 1001 © 2003 by CRC Press LLC . Fiber Optics Illustrated Dictionary von Neumann, Janos (Jobann "Jobn") (190 3- 1957) A Hungarian-born American mathematician who developed novel and influential theories in ad- vanced mathematics, game theory, and quantum me- chanics. He was fluent in several languages, gregari- ous, and considered brilliant even by the elite scien- tists he worked with on the Manhattan nuclear bomb project. Von Neumann produced a body of work in the mid- 1900s that. Press LLC Fiber Optics Illustrated Dictionary component that changes the wavelength of applied energy to re-emit it at another wavelength. For ex- ample, a scintillator can convert X -ray energy into light energy which, in turn, can be converted to elec- trical impulses to make practical use of the informa- tion. Fiber is sometimes used in a. wireless Palm PDA device. These have also been called Palm Query applications (PQAs). A WCA is a form of application partition- ing in the sense that part of the application is on the device and part of the information is presumably be- ing accessed from a remote proxy server that con- nects, for example, to a remote Web site on the Inter- net. This approach is intended to reduce download times and to provide a solution for Web access with appliances with limited resources (as with wireless handheld devices). A Web clipping application uses a subset of HTML (hence the tenn clipping) to create basic forms, graph- ics, and hyperlinks, which is then compiled with the Web Clipping/Query Application Builder (WCAB or QAB). The application runs inside the Web Clipping Application