Fiber Optics Illustrated Dictionary - Part 58 pot

Fiber Optics Illustrated Dictionary While Hansen went on to develop linear accelerators, the Varian brothers and other scientists, including their friend and associate, Edward L. Ginzton, used the technology to develop radar systems during World War IT, cofounded Varian Associates in 1948. The radio waves in historic Klystron tubes are drawn from a high-voltage electron beam in such a way that much of the energy is dissipated, resulting in low efficiency levels compared with succeeding technologies. However, klystron technology was never fully superseded, especially in broadcast applications, and some scientists felt the efficiency could be improved. The LewisNarian version of the klystron technology, developed in the mid-1980s, recovers the wasted energy by recycling the electron beam, effectively dou- bling the usable portion of the radio frequency and, consequently, reducing power consumption in UHF television transmitters. Commercial production of the new technology began in 1990 on the product now known as the CPI MDC klystron. Commercial broadcasting klystrons come in a variety of configurations supporting frequency bands such as the C-band at different channel capacities (usually 6, 12, or 24). There may be separate tubes for image and audio amplification. Cooling with water is typical in klystron applications where the tube becomes hot. See bunching; Ginzton, Edward; cavity magnetron; magnetron; Varian, Sigurd and Russell; Varian Associates. KMI Corporation A fiber optics and telecommunications market research and consulting firm founded in 1974. KMI is a subsidiary of Penn Well and part of Penn Well's Advanced Technology Division, with research headquarters located in Providence, RI. KMI publishes Fiberoptics Market Intelligence® as a semi-monthly newsletter and provides various commercial market studies, fiber optic systems wall maps, marketing workshops, and databases. See FiberFax, Fiberoptics NewsBriefs, Fiberoptic Undersea Sys- tems, Undersea News Service. KMID key material identifier. A term associated with Message Security Protocol. KNET See Kangaroo Network. knife-edge focusing Focus (wavefront) testing, as for scientific instruments such as telescopes. This is an aid to visually assessing a lens or mirror. Often a Ronchi screen or knife-edge bushing is placed as a mask at right angles to the light path before or behind the point of focus in relation to a lens or concave mirror to provide the knife edge. Focusing is then adjusted until the edge "cuts" the light beam exactly at the point offocus. If the lens/mirror is per- fectly shaped, the lens aperture should darken evenly. If there are aberrations, the combination of light rays before or behind the knife edge will create lighter spots. The technique, developed by Foucault (sometimes called Foucault s knife-edge test or Foucault s test), facilitates that testing of the surface quality of various lenses and reflecting elements. It is actually a special case of the Ronchi test, for components where the radius of curvature is double the focal length. 562 F or more complex instruments, or those commercially fabricated, interferometric testing is now routine. How- ever, for home-brew or less expensive components, the knife-edge test is still practical and can be set up with readily available materials. A wavefront spatial filtering technique was suggested by O. von der Loehe (1988), developed from the Fou- cault test. It uses two orthogonal knife edges to measure the two components ofa wavefront gradient. See pyramidic wavefront sensor, Ronchi grating. Knife-Edge Focusing Knife-edgefocusing is afairly straight fOlWard concept. In this example, incoming (incident) light that has been collimated (parallel beams) is aimed at a knife edge (B) used as a reference mask to determine the bestfocal point. A Ronchi grating or knife-edge bushing may be used as the mask. It is moved back andforth through the focal plane such that the pat- terns in the grating change as the light interacts with the pattern and will appear clear and even (rather than stripedorpatterned) at the sharpfocus point between the beforefoeus (C) andbeyondfoeus (D) points. It takes alittlepractice andis abiteasier with aRonchi bushing (rather than with a Ronchi screen). Knife-Edge Testing - One Example A knife-edge tester (Foucault tester) can be made fairly readilyfrom afewmaterials. It is important that the supportfor the tester is stable and still. The light source (A) projects onto the surface being tested (in this case, a concave reflector - B) and is reflected back through the knife-edge Ronchi grating or bushing (C) to the eye of the viewer (D). The eye is positioned so that the returning light is blocked by the knife edge. Aberrations in the evenness of the surface will show up as bright spots, indicating a flaw. Many commercialknife-edge testers magnify the image so thatflaws are more readily apparent. knife switch In old telegraph keys, a type of switch that could short key contacts in a series so the idle line was in a steady mark condition, with current flowing - also called a break switch. Opening the knife switch interrupted the current in all the sounder © 2003 by CRC Press LLC electromagnets on the line so that operators were made aware that a message was imminent. knockout A raised or indented region ofa receptacle which can be punched out or othetwise removed to provide access for wires,jacks, or other fittings. Com- mon in general purpose electrical junction boxes. Knowbot Information Service KIS. A uniform client/server means ofinteracting with, and displaying, information from a variety of remote directory services typically found on Unix systems, such as Fin- ger, Whois, and others. A query to KIS uses white pages services to these types of systems and displays the results of the search in a consistent format. See Knowbots. Knowbots In a Knowbot Information Service, programs that search and retrieve information from distributed databases as requested by the user. Knowbots may carry the information or may pass it among one another. See Knowbot Information Service. knowledge base system, knowledge-based system, expert system A computerized system of storing the accumulated knowledge of humans in a system which accesses and manipulates the information using artificial intelligence programming strategies and rules to accomplish information delivery and problem- solving at a sophisticated level. knowledge engineering Acquisition of knowledge from a human expert or experts and its incorporation into a computerized expert system. Knowledge Interchange Format KIF. Computer language for the manipulation of knowledge data and interchange of knowledge among disparate programs. Intended not as a user interface, but as an internal representation for knowledge within programs or related sets of programs. Knowledge Query and Manipulation Language KQML. A high level language that is part of the DARPA Knowledge Sharing Effort. It is a language and messaging protocol for exchanging information and knowledge as part of the larger project to create technology to facilitate development of large-scale, shareable databases. KQML can be used to support interoperability among intelligent agents in distribution applications. See Reticular Agent Definition Language. Knowlton, Kenneth C. (1931- )An American pio- neer in computer graphics and researcher at Bell Laboratories, Knowlton studied and experimented with many aspects of computer imagery, computer art, motion automation, and fast data storage, often in collaboration with L.D. Harmon. In 1959, Knowlton co-authored a report for the U.S. Patent Office entItled A Notation System for Trans- literating Technical and Scientific Texts for Use in Data Processing Systems. As his explorations turned to computer imagery, Knowlton grasped a concept often overlooked by artists using traditional "paint" tools in a computer environment: the computer can be used to generate types of art and images that cannot (or should not) be executed by human hands. In the course of his research, he and his collaborators produced a rich variety of mosaics, plots, grayscale images, and even computer-based films. Remember that these pioneers had to invent and write their own software systems for accomplishing their goals. In the 1960s, no commercial desktop paint and animation programs were available off-the-shelf (they weren't common until 1986). Many goals were attained by typing in raw numbers in low-level languages. To aid him in automating the animation process, Knowlton developed a motion language for creating short films. Together with filmmaker Stanley VanDerBeek, he developed a series of abstract ani- mated films called Poem Fields. The tools invented to enable artistic visions to be derived from computer technology are applicable to many areas of scientific research and manufacturing including digitization, pattern recognition, artificial intelligence, robotics, and more. In 1979, Knowlton coauthored articles on visual perception and the use of sign language as a form of telephone communication, with Vivien Tartter. Over the decades, Knowlton's interests in image processing and image generation remained strong and he has been awarded numerous patents for his work. As examples, in 1990, Knowlton and Wang Labora- tories applied for au.S. patent for what is essentially an ebook, an electronic book viewed through a video display (#5283864, 1994). Following this, in 1994, Knowlton and Wang applied for a patent for a document processing system including an optical scanner (#5517586, 1996). See Harmon, Leon; Shroeder, Manfred. Knuth, Donald (1938-) Knuth's texts on data struc- tures and algorithms are heavily used, and widely considered by programmers to be the "bible" of important basic programming structure information. Fundamental search and distribution trees and much more are in the Knuth texts. It would be difficult to develop sophisticated database software without them. Knuth is also known for authoring the powerful document system called TeX (pron. tek), which is one of the few that can handle complex mathemat- ics-related text formatting. KOLD- TV A pioneering digital broadcast station, KOLD 13 began using a networked digital video server in daily broadcasts in 1995. In October 1998, the Federal Communications Commission granted a number of commercial digital television station li- censes, including Station KNSV-TV, Phoenix, and KPHO- TV, Phoenix. Kompfner, Rudolf(1909-1977) An Austrian architect and engineer who worked in England as an ap- prentice architect in the mid-1930s where he invented a split-beam oscilloscope tube. Much of his physics background was self-taught, hands-on knowledge. Following a World War II interment, Kompfuer was put to work on the development of a low-noise Klystron amplifier. By 1943, he had invented a traveling-wave tube after which he became a scientific officer and Distinguished Scientist. Following the war, he earned his doctorate at Oxford and went to work for Bell Laboratories, studying microwave tubes and continuing work on traveling-wave tubes. 563 © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary He became one of the lead workers on the historic Echo satellite project. Kompfuer has received many engineering awards, including the Duddell Medal and the Stuart Balantine Medal of the Franklin Institute. In 1973, he received the IEEE Medal of Honor for his contributions to global communications technologies for his development of the traveling-wave tube. See Klystron, traveling-wave tube. Konen Modem Koupler A battery-powered commercial modem/modem adapter combination from Unlimited Systems. Konexx enables a modem to be hooked into various types of phone lines and cellu- lar phone systems while traveling. Kotel'nikov, VladimirAleksandrovich (1908- )A Russian contributor to fundamental research in communication theory, and theory and practical research in astrophysics. He is especially well known for the use of radio waves to locate and measure distances to planetary bodies and for contributions to early satellite communications. He is also remembered for publishing "On the carrying capacity of 'ether' and wire in electrical communication" (1933) that describes a theory of sampling and the representation of a continuous signal from discrete samples. His theories were later supported by the work of Claude Shannon. Kotel'nikov served as V.P. of the USSR Academy of Sciences and chaired the Scientific Council on radio astronomy. While at the Institute of Radioengineering and Electronics, he initiated research in the submillimeter wave band. See pulse code modulation; sampling theorem; Shannon, Claude. KPI See Key Performance Indicator. KQML See Knowledge Query and Manipulation Language. Krum, Charles and Howard An American father and son team who worked together in the early 1900s to develop and patent a variety of telegraph transmitters and printing machines. One of their early suc- cesses was a printer created by interfacing a modi- fied typewriter with a telegraph line, developed at the end of 1908. With a mechanical apparatus ready to use, it became necessary to develop some way to syn- chronize the pulses and the printing. For this, Howard Crumb applied for a start-stop patent in 1910. krypton laserA type of gas laser which is primarily krypton that can be used to produce intense red light, or when used with certain optic enhancements, several colors. This is similar to an argon laser, except 564 that it produces a little less light; sometimes argon and krypton are combined. Krypton lasers are typically water-cooled. Kurz, Karl Information on this German experi- menter is scarce (he seems to be overshadowed by Barkhausen), but he apparently collaborated with Heinrich Barkhausen in discovering Barkhausen- Kurz oscillations. See Barkhausen-Kurz tube. KS See Kearney System. KTH Kungliga Tekniska Hogskolan. The Royal In- stitute of Technology in Stockholm, Sweden. The institution provides education in optical communications within its photonics courses. KTI Key Telephone Interface. KTS 1. See key telephone system. 2. See Kill the Spams. Ku-band A range of microwave broadcast frequencies from approximately 11 to 14.5 GHzwhich is further subdivided into fixed satellite service (FSS) and broadcasting satellite service (BSS). Ku-band is used primarily for data transmission, private networks, and news feeds. Satellites transmitting Ku-band signals tend to be powerful enough for the receiving dish to be small and convenient. Uplinks are in the 14- to 14.5-GHz range and downlinks in the 11.7- to 12.2-GHz range. In November 2000, The Federal Communications Commission (FCC) extended permission to provid- ers of nongeostationary satellite services to operate in certain segments of the Ku-band and issued rules and policies to govern their operations. It was felt that this would stimulate new competitive services such as high-speed Internet access, telephony services, and media broadcasts. It was further hoped that satellite transmission availability would increase services to rural areas. The FCC determined that Multichannel Video Distribution and Data Services (MVDDSs) could operate in the 12.2- to 12.7-GHz frequencies without interfering with incumbent Broadcast Satel- lite Services (BSS). See band allocations for a chart. See broadcasting satellite service, direct broadcast satellite, fixed satellite service. KV Bell Telephone jargon for key telephones (K = key, V= voice). The term was derived from the Universal Service Ordering Code (USOC) commonly used until the time of the AT &T divestiture in the mid- 1980s. KVW Bell Telephone jargon for wall-mounted key telephones. See KV. KWH See kilowatt-hour. © 2003 by CRC Press LLC A, A Lambda, the 11 th letter of the Greek alphabet, used to symbolize wavelength, especially optical wavelength. L symb. inductance. See inductance. L CXRA backbone communications system based upon L carrier coaxial technology developed in the 1930s in the U.S., known generically by the public through warning signs as the Transcontinental Cable system. The system was intended for key government communications and civil defense, interconnected through facilities with underground repeaters, and maintained by Bell telecommunications workers, designed to transmit both telephone and television signals. In the postwar years, the system was upgraded about every 10 years. The L-l system of the 1940s gave way to an L-3 system by the 1950s and 1960s. (L-2 was used for a special installation between Washington, D. C. and Baltimore.) Later, through the use of repeaters every couple of miles, 20-tube L-4 cable centers were established approximately every 150 miles. By the 1970s, L-5 circuits had been established. The capacity of the system improved from a few MHz in the 1940s to 57 MHz in the 1970s with voice capacities increasing from a few hundred voice channels to more than 100,000. Following the Cold War, the repeater stations, which resembled stone garden sheds over concrete vaults every few miles along the cable route, were sold. The old physical infrastructure was gradually replaced with fiber optic cables (with 20 times the capacity of the L-5 system) and satellite links. See L carrier. L carrier An older, analog, frequency division multiplex (FDM), long-haul phone system that was common before digital services became prevalent (met- ropolitan areas using FDM more commonly used N carriers). u.s. Department of Defense Lcarrier communication systems in the post-World War II period stretched in two main east-west links from Washing- ton, D.C., west to California and south to the tip of Florida, with many smaller trunk tributaries. See L CXR. L multiplex LMX. Analog multiplexing circuits in Lcarrier coaxial transmissions media. L Series Recommendations A series oflTU-T rec- ommended guidelines for construction, installation, and protection of cables and other elements of outside plant telecommunications. These guidelines may be purchased from the ITV-T. Since lTU-T specifi- cations and recommendations are widely followed by vendors in the telecommunications industry, those wanting to maximize interoperability with other systems need to be aware of the information dissemi- nated by the ITU-T. A full list of general categories is listed in Appendix C and specific series topics are listed under individual entries in this dictionary, e.g., K Series Recommendations. See L Series Recom- mendations chart. L system See L CXR. Ll cache See level 1 cache. L2 cache See level 2 cache. L1 & L2 Designations for the two radio frequencies (1227.6 and 1575.42 MHz) broadcast by Global Po- sitioning System (GPS) satellites. See Global Posi- tioning System. L2F 1. See Layer 2 Forwarding Protocol. 2. Legacy to the Future. L2TP See Layer 2 Tunneling Protocol. L2TPext See Layer 2 Tunneling Protocol extensions. L-band A portion of the electromagnetic spectrum assigned for radio communications, ranging from 500 to 1500 MHz. Within this range, the frequencies between 950 and 1450 MHz are set aside for mobile communications. Global Positioning Systems (GPSs) use the L-band frequencies, as do some of the planet probe systems. See band allocations for chart. L-band, optical In optical communications, an lTU- specified transmission band in the 1565- to 1605-nm frequency range. Until 2001, this spectrum was not widely supported. The development of better efficiency, high-density erbium doping in the early 1990s facilitated the development of practical L-band systems. Benchtop erbium-doped fiber amplifiers (EDFA) may now be used with DWDM L-band networks (as they are for C-band), enabling optical amplification without hav- ing to convert optical signals to electrical and back again. In January 2001, Lucent Technologies announced it had completed the first installation of a C+L-band optical network for NTT Communications (Japan). This increased capacity by opening up the previously 565 © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary ITU-TLSeriesReeommendations Recommendation/Description L.l Construction, installation and protection of telecommunication cal?les •• in publiC;. networks L.2 ImpregnatioQofwoodenpoles L.3 Armouring of cables L.4" AluminiumcabJe sheaths L.5 Cable sheaths made of metals other than lead or aluminium L.6 Methods· ofi-eeping cables und~r gas pressure L.7 ApplicatiOtl()fjoint cllthodic protection L.8 Corrosion caused by alternating current L.9 Methods offenninating"metalUc cable conductors L.I0 Optical fiber cables for duct, tunnel, aerial, and buried•application L ll Joint use of tunnels by pipelines and telecommunication cables, and. the staridardizatjoD of underground duct plans L.12 Optical fiber'joints L.l3 Sheath jointS<andorganiZersof optical fiber cables in the outside plant L 14 Measuremenfmethodto determine the tensile performance of optical fiber cables under load L.IS OpticallocaFdistribution networks - factors to be considered for their construction L 16 Collductive plastic material (CPM) as protective covering for metal cable sheaths LJ 7 Implementation of connecting customers into the public switched telephone network (PSTN) via optical fib~rs L.18 Sheath closures for terrestrial copper telecommunication cables L.l9 Outside plantcopper networks for ISDN services L.20 Creation of a fire secllrity code for telecommunicationfacilities L.21 Fire detection and alarm systems, detector and sounder devices L 22 Fire protection 566 Recommendation/Description L 23 Fire extinction- classification and location of fire extinguishing installations and equipment on premises L.24 Classification of outside plant waste L.25 Optical fiber~able network maintenance L.26 Optical fiber cables for aerial application L.27 Method .fo17estimating .the concentration of hydrogen in optical fiber cables L.28 EXffim.alad<iitional protection for marinized terrestrial·cables L.29 As-laid report and maintenance/repair logror marini:l;edterrestrial cable installation Markers on marinized terrestrial cables L.31 Optical fiberattenuators L 32 Protection devices for through-cable penetrations offrre-sector partitions L.33 Periodic control of fire extinction devices in telecommunication buildings L.34 Installation of OpticalFibre Ground Wire (OPGW) cable L.35 Installation of optical fiber cables in the access network L.36 Single mode fiber optic connectors L.37 Fiber optic (non-wavelength selc;qtive)brapcbingdevices L.38 Use of trenchless techniques for the construction of underground infrastructures for telecommunication cable installation Investigation of the soil before using trenchless. techniques L.40 Optical tiber outside plant maintenance support, monitoring and testing system L.41 Maintenaqcewavelengthonfibers carrying signals L.44 Electric power supply for equipment installed;is outside plant L.45 Minimizing the effect on the environment from the outside plant in telecommunication networks L.46 Protection·oftelecommunication cables and plant from biological attack L.47 Access facilities using hybrid fiber/ copper networks © 2003 by CRC Press LLC unused L-band frequency range. The improvement was made possible by Lucent's new DWDM L-band optical amplifier and dispersion-shifted fiber that is more suited to carrying multiple wavelengths in the L-band than in the C-band. By the end of2001a number of leading optical firms were supplying L-band components, such as dynamic gain equalizers that could be configured by the customer for L- or C-band ranges. Optical circulators optimized for DWDM L-band applications typically come in two grades (A & B) and feature low insertion loss, high isolation and minimal distortion. LAAS See Local Area Augmentation System. label 1. A symbol, or group of symbols, often mne- monic, that identifies or describes an item, routine, record, file, application, or process. 2. In programming, a reference point, usually for a procedure, function, or subroutine. The label may have a specific meaning to the interpreter or compiler that processes the code instructions or it may be a convenience for the programmer for organizing code and simply be ignored when the code is processed, depending upon the environment. 3. In networks, a convenient name for a device to facilitate access. For example, a printer on a network known to the system as LZPTX5103, may be assigned a label such as Building 3 Laser, to make it easier for people to recognize. 4. In ATM and Frame Relay networks, a short, fixed-length identifier that facilitates packet/frame forwarding. See label switching. labelswapping In label switching networks, a router will commonly assign a new label to the received transmission in preparation for forwarding it to the next "hop" or leg in its journey toward the destina- tion. See label switching. label switching In ATM networks, a switching mechanism intended to take advantage of the flex- ibility and scalability ofInternet Protocol (IP) routing. Label switching combines some of the aspects of Layer 2 switching with Layer 3 routing, so the dis- tinction between switching and routing is not as clear as in other transmission schemes. Alabel-switching router can forward IP datagrams based upon a label associated with the packet and will usually assign a new label for the subsequent routing "hop" in the connection. See Multiprotocol Label Switching, optical-label switching, tag switching. label-switched path A network route that is established based upon a label associated with a data packet in a network, with a new label typically assigned dynamically for each subsequent hop in the path (most routers do not spport static LSPs). The path must be established before test data or communications data can be effectively routed through the LSP. A signaling protocol is typically used to set up paths. See label switching. labeled multiplexing In integrated services digital networks (ISDN) and ATM networks, a routing mechanism in which multiplexing is carried out by concatenating blocks of channels with different iden- tifiers in their labels. labeling algorithm I. A means of calculating the shortest path in network routing. 2. A means of in- serting copy protection labels into data, such as com- pressed video data, so the information can be tagged, or otherwise identified, and can only be written or read under prescribed circumstances. This type of system is being developed to enable vendors to provide digital services to home consumers without fear that the products will be widely pirated and redistrib- uted. It is being experimentally applied to the design of copy-protectable mass storage devices. Laboratory for Computer Science LCS. An inter- departmental facility at the Massachusetts Institute of Technology (MIT) engaged in computer science research and engineering. LCS was founded in 1963 with support from the u.S. Defense Department as a result of the launching of the Sputnik satellite. Members of the LCS have been involved in many important historical computer network developments including the ARPANET, Ethernet, Internet, and World Wide Web. They have also been involved in research and development of encryption technolo- ~Pi~~~E~?=~~~~i:~~~~~Ci~:~~~~ '. opment, and RSA Data Security. LCS works coop- eratively with relevant departments and with the MIT Artificial Intelligence Laboratory. LAC Loop Assignment Center. LACE See Low-power Atmospheric Compensation Experiment. lacing cord A strong cord, sometimes coated or waxed, used to bundle wires strung along the same path. ladar laser Doppler radar. See Doppler, laser, radar. LADT See Local Area Data Transport. lag To delay, linger, slacken, slow, be retarded, or tarry. Lag occurs in computer applications when the speed of the system is unable to match the speed of the interaction of the user. Lag is characteristic of dialup modem communications, where the speed of the data transmission doesn't match the speed of the computer processor. Lag occurs on data networks when congestion occurs; that is, the number of pack- ets may exceed the ability of the system to handle and transport them. See cell rate, hysteresis, leaky bucket. LAGEOSI The Laser Geodynamics Satellite, developed and launched by the Marshall Space Flight Cen- ter in May 1976. LAGEOS was one of the earlier remote-sensing satellites used for Earth sciences research. Lakeside Programming Group A collaboration of programming friends, which included Bill Gates, Paul Allen, and Ric Weiland. The group created a payroll program in COBOL for a company in Port- land, Oregon. They were informally named after the Lakeside private school attended by its members. At the same time, the group had a programming contract to build scheduling software for a school. Eventually Gates and Allen formed Traf-O-Data in the early 1970s, to create a traffic analysis program. The partnership that led to the formation of the 567 © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary Microsoft Corporation. See Gates, William; Allen, Paul; Microsoft Corporation. LAI See Location Area Identity. LAM 1. line adapter module. 2. See Lobe Attachment Module. LAMA See Local Automatic Message Accounting. lamb dip In laser technologies, a point in the absorption spectrum that dips (is lower in intensity) in relation to the overall absorption cross-section (which is generally Gaussian). When plotted, it graphically re- sembles a small crater (there may be small subsidiary peaks within the overall transmittance dip). The location of the lamb dip provides a reference for tran- sition frequencies that are Doppler-shift-free, which is useful in certain laser spectroscopy applications. A lamb dip may be observed in laser operation or may be generated by a sodium cell, for example, for tun- ing and actively stabilizing a laser (e.g., a dye laser). Passing a same-frequency probe beam through a laser in the direction opposite the laser pumping beam reveals the transitional lamb dip pattern. lambda (symb. - A) The 11th letter of the Greek alphabet, used as a symbol in a number of mathematical and logical contexts. Lambda symbolizes the null class, von Mangoldt's function, and wavelength. Lambda-Connect Project A Lawrence Livermore ultracomputing development project funded by the Laboratory Directed Research and Development Pro- gram. In recent years, the performance gap between processing units and the links between the processors has been widening. This interesting project in parallel multiprocessing seeks to narrow the gap by overcoming the bottlenecks in transmitting data among processors via traditional electronic connections. The LL team believes it can replace electron flow with photon flow (light pulses of different wavelengths). Speed improvements of up to 32 times are considered feasible. The use of optical interconnects also makes it practical to pack microprocessors in higher densities which, presumably, also improves data transport speeds and processing times. Ultracomputing projects are ofparticular interest to strategic and scientific computing applications and may be used by the U.S. Department of Energy (DoE) Accelerated Strategic Computing Initiative for nuclear technologies simulations and testing and to the Department of Defense (DoD) for strategic planning and intelligence gathering and processing. See lambda switching, optical burst switching. lambda switching Also called wavelength switching, this is a technique used in high-speed optical networks to switch individual optical wavelengths into different paths to route data through the network. It is more akin to circuit switching than packet switching and can be implemented as end-to-end connections. Fiber optic networks typically use lambdas (wavelengths) in the near infrared spectrum, trans- lating into frequencies of around 100 terahertz (THz). In conjunction with multiplexing, which enables many separate wavelengths to be transmitted along a single fiber, lambda switching can be used to create virtual circuits. Qwest and other carriers began 568 to deploy lambda switching in their telecommunications networks ca. 2000 and 2001. See dense wavelength division multiplexing, Gilder's law, lambda, optical cross connect. lambdasphere The environment within optical transmissions paths that channels many wavelengths. George Gilder is a speaker and well-known propo- nent ofoptically switched networks and is credited with coining the term lambdasphere. See Gilder's law, lambda switching. lambert (symb. - L) A centimeter-gram-second (CGS) system unit of luminance, equal to the bright- ness of an ideal diffusing surface that radiates or reflects light at 1 lumen per square centimeter. Lambert's law, Lambert's cosine law The reflec- tion of radiant energy incident upon a small surface in a particular direction is proportional to the cosine of the angle between the reflected direction and the perpendicular (normal) of the surface. This relationship provides a means to calculate how much of the incident light (or sound) is reflected, as- suming the reflected light is constant in all directions (essentially an ideal diffuser) and the angle of incidence and associated angle of reflectance are small. Given these parameters, the perceived intensity of the light is independent of the angle at which the reflecting surface is viewed, but will vary according to the angle of incidence at which the radiant energy en- counters the diffusing surface, as governed by Lambert's law. Stated another way, the intensity of the incident light is relative to the angle ofincidence. Body reflectance models follow Lambert's law. Lambert's law was a prevailing relationship until the 1980s. Then, the advent of graphics and acoustics modeling software and semiconductor-based instruments (e.g., goniometers) caused it to be more closely scrutinized for its generalizability for wider angles and different surfaces. In graphics, Lambert's law has been adjusted and generalized for smooth surfaces by L.B. Wolff, thus overcoming some of the "small angle" limitations of Lambert's law. In acoustics, Lambert's law's generalizability to diffusers was questioned, leading to the development and dissemination of diffusion coeffi- cient data in much the same way absorption coeffi- cient data has been available. See Bouguer's law, incidence angle. Lambertian reflector A material that reflects light in many directions (essentially an ideal reflector), thus diffusing it according to Lambert's law. See Lambert's law. lame A colloquial term often used in programming or electronics to derisively describe an uninspired or poor device, program, or solution to a problem. The term is based upon the concept of limping along on one leg and thus not embodying positive qualities such as speed, efficiency, or grace. A person who fre- quently comes up with weak or lame comments or solutions may be dubbed a "lamer." lame delegation On the Internet, a situation in which one or more authoritative domain name servers (DNS) that convert Internet Protocol (IP) addresses © 2003 by CRC Press LLC into registered names are not responding correctly for the specified domain (which may have been called by a system higher in the hierarchy). Lame delegation occurs for a number of reasons: Secondary servers, which are expected to function as authoritative servers, may not respond correctly. Ifa secondary server is un- specified, or not working correctly, the situation is lame in the sense that the second "leg" isn't working properly. Since secondary name servers are not mandated, only rec- ommended, this is not an uncommon occur- rence; most people associate this meaning with the term. • The name server may respond incorrectly from a cache rather than directly or may be configured incorrectly. • There may be a lack of communication. If users change domain names, manage their own IP numbers, or switch Web hosts without co- ordinating with the name serving authority and the ISP, all sorts of lame delegation er- rors can occur. Lame delegations can result in email delays, lookup slowdowns, and even a Web site "disappearing" from the Internet (not being accessible). If the primary and secondary servers are on the same physical machine and that machine goes down, there is no backup name server and a lame delegation would be in effect until the system came back online. See domain name server, lame. laminate n. A structure composed of layers, often tightly sandwiched or bonded together. Laminated materials are often used in electronics, from early voltaic piles, which sandwiched moistened materials between layers of metal plates, to magnetic cores and semiconductors, in which layers of various materials are combined according to their electromagnetic properties. An individual layer in a laminated structure is called aply. See semiconductor, thin film, voltaic pile. Lamm, Heinrich (ca. 1908- ) A German inventor who studied medicine at the University of Munich, Lamm was interested in creating an analogy to in- sect vision using a bundle of optical fibers. He acquired fibers from the Rodenstock Optical Works and painstakingly positioned the fibers to create a bundle that could transmit an image for a short distance. The practical limitations deterred Lamm and a similar concept had been patented already by Clarence W. Hansell who collaborated with television inventor John L. Baird, so Lamm ended up as a surgeon in America rather than a well-known inventor of fiber optics transmission systems. See Hansell, Clarence; Kapany, Narinder. lampAn illuminating device that converts energy into light (usually visible light). In its basic form, a lamp consists ofa light-producing source and a holder such as a wick in an oil-holding vessel, bulb in a handheld, battery-operated container (flashlight), fluorescent bulb in a fluorescent receptacle, light-emitting diode in an electronic device, or filamented vacuum bulb in a desk or floor stand. Lamps were used in some of the earliest communications technologies. By blocking the light from a lamp to signify dark or light, a binary communications code could be devised to send signals over distances. A shutter made the process easier. Shuttered lamps were used for many decades to send signals overland and among ships at sea. Lamps are also used as sources for photographic lighting, especially as "flash bulbs" to provide supple- mental illumination in low-light conditions. Not all lamps emit light in the visible frequency ranges. In- frared or ultraviolet light cannot be directly seen by humans, but the subjects illuminated may be seen with special equipment that translates the reflected light into visible frequencies or other forms of energy. See Edison, Thomas A. LAMP See Large Advanced Mirror Program. lampblackA sooty, dark carbon dust deposited by a smoking flame, as on the inside ofa glass lamp globe. While its presence in lamps is usually undesirable, lampblack has commercial applications in the fabri- cation of some types ofresistors. LAN See local area network. LAN adapter A hardware peripheral device or card that connects a computer to a local area network (LAN). Not all computers require LAN adapters; some come equipped with network cards and ports ready to attach to various connectors, commonly 1 DBase-Tor 10Base-2. However, some require an in- termediary device between the network card and the network cable in the form ofa LAN adapter. LAN aware Applications, systems, and devices that can recognize and appropriately respond to an inter- faced connection to a local area network (LAN). This usually involves communicating with other devices on the net as security permits, locking and unlock- ing files as needed, querying appropriately, etc. Some operating systems are designed to be LAN aware, others run with third-party software. LAN Channel Station LCS. 1. In frame-based networking, a channel protocol for LAN/mainframe in- tercommunications. In ffiM mainframe-related LCS, host applications define a consecutive pair of subchannels for channel reads/writes through TCP /IP. LCS enables a local area network (LAN) MAC frame to be transported and provides a command interface for activating/deactivating and querying LAN interfaces. 2. A Bus-Tech commercial control unit emulation (also known as 8232) that provides a pass-through for exchanging data between a local area network! wide area network (LAN/WAN) and a mainframe through TCP/IP. LAN Emulation See asynchronous transfer mode, LANE. LAN Manager An early, commercial OS/2-based multiuser network operating system intended to run over TCP/IP or NetBEUI protocols. Microsoft and 3Com's LAN Manager came in two versions: for MS- DOS, Microsoft Windows, and IBM's OS/2, and for UnixlUNIX connections. 569 © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary LAN Protocols A catchall phrase for a wide variety ofprotocols developed for local area computer networks, such as AppleTalk, Ethernet, TCPIIP, IPX, and others. LAN segment In Frame Relay, a LAN linked to another LAN using the same protocol through a bridge. See bridge, hop, router. LAN ServerA commercial multiuser network operating system from ffiM, based on OS/2 and NetBIOS. LAN Server supports a variety of client computer operating systems, including OS/2, Microsoft DOS and Windows, and Apple Macintosh. It has been superseded by the OS/2 server version. LAN switch A local area network (LAN) switch, in its simplest sense, is a stand-alone box with connections, which simply directs traffic along one or more pathways. However, with improved technology, LAN switches are incorporating more and more intelligent processing capabilities, and some are almost indistin- guishable from routers. Some are available as modu- lar peripheral cards that fit into multi switch card chas- sis. LAN switches can help reduce or more efficiently handle congestion and can improve response time on networks. They have the capability to redirect the World Wide Web queries of users to local caches, and reduce Internet queries and can help balance network traffic among servers. LANCE Local Area Network Controller for Ethernet. Land, Edwin Herbert (1909-1991) An American inventor who studied briefly at Harvard University, Land is best known for his development of polarizers, in the form of polarizing film sheets, in 1929. It is less well known that Land was a prolific inventor who earned more than 500 patents in his lifetime, most of them directly related to optics (especially photography). He cofounded the Polaroid Corporation (origi- nally the Land-Wheelwright Laboratories) with G. Wheelwright, in 1937, to develop and market his in- ventions and demonstrated "instant" photography to the Optical Society of America in 1947. He received a patent for this historic photographic technology in 1951 (U.S. #2,543,181). In 1982, Land left the Polaroid Corporation but continued research on human visual perception. The Edwin H. Land Medal was established by the Optical Society of America (OSA) and the Society for Imaging Science and Technology in his honor in 1992. Land attack, land.c A malicious software program that became prevalent on the Internet in 1997, the Land attack was similar to an earlier SYN attack program. Land was programmed to attack systems using Internet Protocol (IF) communications by interfering with the stack. Certain routers were also vulnerable. A broad segment of operating systems from Apple, Cisco, Microsoft, and Sun and several BSD systems were found to be vulnerable. Some machines crashed while others hung or experienced slowdowns, depending upon how robust the operating system was and whether it could still function while one aspect of it was caught in an endless loop through spoofing 570 that tricked the system into calling itself. A more Microsoft-aggressive version called latierra.c was later released on hacker sites. Vendors posted patches to reduce or remove the vulnerability and updated subsequent releases of software to reflect these changes. See Denial of Service attack, Trojan horse, virus. land/groove recording, land and groove recording A high-density recording technology for magneto- optical media. DVD disc surfaces are divided into annular zones, keeping the length ofa sector and the recording density mostly constant through the disc. The zones are divided into two types of tracks: land tracks and groove tracks. These tracks, in turn, are divided into sectors. The hierarchical division into smaller units is similar to the storage and access formats used on hard disks, with adaptations to fit the nature of optical disks. Data are recorded on the land (the higher surface) and the groove (the indented surface), while address information is encoded in the pits. Permanent data that are readable but not writ- able by the user are kept separate from the user recording fields. See wobbled groove, wobbled land groove. LANDA Local Area Network Dealers' Association. This is now called NetPros by LANDA. The organi- zation promotes and supports excellence among Ca- nadian resellers, consultants, and systems integrators in the information technology (IT) industries. http://www.netpros.ca/ landline, land-line, land line Communications circuits, especially telegraph and telephone, which travel through terrestrial wires and stations. Many mobile units interface with landlines, so that even if a call originates as a wireless call, it may be completed as a landline call to extend distance and free up wireless channels. LandsatA series of satellites first launched through federal funding in the mid-1960s for remote sensing of the Earth from space. The Landsat Earth sensing system launches were initiated in 1966 as a response to the announcement of plans for launching civilian Earth Resources Obser- vations Satellites (EROS). As a result, NASA began to plan a satellite launch in order to secure information on Earth resources and provide for national security provisions in space. This led to the launch of the Earth Resources Tech- nology Satellite (ERTS-l) in 1972, with similar satellites launched in 1975 and 1978. The program was renamed Landsat in 1975. Landsats 4 and 5 were launched in the early 1980s, and jurisdiction was transferred to the U.S. National Oceanographic and Atmospheric Administration (NOAA). In 1986, during the Reagan administration, jurisdiction was changed to a commercial company, EOSAT, and the primary users became large institu- tions that could afford expensive satellite data. Com- plete archiving of data was not always undertaken. EOSAT designed and built Landsat 6, which failed on launch. In 1992, legislation was passed to return future Land- © 2003 by CRC Press LLC sat missions to the public, and Landsat became part of NASA's Mission to Planet Earth program in 1994. Planning began for the Landsat 7 project. Landsat satellites are in near-polar orbits, designed to be sun synchronous; that is, the satellites cross the equator at the same local sun time in each orbit. Thus, lighting conditions are kept uniform. The satellites are equipped with telemetry and remote sensing equipment, including cameras and multispectral scan- ners. Data collected from early Landsat projects were stored in X-format, that is, band-interleaved by pixel pair (BIP-2). This format was superseded by EDIPS (EROS Digital Image Processing System) with a resolution of3596 pixels x 2983 scanlines, in band- sequential (BSQ) or band-interleaved-by-line (BIL) formats. LANE LAN Emulation. Local area network (LAN) emulation services and protocols running over asynchronous transfer mode networks. See asynchronous transfer mode and the appendix for greater detail. language In computer programming, a means of rep- resenting instructions, procedures, functions, and data through symbols and syntax which can be interpreted into machine instructions to control the computer. Common high- and medium-level programming, scripting, and page description languages include Perl, Java, C, C++, PostScript, LISP, Pascal, BASIC, Cobol, and FORTRAN. A common markup language used on the Web is HTML. There are also job con- trollanguages, description languages, graphics languages, and low-level assembly and machine languages. Language of Temporal Ordering Specification LOTOS. A language for the formal process and al- gebraic specification of computer network protocols for concurrent and distributed networks, described as ISO 8807-1990. LOTOS has been used internation- ally to specify many systems, especially by university groups. LOTOS is applicable to the specification of Open Systems Interconnect (OSI) model systems, for example. Lankard, John R. In collaboration with Peter P. Sorokin, Lankard described tunable organic dye lasers in the IBM Journal of Research and Develop- ment in 1966 at about the same time dye laser technology was being developed by Schmidt et al. in Germany. Lankard continued to study lasers over the subsequent decades, coauthoring articles on organic dye lasers in the 1960s, Q switches in the 1970s and laser applications in the 1980s and 1990s, such as laser etch- ing and thin film packaging. See laser history; Sorokin, Peter P. LANNET 1. large artificial neuron network. 2. A subsidiary company of Madge Networks, N. V., and leading supplier of next-generation Ethernet and ATM switching technologies for local area networks (LANs). LANNET was acquired by Lucent Tech- nologies in 1998. LANtastic A commercial peer-to-peer NetBIOS- based network operating system from Artisoft. It supports a variety of client computer operating systems, including Microsoft DOS and Windows, ffiM's OS/ 2, Apple's Macintosh, and various Unix clients. lap A device used for grinding piezoelectric crystals. Since the resonance frequencies of crystals are due in part to their size and shape, the lap provides a means to fine-tune the crystal. See detector, piezoelectric, quartz, Y cut. LAP 1. link access procedure. 2. See Link Access Protocol. laplaciometer An early analog calculator designed for complex mathematical work by J. Atanasoff and some of his graduate students in the 1930s. The laplaciometer was used to analyze the geometry of surfaces. These developments led to the design and creation of the historic Atanasoff-Berry Computer (ABC). See Atanasoff-Berry Computer. LaplinkA popular, practical commercial hardware/ software networking utility introduced in 1986 for transferring files between computers, especially between laptop computers and office workstations. It is very common for mobile computer users to want to transfer the information from their laptops to their desk computers, and sometimes to transfer in the other direction as well (e.g., sales leads). Laptops typically have smaller hard drives and higher security risks than desktop computers, making it advis- able to regularly move the data off the laptop. Trans- fers can be achieved in a number of ways, through a serial port, over a parallel connection, or through phone lines. In 1995 LapLink Host was added to the product line to provide technical support to remote workers. Laplink was developed by Traveling Software, Inc., a Washington State company devoted to supporting the needs of mobile users, founded in 1982 by Mark Eppley. lappingA technique for wrapping electrical tape, foil, or other ribbons around a central core so that the next edge overlaps the previous one, in order to create close contact and a good seal. lappingfilm A finely abrasive polyster substrate sold in color-coded sheets according to grade. It is commercially available in a variety of minerals, micron grades, and backings. The film may be in resealable bags to preserve its properties and prevent contami- nation by moisture and solid particles. It is available in different shapes for manual or machine polishing applications. Successive grades allow finer and finer polishing, similar to the process of using finer grades of sandpaper to finish a wood product. Plain and ad- hesive backings are available. Aluminum oxide, sili- con carbide, and cerium oxide lapping films are used for a variety of types of surfaces. Diamond lapping films are suitable for harder surfaces such as metals. Diamond lapping film is available in several styles: fine or course diamond particles can be bonded directly to film backing or the diamond particles can be encapsulated within a soft ceramic coating which is then bonded to the film. Lapping film may be used to polish fiber filament ferrules, magnetic media, oxide and thin film disks, 571 © 2003 by CRC Press LLC . LLC Fiber Optics Illustrated Dictionary He became one of the lead workers on the historic Echo satellite project. Kompfuer has received many engineering awards, including the Duddell Medal and the Stuart Balantine Medal of the Franklin Institute. In 1973, he received the IEEE Medal of Honor for his contributions to global communications technologies for his development of the traveling-wave tube. See Klystron, traveling-wave tube. Konen Modem Koupler A battery-powered commercial modem/modem adapter combination from Unlimited Systems. Konexx enables a modem to be hooked into various types of phone lines and cellu- lar phone systems while traveling. Kotel'nikov,. included Bill Gates, Paul Allen, and Ric Weiland. The group created a payroll program in COBOL for a company in Port- land, Oregon. They were informally named after the Lakeside private school attended by its members. At the same time, the group had a programming contract to build scheduling software for a school. Eventually Gates and Allen formed Traf-O-Data in the early 1970s, to create a traffic analysis program. The partnership that led to the formation of the 567 © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary Microsoft Corporation. See Gates, William; Allen, Paul; Microsoft Corporation. LAI See Location Area Identity. LAM 1. line adapter module. 2. See Lobe Attachment Module. LAMA See Local Automatic Message Accounting. lamb. magnetron; Varian, Sigurd and Russell; Varian Associates. KMI Corporation A fiber optics and telecommunications market research and consulting firm founded in 1974. KMI is a subsidiary of Penn Well and part of Penn Well's Advanced Technology Division, with research headquarters located in Providence, RI. KMI publishes Fiberoptics Market Intelligence® as a semi-monthly newsletter and provides various commercial market studies, fiber optic systems wall maps, marketing workshops, and databases. See FiberFax, Fiberoptics NewsBriefs, Fiberoptic Undersea Sys- tems, Undersea News Service. KMID key material identifier. A term associated with Message Security Protocol. KNET See Kangaroo Network. knife-edge focusing Focus (wavefront) testing, as for scientific instruments such as telescopes. This is an aid to visually assessing a lens or mirror. Often a Ronchi screen or knife-edge bushing is placed as a mask at right angles to the light path before or behind the point of focus in relation to a lens or concave mirror to provide the knife edge. Focusing is then adjusted until the edge "cuts" the light beam exactly at the point offocus.