Fiber Optics Illustrated Dictionary continuous wave A wave that is constant or unvary- ing in its major characteristics, such as amplitude. continuous wave transmissions Any transmissions technology that employs continuous signals rather than pulses. Since most communications media rely on pulses or modulation to send meaningful informa- tion, continuous wave transmission is more special- ized and generally used in signaling situations, such as security systems, in which an interruption of the continuous wave serves as an alert or system startup signal. control field In many types of data communications that employ fields as information units, a control field is assigned to contain information about how to pro- cess related data. control panel A console used to control operations of a system, vehicle, aircraft, or network. The con- trol panel may consist ofphysical switches or dials or may be a text or graphical interface on a computer screen (often simulating switches and dials). Control Panel In Apple computer operating systems, a collection ofutilities, accessible through the Apple Menu, that provides access to many basic operating parameters, including sound, memory, monitor set- tings, network configuration settings, etc. control segment In the Global Positioning System (GPS), the control segment is a global network of control and monitoring stations that ensure the accu- racy ofsatellite positions and their clocks. This co- ordination is an important part of GPS, as the data is derived in part from the relationship of the satellites to one another and their signals. See atomic clock. control terminalA workstation or personal computer configured to provide control ofa network from any routing node. It acts as a command input and display console. Through remote access commands, it is pos- sible to control a network from a node other than the one that is physically connected to the terminal (vir- tual terminal). controlled access unit CAU. In the generic sense, a device in a link that selectively controls the entry and! or exit of people, things, or data to a system. A door with a lock is a simple example ofa physical CAU. Arevolving entry gate at a circus, with security per- sonnel and ticket sellers, is another access unit in that people are funneled through a specific physical lo- cation. A firewall is an example of a computer net- work CAU in the sense that it controls access to or from the system behind the firewall. See Controlled Access Unit. Controlled Access Unit When spelled with capitals, a CAU more specifically refers to an active wiring concentrator used in Token-Ring networks. The CAU transforms the logical ring topology into astar topol- ogy, for example, to facilitate installation in larger building environments. Two or more CAUs can be interconnected to produce a segmented network. Multiple CAUs intercommunicate through the main ring path. The CAU provides a means to attach units to the ring network as though it were a star topology, while still maintaining the basic ring configuration for the network traffic logic. However, it is more robust 212 (more tolerant ofa bad unit on the system) and more flexible (accommodating additional computers) than a basic ring network. See Lobe Attachment Module, Multistation Access Unit, Token-Ring network. Controller Area Network CAN. A multimaster se- rial network bus originally developed for controller circuits in the automotive industry by Robert Bosch GmbH, Germany, in 1986. CAN is now being adapted for marine, medical, industrial, and other control and automation applications. The CAN bus is a high-speed (up to I Mbps), half duplex network communicating among microcontrollers. It is capable of interconnecting over 2000 devices and is often used in imbedded systems. It is particularly useful for short messages. Data in a CAN system are transmitted and received using Message Frames. Standard CAN uses II-bit identifiers, Extended CAN uses 29-bit identifiers. There are two ISO standards for CAN, specified for two different speeds. See CAN in Automation. controllerAsoftware-supportedcomputer hardware device that works in conjunction with the operating system, through the various system interfaces, han- dling input and output and control of that device. Thus, a disk controller provides functions to handle a hard drive. The most common desktop computer disk controllers follow SCSI and IDE standards. SCSI controllers are also commonly used for scanners, CD- ROM drives, and many types ofcartridge drives. A serial controller handles serial communications into and out of the computer, usually to a printer or mo- dem. RS-232 and RS-423 are two of the most com- mon desktop serial interface standards. When acomputerfirst boots up, one of the processes that occurs is bringing the controller hardware and software online. The computer needs to locate the various devices and will often load a variety of soft- ware device drivers that support the hardware func- tions. See controller card. Controller Area Network CAN. Amultimaster-ca- pable serial bus system that facilitates the network- ing ofintelligent devices, including sensors and ac- tuators. CAN is associated with the lowest layers of the ISO/OSI reference model. controller card A computer circuit board card that connects through a slot (e.g., PCI), to provide an elec- trical and logical connection between a device and the main circuitry of the computer. There are a lim- ited number of slots available for controller cards, usually more in a tower model, and extra power may be needed to handle the extra load. There may be jumpers or dip switches on the controller card to fine tune the settings, as on a graphics card or hard drive controller. The communications standard used by the controller card must fit that of the slot into which it is inserted. An EISA card call1iot be put in a PCI slot, and vice versa. Software may need to be loaded onto the computer for the operating system to recognize the controller card functions. See controller. CONUS Contiguous United States. A designation for the continental, contiguous U.S. consisting of 48 states. The term is used when referring to U.S. travel, © 2003 by CRC Press LLC transmission, or broadcast regions. converter A very broad term for anything that changes the incoming signal to a different outgoing signal or that converts one type of physical connec- tion to another. Converters are frequently used to con- vert between alternating current (AC) and direct cur- rent (DC) or to convert one cable type to another. A converter may be used to convert a frequency spec- trum from one range to another, but this is pushing the boundaries of the tenn, as converter usually im- plies fairly simple conversions. More complex ones tend to have their own descriptive tenns. When a con- verter is used simply to change one type of plug or jack into another without any electrical changes, it is more commonly called an adapter. When it simply links two components with no changes in the signals, it is called a connector. convex Smoothly protruding and curving outwards, like the outside surface of a bowl. A continuous or mostly continuous surface that follows the outer sur- face ofaspherical/elliptical shape. The tenn is gen- erally applied to surfaces that do not constitute a full sphere. Thus, the outer surface ofa ball is considered spherical, but if it were chopped in half or less than half, the smaller portion would be considered con- vex, whereas the larger portion, while still being pri- marily convex in geometry, tends to be semantically called spherical rather than convex. If an elongated, rounded-end lozenge-shaped object like a vitamin pill were cut exactly in half between the two rounded ends, the portion that curves toward the midsection would be considered convex, but the portion where the curve straightens out to include the straight midsection of the pill would not. The outer surfaces of many lenses are convex as are the "back" surface of parabolic antennas. Contrast with concave. Conway's law This saying has been variously re- stated (and probably improved over time). The idea is that there is congruency between the composition of the software team and the final design of the soft- ware (and in this version, an implied dig that a single programmer wouldn't ever finish the project), stated as, "If you assign n persons to write a compiler, you'll get an n-J pass compiler." Another version, not quite as apropos to computereze as the one just stated, but perhaps closer to the original, is "If you assign four groups to working on a compiler, you'll get a 4-pass compiler." It is attributed to Melvin Conway, an early Burroughs computer programmer. Another Conway's law has been stated in Dilbertian fashion as follows, "There is always one person who knows what is going on. That person must be fired." Cook, Gordon Author of the Cook Report on Inter- net, a newsletter devoted to issues concerning the commercialization and privatization of the Internet. Cook was formerly science editor at the John von Neumann National Supercomputer Center. Later he served for 18 months as a director for the U.S. Con- gress Office of Technology Assessment, assessing the National Research and Education Network (NREN) Cook Report on Internet An independent, opinion- oriented by-subscription monthly online newsletter focusing on Internet infrastructure policy and tech- nology. The publication monitors telephony and com- puter convergence and new technologies being adapted by forward-thinking telecommunications providers. Cooke, William Fothergill (1806-1879) A British researcher who collaborated with Charles Wheatstone in developing the telegraph. The two met in 1837 at a time when both were researching similar telegraph technologies. See telegraph history; Ronalds, Francis; Wheatstone, Charles. cookieA token or other transaction acknowledgment or ill passed between transacting processes or pro- grams to keep a record of an access or action. Cook- ies may be passed transparently between systems as part ofnonnal operational protocols. Data cookies are an integral part of Internet com- merce, especially in the fonn of identifiers in Web link referrals and shopping cart purchases made online. Cookies can be passed from the ~rowser to the shopping cart site to identify the visitor for later purchasing or statistical purposes and mayor may not be acknowledged with infonnation from the vendor being deposited on the buyer's system. The cookie may also track customers as they browse other sites (common on the Internet) and then return to finish their online shopping. Some people object to these types of cookies, which are automatically offered to the visited site by the browser and will disable this capability, and many people have objected to the re- verse cookie, one that is deposited on the visiting browser's system, often without the knowledge of the user, as this opens a porthole for viruses, vandalism, and unfair trade practices. See Caller ill. cookie monster An invasive software program, widely distributed in the mid-1980s, named for the popular children's television program character. The program would prompt the user with "Give me cookie " at increasingly shorter intervals, gradually taking up more and more CPU time, and if the user didn't type the word "cookie" it would eventually print so frequently, and steal so much CPU time, that it would make the terminal unusable. The original was ru- mored to have come from MIT. See virus. Cooperative Research Action For Technology CRAFT. One ofa number of programs of the Euro- pean Union, CRAFT is a means to enable small- and medium-sized enterprises (SMEs) to engage third parties to carry out research on their behalf. The third parties may be commercial research organizations or research departments of academic organizations. In a CRAFT project, the SMEs are made up of at least three participants from at least two different EU states and the area of research must fall within the umbrella of the RTD Framework Programme which can in- clude software development, for example. Coordinated Universal Time, Temps Universal Coordonne UTC. An international astronomical time reference devised in 1970 by the lTV. UTC is related to the Greenwich meridian, that is 0 degrees longi- tude on the Earth's surface. UTC uses a 24-hour clock, thus, 2:00 pm is 1400 hours. 213 ~~.~' .; ; ': ~ . .V,· © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary Since UTC cannot exactly match Earth's slightly varying rotation, UTC was set to a UT 1 reference with the Earth's position as of 0000 hours on 1 Janu- ary 1958. Deviations are adjusted with leap seconds. Coordinated Universal Time is based upon the aver- age period of the rotation around the Sun. UTC re- ceives its frequency and time information from over 50 centers around the world and broadcasts it over a number of radio frequencies, with tones to indicate seconds and spoken words for upcoming minutes. copper A malleable, metallic chemical element with high conductivity, which makes it invaluable in the manufacture of electrical wire and heating imple- ments. It is the most widely used conductor in elec- trical work due to its properties, availability, and price. Gold and silver are also good conductors but not economically practical for most electrical work. Copper Distributed Data Interface COOL An ANSI standard version ofFiber Distributed Data In- terface (FDDI) that runs on twisted-pair copper wir- ing rather than on optical fiber. copper twisted pair Copper is very commonly used for electrical wires, and twisting two copper wires to- gether can improve its transmission properties. A pair of wires is intertwined in a helical pattern over dis- tance in order to reduce capacitance. Over longer dis- tances, the distributed capacitance can build up, and load coils are introduced, at intervals, to help balance capacitance and inductance. The use of load coils for telephone voice connections is common; however, they can cause problems when the same wires are used for data transmission. Copper pairs used for data transmission may be constructed differently from voice lines, with the insertion ofa metal screen to dif- ferentiate the transmit and receive. Compared to fiber optic cable, it is very easy to con- nect twisted pair. Cutting and splicing is relatively straightfolWard, whereas the cutting and splicing of fiber optic must be done with great care so as not to alter the alignment properties of the optic wave- guides. Sometimes the twisted pairs are further aggregated into binders, a group of 25 twisted pairs. This sim- plifies installation in multiconnection installations. Color coding is often used to keep track of the con- nections and binder bundles. See copper wire, load coils. See twisted-pair wire for a diagram. copper wire The most commonly used transmissions medium for telephone calls and related telecommu- nications. Copper wires were first widely installed in the 1880s, superseding some of the earliest galva- nized wires used for telegraph signals. Copper wire with an iron core was developed by Bell's Thomas B. Doolittle in 1883, and it became popular due to its combination of conductivity and durability. Copper wire for phone communications was most commonly installed as a single wire, strung on util- ity poles, or as twisted pair. More recently, gel-filled multicables comprising up to almost 5000 twisted pairs have been used where many connections are required. Many bare conducting wires have been strung with- 214 out insulation, but insulation is often used to protect the wire from damage, interference, and corrosion. Rubber, gutta-percha, latex, plastic, and wound pa- per have all been used as wire insulators, as have air and jelly inside an outer core. See coaxial cable, cop- per twisted-pair, CoppelWeld, fiber optic. Copperweld A trademark name for an early combi- nation of copper wire with an iron core. It combined the flexibility and conductivity of copper with the durability of iron and increased the longevity of the wires. coprocessor A computer processor that is not con- sidered the main or central processing unit (CPU) but assists the CPU in handling heavierprocessing loads or specialized processing loads. CPU s are designed as general-purpose chips, and are not intended spe- cifically for anyone type of task. The Amiga com- puter, released in 1985, is an example of one of the first desktop computers to make extensive use of coprocessing chips to handle resource-hungry graph- ics and video operations in order to prevent these computations from slowing down the CPU. This ar- rangement is now more common. The interaction ofa CPU with support circuitry such as coprocessors is one of the reasons the raw speed of the CPU is not a perfect indicator of the perfor- mance of a system. Computers with coprocessing chips and average speed CPUs have often been shown to outperform faster CPUs if they don't have coprocessing support. Coprocessor chips are gradu- ally becoming more common in desktop systems, with math coprocessors becoming prevalent in the 1980s, and graphics and sound coprocessors beginning to show up in many consumer systems in the 1990s. COPS See Common Open Policy Service Protocol. COPT Coin-Operated Pay Telephone. copyright Certain legal safeguards conferred by gov- ernment agencies. Copyright protections are granted to original works for a specified period of time, de- pending upon the type of work. Original drawings, musical compositions, software programs, and sto- ries are copyrightable. Inventions are sometimes copyrightable, sometimes patentable, and sometimes both. It is important to include a copyright symbol © and a date with the name of the copyright holder, or the word copyright and the date, on each presenta- tion of the original work or reproduction thereof. The C with the circle is recognized internationally by those countries cooperating in international copyright treaties, such as the Berne Convention. A fee-based fonnal copyright process is available in most countries to provide a record of the type and date of the copyright materials. This record is a good source of evidence in a legal dispute, but the copy- right registrar does not police the copyright; that is the responsibility of the copyright holder. Many researchers, academics, and business employ- ees are mistakenly under the impression that they automatically own the copyright for something they create. This is often not true, although the laws have swung slightly more in the direction of the creator in recent years. However, if it is work for hire or work © 2003 by CRC Press LLC paid for in the normal course of an employee's du- ties, the educational institution or the corporation usually owns the copyright to the work, unless there is a specific written agreement stating otherwise. If the employee, on the other hand, creates some origi- nal work outside of working hours and can prove it wasn't done under the direction of or using the re- sources of the employer, the employee may have a case for copyright ownership. Copyright does not protect the owner if someone in- dependently comes up with the same idea and has not copied the original idea. However, it can be difficult to prove the idea was conceived independently, if it is very similar to another, and that proof may be nec- essary in court ifa legal proceeding is initiated. Most public libraries have excellent references on copy- right requirements and registration guidelines, as do all U.S. government documents repositories. See in- tellectual property, patent, trademark. CORBA Common Object Request Broker Architec- ture. In the current state of computing, there are many different vendors, many different computer platforms, and many different software applications, resulting in much duplication and incompatibility. Now that we have the Internet as a common ground for shar- ing development strategies, applications, and appli- cation-development tools, it is not necessary for these incompatibilities to exist, and neither is it necessary for a consumer to be forced to use anyone particular computer platform. CORBA is a strategy and a set of tools. It enables re- usable programming objects to be used by many ap- plications in a platform-independent manner. It is the combined effort of more than 500 vendors, engineers, and end users, organized as the Object Management Group (OMG). CORBA is a set of specifications for platform-independent, interoperable, distributed ob- ject-oriented applications. By using CORBA speci- fications, software vendors can create truly global software that can be distributed over the Internet and run on a multitude of systems. CORBA is an infrastructure that provides general services, and request and response capabilities at a low level. The distribution of objects written in a va- riety of programming languages is supported. CORBA does not define the upper level architecture; this decision is left to individual developers. See Ob- ject Request Broker. cord lamp In manual switchboards, or any type of cord panel where indicators are used, the lamp is a small bulb associated with a physical socket connec- tion for a cord jack that lights up if the associated cir- cuit is active. Cord lamps were used on old telephone switchboards to signal active switches. The modem equivalent is an indicator light on a multiline tele- phone console. cordboard A historic switching panel, human-oper- ated with long cloth-wound patch cords which plugged into jack receptacles on the desk level and interconnected, as needed, with jack receptacles on the wall corresponding to the local phone desk. See swi tchboard. cordless switchboard Unlike cordless phones, which are used in wireless systems, a cordless switchboard is not a new wireless technology, but rather an older switching technology in which human operators used keys instead of patchcords to connect call circuits. While this was a great improvement over patchcords and was still used on many long-distance circuits until the 1970s, it was slow and expensive compared to all- electronic automatic switching systems. cordless telephone A battery-powered wireless tele- phone handset with a short antenna and a separate charging element and AC adaptor, usually using very short-range radio signals. While acellular phone is a type of cordless phone, the phrase cordless telephone is usually used to refer to very short-range phones used within buildings or circumscribed areas. Cordless phones are predominantly analog, but more digital phones are being produced, resulting in more options for interfacing with a computer or providing secure or semisecure communications. core 1. Center, inner, inmost. 2. A central strand or wire around which other conductive or protective lay- ers, strands, or insulating materials may be wound. Usually the main conducting portion ofa wire assem- bly. In most electrical installations, copper wire is used as a conductive core. In fiber optic cable, the core glass is usually surrounded by a layer of lower refractive cladding glass. See cladding. 3. A central bar, often of iron, around which a coil is wound to create an electromagnetic part. See armature, coil, electromagnet. 4. A small doughnut-shaped magnetic component used for computer storage, with polarity representing binary states. See core dump. 5. A cen- tral, removable strand around which other materials may be wound or braided in order to provide a brace for molding their shape. Core, the 3D Core Graphics System. A baseline specification developed in the mid-1970s to encour- age standards for device-independent graphics. This specification led to development of the Graphical Kernel System (GKS), an official standard for 2D graphics. For 3D graphics, GKS-3D and the Programmer's Hierarchical Interactive Graphics Sys- tem (PRIGS) became official standards in the late 1980s. core diameterA description of the thickness of an inner, usually conducting material, as of copper wire or the inner lightguiding core in a fiber optic cable as measured in cross-section through the center perpendularto the axis of the length of the cable. See American Wire Gauge, Binnington Wire Gauge. core dump A copy of the contents of core memory from a process error condition, usually consisting of undecipherable symbols and unprintables that can make a terminal or printer go crazy. On large systems, the output can be voluminous. Irate receivers of spam, unsolicited commercial email, have been known to retaliate by sending back large core dumps. core to cladding offset See concentricity error. core-to-core splicer An industrial fusion splicing device for joining fiber optic cables. A core-to-core splicer allows active alignment in three axes, compared 215 © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary to two-axis cladding alignment splicers. A core-to- core splicer provides alignment of single-mode, mul- timode, and active fiber cores and may include a built- in thennal sleeve shrinking mechanism. A splice log memory or computer link may be provided for keep- ing a record of splices and their statistics. Since this type of splicer may be portable, for field work, it may also include a pigtail port for facilitating cable ter- mination and may have a built-in cleaver. See clad- ding alignment splicer, fusion splicer. Cornell, Ezra (1807-1874) Cornell was talented in both business and mechanics and was associated closely with Samuel Morse and Hiram Sibley, founder of the company that became Western Union. Cornell contributed to early telegraph installations and helped Morse construct the historic Washington, D.C. to Baltimore, MD line that was funded through the U.S. Congress. Cornell designed early insulators from glass plates. Cornell remained a lifetime direc- tor of Western Union and was the chief founder of Cornell University. corner reflector In its simplest fonn, two intersect- ing or joining flat reflective surfaces with sufficient angle between them (usually 20 to 160 degrees, and often 90 degrees on the reflective side) to allow re- flectance ofa beam. The comer may also be in three planes, shaped like the comer ofa room where the walls join the floor or ceiling. Comer reflectors are common in radar applications. The materials vary, but mirrored glass and metals are often used. corner reflector antenna A type of antenna which combines a primary radiating element in relation to two angled metallic surfaces, or rods arranged in a plane. Various styles of comer reflectors are used in UHF television reception and radar applications. Corning Cable Systems A leading global manufac- turer of copper and fiber optic communications prod- ucts for voice, data, and video network applications. Coming Cable is wholly owned by Coming Incor- porated, a publicly trading company that was origi- nally established in 1851. Coming Cable was involved in a number of impor- tant mergers in the early 2000s, including the acqui- sition of Siecor and Siemens' global cable and hard- ware businesses. Corning Glass WorksA historic glass company that employed many significant pioneers in glass tech- nologies and their application. While working at Corning's Sullivan Park Research facility, scientists D. Keck, R. Maurer, and P. Schultz demonstrated a practical fiber optic waveguide that overcame the limitations of earlier attempts by reducing the losses associated with lightguiding over distances. For their work, they have received numerous awards, includ- ing the 2000 National Medal of Technology. Corning Glass Works became Coming, Inc. In 1943, Dow Coming Corporation was formed and now pro- duces a wide variety of silicon-based products. Corning Museum of Glass From decorative art works to fiber optic components, glass has a long and colorful history that is exhibited in the extensive col- lections held in the Coming museum, located in Com- 216 ing, New York. Scientific aspects of glass are docu- mented and demonstrated in the Glass Innovation Center. http://www.cmog.orgl corona A halo, glow, or other luminous surrounding from various causes including refraction, particle movement, ionization, radiation, reflection. St. Vitus' fire, as reported by sailors, is likely a kind of corona effect. Voltages around power lines and antennas can sometimes ionize the surrounding air, resulting in a whitish-blue corona effect. Corporation For Open Systems International COS. A nonprofit vendor-supported organization cre- ated in 1986. It was established to further the accep- tance and use of data processing and data communi- cations equipment, and to encourage multivendor product compatibility in these areas. COS is involved in various standards efforts, particularly those in- volved with test methods and certification require- ments. Corporation for Research and Educational Net- working CREN. A nonprofit organization fonned in 1989 when BITNET merged with the Com- puter+Science Network (CSNET) to promote and assist accessible, worldwide academic infonnation exchange. In 1994, CREN announced a system to facilitate communications called Internet Resource Access (IRA), in essence an Internet-in-a-box sys- tem. In 1996, it recommended to its members that they discontinue support of BITNET in favor of other systems, primarily the Internet. Since the Internet has superseded BITNET as the dominant global commu- nications network, CREN has increased its focus on seminars, educational materials, and software utilities that enable academicians and technology profession- als to use and implement widespread, inexpensive network access for the purposes of research, commu- nication (especially discussion lists), and distance education. CREN is a founding member of the Inter- net Society (ISOC). See BITNET, Internet Resource Access, LISTSERV. http://www.cren.net! corresponding entities In ATM networking, peer entities with a lower layer connection between them, coordinated through protocol control infonnation. corrosion A wearing away, or alteration by chemi- cal action, often leaving a residue such as rust or film as a byproduct of the corrosion. Many electrical wires and components are coated or bonded in order to pre- vent corrosion. Some elements resist corrosion, mak- ing them useful for applications in corrosive environ- ments. See oxidation. CoS See class of service. COS 1. compatible for open systems. 2. See Corpo- ration for Open Systems International. COSETI Columbus Optical SETI. See SETI. COSINE Cooperation for Open Systems Intercon- nection Networking in Europe. A program established by the European Commission to utilize Open Systems Interconnection (OSI) to interconnect various Euro- pean research networks. COSPAS/SARSAT A cooperative effort begun by the United States, the USSR, France, and Canada in the later 1970s. It supports satellite communications- © 2003 by CRC Press LLC related search and rescue operations which enables information such as the location ofdistressed aircraft or marine vessels to be communicated to rescue sys- tems. COSPAS/SARSAT operates in conjunction with the emergency position-indicating radiobeacon (EPIRB) to support the Global Maritime Distress and Safety System (GMDSS). COTS I. commercial off the shelf. 2. See Connec- tion-Oriented Transport Service. Cotton-Mouton effect When light passes through a pure liquid in a direction perpendicular (normal) to an applied magnetic field, the liquid becomes dou- bly refracting. See Kerr effect. coulomb A unit of electrical quantity named after Charles A. de Coulomb. Aunit for the amount of elec- trical charge in the meter-kilogram-second (MKS) scale that passes through a circuit in one second at one ampere (unvarying) current. The international coulomb is the quantity of electricity that will deposit 0.0011180 grams of silver when passed through a neutral solution ofsilver nitrate in water. Acoulomb can also be expressed as the quantity ofelectricity on the positive plate of a condenser of a capacity of one farad when the electromotive force is one volt. See ampere. Coulomb, Charles Augustin de (1736-1806) A French physicist and engineer who experimented with applied mechanics and electromagnetism. In 1785, he demonstrated the laws ofelectromagnetic force between elements using artificial magnets with well-defined poles in which the associated phenom- ena could be more clearly observed. The Crater Cou- lomb on the moon and the coulomb unit of electric charge are named after him. Coulomb'slawAdescription of the magnitude of an electromagnetic charge. Two electromagnetic point charges will attract or repel one another with a force directly proportional to the product of their charges, and inversely proportional to the square of the dis- tance between the two point charges. This phenom- enon is more easily observed than many in the field ofphysics. Named after Charles de Coulomb. Council for Access Technologies CAT. Originally founded in the early 1990s as the National ISDN Council, with the wide deployment of ISDN tech- nologies, the group broadened its focus and became the Council for Access Technologies. CAT is an in- dustry trade association promoting the implementa- tion, standardization, and simplification of new tele- communications services offered over a variety of access technologies. CAT supports the exchange of technical information and information about compabitility and works with other organizations and end users to introduce new networking services. http://www.CATcouncil.org/ counter-rotating ring In ring network topologies, data typically travels in one direction along each path. In a counter-rotating ring, there are two signal paths, each one traveling in the direction opposite to the other. See Fiber DistributedData Interchange, Token- Ring. counterpoise 1. A state of balance, counterbalance, equilibrium. 2. Apower or force acting in opposition such that the opposing forces are equivalent, or bal- anced. 3. A structure designed to balance the trans- mitting or conductive properties of a circuit. counterpurpose Working towards one goal and para- doxically achieving the opposite result to what was intended. This term was coined by Doug West and has many applications in telecommunications tech- nology. For example, when the Federal Communi- cations Commission frees more radio frequency spec- trum to ease a situation where demand exceeds sup- ply, it often spurs the development of new technolo- gies to take advantage of the newly available spec- trum, with the result that demand exceeds supply by even more than was originally the case. coupler In general, aconnector to facilitate the join- ing of two elements; an elbow joint can couple two sections ofpipe or a threaded (or bayonet) coupler can connect a camera to a microscope. In technology, the term often describes a mechanism for combining two or more cables or signals or for splitting a cable or signal into two or more paths. A coupler is a ge- neric component with applications for mechanical, electrical, and optical media. Optical couplers are used to branch optical power from a single fiber into multiple fibers or vice versa. A standard optical coupler handles single wave- lengths with designated ratios. Broadband couplers may branch or combine optical power within a des- ignated wavelength range in aconstant ratio. For sys- tems design or troubleshooting, couplers may be used to isolate circuits. Optical couplers can be fabricated by aligning opti- cal fiber cores closely enough for the signal to 'Jump" from one fiber to another. By twisting and heating the fibers, the conductive fiber cores will fuse to facili- tate the transfer of light energy. The portions of the fiber that are tapered in the fabrication process will influence the reflective properties of the light beams and trap the higher order modes in a multimode fi- ber. These are known as cladding modes, as they are at the surface of the fiber where it is shielded by the cladding materials that keep light within the fiber waveguide. As the signal moves through the fused region, lower order modes remain in the original fi- ber. As the beams exit from the coupler and the ta- pered, fused region is left behind, cladding modes are converted back to core modes. The degree of taper, the proximity of the fibers, the length of the coupling region, and the wavelengths coming down the fiber are important parameters that hinder or facilitate sig- nal resonance and coupling. A 1 x 2 coupler, also known as aYcoupler or Ysplit- ter, is a directional coupler that enables two paths to be joined into one or one path to be split into two. Y couplers/splitters are commonly used in fiber optic networks. A 2 x 2 coupler has eight possible indi- vidual paths through which the signal may travel for a bidirectional signal and four possible individual paths for aunidirectional signal. Combining the cou- plers increases the number of paths (and the complex- ity of the combinations and control mechanisms). 217 © 2003 by CRC Press LLC Fiber Optics Illustrated DictionanJ Couplers can be combined in tree-like branching structures to form multiple outputs from a single source. Note that loss is typically associated with splitting a signal. Asufficientlly powerful source sig- nal or signal amplification may be needed in a cir- cuit with many branches. Acoupler may be connected to a fiber optic network by fusion splicing or through low-loss connectors at- tached to the coupler. Pigtails are protruding fila- ments intended for making connections. Commercial housings, some of which are rack mountable, are available for supporting multiple couplers. Depend- ing upon the configuration, the coupler may require a termination adapter. See SC-connector, ST-connector. coupler, star A type of coupling configuration in which a signal is split into multiple paths which may continue on through a circuit or be reflected back to multiple positions adjacent to and including the sig- nal source. In optical star couplers, an input light beam is transmitted to all output ports. coupling loss Loss in a conductive medium that is directly related to the physical properties of the cou- pling mechanism. Coupling losses can be due to poor materials, poor shielding, loose connections, rota- tional incongruities between the coupled ends, par- ticles, heat expansion, humidity, etc. Coupling loss is more prevalent and more significant in fiber optic cables than in most wired connections due to the precision needed to guide light along a link in a path. The units for expressing coupling loss depend upon the type of conducting medium and conductive phe- nomenon. In other words, it will be expressed differ- ently depending upon whether it is a wire or optical cable and whether the conducted signal is electric- ity, light, X-rays, or sound. It will also depend upon the relative magnitude ofa typical loss and the type ofsignaling that is used. For example, coupling loss in a light transmission may be expressed in terms of loss of power (e.g., light intensity), whereas coupling loss in an acoustic medium may be expressed in terms ofloss of intelligibility (e.g., the number of words cor- rectly understood). See attenuation, coupler, fusion splice. cover page The first page ofa printout or facsimile that identifies information about the nature and date of the printout, and often the sender and intended re- cipient. On networks with shared printers, it helps identify the owner of the hardcopy. See banner. coverage area In news and entertainment broadcast- ing and cellular communications, the geographic range ofusers/subscribers. Outside of the coverage area, signals will be weak or absent. This is not a prob- lem for broadcast subscribers, who usually know they are either inside or outside the range ofa certain chan- nel, but for mobile communications users driving out of range in the middle ofa conversation, it can be a problem. For this reason, some mobile communica- tions will provide a signal that indicates that the lim- its of the range are nearby, and some handsets will have a light or message that indicates the user is out- side the service range. 218 Fiber Optic Coupler - Duplex Duplexfiber optic cables can beinterconnectedwith a duplex multimode opticalcoupler for about $18. 00. Bel/Core has published compatibility specifications that are followed by a number of manufacturers. Cou- pling ratios may vary, depending upon the applicatioll. CP/M Control Program/Monitor, Control Program for Microcomputers. An operating system that came into widespread use in the late 1970s and early 1980s, written by programmer and professor Gary Kildall. It had atext-based, line-oriented interface and ran on the Intel 8080 and Z80 microprocessor families. Kildall formed Inter-Galactic Digital Research, later Digital Research, to market his computer software products. The forerunner of MS-DOS was derived from a CP/M manual by Tim Paterson and is basi- cally the same in syntax and functionality. Digital Re- search continued to develop CP/M into CP/M86, and later DR-DOS. Kildall also created a multitasking version of the operating system and personal com- puter networking software long before they became common on personal computers. See Digital Re- search. CPA 1. Charter Public Accountant. 2. See Chip Pro- tection Act. CPCS See Common Part Convergence Sub layer. CPE See Customer Premises Equipment, Customer Provided Equipment. CPI See common part indicator. CPL commercial private line. CPN See Calling Party Number. cps See characters per second. CPS See Cellular Priority Service. CPU See central processing unit. CQ In early radio transmissions, CQ was often used as a call to operators (all stations) as a way ofgetting general attention. There are some historians who believe CQ may also have been used as a distress call, and some have interpreted it as meaning "Come Quick" although this may have been attributed after the abbreviation had been around for a while. Baarslaq has written that the Marconi Company re- quested CQD to be established as adistress call (pre- © 2003 by CRC Press LLC sumably CQ Distress) to distinguish it from a gen- eral CQ call in early 1904. CQD Aradio distress call which predated SOS. See CQ. CR 1. See carriage return. 2. call reference. 3. symb. right-hand circular or direct polarization (ITU). 4. connection request. An Open Systems Interconnect (OSI) transport protocol data unit. 5. customer record. crackerA specific subset or connotation of"hacker" for someone who gains unauthorized access to sys- tems or applications. Since breaking into systems can sometimes be done through sheer persistence and brute force techniques, not all cracking is hacking in the sense of applying brilliant and elegant solutions. The term was derived from safe cracker since crack- ing a software password is somewhat analogous to cracking the combination on a safe. One of the most widespread activities of crackers is the deciphering of passwords for computer games so they can be dis- tributed and played without paying fees to hard work- ing game producers. See hacker. CRAFT See Cooperative Research Action For Tech- nology. crankback In ATM networks, a mechanism that al- lows the release of a connection setup that has en- countered an error condition (as in a failed Call Ad- mission Control) to permit rerouting of the connec- tion. crammingAn undesirable practice in which telecom- munications services customers are billed for a num- ber of enhanced features (e.g., Call Waiting) that were not requested or ordered. crash System failure, lockup. On a computer, a crash usually implies a complete lockup of the operating system (this shouldn't happen and very rarely hap- pens on good operating systems) and usually requires a reboot. If the operating system is robust and remains functional after an applications crash, the offending application can often be "killed" to remove it from the system and to prevent it from affecting other ap- plications. It is generally done this way on Unix sys- tems. Killing the application and processes associ- ated with the application will also free any memory that may be inaccessible due to the crash. There are many ways in which a system can crash. Less common causes are hardware failures or elec- trical anomalies. The most prevalent causes are soft- ware problems, especially applications memory man- agement and operating system memory management. Endless loops and bad pointers can also cause crashes. Cray, Seymour (1925-1996) For a whole generation of computer users, Seymour Cray's name was asso- ciated with some of the most powerful supercom- puters in the world. Cray grew up with a strong in- terest in electronics and computing at a time when computers were mainly used by the military and not much was known about them. Cray founded Cray Re- search Inc. in 1972 and Cray Computer Corporation in 1989, companies known for high-end computers for over 20 years. The Cray 1 supercomputer was announced in 1975 and the Cray 2 in 1983. Supercomputers attract less excitement now than they did a decade ago because the general processing speed and level of functionality of desktop comput- ers have increased so dramatically that the distinc- tion between high-end and low-end systems is less dramatic. Many supercomputing operations are now run on desktop computers internetworked with the Linux operating system. This operation is very cost- effective for research labs, educational institutions, and government agencies. CRC 1. See Communications Research Centre. 2. See cyclic redundancy check. CRC Press The publisher of this reference, CRC is one of the world's oldest and most well-respected technical publishers, based in Boca Raton, FL. CRC first published the Handbook of Chemistry and Phys- ics in 1913, an enduring reference that has been re- printed more than 80 times as a definitive source for generations of science students and professionals. The company now has several imprints and ships books all over the world. http://www.crcpress.com/ credentials In computer security, documents or ex- pressions of trust and confidence, particul~ly those that indicate the capability to perform a function or task. The Pretty Good Privacy data encryption sys- tem has an interesting aspect related to credentials in that parties can vouch for the good name and verac- ity of public key holders. See Pretty Good Privacy. credit card phoneA pay telephone equipped with a card slot instead of or in addition to a coin slot to read magnetized credit cards and calling cards. These are becoming increasingly common and are handier than phones where long credit card numbers and pass- words have to be manually keyed. Creed Telegraph SystemA system designed by Ca- nadian inventor Frederick Creed with a typewriter- style tape-punching machine. It improved upon the speed and utility of existing manual punchers and began commercial distribution in 1908. His auto- mated perforators could operate up to 150 words per minute. To this he added a translating and printing system, which eventually became a teleprinting trans- mitter/receiver system sold in England by 1927. Creed,FrederickGeorge (1871-1957) A Canadian inventor and telegraph operator who developed the Creed Telegraph System, an automated teleprinting transmitting/receiving system, in 1889. He then trav- eled to England to manufacture the Creed Printer. By 1898 he had demonstrated he could send telegraph messages at sixty words per minute, and his inven- tions were put into commercial use by 1913. Creed was a member of the Board of Directors for the In- ternational Telegraph & Telephone Company (ITT). See Creed Telegraph System, telegraph history. creel 1. A woven basket for storing objects or crit- ters (installation tools, caught fish, birds, picked apples). 2. A quantity, as might traditionally be held in a basket. The tenn is applied to fishing limits, for example. 3. A single support frame or multiple as- sembly for holding spools of cable on winding pegs. Winders may be attached to each peg or spools may be wound before hanging on the creel pegs, depending upon the application. The term comes from the fab- ric industry (e.g., woollen mills), where multiple 219 © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary spools of thread can be wound on a creel assembly and drawn off to other creels or mechanisms (warp- ing creels or looms). Creels can support and organize multiple cables for production or storage. They are also used for supporting and spooling raw fiber in preparation for cladding. Creighton, Edward (1820-1874) Creighton was ex- perienced in building communications lines and roads and thus became the organizer of the western expan- sion of the telegraph system for Western Union, un- der Sibley and Cornell. Creighton surveyed the first transcontinental route across the wilderness in 1860, which followed the trails of the recently established Pony Express. Creighton worked in conjunction with the Overland Telegraph Company to carry out con- struction on the section west of Omaha. In those days, building a line involved more than muscle and materials; it required bushwhacking through roadless, supplyless, lonely wilderness areas inhabited by wolves, coyotes, snakes, and bears. The vast tracts were without urban comforts of any kind. It also involved negotiating with native inhabitants and working out problems associated with roaming herds of buffalo who thought the telegraph poles were installed for their convenience as backscratchers. The line construction was originally estimated to take two years at a cost of over a million dollars. Under Creighton's supervision, the job was done in four months at a fraction of the original cost estimate. F or- tunately, Creighton owned stock in Western Union and was able to benefit from this astonishing engi- neering feat. He used his gains to found Creighton University and to contribute to many civic projects. CREN See Corporation for Research and Educa- tional Networking. CRF 1. See cell relay function. 2. See connection- related function. crimp To squeeze so as to confine; to push in upon. crimp tool, crimping tool A common handheld wir- ing installation tool that resembles a fat, snub-nosed set of pliers. It is designed to facilitate the cutting, stripping, and crimping of wires or fiber optic cable by providing rounded pressure points and leverage for exerting pressure. Crimp tools may have more than one gauge or setting for related tasks. In fiber optic cable assembly, a crimp tool makes it easier to tighten and secure a crimping sleeve that slides over the jacketed fiber and its attached connec- tor. It may also be used to tighten a strain relief boot that fits over the crimpling sleeve. Care must be taken to exert the correct amount of pressure when crimp- ing, to avoid breaking a wire or fiber filament. See lapping film. CRIS See customer record infonnation system. critical angle The angle at which a beam is reflected within a transmissions medium such as optical fiber. This angle can be very important to the strength of the signal over distance and the total distance the sig- nal can travel. It may be modified by the angle of the beam, the thickness of the fiber, and various impuri- ties (doped elements) that may have been introduced. See acceptance angle. 220 critical charge The amount of charge needed to ini- tiate a process or to change the state of or value of data being stored or processed. critical fusion frequency CFF. In a display device, the refresh rate frequency above which the individual scans are fused by human perception into a single frame or image. It is not a set number, as, for example, on a cathode-ray tube (CRT) display; it is related to the rate of persistence of the visible light from the excitation of the phosphors. As a rule of thumb, though, most systems show a nonflickering image at about 60 frames per second, or at about 85 Hz. Critical Technologies Institute CTI. Organization established within RAND by an Act of U.S. Congress in 1992 and primarily sponsored by the White House Office of Science and Technology Policy. CTI works with the Federal Coordinating Council for Science, Engineering, and Technology to assure that technolo- gies critical to national interests are identified and supported. CRITO See Center for Research on Infonnation Technology and Organizations. CRM See cell rate margin. CRMA See Cyclic Reservation Multiple Access Pro- tocol. Crookes Dark Space In a cathode-ray tube (CRT), as the gas pressure in the tube is gradually diminished, the glow surrounding the cathode detaches, leaving an area that is dark around the electrode, an area that may become quite large at low pressure levels. In a tube that has some air in it, this region can be more easily distinguished as being between the cathode glow on the inside and the negative discharge glow on the outside. Outside the negative glow is another region called the Faraday Dark Space. See Faraday Dark Space. Crookes tube A simple experimental tube developed by William Crookes in the 1870s for studying elec- trical discharges. Essentially a variation on the Geissler tube, which was filled with various types of gases to observe their effects, the original Crookes tube was attached to a pump to evacuate the gases, and the two ends supporting the cathode and anode electrodes were sealed off to maximize the stability or controllability of the environment within the tube. (In fact, a complete vacuum was not achieved and, in some cases, the effect ofrarified gases in the tubes was being studied.) The electrodes were connected to a source of electrical charge with the voltage con- trolled to fonn a crude ampmeter for detecting cur- rent. The Crookes tube also facilitated the discovery of X-rays (Rontgen rays). In some cases, a mineral substance was mounted within the glass tube to cre- ate fluorescing effects when voltage was applied across the tube electrodes. Like the Geissler tube, this illuminated effect made Crookes effects popular in English parlors at the time. Later refinements of the Crookes tube made it pos- sible to control cathode rays, an important step in the development of cathode-ray tubes, which are used in television, imaging, and display technologies. Crookes tubes are used in educational settings for © 2003 by CRC Press LLC studies in atomic structure for investigating electron flow and the influence of magnetic forces on this flow. See cathode-ray tube, Geissler tube. Crookes Tube The Crookes tube was an important experimental electron tube that was used by William Crookes be- ginning in 1870s, and later by other scientists, to re- search voltage levels and electromagnetic radiation. It also contributed to the development ofpioneer dis- play technologies such as cathode-ray tubes. Crookes, William (1832-1919) An English physi- cist, chemist, and editor who developed scientific in- struments for studying various phenomena and used them to make some important basic discoveries. Crookes founded the Chemical News, a weekly pub- lication he edited for almost 50 years, though he is better known for investigating the effects obtained by passing electrical charges through various gases. One of his more notable achievements is the discovery of thallium in the 1860s. Further studies of thallium led to the invention of the Crookes tube in the late 1870s. He designed a vacuum-sealed glass tube for detect- ing charge that could be used to investigate the rela- tionship between voltage and pressure. He later de- veloped an instrument for detecting radioactive par- ticles. Crookes tubes were subsequently used by Rontgen in his discoveries of X-rays. See Crookes Dark Space, Crookes tube. cropping The process of truncating infonnation, usu- ally an image. Cropping refers to the removal of un- needed elements or data. For example, excess blue sky may be cropped from a photo during the devel- opment process or after the photo is printed. Crop- ping does not imply any change in size or proportions to the remaining portion of the image. In computer imagery, the cropping may involve removing the data only from the display area, the data regarding the 'hid- den' or cropped information may still be in the computer's memory so it can be quickly restored, if needed. Cropping or trimming is often done by print- ers when cutting down print jobs that bleed outside print boundaries. See clipping, scaling. cross assembler An assembly language program- ming and translation tool that enables assembly lan- guage symbolic coding to be written on one system to run on a different type of system. This is conve- nient because development machines often require more resources (more speed, memory, etc.) than the system on which the software will eventually run. There may not even be a machine available on which to run the software until the software is partly or mostly written, due to production schedules or cost. A cross assembler enables software development to get underway and continue somewhat independently of the hardware schedule. cross connectA point in a circuit where a new or tem- porary connection is created by wiring between ex- isting circuits or between facilities. Used variously for diagnosing problems, rerouting, or adding circuits. Cross-Industry Working Team XIWT. An organi- zation established to promote the understanding, de- velopment, and application of cross-industry National Information Infrastructure (NIl) visions into practi- cal technologies and applications, to facilitate com- munication between stakeholders in the public and private sectors. The XIWT Web site provides links to information, many reports, and white papers. http://www.xiwt.org/ crossbar switch In older mechanical telephone switching systems, a crossbar switch was similar to a relay, except that it was controlled by two external circuits and was used in more complex switching ar- rangements, such as those needed for long-distance connections. It was devised in the late 1930s, and AT &T developed a version based upon pioneer work by Swedish engineer Gotthilf Ansgarius Betulander. In 1938, the first crossbar central office went into service in Brooklyn, the same year the infamous "War of the Worlds" broadcast frightened credible residents of the area (who tied up phone lines in their panic). The crossbar switch eventually succeeded the widely used but troublesome panel switch in the 1950s and step-by-step switches in the mid-1970s. See Callender switch, Lorimer switch, panel switch, step- by-step switch. crossover cable A cable in which apair of wires are reversed at one end of the connection. This reversal is commonly done to convert a serial communications cable to a null modem cable. In this case, the trans- mit (Tx) and receive (Rx) wires are crossed, or switched over. In RS-232 specification cables these are lines two and three. crosstalk A term for undesirable electrical interfer- ence, usually from nearby lines, in which the signal from one cable or component is close enough and strong enough to impinge on the signals in another cable or component. In telephone cables or switches, the crosstalk may be so excessive that a telephone conversation from another line can actually be heard. Crosstalk usually occurs in installations with inad- equate spacing or shielding. crosstalk, optical Fiber optic cables do not exhibit the same electrical leakage and crosstalk character- istic oftightly bundled or poorly shielded electrical 221 © 2003 by CRC Press LLC . LLC Fiber Optics Illustrated Dictionary to two-axis cladding alignment splicers. A core-to- core splicer provides alignment of single-mode, mul- timode, and active fiber cores and may include a built- in thennal sleeve shrinking mechanism. A splice log memory or computer link may be provided for keep- ing a record of splices and their statistics. Since this type of splicer may be portable, for field work, it may also include a pigtail port for facilitating cable ter- mination and may have a. Universal Coordonne UTC. An international astronomical time reference devised in 1970 by the lTV. UTC is related to the Greenwich meridian, that is 0 degrees longi- tude on the Earth's surface. UTC uses a 24-hour clock, thus, 2:00 pm is 1400 hours. 213 ~~.~' .; ; ': ~ . .V,· © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary Since UTC cannot. offset See concentricity error. core-to-core splicer An industrial fusion splicing device for joining fiber optic cables. A core-to-core splicer allows active alignment in three axes, compared 215 © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary to two-axis cladding alignment splicers. A core-to- core splicer provides alignment of single-mode, mul- timode, and active fiber cores and may include a built- in thennal sleeve shrinking mechanism. A splice log memory or computer link may be provided for keep- ing a record of splices and their statistics. Since this type of splicer may be portable, for field work, it may also include a pigtail port for facilitating cable ter- mination and may have a