Fiber Optics Illustrated Dictionary signals such as those from distant objects (stars or military targets) or night vision devices. An image intensifying system may be configured with shutoff circuits to prevent eye damage that could result from an image display that is too bright (as in night vision goggles). Commercial products are typically classi- fied according to image resolution and degree of in- tensification that is possible. Image intensifiers are also used outside the optical spectrum. They are particularly useful for intensify- ing X-rays, since there is a hazard involved with us- ing strong X-rays and the lowest dosages possible should be used. Intensification enables the technician to get more information out of a weak signal. See Johnson, John. Image Intensifier- Night Vision Goggles Night vision goggles are an example of image in- tensifying technology. Fiber optic components are used in 2nd-, 3rd-, and 4th-generation image intensifier tubes that are used as step plates (2nd generation) andfaceplates (3rd and 4th). Fiber optic invertersform the output component of the intensifier andmay Hjlip over II the image inverted by an imaging lens. This is accomplished by twisting the axis of the fibers so the output at the end of the filaments is rotated 180 0 from the input light. Officer M Lewis of the U.S. Army positions night vision goggles on aflight helmetfor a helicopter mis- sion. [DefenseLink News Photo, April 1997.J image inverter A software algorithm or physical mechanism for "flipping" an image right to left or top to bottom, or both. Many optical lenses will invert an image in the process of focusing or directing light through their structures and the image may need to be returned to its original orientation to be viewed. Many of the newer display devices, including wall- hung thin-screen displays and TFT displays for ve- hicles, are designed to invert an image so the display can be hung from the ceiling rather than being set on a shelf or mounted from the floor. An array of fiber optic filaments with a 180 0 twist may be used to in- vert an image that has been previously inverted with lenses or imaging plates. imagesetter Aprofessional-level graphics and type imaging machine, an image setter is similar to a high quality computer printer. Imagesetters are used in 472 service bureaus, and traditional and digital printing houses, to create the image or the color separations used to control the ink distribution on the press. Typi- cal resolution on these industrial quality machines is 1200 dpi to 2700 dpi (compared to 300 to 800 for most consumer machines) and they print on paper or film, or both. While the distinction between consumerprinters and images etters is blurring, with consumerprinters now able to print up to 1200 dpi, there are still technical differences between commercial and consumer ma- chines which are important to design, desktop pub- lishing, and printing professionals. Imagesetters do more than just print at higher reso- lutions; they also include more sophisticated and pre- cise algorithms for halftone screens, may include higher quality fonts, may be able to print on special papers and even directly on aluminum, asbestos- based, or other more robust printing plate media. In addition, the distribution of the imaging materials on the printing medium is typically more precise and even. Further, a professional quality imagesetter has better alignment for subsequent printouts. When printing color separations, especially for four- or five-color process printing, the consistency of the printing from one separation to the next is extremely important to the outcome of the final color printout, especially at resolutions of 175 lines or higher used in calendars, posters, and art prints. In modem digital presses, the trend is to eliminate the separate imagesetter and incorporate the technology into the press itself. In the past, a computer file or traditionally photographed image was taken to a pa- per or metal plate through an imagesetter and, from there, the physical plate was attached to the press in order to create the printing job. Now it is possible to put a file on a floppy disk or cartridge and have the digital image sent directly to the press without the intermediary steps. It is even possible for a four-, five-, or six-color printjob to be printed in one press run, rather than sending each color through the press in a separate pass, and aligning the plates each time. This new technology is revolutionizing the printing industry and eliminating a lot of intermediary steps and jobs in the process. Image Inversion One of the more common ways to invert an image is to use a doubly convex lens, which directs the light to opposite sides from the incoming (incident) light. More recently,jiber optic arrays with 180 0 bends have been used to invert incoming light, sometimes to a remote viewing location. © 2003 by CRC Press LLC IMAP See Internet Messaging Access Protocol. IMASS Intelligent Multiple Access Spectrum Sharing. Immediate Ringing A telephone or private branch system option in which there is no delay between the time of the reception ofa call and the ringing of the telephone itself. Favored by those who want to pro- vide quick responses to calls, such as emergency and crisis lines and certain businesses. Immunity from SuitA legal agreement in which a license holder agrees not to sue the provider ofa prod- uct or service. Microsoft and certain other large ven- dors are alleged to be asking for immunity from suit from some of their clients. In the author's opinion, purchasers should avoid signing any licenses that sanction neglect or mismanufacture on the part of the provider and should never sign anything that conflicts with constitutional rights or is coercive. Read license agreements carefully, especially the smallprint, and question and renegotiate anything that gives cause for concern. IMPATT impact avalanche and transit time. IMPDU See Initial MAC Protocol Data Unit. impedance (symb. - Z) The total opposition, mea- sured in ohms, offered by a circuit to the flow of al- ternating current (AC) at a given frequency. The ra- tio, in ohms, of the potential difference across a cir- cuit to the current moving through that circuit. De- sign and insulating materials can substantially affect the level of impedance in a data cable, with low im- pedance cables generally costing more, but provid- ing less noise and interference, and sometimes longer transmission distances. See admittance. impedance bridge A device for measuring in ohms the impedance (combined resistance and reactance) ofa portion ofa circuit. impedance compensator An electrical line which affects another circuit in such a way that the combi- nation provides a desired consistent level across a specified frequency range. A compensator is used to minimize fluctuations and distortion. impedance triangle A diagrammatic model for de- scribing an impedance relationship. Imagine a right triangle with the sides respectively representing re- sistance and reactance, which change proportional to one another, and the hypotenuse representing imped- ance as related to the amount of the resistance and reactance combined. implementation agreement IA. A generally agreed- upon means of describing a technology so that it can be put into production and/or commercial use. In or- der to support interoperability with global networks, many trade organization have adopted lAs as a means to standardize interfaces, protocols, and other net- work-related architectures and equipment in order to be able to produce commercially viable products. These lAs often become de facto standards or are in- tegrated into the standards-development process of major standards-ratifying organizations. See Frame Relay Implementation Agreements. import 1. Bring in from another source, region, or country. 3. Bring in from a non-native file format, protocol, or transmissions source. import, file In software applications, to import is to bring in data from another program, file, or transmis- sions source, usually in a non-native file format. This is usually done through an applications filter or through drag-and-drop capabilities. In drag-and-drop imports, the program will either maintain links to the original imported file or convert the format to one consistent with the program into which it is imported. import filter Many word processing, desktop pub- lishing, and graphics programs have import filters, plugins, or modules which allow a number offile for- mats to be brought into an application and then saved in the native format of the application, or exported in the original format or a new one. This provides better compatibility between programs developed by different vendors. See export; import, file. import script 1. A script which controls the assem- r~t~:::~;~~~~~!i~~~r~1::~;~~n;~. in which you can set up a form letter, and then have the script selectively build dozens or hundreds of per- sonalized letters in a few minutes by automatically drawing in names, addresses, and variables from a database to merge with the form letter. Bulk mail companies often use import scripts to personalize let- ters' contest offerings, and envelopes. 3. In program- ming, an import script can set up documents or source code by selectively merging modules such as header files, modular routines, Unix "man" pages, etc. Improved Definition Television IDTV. A picture broadcast and display system that provides better pic- ture quality than conventional NTSC standards by in- corporating field store techniques in the receiving circuitry. For example, the signal can be de-interlaced prior to display to reduce flicker. The originating sig- nal is not changed. Improved Mobile Telephone Service IMTS. Early mobile phone services were set up on systems based on large antenna transceivers with limited coverage and public operator-assisted broadcast services. The system had little flexibility or privacy, but it served as a forerunner for IMTS, in which the subscriber could place the calls directly; this in tum developed into current cellular systems where a larger number of smaller, automated transceiver systems allowed broader geographic coverage. IMPS See Infinite Monkey Protocol Suite. impulse 1. A nonrepetitive pulse so short as to be mathematically insignificant. 2. A very short nonre- petitive pulse which may not seem significant by it- self, but which may impede transmission of the af- fected line or signal. Data transmissions are more sensitive to impulse interference than voice commu- nications. 3. The uncontrolled desire to run out and get the latest techie toy, even though you don't really need it. Cell phones, faster computers, and scanners often fall into this category. IMSAI 8080 An early 8080A-based microcomputer that used the MITS-developed Altair bus (8-1 00 bus); it was, in a sense, the first microcomputer clone. The 8080A was an enhanced version of the 8008 used on 473 © 2003 by CRC Press LLC Fiber Optics Illustrated DictionanJ the first Altair. The IMSAI was introduced in 1975 by IMSAI Manufacturing with ads that compared it competitively against the Altair. See Altair. IMSI See International Mobile Subscriber Identity. IMTC The International Multimedia Teleconferenc- ing Consortium. Their Web site includes information. http://www.imtc.orglimtc IMTS See Improved Mobile Telephone Service. IMUX See Inverse Multiplexer. IMW See Intelligent Music Workstation. in-bandA transmissions scheme in which control and data signals are sent together over the same set of wires, or over the same frequencies, sometimes more or less simultaneously and sometimes interspersed with one another. in-band signaling A type ofsignaling which is in- corporated together with the data being transmitted. This is found, for example, in systems which encode signaling codes along with voice transmissions on the same wires (commonly copper twisted pair). In-band signaling has advantages and disadvantages. It doesn't require a separate set of wires to send con- trol signals and thus is less expensive, but it does re- quire more sophisticated handling of data and signals and has a higher potential for slowdown, errors, in- terference, or fraud. In-band phone systems are at greater risk for secu- rity breaches and unauthorized use of services, be- cause users can send in-band signals over the voice line and control certain telephone functions with il- legal control devices such as blue boxes. Newer out-of-band phone systems, based for example on Signaling System 7 (SS7), make unauthorized use through control signals on the transmissions line im- possible, and these types of networks are increasing in prevalence as older equipment is replaced by newer networks. See ISDN, Signaling System 7. in-line device A hardware device, commonly a pe- ripheral which can be interposed between two other devices without interfering with the operation of the other devices, or intended to interface between two other devices to perform its function (and mayor may not change the functioning of the other devices). Daisy-chainable devices are a type ofin-line device, though not all in-line devices can be daisy-chained. See daisy chain. INA See Information Network Architecture. incandescent lamp A common type ofilluminating bulb developed by Thomas Edison, originally con- sisting ofa carbonized filament in a glass globe from which the air had been removed. However, the car- bon tended to blacken the inside of the bulb and other solutions were sought, with tungsten coming into general use because of its high melting point. Experi- mentation with the internal environment of the bulb also resulted in the discovery that various gases could alter the glow or extend bulb life. INCC Internal Network Control Center incidence angle, angle of incidence The angle be- tween the line of travel ofradiant energy and the nor- mal (perpendicular) of a reference surface (usually in the path of the emission). When the angle of incidence 474 is equal to the normal of a reflective surface, the ra- diant energy will be reflected back in the same di- rection from which it came, resulting in a Littrow condition. When the angle of incidence of radiant energy encountering an obstacle diverges from the normal ofthat object, interference patterns may re- sult. In optics, when reflective surfaces are built into a component, as in fiber optics cladding or a diffrac- tion grating, the direction of travel oflight energy can be controlled to propagate, concentrate, or filter de- sired wavelengths. See blaze angle, cladding, diffrac- tion, grating, normal. incipient failure A failure from degradation ofa pro- cess or equipment in its early stages. inclination I. The angle ofa surface or vector in re- lation to an associated horizontal. 2. Adeviation ofa surface or vector from horizontal or vertical. incoherent scattering I. Abehavior oflight in some circumstances whereby the phase of the light is ran- dom and unpredictable, as in LEDs. 2. A disordered scattering of transmission waves, such as radio, when they encounter a surface and are deflected. incoming address message lAM. See initial address message. increment I. n. A small change in value. 2. v. To add to an existing quantity, as in a software programming loop. Incrementing an integer counter in aprocedure is a very common way to keep track of quantities, op- erations, timing, and events. Although technically a negative value can be incremented, in programming this is usually called decremented. incremental sensitivity A measure of the least amount ofchange that can be detected by a specific instrument or process. incremental service delivery ISD. The delivery of a service in stages, as the user develops a need for more or different services. Many industries are "bootstrapped" this way to allow users to become ac- customed to a technology at a low cost or at a beginner's expertise level while providing a means to "move up" when there is a need for next-level or enhanced services. Incumbent Local Exchange Carrier,Independent Local Exchange Carrier ILEC. Sometimes called dominant carriers, ILECs comprise the RBOCs, in- dependent phone companies, GTE, and others. See Competitive Local Exchange Carrier. Incumbent Local Exchange Carrier duties The Federal Communications Commission (FCC) stipu- lates a number of duties, in addition to the Local Ex- change Carrier duties, in the Telecommunications Act of 1996 as shown in the Incumbent Local Exchange Carriers chan. Independent Cable & Telecommunications Asso- ciation ICTA. A national, Washington, D.C based in- dependent trade organization supporting private and alternate cable and telecommunications systems pro- viders. ICTA members provide video progr1unming and other services to residents of multiple dwelling units, primari ly through shared tenant services (STSs), although a trend toward geographic clusters © 2003 by CRC Press LLC has been recently seen. Customers served by these services include apartment, condominium, and co-op dwellers, as well as motels, college campuses, and prisons. independent flow control message IFCM. In Switch-ttl-Switch Protocol (SSP), the IFCM is trans- mitted as a 16-byte information message header of type 0x21 separate from the control message header. index An organizational tool that provides a key to other types of information, or alarger body of infor- mation, stored elsewhere. Indexing is an extremely important aspect of database design, search, and re- trieval. It provides a hook or jumping off point, abrief means of indicating the subsequent location ofa hi- erarchy or list. An index in its broadest sense can point to records, further indexes, keywords, locations, Incumbent Local Exchange Carriers (LECs) - FCC-Defined Duties As defined in the Telecommunications Act of 1996: "In addition to the duties contained in subsection (b), each incumbent local exchange carrier has the following duties: (I) DUTY TO NEGOTIATE - The duty to negotiate in good faith in accordance with section 252 the particular terms and conditions of agreements to fulfill the duties described in para- graphs (I) through (5) of subsection (b) and this subsection. The requesting telecommunica- tions carrier also has the duty to negotiate in good faith the terms and conditions of such agree- ments. (2) INTERCONNECTION - The duty to provide, for the facilities and equipment of any requesting telecommunications carrier, interconnection with the local exchange carrier's network- (A) for the transmission and routing of telephone exchange service and exchange ac- cess; (B) at any technically feasible point within the carrier's network; (C) that is at least equal in quality to that provided by the local exchange carrier to itself or to any subsidiary, affiliate, or any other party to which the carrier provides inter- connection; and (D) on rates, terms, and conditions that are just, reasonable, and nondiscriminatory, in accordance with the terms and conditions of the agreement and the requirements of this section and section 252. (3) UNBUNDLED ACCESS - The duty to provide, to any requesting telecommunications car- rier for the provision ofa telecommunications service, nondiscriminatory access to network elements on an unbundled basis at any technically feasible point on rates, terms, and condi- tions that are just, reasonable, and nondiscriminatory in accordance with the terms and condi- tions of the agreement and the requirements of this section and section 252. An incumbent local exchange carrier shall provide such unbundled network elements in a manner that al- lows requesting carriers to combine such elements in order to provide such telecommunica- tions service. (4) RESALE - The duty (A) to offer for resale at wholesale rates any telecommunications service that the carrier provides at retail to subscribers who are not telecommunications carriers; and (B) not to prohibit, and not to impose unreasonable or discriminatory conditions or limi- tations on, the resale of such telecommunications service, except that a State com- mission may, consistent with regulations prescribed by the Commission under this section, prohibit areseller that obtains at wholesale rates a telecommunications ser- vice that is available at retail only to a category of subscribers from offering such service to a different category of subscribers. (5) NOTICE OF CHANGES - The duty to provide reasonable public notice of changes in the information necessary for the transmission and routing of services using that local exchange carrier's facilities or networks, as well as of any other changes that would affect the inter- operability of those facilities and networks. (6) COLLOCATION - The duty to provide, on rates, terms, and conditions that are just, reason- able, and nondiscriminatory, for physical collocation of equipment necessary for intercon- nection or access to unbundled network elements at the premises of the local exchange car- rier, except that the carrier may provide for virtual collocation if the local exchange carrier demonstrates to the State commission that physical collocation is not practical for technical reasons or because of space limitations." 475 © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary sequences, arrays, and much more. An index can comprise numbers, symbols, or lexical mnemonics, depending upon the context of the application. Some indexes are seen by the user and set manually; others are transparent to the user and set by the software. Databases, mass storage directory structures, and file hierarchies are typically indexed in one way or an- other for quick storage and retrieval. An index is intended as a shortlist of what is contained in the database. It is a means of describing in brief what related information is held where in order to en- hance the speed with which the related information can be found. The efficiency of an indexing system depends upon the the type of index used, the quan- tity of infonnation being indexed, the overall struc- ture of the database, and the types of information sought and retrieved from the system. If a system in- volves a small amount of data and a complex index- ing system, then it is not likely to be efficient. If, on the other hand, a large amount of data can be rela- tively objectively categorized, based on objective in- formation or good guesses as to what types of in for- mation will be sought, then an indexed structure is one way to store and utilize the information. See da- tabase. index counterA very common fonn of feedback that allows a user or technician to monitor usage, or elapsed time or distance. Index counters and their electronic counterparts are found on tape drives, VCRs, microwaves, cars (odometers), photocopiers, and almost any appliance in which the location of in- formation or tracking of usage for billing purposes is desired. Counters that give a rough estimate of the number of users who have visited a Web site, or at least the number of accesses to aparticular page. index of refraction, refractive index (symb. - n, abbrev. - RI) A numeric description of the refractive ("ray-bending") properties ofa material, which de- pends upon its composition and density in relation to the composition and density of the immediate sur- rounding material( s). Depending upon the reference scale, the index of re- fraction ofa vacuum is given as 1.0 and other mate- rials, which are naturally denser than a vacuum (which by definition has no matter), have higher num- bers as given by n = c/v where c is the speed of light in a vacuum and v is the speed of light in the medium. Air, which only very slightly refracts light, has a re- fractive index of 1.00029, very near that ofa vacuum. The refractive effect can be observed with common materials. For example, a broom handle placed partly in water (RI 1.333) will appear to bend from the point at which it passes into the water. If the same handle is placed in a more viscous (denser) substance, such as benzene, which has a higher refractive index, it appears to bend even more and will be associated with a higher refractive index than water. Faceted materials like gems that glitter when moved about in light tend to have higher refractive indexes than dull materials such as plastic. Crown glass, which is used in many optical components, has a RI of 1.52 while diamond has an even higher index of2.42. 476 That's the basic explanation. Actually, there are a couple of other important factors that are built into assumptions about the refractive index reference val- ues. Light is not a homogenous phenomenon - it stretches from infrared to ultraviolet, with different properties at different wavelengths in the invisible and visible spectrums. Longer wavelengths tend to pass through matter more readily and shorter wave- lengths tend to scatter more readily, so refractive in- dex charts generally also specify the wavelength at which materials are referenced (e.g., 589 nm). Tem- perature is a factor, as well. Since the index ofrefrac- tion is related to the density ofamaterial and density changes when temperature changes, the temperature at which the index is referenced needs to be speci- fied. Changes in density related to temperature are due to differences in molecular interaction. For ex- ample, the molecules in warmed air become more active and expand overall, thus becoming less dense and rising over colder air, the phenomenon that en- ables hot air balloons to fly. Thus, temperature influ- ences density, which in turn influences refractive in- dex. Thus, RI charts will generally specify the tem- perature at which materials exhibit a certain refrac- tive index (e.g., 20°C). (Since this is a reference on optics, the above expla- nation focuses on light as the incident beam, but re- member that refractive concepts can be somewhat generalized to electromagnetic phenomena outside the optical spectrum.) Index of Refraction - Basic Concept In this simple example, light traveling through air encounters matter with a different composition from the air. There is an interaction between the light and the molecules of matter such that the direction and speed of travel (velocity) of the light are affected. /fit were aperfect mirror, all the light would be reflected, but assume it has some conductive (dielectric) prop- erties. In this case, some of the lightcontinues to travel through the material, but, thegeneral path of the light is "bent II or refracted. In other words, it continues in a slightly different direction from the incident light, causinga refractiveeffectthat continues untilthe light exits the material (or encounters structural changes or impurities in the material through which it is trav- eling). The degree of refraction can beexpressedwith a value relative to a baseline of no refraction = 1. O. Different materials refract light in different ways. Materials with homogenous structures may havefairly simple, straightforward light-refracting properties. Crystalline or crystal-like materials such as Iceland spar and Ulexite refract light in unusual ways. © 2003 by CRC Press LLC The index of refraction is one of the most important concepts in optics. The capability of refracting light in a particular direction by selecting a material with certain refractive properties and shaping it to exploit those properties is integral to the fabrication and im- plementation of fiber optics devices and all instru- ments that use lenses. The cladding in a fiber optic cable has a slightly higher refractive index than the light-conducting core, which accounts for its ability to refract light back into the core within certain angles to achieve total internal reflectance (TIR). Traditional lenses in telescopes, microscopes, and laser assem- blies exploit the refractive properties of optical com- ponents to concentrate or diffuse light. F or practical purposes, when designing components, the index of refraction is related to the angle at which light diffracts through a medium relative to the "nor- mal " (perpendicular) to the surface at which the in- cident radiation encounters the material. In a flat, pla- nar surface such as calm water or window glass, this is a fairly straightforward calculation. For more com- plex surfaces (e.g., rough water, curved lenses), the tangent ofa specified region around the point of con- tact of the incident light facilitates the geometric cal- culations for determining suiface normal. See diffrac- tion, diffusion, Iceland spar, Snell's law, Ulexite. indicator light A light signaling a transmission, fault condition, readiness, or other state that requires at- tention. Indicator lights are common on appliances, modems, surge suppressors, hard drives, etc. indirect addressing A common method in computer programming for creating a cross reference to addi- tional related data. Since much of computer data stor- age cannot be determined in advance, indirect ad- dressing makes it possible to use small segments of memory, or noncontiguous memory, hard drive space, etc. by creating pointers, directories, and other links to the main body of information. indirect light Light that is not self-emitted, but rather is reflected from another source. For example, the Moon does not generate light on its own, but reflects light from the Sun. indium gallium arsenide nitride InGaAsN. A semi- conductor alloy developed in the early 1990s in Ja- pan that can be produced through a metal-organic chemical vapor deposition (MOCVD) process. A small amount of nitrogen added to gallium arsenide gives the alloy some remarkable electrical and opti- cal properties, dramatically altering its bandgap struc- ture. The material holds potential for fabricating pho- tovoltaic power sources for lasers and satellite com- munications. It may enable the development of solar power cells significantly more efficient that current silicon solar cells. At Sandia labs, the material is produced in a chemi- cal reactor in which indium, gallium, arsenic, and nitrogen are heated within the chamber, causing a chemical decomposition and crystal-forming process that results in the alloy. This brings the bandgap into more practical ranges than another popular semicon- ductor material- gallium arsenide. See gallium ars- enide. indium phosphide An alloy used in the production of semiconductor lasers, favored because its band- gap properties are suitable for producing laser light that can be used in short-haul fiber optics transmis- sion lines. INDIX See International Network for Development Information Exchange. Indo-European Telegraph Company The company that successfully installed a wire communications cir- cuit all the way from London to Calcutta, in 1884. The feat was largely inspired by the successful lay- ing of the transatlantic telegraph cable two decades earlier. induced Produced by the influence of an electric cur- rent or a magnetic field, usually by proximity. inductance (symb. - L) The property of a material (generally in a circuit) to tend to resist change in the flow of electromagnetic current, resulting in chang- ing lines of force. This tendency occurs where there is a flow of alternating current (AC) moving through a conductive material. The term is used specifically with reference to alternating current, as direct cur- rent (DC) does not exhibit the same alternate changes. Higher inductance values are generally associated with higher impedance values. Inductance is typically expressed in henries (H) or microhenries (flH). A basic inductor can be created by winding a con- ducting wire, such as copper, into a coil. An under- standing of the properties of inductance was a very important step in the development of induction coils. These could be devised to generate high-voltage charges, and thus a source of electricity. Phone lines have been optimized over the decades for the cost-effective delivery of basic voice communi- cations and were not designed for the specific elec- trical needs of data communications. Electrical surges, EM! interference, balun noise, and other prob- lems can interfere with data delivery and slow down transfer speeds or even cause the line to be dropped. Thus, high-inductance noise filters are marketed to dialup modem users to process the electrical signals and improve data transmissions. Heat-resistant, low-inductance power cables are in- creasingly available for telecommunications applica- tions. These may be constructed in various ways, but PVC-insulated stranded, annealed, tinned copper wires are common. See induction, induction coil, re- sistance. inductance analyzer A device for testing inductors and coils in telecommunications devices, switching power supplies, filter circuits, and similar products. Inductance analyzers typically test in a wide range of programmable frequencies and may include addi- tional impedance, capacitance, and DC resistance testing capabilities. Automatic calibration and inter- nal memory for storing and recalling settings and test setups may also be included (calibration kits may also be sold separately). Newer models may support sev- eral impedance settings in order to compare test re- sults with those from older test sets and may include a serial or other standard interface for downloading settings to a computer system for storage and analysis. 477 © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary The understanding ofinductance and the use of test equipment for troubleshooting is an important part of courses for telecommunications technicians and generally involves about 30 hours of class instruc- tion. See crosstalk, induction. inductance bridgeA diagnostic circuit configuration instrument that enables comparison of an unknown with a known inductance, similar to the concept used in a Wheatstone bridge. See Wheatstone bridge. induction, electromagnetic An electric charge or magnetic field in a material resulting from the influ- ence ofa proximate electric current or magnetic field. In a circuit, induction may be deliberately created or may result from undesired influences from nearby cir- cuits or electromagnetic components. In computer circuits, especially those tightly inte- grated on a single chip, induction can be an impor- tant hindrance or limitation that must be taken into consideration in the chip's design and fabrication. Since it is difficult to build hundreds (or thousands) of prototype chips in order to test or measure the in- duction properties ofa particular design, computer modeling programs have been developed to simulate the induction characteristics of prototype circuits. Sequence's Columbus-RF, for example, is a patent- pending technology for modeling resistance, capaci- tance, and inductance of chip circuitry. On a larger scale, in structured cable systems, data cables that are very near to voice cables may gener- ate undesired noise in the voice lines, partly through induction. See crosstalk, far end crosstalk, induc- tance, induction coil, near end crosstalk. induction, logical A reasoning process in which gen- eral principles or overall concepts are derived by dis- cerning patterns or relationships among individual or particular observations. The modeling ofinduction through heuristic problem-solving algorithms is of interest in robotics, artificial intelligence, and intel- ligent discovery and search procedures in advanced database systems. Inductive reasoning has applica- tions for data mining on the Internet and might spe- cifically be applied to discerning patterns in user in- quiries that could be used to anticipate future que- ries or general needs. It can also be used to try to an- ticipate the needs ofhandicapped telecommunica- tions product users based on overall observations of their patterns of use. induction coil A historic electrical device that played an important role in early electronics inventions. It was asignificantprovider of high voltage current for many decades, and led to the creation of transform- ers for converting between alternating current (AC) and direct current (DC). It also led to various induc- tion-based frequency converters. Today, induction coils are still used to offset capacitance in long com- munications wirelines. A basic induction coil was created in 1836 and de- scribed the next year in The Annals of Electricity by Nicholas J. Callan. It consisted ofa horseshoe-shaped bar of iron, wound with many feet of thick copper wire, and hundreds of feet of thin iron wire. By in- terrupting the primary circuit with acontact breaker, 478 Callan could induce a charge sufficient to power an arc light. Ayear after Callan published his findings, an American, Charles Grafton Page, created an in- duction coil. See loading coil. induction field In a transmitting antenna, a region associated with the antenna in which changing elec- tromagnetic lines of force are active as current flows through the device. In long wireline installations, a field that is deliberately generated in order to offset capacitance. See induction coil, loading coil. induction frequency converter A mechanically powered induction device connected to a source of fixed frequency current that utilizes secondary cir- cuits to deliver a frequency proportionate in speed to the magnetic field. In its most general sense, fre- quency conversion has become avery important part of communications technology. The conversion of frequencies allows signals to be carried over a vari- ety of media with different transmission characteris- tics, and further enables signals to be shifted so that incoming and outgoing signals are less likely to in- terfere with one another. inductive connection, inductive pickup An electro- magnetic connection between two devices or objects without direct electrical contact. The communication between the devices occurs from an electromagnetic influence through proximity to the changing electro- magnetic lines of force. Some types of diagnostic tools use inductance to monitor or observe circuits without physically contacting the line. A number of surveillance devices also use this method for bugging a line, in order to avoid detection. Regulations to protect privacy prohibit the unautho- rized monitoring of communications through induc- tive surveillance devices. Fiber optic transmissions are immune to inductive pickup as the transmission of signals through light does not have the same char- acteristics as electricity ofextending beyond the me- dium through which it is traveling. See wiretap. inductive coupling The transfer of energy between two circuits that are close together, but not directly electrically connected. Thus, the interaction of the electromagnetic lines of force associated with the in- teraction of the circuits causes the transfer. The trans- fer may also occur due to self-inductance of each of the circuits (direct coupling). The transfer ofenergy may be desirable or undesirable. Unshielded or mini- mally shielded conducting wires that are too close to- gether may create unwanted noise and interference through inductance. inductive postA conducting bolt, screw, or post as- sociated with a waveguide that provides inductive susceptance to allow tuning of the waveguide. It is usually mounted across the waveguide, parallel to the E field. See E field, waveguide. inductive tuning In electronic devices such as radio tuners, a means ofadjusting the tuning by moving a core in and out of a coil within which it is contained. The core is not in direct contact with the coil, but re- acts to the changes in the electromagnetic field asso- ciated with the coil by inductance. inductor Apassive component that provides power © 2003 by CRC Press LLC or power-related electromagnetic energy or energy control, traditionally called a coil. An inductor is able to "store" energy and to resist electromagnetic changes associated with the flow ofcurrent. Induc- tors come in a wide variety of types and are used in many aspects oftelecommunications circuitry. Varia- tions in the core material, the shape of the coil, and the number ofwindings will influence an inductor's properties. Tables listing tolerance codes have been standardized for inductors. For example, a tolerance code ofK signifies ±10% tolerance. Inductors are categorized in a number of ways: by their specific function (e.g., suppression), by their types of cores, or by their general size (e.g., minia- ture inductors for microelectronics). Inductor types include suppression, VHF, ring core, air core, lami- nated core, and many more. Suppression conductors are typically ferrite wound with enamelled or tinned copper wire all sealed with resin and/or a plastic sheath. The ferrite substance is chosen for having good magnetic properties, commonly manganese or nickel and zinc. Air core conductors have the wind- ing built over a nonconductive core, commonly ce- ramic. See inductance, induction. inductor, axial This inductor style is builtwith a cen- tral core and concentric leads on either end of the core. The core may be constructed from a variety of con- ductive materials. Axial conductors are used in power and radio frequency (RF) applications. inductor, air core An inductor with a core with no magnetic properties (e.g., ceramic) that is used as the base or support for the conductive winding. Air cores are used in situations where low loss and low induc- tance are desired, as in high-frequency applications. Industrial, Scientific, and Medical ISM. A set of segments of electromagnetic frequencies which do not require licensing by the Federal Communications Commission (FCC), excluding telecommunications applications. Typical ISM applications include par- ticle acceleration, vibration generation, heating, ul- trasound equipment, microwave ovens, humidifiers, etc. Class A ISM refers to industrial environments and Class B ISM is intended for domestic environments. In Canada, ISM is addressed by ICES 001. ISM equipment operators are required by the FCC to "take appropriate measures to correct" interference to radio services unless those services are operating in the ISM frequency band. The conduction and field- strength limits for interference are dependent upon the equipment generating the radio frequencies and the specific frequency bands being used. Commonly used frequencies are in the 902- to 928-MHz and 2.4- to 2.4835-GHz ranges, but there are others. An important growth area in ISM unlicensed frequen- cies is spread spectrum and frequency-hopping tech- nology for local area wireless networks (LAWNs) for data communications. By the late 1990s, vendors had developed scalable high-speed ISM-frequency wire- less networks that they felt would comply with all the FCC ISM regulations. With important approvals by the FCC beginning about 1999, the systems began to be put into commercial production. There is also a high degree of correspondence be- tween ISM and designated amateur radio bands, which sometimes causes problems for ham radio op- erators, especially given the recent increase in wire- less consumer communications devices. These issues are being evaluated and debated by the ARRL and the FCC as the demand for radio frequency resources increases. Industry Advisory Council lAC. A national trade organization representing information technology (IT) professionals who provide products and services to government agencies in the u.S. The lAC also serves as a liaison between the IT industry and the Federation of Government Information Processing Councils (FGIPC). http://www.iaconline.org/ IndustryCanadaA Canadian federal agency respon- sible for the protection of intellectual property and the allocation oflicenses for use of radio frequencies. Formerly the Department of Communications. See Canadian Radio Television and Telecommunications Commission. IndustryCanadaEmergencyTelecommunications Branch Aservice department of Industry Canada that provides support for crisis situations. It administrates and liaises with a wide variety of communications and disaster departments and external organizations, in- cluding emergency broadcasting, priority access, emergency response coordination, and more. Several emergency and planning committees and working groups further the aims of the ETB. Working groups include the United Nations Working Group on Emer- gency Telecommunications (WGET), the Long-Dis- tance Emergency Telecommunications Working Group, and the Wireless E-911 Working Group. http://spectrum.ic.gc.ca/urgentJ Industry Circuit Topography Act ICTA. A Cana- dian Act intended to protect integrated circuit topog- raphies. See Semiconductor Chip Protection Act. Industry Standard Architecture ISA. Formerly, a very common inputJoutput bus architecture on Inter- national Business Machines and licensed third party computers developed originally on the ffiM XT mod- els, and carried through to later models. Originally it was an 8-bit architecture, but was upgraded to 16-bit. The expansion slots inside a computer have to fol- Iowa standard format so various manufacturers can create compatible peripheral cards. ISA was one of the common types of slots found in personal com- puters until the mid-1990s when it was superseded by Peripheral Component Interconnect (PCI), Video Electronic StandardAssociation (VESA), Extended Industry Standard Architecture (EISA) and others. See Extended Industry Standard Architecture, Periph- eral Component Interconnect. INETPhoneAdata telephone service connected and handled through the Internet, thus substituting the Internet for the long-distance segment of a phone call in a way that is transparent to the users. See RFC 1789. Infineon TechnologiesApublicly traded leading glo- bal provider of integrated circuits for advanced com- munications sytems. See GEMINAX. 479 © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary Infobahn colloq. The Information (Super) Highway, based on the German word bahn. The Information Superhighway is also colloquially called the I-way. See Information Super Highway. Information Access Company IAC. A commercial electronic information vendor (purchased by the Thomson Corporation from ZiffCommunications for almost halfa billion dollars). IAC is one of the firms being watched by intellectual property rights advo- cates and writers to assess whether firms that distrib- ute electronic information, especially over public networks, are tracking and compensating contribu- tors fairly. Information Analysis Center IAC. An interagency intelligence center located in the U.S. Embassy in Mexico City to assist the U.S. Ambassador to Mexico to collect and process intelligence for use by U.S. and cooperating Mexican law enforcement personnel. The information is collected and stored in electronic databases. Information and Communications Industry Asso- ciation, Ltd. ICIA. A U.K. trade association support- ing information and service providers and operators, and hardware and software developers, especially those involved in electronic publishing and data dis- tribution. Founded in 1978, ICIA evolved from the Videotex Industries Association. http://www.icia.co.uk/ Information and Software Industry Association ISIA. A trade association promoting the recognition, profitability, and standards of the information and software industry in Hong Kong, founded in July 1999. ISlA promotes awareness and use of informa- tion technologies, and represents and safeguards the interests of its members. It further promotes coop- eration between Hong Kong and mainland China. http://www.isia.org.hk/ information content provider This is defined in the Telecommunications Act of 1996, and published by the Federal Communications Commission (FCC), as " any person or entity that is responsible, in whole or in part, for the creation or development of information provided through the Internet or any other interactive computer service." Information IndustryAssociation IIA. A U.S. trade association supporting businesses that develop and globally deliver innovative information products and services, founded in 1968. The lIA represented its members to government and inputs to the Federal Communications Commission (FCC) and the Federal Trade Commission (FTC). In 1999, lIA merged with the Software Publishers Association to form the Soft- ware & Information Industry Association. See Soft- ware & Information Industry Association. Information Industry Association, Australian AlIA. A trade organization representing and promot- ing the information industry in support of the Aus- tralian economy. AlIA represents its members in gov- ernment policy, promotes the value and applications of Australian information technologies, and provides educational and networking support to its members. http://www.aiia.com.au/ 480 Information InfrastructureStandards Panel liSP. A national voluntary standards support panel estab- lished to facilitate the development of standards im- portant to the Global Information Infrastructure (Gil) and the U.S. National Information Infrastructure (NIl). IISP promotes cross-sector efforts to identify, highlight, and resolve major standards issues, a mis- sion that was approved in November 1997. http://www.ansi.org/public/iisp Information Network Architecture INA. In the mid-1980s, Bell Communications Research began building its Intelligent Network (IN) to provide a broader range of telephone services and support for data transmission over traditional phone lines. From this grew Advanced Intelligent Networks (AIN), and then Information Network Architecture (INA) with its improved broadband support. There is some dis- cussion as to whether INA will succeed or coexist with AIN, as AIN will meet the needs of many users for some time, considering the lag that exists between the time a new technology is introduced and when it is generally adopted by consumers. Information Security Exploratory Committee ISEC. A committee tasked with the study and sup- port ofprivate sector information security. The ISEC was hosted by the Information Technology Industry Council. information service This is defined in the Telecom- munications Act of 1996 and published by the Fed- eral Communications Commission (FCC), as mean- ing " the offering ofa capability for generating, ac- quiring, storing, transforming, processing, retriev- ing, utilizing, or making available information via telecommunications, and includes electronic pub- lishing, but does not include any use of any such capability for the management, control, or opera- tion ofa telecommunications system or the man- agement ofa telecommunications service." See Federal Communications Commission, Telecom- munications Act of 1996. Information Service Industry Association of China CISA. A trade organization representing the Chinese information industry. CISAaids its members in creating and maximizing their competitive busi- ness strategies. CISA promotes the application of in- formation technology (IT) in business, government, education, and individual market settings. http://www.cisanet.org.tw/ Information Services Association, Japan JISA. A nonprofit trade organization representing Japan's in- formation technology (IT) services industry. Founded in 1984, JISA evolved from two organizations, the Japan Software Industry Association and the Japan Information Processing Center Association. JISAco- operates with the World Information Technology and Services Alliance (WITSA) and the Asian-Oceanian Computing Industry Organization (ASOCIO). http://www.jisa.or.jp/ Information Superhighway A catchphrase pro- moted by U.S. government representatives, particu- larly Al Gore of the Clinton administration, and the © 2003 by CRC Press LLC press, for the domestic and global communications infrastructure. See National InformationInfrastructure. Information Systems Auditability and Control Association ISACA. A global not-for-profit trade association ofmore than 17,000 information system (IS) professionals providing education, training, and certification support. http://www.isaca.org/ Information System SecurityAssociation ISSA. A not-for-profit international trade organization sup- porting the interests ofinformationsecurity (IS) pro- fessionals. ISSA supports communication among members, educational activities, and information se- curity publications. ISSA is a founding contributor to the International Infonnation Systems Security Information Technology Research Centers - Brief Selection Title Description Abbreviation Information Technology Research Center ITRC An interdisciplinary research unit at the University of Arkansas devoted to advancing the state of research and practice in the development and use of information technology (IT). http://itrc.uark.edu/ Information Technology Research Center ITRC Anonprofit organization dedicated to the development, evaluation, and application of advanced technologies to enhance scientific research and education in information technology (IT). The Center is international in scope, operating out of Missoula, Montana. An example of an ITRC project is the TRIO ThinkQuest Project, U.S. Department of Education-funded project for sponsoring an online educational Web site development contest. http://www.itresearchcenter.org/ Information Technology Research Center ITRC A funded project in which the Innovative Computing Laboratory at the University of Tennessee Knoxville campus will be transformed into an IT research center with a broader scope, under the direction of Dr. 1. Dongarra. AdvancedInformation Technology Development Research Center A Japanese center to support research to improve road traffic systems, traffic information provision systems, and home information systems, as well as research on the application ofgeographic information systems (GIS) and other information technologies to design and construction. Centerfor Information Technology Research in the Interest of Society CITRIS A California Institute for Science and Innovation, endorsed in December 2000. CITRIS is located at the University of California, Berkeley and is dedicated to promoting scientific advances in information technology fields critical to the California economy. German National Research Centerfor Information Technology GMD A cutting-edge national and international research facility devoted to applications-oriented research in the information and media industries with a view to developing new products. http://www.gmd.de/ Information Technology Research Centre ITRC An Ontario-based Canadian information technology (IT) research center. Research Centerfor Communications and Information Technology ReCCIT A Thai institute of King Mongkut's Institute of Technology Ladkrabang (KMITL), ReCCIT supports a number of cooperating labs in telecommunications, information technology, signal processing, and signal transmissions. Research projects are wide-ranging, including mobile and satellite communications, information science, multimedia, virtual modeling, circuit design, signal processing, and more. http://www.kmitl.ac.th/ reccit/ Research Center Information Technology RCIT Since 1990, RCIT has been developing large-scale, dynamic information systems for public institutions and companies in Europe. RCIT is also the European Telework Development (ETC) national coordinator. 481 © 2003 by CRC Press LLC . signal. See Johnson, John. Image Intensifier- Night Vision Goggles Night vision goggles are an example of image in- tensifying technology. Fiber optic components are used in 2nd-, 3rd-, and 4th-generation image intensifier tubes that are used as step. file In software applications, to import is to bring in data from another program, file, or transmis- sions source, usually in a non-native file format. This is usually done through an applications filter or through drag-and-drop capabilities. In drag-and-drop imports, the program will either maintain links to the original imported file or convert the format to one consistent with the program into which it is imported. import. con- trol signals and thus is less expensive, but it does re- quire more sophisticated handling of data and signals and has a higher potential for slowdown, errors, in- terference, or fraud. In-band phone systems are at greater risk for secu- rity breaches and unauthorized use of services, be- cause users can send in-band signals over the voice line and control certain telephone functions with il- legal control devices such as blue boxes. Newer out-of-band phone systems, based for example on Signaling System 7 (SS7), make unauthorized use through control signals on the transmissions line im- possible, and these types of networks are increasing in prevalence as older equipment is replaced by newer networks. See ISDN, Signaling System 7. in-line