Fiber Optics Illustrated Dictionary - Part 39 docx

Fiber Optics Illustrated Dictionary of force in a magnetic field taken as a group (symb. - B). When expressed in terms of density per unit area, it is calledflux density (symb. - D). fly-by n. Arepresentation of movement from a point of view above the ground, commonly used in anima- tions, especially video games with flight simulation. Fly-by animations give a wonderful sense of being inside the scene that is imaged. NASA has produced some wonderful fly-by animations of the surfaces of other planets such as Mars. Satellite geophysical data make it possible to create fly-bys ofEarth's surface right down to individual buildings and streets. Vir- tual reality fly-by simulations are startlingly real, with participants ducking moving images so as not to be hit. See virtual reality. fly-page See banner. flyback retrace. In a cathode-ray tube (CRT), the movement of the electron beam tracing the image on the screen from the end of the trace to the beginning where it starts over on the next line. Flyback is usu- ally associated with a blanking interval in which the beam is turned off so as not to interfere with the im- age already displayed. There is more than one type of flyback on a monitor. The flyback associated with scanning each line is similar to the line feed and car- riage return on a typewriter, in that the scan finishes at the end of one line and flies back to the next line down (or two lines down in interlaced screens) and the beginning of the subsequent line, in a zigzag (sawtooth) pattern. The other type offlyback is when the full video frame is finished, the beam is at the bottom or last line of the screen and then flies back to the top or first line of the screen. (This example assumes a typical CRT in which the scanning is left to right and top to bottom.) See blanking, frame. flying erase headA mechanism on prosumer and in- dustriallevel VCRs and camcorders that erases pre- viously recorded video traces that might otherwise interfere with new information being recorded on top of the same section. This head is typically found on systems that support insert editing. Rainbows and other undesirable artifacts are thus avoided. flytrap A fIrewall or other security system that logs unauthorized attempts at access to provide informa- tion that can help identify or apprehend the intruder. flywheel 1. A wheel that works with other mecha- nisms to smooth out and reduce inconsistencies in the rotational speed of the equipment. 2. A wheel that is used with other mechanisms, whose purpose is to store kinetic energy. Flywheels are often coupled with power generators to continue the motion when the generator mechanism slows or is idle. flywheel effect In a transmission that experiences fluctuations, the maintenance ofa steadier, more con- sistent level of current, information, or oscillation by physical or logical means. Analogous to the function ofa flywheel. FM 1. fault management. 2. See frequency modu- lation. FM broadcasting Transmission through frequency modulation technologies on approved FM frequen- cies with the appropriate FM broadcasting license. In 372 the United States, FM stations are spaced at 0.2 kHz intervals, ranging from 88.1 to 107.9 kHz. Low power FM broadcast signals are used for mobile intercoms, indoor intercoms, monitors, and cordless phones. See broadcasting, FM broadcasting, frequency modula- tion. FM transmitter In its basic form, an FM transmit- ting system includes a microphone, a circuit, and a frequency modulating (FM) transmitter. In more so- phisticated forms, it includes the various commerciaV industrial transmitters costing thousands of dollars for broadcasting from licensed radio news and en- tertainment and other FM communications stations. Building simple FM transmitters in the 88- to 108- MHz frequency range is a very popular hobbyist in- troduction to electronics. With current technology, it is possible to create very compact, working FM trans- mitters for under $30, to broadcast a few hundred feet or even up to two miles under good conditions. Be- fore conducting hobbyist experiments with low power FM transmitters, it is important to learn the various Federal Communications Commission (FCC) restrictions on broadcasting, and to honor laws pro- tecting the safety and privacy of individuals. FMAS 1. Facility Maintenance and Administration System. 2. Fund Management Accounting System. FMV See Fair Market Value. FNB See Fiberoptics NewsBriefs. FNC See Federal Networking Council. FNEWS A fast full-screen news reader for UNIX, ALPHA-VMS, and VAXNMS systems, similar to NEWSRDR and ANU-NEWS. News articles for groups are cached and dynamically loaded. Version 2.0, released in 1995, included access security for newsgroups and removed the limits on the size and number of newsgroups that could be loaded FNEWS is a commercial shareware product. FnorbA CORBA 2.0 Object Request Broker (ORB) written in Python and a tiny bit ofC by the Hector Project participants at the CRC for Distributed Sys- tems Technology at the University of Queensland, Australia. Fnorb supports CORBA datatypes and full implementation ofIIOP. It is freely distributable for noncommercial use. See CORBA, ORB. FNR 1. Faculty Network Resources. 2. fixed network reconfiguration. Configuration of an existing network with static transmission lines to support upgraded services or a wider variety ofservices, often used as an interim solution instead of completely replacing a network. FNS Fiber Network System/Service. FO-2 A committee of the Telecommunications Indus- try Association (TIA) developing physical-layer test procedures and system design guidelines and speci- fications for distributors and users of fiber optic com- munications technologies. Since 2000, plenary meet- ings have been held jointly with FO-6, a TIA com- mittee on Fiber Optics. FOA 1. fiber optic amplifier. 2. See Fiber Optic As- sociation, Inc. 3. First Office Application. Testing of systems within an office application once in-house testing is complete or nearly complete. Most of the © 2003 by CRC Press LLC problems in the system have been worked out and what is now sought is relevance and feedback from a real-world installation. In software development, it is known as beta testing. FOe Firm Order Confirmation. A product or service agreement confirmation document. foam dielectric cable A cable assembly that utilizes foam as a nonconducting medium around the con- ducting medium to reduce noise and increase trans- mission speed. Foam dielectric cables are sometimes substituted for air dielectric. They don't quite meet the performance characteristics of the best air dielec- tric cables, but they have advantages such as good moisture-resistant properties and no requirement to pressurize the cable housing. See air dielectric cable. focal length (symb. - f) In a viewing or recording mechanism, the distance from the focal point on the surface being viewed or recorded to the center of a lens or surface ofa mirror, as on a camera. focus n. 1. In an optical viewing or recording mecha- nism, the point at which rays diverging or converg- ing from a surface intersect in the mechanism (through a lens or on a mirror) to produce a clear, un- blurred image of the surface. 2. In aprojected image, the point on the projection surface in which the rays converge to produce a clear, unblurred image. 3. In a color cathode-ray tube (CRT), convergence of the electron beams on a precise point on the coated in- ner surface of the glass to provide a clear image on the front surface of the tube. 4. In human vision, the point at which the distance of the object being viewed, the angle of the individual parts of the eye, and the angle of two eyes are correlated so that the image appears clear and unblurred. 4. Center of attention or activity. focus group A group organized to concentrate on or discuss a specific issue. FOD fax-on-demand. FODB See Fiber Optic Data Bus. FODTE See Fiber Optic Data Transmission Ex- periment. FOLDOe Free Online Dictionary of Computing. FOLDOC is a popular, searchable resource contain- ing over 13,000 concise definitions related to com- puting topics. FOLDOC was established in 1985 and is edited and copyrighted (1993) by Denis Howe. The information is distributed for use under the terms of the GNU Free Documentation License. http://www.foldoc.org/ FOLM See fiber optic lever microphone. FOLS See Fiber Optic LAN Section. FOM See fiber optic modem. footprint 1. An area or impression on a surface com- prising a more or less contiguous region of contact with the bottom of some object or signal. 2. The desk space or floor space taken up by a piece of furniture or equipment, usually considered the area of actual contact, or the area of contact plus everything within its boundaries, and the small area surrounding it, which may be taken up by connectors or protruding knobs. 3. The terrain or surface of the Earth over which a transmission signal can be received. A trans- mission footprint is alittle less defined than a physi- cal footprint, as a transmission tends gradually to decrease in intensity (this may be shown by contour lines on a map or chart), and there is often no defi- nite cutoff point, unless specified as signals below a certain level. 4. An audit trail or traces left by a trans- action or process which has concluded or aborted. 5. The resource requirements ofa system. For example, the Amiga is said to have asmall system footprint be- cause it can adroitly handle preemptive multitasking, sound, and simultaneous animated graphics in a Megabyte of memory on a 25- or 40-MHz processor. forecasting Predicting future events, usually based on an analysis and evaluation ofpast events. F ore- casting is needed in all areas of telecommunications to choose technologies that are powerful and eco- nomical and that won't be quickly outdated. It is also used by system administrators to configure and tune systems to handle predicted needs and traffic loads. Businesses use forecasting to select local area net- work topologies and workstations, and by managers to organize employee loads and working schedules. See erlang, queuing theory, traffic management. Foreign Agent A service enabling nodes to register at a remote location, providing a forwarding address to a home network in order for forwarded packets to be retransmitted to the remote location. Foreign agents are an important aspect of Mobile IP systems. Foreign Exchange Service FX, FEX, FXS. A ser- vice that connects a subscriber's telephone to a re- mote exchange as though it were a local exchange. Commercial vendors provide avariety of multiplex- ing interface cards to telecommunications carriers to facilitate provision of subscriber Foreign Exchange Services. Forrester, JayWright (1918- )A computer pioneer who investigated memory devices for computers in the 1940s and 1950s while working on the construc- tion of the Whirlwind computer at the Massachusetts Institute of Technology (MIT). Forrester was at the forefront of transition technology from analog to digi- tal systems and invented core memory with assistance from William N. Papian in 1951. FORTH 1. Foundation of Research and Technology- Hellas. 2. Fourth Generation Language. An exten- sible, high-level programming language typically used in calculators, robotics, and video game devices. FORTRANFonnula Translation. A high-level com- puter programming language that was commonly used in the 1980s for math-oriented applications, and from which BASIC has derived many of its syntacti- cal characteristics. It grew partly out of conceptual ideas and examples of reusable code promoted by Grace Hopper, and further from the encouragement of John Backus that a language be developed that could express and solve problems in terms of math- ematical formulae. With the advent of other languages such as BASIC, C, C++, Perl, and Java, the use of FORTRAN is declining. forum Discussion group, private or public meeting, judicial assembly. Electronic forums are common on the Internet. See USENET. 373 © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary forum, online A network virtual environment for dis- cussions. Internet Relay Chat (IRC) channels, USENET newsgroups, discussion lists, and various meeting places on Web sites are examples of global forums where topics are ardently and enthusiastically debated. When forums include celebrities, they are usually moderated to keep the questions and com- ments to a manageable level. Forum for Responsible and Ethical Email FREE. An organization for education and assistance to in- dividuals and groups seeking to balance the need for freedom to send email and the need for respecting the personal privacy and economic rights of email recipi- ents. FREE sponsors an informational Website, dis- cussion groups, and provides up-to-date news on spam-related issues in the media and the legislature. http://www.spamfree.orgl Forum ofIncident Response and Security Teams FIRST. A global coalition established in 1990 to fos- ter the exchange of information and response coor- dination among computer security teams. Participants come from a variety of academic, commercial, and governmental organizations. Part of the motivation for establishing FIRST came from the 1988 events associated with the spread of the Internet Worm, which made it clear that economic damage and loss of productivity were very real threats to the global Internet and that coordinated efforts to respond to such incidents would be more efficient than the hit- or-miss response to the spread of the Internet Worm. FIRST fosters cooperation among technology and security experts and facilitates research and opera- tional improvements to support secured networking. See Computer Incident Advisory Capability, Com- puter Emergency Response Team, WORM, virus. http://www.frrst.orgl forward error correction FEC. A means of ensur- ing a transmission in advance by duplicating infor- mation or otherwise improving the chances of its be- ing received the first time. For example, characters or groups of characters may be sent two or more times (called mode B in amateur radio transmissions) ac- cording to a predetermined arrangement. Repeating characters, or groups of characters, in data transmis- sions gives a receiver an opportunity to compare the groups and, if any of the information doesn't match, request a retransmission. The basic idea is to mini- mize the back -and-forth nature of handshaking to speed a transmission while still giving information that may be used to check the integrity of the infor- mation being received. Forward Explicit Congestion Notification FECN. In a Frame Relay network, a bit used to notify an in- terface device to initiate congestion-avoidance pro- cedures in the direction of the received frame. See Backward Explicit Congestion Notification. Forwarding Equivalence Class FEC. In Multipro- tocol Label Switched (MPLS) networks, the FEC is a networking categorization scheme associated with packet-forwarding. A specific FEe includes destina- tion address information and may include service information. FEe details are managed within a 374 router's forwarding information base (FIB). See Multiprotocol Label Switching. FOS2 See Fiber Optics Sensors & Systems. FOSS 1. Facilities Operations Support Services. Ser- vices at the Stennis Space Center. 2. See fiber optics sensing system. 3. Future of Space Science. FOT Fiber Optic Terminal. A connection point or de- vice at which a fiber optic circuit connects to a cop- per wire circuit. FOTS fiber optic transmission system. Foucault test A type ofoptical null test (a test using the instrument itself) for determining the optical qual- ity ofaspherical surface relative to the center of cur- vature of the component with a point light source. See Dall test, Ronchi test, star test. Foucault, Jean Bernard Leon (1819-1868) A French physicist best known for his studies of the speed oflight and the rotation of the Earth through the use of pendulums, Leon Foucault also developed a gyroscope (1852) and a mechanical telegraph. In 1850 he was awareded the Copley Medal by the Royal Society of London for his work on the rela- tionships between heat, magnetism, and mechanical energy. He also studied photographic processes and vision. See knife-edge focusing. Fourier, Jean Baptiste Joseph (1768-1830) Fourier, a French mathematician and lecturer, discovered in the early 1800s that the superposition of sines and cosines on time-varying periodic functions could be used to represent other functions. He made practical use of these techniques in the study of heat conduc- tion, work that was developed further by G. S. Ohm in the 1820s in his mathematical descriptions of con- duction in circuits. Work on linear transformation mathematics that predated Fourier's publications was carried out by Karl. F. Gauss but went unpublished until after Fourier's descriptions. See Fourier trans- form. Fourier analysis A means of representing physical or mathematical data by means ofFourier series or Fourier integrals. Fourier transform Alinear mathematical data ma- nipulation and problem-solving tool widely used in optics, transmissions media (antennas), and more. The superposition of sines and cosines on time-vary- ing functions can be used to represent other functions, in other words, to represent the data from another point of view. The result of such a transformation is to decompose a waveform into subsets ofdifferent frequencies, which together sum up to the original waveform. In this way, the frequency and amplitude can be separately and more easily studied. A rudimentary application ofFourier series calcula- tions were used to utry nderstand planet orbits in Greek times. Their development was in part ham- pered by the Greeks' mistaken assumption that the Earth was the center of the universe. Fourier transforms differ from wavelet transforms in that they are not localized in space; however, they also share many common characteristics. Named after J.BJ. Fourier. See discrete cosine transform, wave- let transform. © 2003 by CRC Press LLC Fourier transform, fast FFT. This optimized ver- sion ofa Fourier transform was developed in 1965 by Tukey and Coo ley. It substantially reduces the number of computations needed to do a transform, hence the name. FFT computations are used in many types of imaging applications (e.g., filtering a 3D image to display a 2D interpretation). fox messageA test sentence that includes all the let- ters of the English alphabet, commonly used to verify if all letters of the English alphabet in a device or coding system are present and/or working correctly. Familiar to most as "THE QUICK BROWN FOX JUMPS OVER THE LAZY DOG" (which may then be repeated as all lowercase, as needed). FPLMTS See Future Public Land Mobile Telecom- munication System. fps See frames per second. FPU See floating point unit. FRA See Fixed Radio Access. fractal A term popularized by Benoit Mandelbrot to describe his geometric discoveries and descriptions of structures that can be described and reproduced as mathematical formulas and have the character- istics of self-similarity in increasingly fine degrees of detail. Fractal concepts have since permeated almost every aspect of computing, especially computer image dis- play, compression, and reconstruction. Fractal geom- etry provides a means to model surprisingly complex and natural-looking structures with simple math- ematical formulas. See the Fractal Geometry ofNa- ture by Benoit Mandelbrot. Fractal Image Format FIF. A proprietary image compression format developed by Michael Barnsley and Alan Sloan, who together founded Iterated Sys- tems, Inc. to exploit the technology. Very high rates of compression are possible. The technology is asym- metric - it takes a while to compress the information, but it decompresses relatively quickly. See fractal transform. fractal transform, fractal compression A resolu- tion-independent, lossy image compression tech- nique providing a high degree of perceptual similar- ity with excellent compression results. Fractal com- pression works by storing image components in terms of mathematical algorithms, rather than as individual pixels ofa particular location and color. The organi- zation of the image is evaluated for its intrinsic char- acteristics of self-similarity, and those characteristics are coded so they can be reproduced by repetitions in increasingly fine detail, up to the resolution of the output device. With their excellent image fidelity and high compres- sion ratios, the trade-off in fractal compression is the time it takes to encode or decode and display the de- compressed image. With faster processors, this is be- coming less ofa limitation. See lossy compression; discrete cosine transform; Fisher, Yuval; JPEG; Man- delbrot, Benoit; wavelet transform. fractals, fractal images A term borrowed from frac- tal geometry to describe visual images that have rec- ognizable visual and mathematical characteristics of self-similar, repeating branches and curves resulting from the rendering of fractal formulas. Colored fractals can be beautiful, and they adorn many cal- endars, posters, and t-shirts. Many familiar fractal for- mulas have been given names, such as Julia Set, Man- delbrot Set, etc. See Mandelbrot, Benoit. FRAD See Frame Relay access device. fragmentation 1. State of being broken up, separated into units or groupings, having lost connections or cohesiveness, or physically or logically separating over time. 2. In hard drive storage, fragmentation is a gradual process of the available or used areas ofa drive becoming smaller and more widely dispersed. When information is stored on a hard disk or other similar directory-based system, files are placed where there is room on the drive and sometimes spread over a number of areas on the drive. When a file is deleted, its directory entry is removed and the space it occu- pied becomes free for other files. However, over time (especially with a lot of disk activity), the free areas get smaller and farther apart, and files stored on the drive need an increasing number of sections and links to keep track. This fragmentation slows down the sys- tem. It is sometimes advisable to defragment or "defrag" a drive to optimize the tables and file data locations. Some operating systems have built-in utili- ties for rebuilding a drive or system. It is important that sufficient memory and swap space are available on a system before de fragmenting a drive, and it is highly advisable to back up the data first. frame 1. A bounded visual or logical unit or block of related information, sometimes delimited with visual or binary flags or markers. A frame is sometimes a natural unit, as in a cyclic event in which the infor- mation repeats in some general sense (though the con- tent may vary), and sometimes it is an arbitrary unit, chosen for convenience or by convention. 2. A physi- cal unit, border, containment area, skeleton (frame- work), or inclusive extent. 3. A full-screen perceiv- able image on a monitor or TV screen consisting of the sum of all the sweeps of an electron gun during a full cycle ofoscillations across the screen. 4. A unit of information in data networks such as Frame Re- lay systems. 5. A contained group ofinfonnation on an HTML layout, such as a Web page. 6. A housing or support structure for components or wiring. See distribution frame, rack. frame, data In most networking architectures, a frame is a group of data bits ofa fixed or variable size, often in a specified format. It is common for frames to be organized into two general types: those which carry signaling, addressing, or error detection! correction information, and those which carry the contents of the communication itself (sometimes called payload), although even these are sometimes combined. The format and organization of the frames are defined by a data protocol, and there are many general purpose and specialized protocols in use, most not directly compatible with one another. Interprotocol frame traffic can be carried or tunneled through other protocols or can indirectly communicate through conversion agents or filters. 375 © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary Frames are organized into larger units comprising a communication and then may be sent together to the destination, or they may be disassembled, sent along different paths, and reassembled at the destination. Frames may also be encapsulated, wrapped in an outer envelope, to carry them through a system that requires another format or to tunnel through a sys- tem without having the contents of the encapsulated package changed in any way. It is then de-encapsu- lated at the exit point or at the destination. When frames carry different types of data, such as graphics in one and sound in another, they are some- times sent simultaneously through separate wires or data paths and reassociated at the receiving end, as in videoconferencing. In these situations, synchroni- zation or alignment of information is important and information for achieving this may be included. See Frame Relay, Frame Relay frame format, protocol. frame, distribution A wiring connection physical supporting structure. See distribution frame. frame, video In video displays that cyclically sweep the full screen to create an image, a frame is the ex- tent of the sweep that is required to cover the full screen. In the NTSC system prevalent in North America, the sweep is 29.97 frames per second and, on an interlaced screen, is further subdivided into two sets offields (all odd lines or all even lines). The for- mats that are common in Europe (pAL, SECAM) dis- play at 24 or 25 frames per second. It is important to time the frame presentations at a broadcast station, so that news briefs, commercials, and regularly scheduled programming can be orga- nized into precise time slots. NTSC displays are generally 525 scanlines, though not all the bottom scanlines may be visible on the screen. European stan- dards are 625 lines. A frame is an important unit in video display not only for physical synchronization of the signals, but also because the rapid sequential presentation ofstill frames creates the illusion of movement, and the properties of this illusion must be taken into consideration if creating still-frame ani- mation sequences. See station clock. See television signal for a chart of common formats. frame alignment signal FAS. In frame-based trans- missions, a sequence of bits intended to provide fram- ing alignment information for synchronization pur- poses. In other words, it provides the necessary in- formation, usually at the head of a sequence of frames, for the receiver to synchronize itselfwith the incoming signal. The signal may also include status, control, and error-relatedbits. The bits following the frame alignment signal are often allocated to more specific alignment or configuration tasks (e.g., chan- nel setup), and thereafter there is usually information content. frame buffer A storage area used for preconstruct- ing digital images in order to facilitate the quick dis- play of those images, especially if they are to be displayed one after another, as in a sequence of ani- mation frames. The image in the frame buffer is not necessarily displayed all at once. For example, in video games, it is very common to store a wide, ver- 376 tically narrow panoramic landscape in a frame buffer and to display only aportion of the scene at anyone time. Then, as the characters in the game move along the landscape, the display scrolls smoothly to right or left, without display artifacts such as flicker or jumping that may be caused by disk reads or off- screen reconstruction of the image. Frame buffers are commonly used for high-speed, high-resolution ap- plications such as computer animations, arcade games, and video walls. See frame store. Frame Check Sequence FCS. A mathematical al- gorithm that derives a value from a transmitted block of information and uses the value at the receiving end of the transmission to determine whether any trans- mission errors have occurred. FCS is used in bit-oriented protocols such as SNA SDLC to determine if sent and received messages are the same. For example, in SDLC the two-byte (16- bit) FCS field includes a cyclic redundancy check (CRC) value used to assess the validity of the re- ceived bits. frame grabber A computer hardware/software pe- ripheral device designed to capture and digitize a frame, or series of frames, from a continuous signal, usually from an NTSC source (a frame-based video signal). The signal generally comes from live video, laserdisc, or prerecorded tape. It is sometimes called a video capture board or video digitizer. The faster a frame grabber can capture frames, the more true to the original signal a playback of the grabbed frames will appear. Generally speeds of about 24 frames per second are required for a video animation to appear natural to the viewer. See frame buffer, sampling. frame merge 1. Over frame-based media, a stream merge. 2. In a Frame Relay network, frame merge can be used as a way to forward IP packets or por- tions of packets inside a frame, rather than on an in- dividual cell basis, to improve the scalability of a network while avoiding problems with scaling vir- tual circuits (VCs). 3. Frame merging is useful in cases where data streams are coming from more than one source, but the software can only handle one in- put stream at a time. In these cases, there are utilities available to merge the data streams in various ways, depending upon the type of data that is being received and how it is intended to be processed. 4. The phrase frame merge is sometimes loosely used to refer to convergence of data and telephony services for com- panies that are seeking ways to integrate their busi- ness telephone services with their data services on the same permanent virtual circuit (VC). Data-tele- phony convergence over Frame Relay is a better way to describe this process. frame mode In video image capture, a mode that cap- tures a full frame of scan lines more or less simulta- neously in contrast to most desk scanners, which cap- ture a line or block of the image at a time. Full frame images preserve image integrity but also take more storage space than some modes. Most digital cameras are frame mode capture devices. See field mode. frame rate, video The speed at which a series of images is presented or a screen of visual information © 2003 by CRC Press LLC is drawn, usually expressed in seconds. Due to per- sistence of vision in human perception, individual still images presented at about 20 frames per second or faster give the illusion of motion. At speeds of over 30 frames per second, no substantial improvement in the animation quality is perceived by most people. Motion picture film is usually displayed on 35mm projectors at 24 frames per second. Home 8mm and Super-8mm projects are somewhat variable around 20 to 24 frames per second, since most have dials to speed up or slow down the film transport rate. North America TV is broadcast at about 30 frames per second. (In actual fact, due to differences between black and white and color technology, the rate is closer to 29.97 frames per second.) On various Eu- ropean systems, such as PAL and SECAM, broadcast frame rates are 24 or 25 frames per second. On computer systems, frame rates vary with the soft- ware that is creating the frames or with the software playing the frames. Smaller video windows can be played back faster than large ones, as they take less time to compose and require less computing power to display. Displays of 256 colors also refresh faster than 24-bit displays (-16.9 million colors), although refresh will vary with the system speed and type of graphics card used. On systems less well adapted to video, rates may vary from 20 to 30 frames per sec- ond. Videoconferencing systems running over analog phone lines may refresh only at frame rates of 5 or 10 times per minute, as the voice-grade lines and mo- dem create a bottleneck. On ISDN and other digital lines that run at faster rates, 20 or more frames per second may be possible, depending upon the type of system and the size of the image window. See drop frame, MIDI time code, SMPTE time code. Frame Relay, Frame Relay network Frame Relay is a networking connection option often selected by smaller businesses as acost-effective way to set up a reasonably fast and powerful wide area network (WAN) or local area network (LAN) that can connect with public networks. Frame Relay can be used across Integrated Services Digital Network (ISDN) and a number of other interfaces to interconnect multiple virtual LAN s at lower rates than the cost of leased lines. Standardization efforts for the technology were initiated in the early 1980s and continued for a num- ber of years. In 1990 and 1991 vendors formed associations to fa- cilitate development and deployment of the technol- ogy. Viable commercial implementations began emerging in the early 1990s. Frame Relay is a connection-oriented, packet -switch- ing protocol designed to provide virtual circuits (VCs) for interconnections within the same Frame Relay net- work. Virtual circuits may be permanent or switched (similar to Ethernet). Permanent virtual circuits (PVCs) are more prevalent, but switched virtual cir- cuits (SVCs) are of increasing interest. Frame Relay evolved from and is somewhat simpli- fied over X.25. For example, Frame Relay is con- cerned with packet delivery without sequence and flow control, resulting in faster throughput and some- times lower cost by trading off error correction at the network level. (Error correction can be implemented by intelligent user terminal equipment, depending upon needs.) Frame Relay has been shown to work in practical situations up to almost 50 Mbps. Frame Relay operates at the physical (PRY) and data link layers of the Open Systems Interconnect (OSI) reference model. It is implemented as a Layer 2 pro- tocol. The physical interface can interconnect mul- tiple remote networks through Frame Relay switches. Frame Relay can transport a number of encapsulated ~~:!Ss::~::s:::'p:::::::: ::i::t:~:e :::~ .~. nection status of the link. In a Point-to-Point (PPP) system, Frame Relay framing is treated as a dedicated or switched-bit-synchronous link. See Asynchronous Transfer Mode, cell relay, Data Link Connection Identifier, framing bits, and additional entries pref- aced by Frame Relay. Frame Relay access channel A user access channel across which Frame Relay data travels. The access channel specifies the physical layer interface speed of date terminal equipment (DTE) and data commu- nications equipment (DCE). An access channel may be categorized as unchannelized, channelized, or frac- tional. When the entire DS-3/TIIEI is used at speeds of 45/1.536/1.984 Mbps, respectively, as a single channel, it is considered to be unchannelized. When DS-3/TllEl lines have one or more channels oper- ating at aggregate speeds not exceeding those just listed for unchannelized transmissions, they are con- sidered to be channelized, with the channel as any of Ntime slots in a given line. In TIIEl, consecutive or nonconsecutive time slots are grouped as Nx56,64 Kbps/Nx64 Kbps where N = 1 to 24 or 1 to 30 DSO time slots per channel, respectively, and are consid- ered fractional. FrameRelay access rate The data transmissions rate of the Frame Relay access channel. It is the maximum rate at which the user can insert data into the Frame Relay network. Frame Relay access device FRAD. Another name for the switch, router, or other network device that assembles and disassembles Frame Relay frames as they are transported through a system. When data frames are sent over a Frame Relay network, they are packaged with various types of information, often at the beginning and end of the block of frames, and unpackaged again, often at the access point to the des- tination system to recover the structure and contents of the original communication. Frame Relaying bearer service FRBS. A service providing bidirectional transfer of service data units (SDUs) from one reference point to another, retain- ing the order of frames. FRBS trades off some aspects of error processing (e.g., acknowledgments) for speed. A local label facilitates device identification over virtual connections. Frame Relay cloud A Frame Relay network that is shared among a small number of participating 377 © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary subscribers in order to get the benefits of the tech- nology at a lower cost. It is a suitable option for smaller businesses that do not have high networking demands but would like higher speeds than are avail- able through dialup modem connections, for example. The system can handle a firm's voice and data com- munications needs. As data passes through the cloud, it is handled by switches, depending upon how the virtual circuit has been configured to accommodate each subscriber's networking needs. Frame Relay devices The common devices that com- prise a Frame Relay network include computers, ter- minals, and circuit-related equipment. They generally fall into two categories, data terminal equipment (DTE) and data circuit-terminating equipment (DCE). The DTEs (desktop computers, terminals, routers, etc.) are usually located on the subscriber's premises, while the DCEs (the various circuit-connecting and -switching devices) may be locally installed or may be managed by the Frame Relay service provider. Frame Relay extensions A consortium of vendors seeking to enhance the basic capabilities of Frame Relay in order to meet the demands of the commer- cial marketplace extended the Frame Relay protocol with a Local Management Interface (LMI) specifi- cation in 1990. Organizations such as CCITT (now lTU- T) andANSI developed versions of the LM! that are now generally adopted. The LM! is a specification for information exchange between devices that is enhanced with capabilities such as global addressing, multicasting, and addi- tional status messages. The frame-relay lmi-type in- terface configuration command provides a means to select the type of LMI interface, and the Frame Re- lay keepalive command enables LMI for serial lines. LMI statistics can be displayed with the show frame- relay lmi EXEC command. Frame Relay flow control Flow control, the man- agement ofmovement offrames within and between networks, is not explicitly defined in the Frame Re- lay specification, and the lTV has defined general concepts and standards for handling flow and con- gestion. In practice, congestion can be prevented in Frame Relay networks by establishing committed in- formation rates (CIRs) to each user, denying the con- nection if insufficient bandwidth is available, and by discarding frames above the CIR. Existing conges- tion can be signaled to the user in the form of back- ward explicit congestion notification (BEeN) and forward explicit congestion notification (FECN). Frame Relay Forum FRF. An international profes- sional association of corporations, vendors, carriers, and consultants promoting the Frame Relay network- ing technology, and supplying commercial Frame Relay products and services, established in 1991. The Forum develops and promotes specifications to sup- port the viability of Frame Relay and sponsors inter- operability events for designers, manufacturers, and vendors to test their Frame Relay-based equipment. http://www.frforum.com/ Frame Relay Forum Implementation Agreements IA. A series of formal, approved agreements (stan- dards) developed and/or supported by the Frame Relay Forum. The preceding chart gives abrief sum- mary of lAs, organized somewhat functionally. The documents may be freely downloaded from the Net. See Frame Relay Forum chart. Frame Relay frame format The format for a frame is based on Link Access Protocol D (LAP-D) for ISDN. Frames are also known as protocol data units Frame Relay Frame Format 012 3 456 7 8 012345678901234567890123456789012345678901234567890123456789012345678901234567890 + / / + I flag I address I information I FCS I flag I + / / + 1 octet 2 to 4 octets variable 2 octets 1 octet Header Structure + + I DLCI upper I C/R I 0 I + + I DLCI lower I FECN I BECN I DE I 1 I + + DLeI data link connection identifier C/R command/response FECN forward explicit congestion notification BEeN backward explicit congestion notification DE discard eligibility 378 © 2003 by CRC Press LLC (PDUs). Frame Relay frames are similar to DXI and FUN!. Flags are used to indicate the beginning and end ofa frame, which may be variable in length. The format specified for a frame includes a I-byte (8-bit) flag, followed by 2 to 4 header address bytes, followed by a variable number of information bytes, followed by a 2-byte CRC code (frame check se- quence), followed by a I-byte flag. There are a num- ber of possible configurations of the address field; it may be two, three, or four bytes in length, as deter- mined by the extended address (E/A) bit. Informa- tion for the Local Management Interface enhance- ments is stored (e.g., DLCI information) in the frame header. FrameRelay installation Frame relay communica- tions connection services are generally available for a monthly subscriber fee or per-data rate from a lo- cal commercial provider, depending upon the speed of transmission. One-time connect charges for instal- lation and port configuration are common. Transmis- sion speeds up to 56-64 Kbps are typical, although most vendors offer higher speeds for more money. In-house installations of Frame Relay networks are also available. Frame Relay physical layer interface The specifi- cation for Frame Relay does not stipulate particular physical connectors or cables. In practice, however, unshielded twisted pair (UTP) is commonly used in ISDN implementations of Frame Relay. Frame Relay service Frame relay network service consists ofa combination ofhardware, software, and transmission services. It provides multiple indepen- dent multiplexed data links to another destination or to several destinations through a process which is at least as transparent as a leased line and less expen- sive. See Frame Relay installation. Frame Relay, voice over VoFR. Frame relay tech- nology provides an opportunity to combine data and voice communications services over the same net- work. Analysis of typical voice communications in- dicates that much of it is unnecessary (background sounds, pauses, etc.) and can be screened out before transmission over data networks. This aspect offers possibilities for processing and compression to pro- vide for efficient transfer of digitally encoded voice conversations. Initially, there was no uniform stan- dard for carrying voice over Frame Relay and vari- ous schemes for its implementation had been devel- oped. In July 2001, the Frame Relay Forum an- nounced FRF.20, an IP Header Compression Imple- mentation Agreement that defines packet encapsu- lation and compression negotiation to facilitate the transmission of voice over IP. Frame Relay-capable interface device FRCID. A peripheral device that performs frame encapsulation within a Frame Relay. See bridge, encapsulation, router. FrameRelayImplementors Forum An association of vendors supporting standards of interoperability for Frame Relay implementations. A common speci- fication was first introduced in 1990 based on the standard proposed by the American National Stan- dards Institute (ANSI). See Frame Relay Forum. Frame Relay Forum Implementation Agreements Number Date Description FRF.6 Mar. 1994 Service Customer Net- work Management Imple- mentation FRF.19 Mar. 2001 Operations, Adminis- tration and Maintenance Implementation FRF.17 Jan. 2000 Privacy Implementa- tion FRF.12 Dec. 1997 Fragmentation Imple- mentation FRF.13 Aug. 1998 Service Level Defini- tions Implementation FRF.l4 Dec. 1998 Physical Layer inter- face Implementation FRF.l.2 Apr. 2000 User-to-Network (UNI) Implementation FRF.4.1 Jan. 2000 User-to-Network In- terface (UNI) Implementa- tion FRF.2.1 July 1995 Network-to-Network Interface (NNI) Implementa- tion FRF.lO.l Sept. 1996 Network-to-Network SVC Implementation FRF.18 Apr. 2000 Network-to-Network FR/ ATM SVC Service Inter- working Implementation FRF.5 Dec. 1994 Frame Relay/ATM Network Interworking Implementation FRF.8.1 Feb. 2000 Frame Relay/ATM PVC Service Interworking Implementation FRF.7 Oct. 1994 PVC Multicast Service and Protocol Description FRF.l5 Aug. 1999 End-to-End Multilink Implementation FRF.16 Aug. 1999 Multilink UNI/NNI Implementation FRF.3.2 Apr. 2000 Multiprotocol Encap- sulation Implementation FRF.9 Jan. 1996 Data Compression Over Frame Relay Imple- mentation FRF.l1.1 May 1997 Voice over Frame Re- lay Implementation FRF.20 Jun. 2001 IP Header Compres- sion Implementation frame store A high-capacity digital video storage buffer. Frame stores are most commonly used in two categories of applications: (I) those that require im- age buffering to provide sufficient speed for continuous 379 © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary display (see frames per second), such as computer editing or display systems, and (2) those that require image buffering in order to create complex, compos- ite, or multiple display systems (such as video walls). In the first instance, the device from which the frames are being displayed or the display software may not be fast enough to read and display at 30 or so fps. By using a frame store, sufficient frames can be buffered in fast access memory (or on a very fast drive) to pro- vide quick display and the illusion of continuous motion. If the display software creates unwanted ef- fects on the screen when loading the next frame, the transition can sometimes be smoothed with double- buffering or grabbing the next frame from the frame store rather than from a hard drive. In other words, the new image is preconstructed in memory while the current image is being displayed, and the buffered image can then be displayed instantly over the pre- vious frame, rather than reading in and decompress- ing the frame and then displaying it line by line over the previous frame. In the second type of application, a frame store can help compose a complex image, such as computer graphic effects for a movie, which may have been raytraced one frame at a time, but which, when com- bined with footage of the actors, needs to match the speed of the action. A frame store can also be used as a component of a video wall, say 20 monitors in a four by five grid, which shows 1/20th of the actual image on each monitor. Since this display takes some computing power to split up an image into 20 sepa- rate subimages, the image grid could be segmented and prestored, so all the monitors display the correct parts of the grid at the same time. See buffer, frame buffer, desktop video. Frame Switching bearer service FSBS. In a sense, an enhanced version ofFRBS, in that it includes the basic functions of FRBS, plus frame acknowledg- ments and other error and flow control services. It is more similar to X.25, from which Frame Relay was derived, than the basic, streamlined FRBS service and reintroduces some of the features ofX.25. frames per second A phrase describing display speed for TV broadcasts, video, and film animations. The two most important aspects that determine this speed are human perception and display technology. Through persistence of vision and expectation, hu- mans perceive still frames displayed quickly one af- ter the other as motion. It requires only about 15 to 30 frames per second (depending upon the amount of detail and speed of the action) for these images to appear to be continuous motion. Most animations are created with 24 to 30 frames per second. Since mo- tion media can be displayed only at the fastest speed of the display medium (usually a cathode-ray tube), the technology also determines the display rate, with speeds of 15 to 60 fps being implemented, and about 20 to 30 fps most often used. See frame; frame rate, video; refresh. framing bit FB. A noninformational bit that can be used for a variety of signals in frame-based networks. A framing bit can signal the frame beginning or end 380 and error conditions, and it can be used for synchro- nization, depending upon the quantity and pattern of frames. In its simplest implementation, the framing bit signals to the receiving equipment that a new frame is about to begin. In North America, Superframe and Extended Super- frame standards are used for implementing Tl net- work services. Each frame in aT1 basic Superframe (SF) includes eight information bits and one fram- ing bit. In SF, there are two types of framing bits: ter- minal framing (Ft) and signaling framing (Fs) bits. In Extended Superframe (ESF), there are three types of framing bits: frame pattern sync (Fps), data link (DL), and cyclic redundancy check (CRC-6). The datalink framing bits differ somewhat, depending upon whether ESF is implemented according to ANSI or AT&T standards. The ANSI format provides for the transmission ofa Performance Report Message (PRM) that allows actual performance to be com- pared with established thresholds and an alert to be generated if anomalous conditions are detected. By evaluating the pattern of framing bits in a series of frames, synchronization can be established. In for- mats such as DS-l C, a framing bit can be stuffed to generate 26-bit information units allowing for syn- chronization and framing. franchise A government granted right to offer com- munity public right-of-way for exclusive commercial communications services, such as phone services or cable broadcast services. The franchise fees, or a por- tion of them, may be used by local government agen- cies, a portion of which may be allocated to local Des- ignated Access Providers (DAPs) for facilities fund- ing. Some of the earliest local phone companies may be partially exempt if they gained their exclusivity prior to regulation (grandfathering). Franklin, Benjamin (1706-1790) An American businessman (printer), statesman, scientist, and phi- losopher who did numerous experiments in electric- ity and printing. He shared his discoveries openly and coined many of the terms now used to describe me- chanics and electricity. He called vitreous electric- ity, demonstrated by rubbing glass with silk,positive electricity, and resinous electricity, demonstrated by rubbing amber with wool, negative electricity. He did experiments with lightning and stored electrical charges in a device called a Leyden jar, and he es- tablished that man-made electricity and atmospheric electricity had the same properties. These experi- ments were enthusiastically received and replicated throughout Europe, spurring much interest and de- velopment in the field of electricity. Ben Franklin also developed some early document duplication techniques which he used on his own printing press to help him manage his voluminous records and correspondence. Ben Franklin was a successful business owner at a relatively young age and always hoped to retire early to devote the rest of his life to scientific inquiry and his various hobbies, but the American Revolution and the overwhelming public demand for his diplomatic skills kept him occupied for long hours right up to © 2003 by CRC Press LLC the time of his death in his mid-80s. See electrostatic, Leyden jar. Franklin Institute Asignificant organizer and pro- moter of activities related to general science, electrical education, professional development, and technologi- cal deveiopment in electronics. The Institute orga- nized many key American and international exhibi- tions starting in the 1800s and is still well known for its educational activities and awards for excellence. The Institute was founded by Merrick and Keating in 1824 as The Franklin Institute of the State of Penn- sylvania for the Promotion of the Mechanic Arts in honor of scientist and statesman Benjamin Franklin. Since 1926, the Institute has been publishing the Journal of the Franklin Institute. In 1933 it began construction of the F els Planetarium and has admin- istrated the Franklin Institute Science Museum since 1934. In the 1990s, multimedia theaters were added to provide enhanced educational presentation capa- bilities. See Benjamin Franklin Institute (not affili- ated). http://www.fi.eduJ fraud n. Deceit, trickery; unauthorized access or use, especially under an assumed identify, such as a false username, or through the use of unauthorized equip- ment; misrepresentation of identity, products or ser- vices, especially for monetary gain. Unfortunately, fraud is now rampant on the Internet. A criminal with fraudulent intent can contact millions of potential victims in seconds at minimal cost. There are many different types of fraud on computer networks. Fraudulent vendors use names that sound or look like recognized businesses and create copy- cat Web sites selling substandard products (or no products at all). They use email with embedded Web page links to fool people into thinking they are veri- fying their passwords on financial sites when in fact a Trojan horse program is capturing their passwords or credit card numbers. Fraudsters also use fictitious email addresses, anonymous emailers, and elaborate mail routing to obscure their locations and identities. Naive users, especially teenagers, children, senior citizens, or adults from small communities, are be- ing defrauded on a massive scale by Internet-based get rich/pyramid/multilevel marketing schemes, fake contests, promises of off-shore commission profits, black and gray market pharmaceuticals, videos, and CDs, identity and credit card number theft, and so- licitations to patronize illegal pornographic sites. Un- solicited bulk email (spam) is one of the primary ve- hicles used by fraudulent companies to contact and negotiate with large numbers of potential victims to perpetrate these crimes. Many of these schemes are so sophisticated that it may be difficult, even for a computer professional, to recognize the deceit. Many existing laws should be sufficient to protect victims from Internet fraud, but existing black market, theft, piracy, embezzle- ment, pornography, and false advertising laws (which cover the majority ofInternet-related crime) are dif- ficult to enforce unless resources for law enforcement and consumer education are increased. http://www l.ifccfbi.gov/ Fraunhofer region In an antenna, a region of the field from which the energy flow proceeds as though emanating from a point source near the antenna, also called far-field region. It is considered to be one of three basic regions without distinct transition bound- aries that are identified as you move away from an antenna source. The Fraunhofer region is the one far- thest from the source beginning at a point where the angular field distribution is considered to be indepen- dent of the distance from the antenna. See Fresnel region. Fraunhoferspectrum The portion of the solar spec- trum visible to humans, i.e., the portion where the spectral absorption lines can be clearly seen. The dark lines have come to be known as Fraunhofer lines. Fraunhofer observed that the range of spectral lines varied depending upon which celestial body was the source of the light. This information was valuable in that it led to observations about light emanating from stars with different chemical compositions, allowing scientists to analyze the composition of bodies in our universe from a distance. The Fraunhofer spectrum can be taken as a baseline reference against which spec- tral shifts can be compared. See Wallaston, William. Fraunhofer, Joseph von (1787-1826) A German physicist who was skilled at applied optics and lens design. As a scientist, he applied his knowledge to the study of the Sun, its spectra, and the diffraction of light. He systematically set about measuring the position of hundreds ofsolar spectral lines and clas- sified the most prominent lines. He then developed a diffraction grating and a general grating equation for measuring the wavelengths of colors and of lines in the dark spectrum. Various aspects of spectral nomen- clature are named after Fraunhofer. FRBS Frame Relaying bearer service. See Frame Relay. Free Software Foundation FSF. A Massachusetts- based association committed to the development, ac- ceptance, and promotion of open, free software stan- dards and applications to benefit the world at large. The freedom to copy and distribute software, and the freedom to modify, enhance, and improve software are encouraged by the FSF. Thus, the programming and user communities benefit by the availability of constantly improving software and standards, and programmers have a broad, ready base of software from which to learn and to improve their skills. The FSF has developed the integrated GNU software system, which includes assemblers, compilers, and more. Donations to the FSF are tax deductible. http://www.fsf.org/ free-space optics FSO. A term for optical transmis- sion technologies that do not require a physical waveguide such as a fiber optic cable. An infrared remote television control is an example of a free- space transmission device that proj ects data through line-of-sight "free space." Free-space optics is pro- moted as a means of completing "the last mile" which is the distance from major optical backbone transmis- sion services that separates most homes and busi- nesses in the U.S. from established light-based 381 © 2003 by CRC Press LLC . test procedures and system design guidelines and speci- fications for distributors and users of fiber optic com- munications technologies. Since 2000, plenary meet- ings have been held jointly with FO-6, a TIA com- mittee on Fiber Optics. FOA 1. fiber optic amplifier. 2. See Fiber Optic As- sociation, Inc. 3. First Office Application. Testing of systems within an office application once in-house testing is complete or nearly complete. Most of the ©. In- terface (UNI) Implementa- tion FRF.2.1 July 1995 Network-to-Network Interface (NNI) Implementa- tion FRF.lO.l Sept. 1996 Network-to-Network SVC Implementation FRF.18 Apr. 2000 Network-to-Network FR/ ATM SVC Service Inter- working Implementation FRF.5 Dec. 1994 Frame. A group organized to concentrate on or discuss a specific issue. FOD fax-on-demand. FODB See Fiber Optic Data Bus. FODTE See Fiber Optic Data Transmission Ex- periment. FOLDOe Free Online Dictionary of Computing. FOLDOC is a popular, searchable resource contain- ing over 13,000 concise definitions related to com- puting topics. FOLDOC was established in 1985 and is edited and copyrighted (1993) by Denis Howe. The information is distributed for use under the terms of the GNU Free Documentation License. http://www.foldoc.org/ FOLM See fiber optic lever microphone. FOLS See Fiber Optic LAN Section. FOM See fiber optic modem. footprint 1. An area or impression on a surface com- prising a more or less contiguous region of contact with the bottom of some object or signal. 2. The desk space or floor space taken up by a piece of furniture or equipment, usually considered the area of actual contact, or the area of contact plus everything within its boundaries, and the small area surrounding it, which may be taken up by connectors or protruding knobs. 3. The terrain or surface