Fiber Optics Illustrated Dictionary Fibre Channel Loop Community FCLC. A Cali- fornia-based organization supporting and promoting Fibre Channel technology with particular attention to mass storage in arbitrated loop topologies. The FCLC merged into the Fibre Channel Assocation as a working group in 1999. Fibre Channel Topologies point-to-point topology Direct connections between two N ports wherein one is a server. This is a nonscalable topology by definition and arbitration is not required. arbitrated loop topology A topology in which multiple devices can share the media. It is a middle solution be- tween the limited point-to-point topology and the more flexible but also more com- plex fabric topology, a compromise suit- able for small local area networks (LAN s). Because resources are shared, only one device con connect at anyone time to a shared resource. Devices can be chained or arbitrated through a Fibre Channel hub. fabric topology The most powerful and potentially com- plex implementation of Fibre Channel, fabric topology encompasses more than one FC switch interconnected to other de- vices through one or more ports. F ports enable connections to other F ports or to N ports (node ports). Fibre Channel specifications FCS. There are two general aspects of FC specifications, the ANSI Fi- bre Channel Standard (X3Tll) and FCSI Fibre Chan- nel Profiles developed by the Fibre Channel Asso- ciation (now the Fibre Channel Industry Association) to assist implementors in understanding and devel- oping the technology while maintaining interoper- ability. See Fibre Channel Standard, Fibre Channel Industry Association. FibreChannelStandard FCS. A high-speed, block- oriented, serial, fully bidirectional data transfer in- terface for interconnecting workstations, main- frames, display peripherals, and storage devices. Both electrical and optical media are supported by the standard. FCS has been standardized by the ANSI X3TII committee. The Fibre Channel Standard is intended to support both wire and fiber optic systems, from 133 Mbps to 1062 Mbps ( and higher) at distances up to 10 ki- lometers (contrast this with a standard SCSI electri- cal cable transmission, for example, which has a practical distance of only a few feet). The actual maximum distance is dependent upon the medium and data rates. For example, single-mode fiber can transmit up to 10 kilometers, whereas shielded 362 twisted-pair wire has a limit of 50 to 100 meters, de- pending upon whether the data rate is 25 or 12.5 MBps. Frame sizes may be up to 2,148 bytes, depend- ing upon the size of the payload (the informational content). Development is underway to support higher speeds (e.g., 10 Gbps). There are three general topologies (architectures) described for Fibre Channel networks. FCS provides excellent opportunities for aggregat- ing peripherals under desks, or in server rooms and secure areas, for standardizing a wide variety of com- puter peripherals, and for increasing architectural flexibility in the placement of equipment. Because it is a hot-swappable format, Fibre Channel devices can be added to or removed from a network without pow- ering down the network. FCS is a hierarchical, layered architecture, with five layers defined from highest to lowest. Six data rate speeds have been defined as part of the Fibre Channel Standard. Cable Rate Payload Rate Max. Distance Mbaud MBps Mini-Coax 9 Ilm Fiber 132.8125 12.5 35m 10km 265.6250 25 25m 10km 531.2500 50 15m 10km 1062.5000 100 10m 10km 2125.0000 200 4250.0000 400 See F port, Firewire, FL port, N port, storage area network. See Fibre Channel Layers chart and other entries prefaced by Fibre Channel. Fibre Channel Systems Initiative FCSI. A group organized in 1993 to promote the interoperability, use, and distribution of Fibre Channel technologies. FCSI Profiles serve as guidelines for the implementation of fiber channel systems that can be used by compo- nent manufacturers and systems and service integra- tors of fiber communications technologies. See Fi- bre Channel Industry Association. Fibreoptic Industry Association Limited FlA. A professional organization representing suppliers, edu- cators, and installers in the fiber industry, inaugurated in February 1990. The FIA is managed from the U.K. by the FIA Secretariat with support from a manage- ment council of elected individuals taken from FIA members and other supporting individuals. The or- ganization includes a number of semi-autonomous regional offices. http://www.fibreoptic.org.uk/ Fick's first law The mass movement of atoms (flux) from one point to another in a given time frame is equal to the negative diffusivity times the delta con- centration (the mass per given volume) divided by the delta diffusion distance as expressed for a one- dimensional system by F=-D(OC/&) For the condition C(A) = 0, the equation can be © 2003 by CRC Press LLC simplified to F = D(C(O)/A.) As applied to biological systems, the net rate of dif- fusion ofa gas across a fluid membrance is propor- tional to (a) the difference in partial pressure, (b) to the area of the membrane, and inversely propertional to the membrane's thickness. Fick's second law describes the time-variant diffu- sion of atoms in a material for a one-dimensional sys- tem (e.g., unidirectional diffusion from aplanar sur- face) for a constant diffusion coefficient. This facili- tates approximations for various factors related to diffusion. See diffusion. FID Field Identifier, part of an ISDN Service Profile Identifier. See SPID. FidoNet Established in 1984 by Tom Jennings with the second node belonging to John Madill, this net- worked bulletin board system (BBS) became a ma- jor communications tool for techie discussions, email, and file transfers as bulletin board operators all over the country started to establish Fido boards for their local users. field In a scanning video broadcast display, a field is every other line of the full picture frame. Thus, it is all the odd numbered lines taken together, or all the even numbered lines taken together, in an interlaced image. field, data A record-holding or record-entering en- tity in a database. The definition offield types facili- tates program setup, management, and data manipu- lation by alerting the software as to the nature of the information being entered into a field. That is, a field may be given a data type (number, string, date, etc.), or it may be untyped, but either way this tells the sys- tem something about the data. field mode In video image capture, a mode that cap- tures only half of the scan lines in order to save an image in lower resolution, thus taking less storage space. See field, frame mode. field winding A mechanism for energizing electro- magnets in a generator. See winding. Field, CyrusWest(1819-1892)An American indus- trialist who contributed significantly to the economic and political negotiations involved in the first trans- atlantic telegraph cable, originally completed in Au- gust 1858 and later successfully installed as a per- manent cable. The concept was championed in part by Canadian inventor Frederic Gisborne, who ap- pealed to the American business community for fi- nancing so he could establish eastern Canadian tele- graphic installations through a combination of steam- ships and undetwater cables. Maritime Canada was a sparsely populated wilderness at the time, with a great need for communications links and limited re- sources for their development. As a youth, Field was apprenticed to a prominent and successful merchant before setting up his own paper manufacturing firm. He thus had an established net- work of contacts in the New York and Washington, D.C. areas that he could draw upon for support. As a successful businessman, he probably could have avoided hazardous and technologically difficult projects, but the telegraph cable idea evidently fired his imagination. After considering the feasibility of the project, with help from his brothers and other busi- ness associates, Field contacted influential people for technical assistance and support (e.g., Samuel Morse). Cyrus Field - Transatlantic Cable Installer Cyrus Field achievedfame for his contributions to the laying of the first transatlantic communications cable. His portrait was widely used in articles and song sheets commemorating the historic event. [Por- trait from the Mathew B. Brady studio, ca. 1850s. Li- brary of Congress American Memory collection.} Over the next decade, Field, Taylor, Roberts, and Cooper made substantial investments in the venture, with the project's promotional lead, Cyrus Field, re- ceiving most of the public acclaim for the ambitious project. In time, the Canadian-American alliance interlinked maritime Canada and, after initial failure, linked Canada to the u.S. through the Gulfof St. Lawrence. These early trial-and-error cable installations no doubt provided valuable technical experience facili- tating the development of longer, ocean-laid cables. In 1856, Field traveled to England on behalf of the transatlantic cable project and formed the Atlantic Telegraph Company. In December 1861, George Opdyke wrote to President Abraham Lincoln in sup- port of the project. No doubt other supporters made similar appeals to prominent dignitaries. The Library of Congress and Cornell archives include examples of correspondence and letters of introduction from Cyrus Field to prominent persons, including the Presi- dent. These were turbulent times in America, how- ever, and the pursuit ofa cable communication with the British Isles wasn't the easiest cause to champion in view ofBritish-American relations. In spite of the technical and political difficulties, success was finally 363 © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary achieved after several failures and temporary successes, with a permanent cable installed in the mid-1860s. Instantaneous intercontinental communi- cation was now possible, a revolution that forever changed humankind's commercial and social inter- actions. After the laying of the transatlantic cable, Field be- came an advocate for the public acquisition of com- munications services. To gamer support for this con- cept, Field penned an article called "Government Te- legraphy" for the North American Review in March 1886 that states, in part: "It appears to me that the time has arrived when the Government of the United States should pur- chase, in the interest of the people, all the telegraph lines in the country Communication by telegraph has become almost as common, and quite as nec- essary, as communication by letter As letters are sent to all parts of the United States for two cents, and papers and magazines at one cent for every four ounces, so, I think, a telegraph message should be sent to any part of the United States at the low- est price at which experience has shown it possible that the transmission can be effected " An illustrated history of the Atlantic Telegraph Com- pany is available on the World Wide Web. See Gisbome, Frederic Newton; gutta-percha; transatlan- tic cable. http://www.atlantic-cable.com/ FIF See Fractal Image Format. FIFO first in, first out. In programming, a means of processing data so the fIrst item to be stored or placed on a stack is the first to be fetched, moved, or dis- carded. Imagine a narrow vertical tube for gerbils (or hamsters, if you prefer fluffy rodents); the first ger- bil to squeeze in through the top is the first to slide out the bottom. In general terms of telecommunica- tions, in a FIFO system the first person who calls is the first to be referred to an agent. Fiber Optic Filament Spools Spools oj fiber opticfilament are soldfor a variety of lighting and hobby applications, including signs, lamps, and artpieces in sizes rangingfrom about .25 to 2.0 mm. Sheathedfilaments that can be separated from the main cable as needed are also available. fllament 1. A fine metal conducting wire commonly used in tubes and bulbs. By passing a current through a filament in a specialized, enclosed environment, it 364 becomes incandescent, giving off tight. See cathode. 2. A fine cylinder of glass or plastic. In fiber optics technologies, glass or plastic filaments with good conducting properties (e.g., clear glass with a mini- mum of fabrication blemishes and impurities) are used as waveguides for the conduction of light sig- nals. They are popular as novelty fiber optic lamps, signs, art pieces, and for communications technolo- gies. See fiber optics. file A collection of associated data stored so that a pointer to the information identifies and encompasses the contents of that file as an accessible, readable unit, even if stored in separate parts. This is one of the most common units of storage in a computer system - file hierarc~ies, file folders, file types, and file manage- ment are all computer structures and processes con- structed to manage files. file attachment Most email systems are text-oriented 7-bit messaging media. So how do you send some- one an 8-bit binary file? To meet this need, many text email systems have the capability of sending binary files as file attachments to a message. Since binary files include symbols and characters which cannot be displayed in aplain text window, and since the sym- bols are not meaningful to humans, it is more practi- cal to send the file (which may be sound, graphics, or a computer application) as an attachment, rather than as a postscript to the email text message. In most cases, all that is necessary is to specify the name of the file in the Attachment: text box or email message header, and the system will take care of the transfer of the information. file cache An area of memory allocated by an oper- ating system or computer applications program to temporarily store a file that may need to be accessed or modified frequently. Many database and spread- sheet programs use file caches to allow quick updates and redisplays of information, and the data may also be periodically stored on disk as a background task so as not to lose information and updates in the case of a software crash or power outage. file extension A syntactic convention that aids in identifying computer data file types. There 8Je many categories of computer files: text files, graphics files, sound files, and within these basic categories are many subcategories, such as JPEG, TIFF, etc. A con- vention of adding a period and a short SUffIX to iden- tify the type of file, so it can be found at a glance, has become widespread, and some applications and systems will even enforce certain file extensions. Since the mid-1980s, every significant microcom- puter and workstation level operating system except MS-DOS has allowed file extensions of reasonable length (up to 16, 32, 64, or 256 characters for the whole file name, depending upon the system). MS-DOS restricted its users to only three characters and enforced the use of the period (dot) as the file extension symbol. Since there were so many DOS- based machines, users of other systems hact to trun- cate file extensions (and the rest of the file name) when transferring files to other systems. This imprac- tical three-character extension limit is still prevalent, © 2003 by CRC Press LLC even though most Windows-based systems now support longer filenames (it is still common to see HTML file extensions on the Web listed as ".hOO" instead of ".hool"). On most other systems, the dot (.) is not mandatory for specifying the extension. The user can save a file with no dots or with a dozen dots. However, since several early systems in the 1970s required a dot, users are used to this naming convention. On many systems, a file extension also lists a ver- sion number, so backups and revision histories can be maintained at all times. For example, the follow- ing extensions may be automatically generated: ~atimage.tiff.locmygreatimage.tiff;l mygreatimage. tiff. 2 or mygreatimage. tiff; 2 mygreatimage. tiff. 3 oc mygreatimage. tiff; 3 If the default for the revision level is three, then the next file to be saved under the same name will su- persede the oldest file, in a first in, first out (FIFO) sequence, so that no more than three files with the same name are stored at anyone time. This version number extension/revision system is very handy when something is saved accidentally, and the pre- vious version needs to be retrieved. fIle gap A blank inserted to indicate astopping point, or adivision between sets of infonnation, especially on a sequential file recording system. On an audio tape or digital data tape, a file gap indicates the be- ginning or end ofa song or file. file server Generally, asystem on anetwork that ad- ministrates the storage of and access to files, often through a client/server model, in which multiple us- ers make requests to the file server through the cli- ent software. This system reduces redundant storage of files on individual systems and makes it easier and faster to update individual files. The server also handles file locks, so data files cannot be simulta- neously updated and saved by multiple users. Usu- ally, a dedicated file server is equipped with high stor- age capacity, and it may manage security levels for access to the files. Network File System (NFS) is a commonly used Unix file server system from Sun Microsystems that is implemented on many plat- fonns. file server, Frame Relay In aFrame Relay network, the file server is a device that provides connections with terminals, controls transmission flow, and pro- vides end-to-end acknowledgment and error recovery. File Service Protocol FSP. A file transfer protocol somewhat similar to File Transfer Protocol (FTP) originally developed for Unix by Wen-King SUo It is a low-load (nonforking), reasonably robust protocol that permits transfers to be resumed from the point at which they stopped if the server goes down tem- porarily or, ifdesired, allows for partial file transfers from a specified point. FSP is somewhat like Anonymous FTP except that it doesn't require a username and password. For iden- tification and logging purposes, the host domain of the user is recorded. It is also claimed that it is less prone to server attacks than systems with FTP setVers. FSP relies on datagrams rather than TCP sockets for its transmission connections and uses the same port for communications. See File Transfer Protocol. fIle sharing Access by more than one user, sometimes at the same time, depending on the nature of the data, to files that may be on one system on a network or spread out over several workstations that are inter- accessible. On the Apple Macintosh, file sharing is easily set up via utilities in the Control Panels so that passwords can be assigned and files shared with des- ignated users on the system. On a larger network, a particular machine or set of machines, usually with large hard disk storage capacity, may be dedicated to file serving and sharing activities. See file server. File Transfer Protocol FTP. A user-level file shar- ing protocol established by the early 1970s on the ARPANET and now widely implemented on the In- ternet in the form of FTP archive sites. The concept of FTP sites was to provide a simple, consistent means of presenting and accessing file information on a variety oftypes of file archive sites, so the user could easily navigate the site and upload or down- load files unassisted. In other words, FTP sites have aconsistent look and feel; once you've learned a few easy commands, you can log in, look around, and get what you need without having to worry about the in- dividual characteristics of the system on which the files are stored. Many FTP sites provide public access through auser login in which you type "anonymous" as the user- name, and your full email address as the password. If you have a Unix shell account with an FTP client, you simply type "ftp"(inalliowercase), followed by "help" when it activates, to learn its basic commands and capabilities. The inset shows an example of a simple anonymous FTP login. In the example session shown, the user logs in as anonymous, supplies a legitimate email address as the password, and is dropped into a limited en- vironment where basic directory traversing com- mands and file download commands can be used The message "Guest login ok, access restrictions apply." is displayed. This session is very typical in that the user is prompted to disconnect if logging of his or her activities is objectionable and is notified that there are restrictions. The user's logon number is shown, in addition to the total number of people on the sys- tem. If the system is at capacity, the user may be asked to try again or may be provided with amessage giving the addresses of mirror sites (sites with the same files in other locations). For file transfers, the get command, followed by a filename, will initiate a file download. The com- mands bye or quit will end a session. On Unix systems, you can type "man ftp" at a shell prompt to read the manual pages for FTP, which in- clude a list of common commands. FTP file down- load capability is built into most Web browsers and works transparently with many Web file archives. Several variations of the File Transfer Protocol ex- ist, and cutdown, easier-to-implement versions have also been developed, which are described on the 365 © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary Internet in various RFCs. See File Service Protocol, Simple File Transfer Protocol, Trivial File Transfer Protocol, RFC 171, RFC 172, RFC 959. file transfer protocol In its general sense, any pro- gram that facilitates the movement of files from one system to another, particularly through phone, null modem or other serial data links, or the Internet. There are many file transfer protocols, but two of the most popular implementations are ZModem, for telephone line transfers, and File Transfer Protocol (FTP) for Internet transfers. Other popular programs include Kermit, XModem, and YModem. More detailed in- formation is included in this dictionary under indi- vidual listings for the various protocols. fIlm n. 1. A thin membrane, skin, or coating. 2. A thin, light- and/or chemical-sensitive material commonly used in the photographic industry. 3. The collective name for a sequential, related set of still frames, taken together, form a story or cohesive idea that is viewed by playing the frames through a projector. Also called movie. filter n. 1. A porous material through which mixtures are screened in order to selectively prevent larger bits of the mixture from passing through. 2. A device or material through which particular waves, frequencies, or particles do not pass. Afilter may be used in com- bination with another device, such as an amplifier, in order to filter out noise, while propagating the de- sired portion ofa signal. Electrical and audio filters are common. fIlter, fIle File filters are not necessarily exclusion- ary tools, as in some senses of the word "filter," but rather may be conversion utilities available in many application programs to input or output files in a for- mat that is not native to the application. Thus, a TIFF file might be imported into a paint program with a proprietary format, through a filter, and may be ex- ported through another filter to a JPEG file, for ex- ample, for use on the Web. A filter may also be coordinated with a database to selectively provide access to higher priority messages or processes, while filtering out, or queuing those of lower priorities. Email filters are especially useful to those who .get hundreds of messages a day, as often happens on email mailing lists. A good email client will let you set up filters that file the messages in sepa- rate folders to be selectively read later, so the user can more easily determine which messages to check first. Exclusionary file filters also exist. For example, an email file filter may exclude all messages received from luser@hotmail.com or relegate them unread to the bit bucket. fIlter, network In network transmissions, there are physical filters and logical filters. Logical filters func- tion on every level of the system from low-end oper- ating functions, to high-end user applications. Logi- cal filters employ algorithms to selectively block the continuation of certain information, such as extrane- ous packets, unrecognized characters, extra informa- tion not supported by the receiving protocol, un- wanted email, messages from sites operating unlaw- fully, etc. 366 filtering Using physical or logical means to selec- tively permit access ofonly the desired information. Thus, unwanted information can be screened out, or a lower capacity system can be used to view or use part of the information according to its capabilities. F or example, filtering out parts ofa transmitted im- age makes it possible to display it on a system with low resolution, or a slow image display, a solution that may be preferable to no image at all. See com- pression, MPEG. filtering agent, filtering client A software program that can be configured to selectively reject or keep information according to a set of parameters or keys. With the excess ofinformation available through the Internet, filtering agents are increasing in importance. See data mining. filtering traffic On a network, the selective accep- tance or rejection ofcertain packets, messages, or processes according to a set ofpriorities and param- eters. High and low usage times may also be factors in setting up filtering instructions. Traffic filtering is usually accomplished by combining a database with a list ofpriorities. See firewall. fm waveguide A structure that can be used in con- junction with circular waveguides to increase the range ofwavelengths that can be transmitted, by at- taching a longitudinal metal fin. Financial Services Technology Consortium FSTC. A not- for-profit consortium of banks, financial ser- vices institutions, technology companies, govern- ment agencies, research labs, and educational insti- tutions. FSTC supports and promotes collaborative research and technical projects affecting the finan- cial services industry in order to further the competi- tive health of the financial industry in the U.S. http://www.fstc.org/ fmderA name used on several computer systems for applications that aid in locating information on a sys- tem, whether it be files, directories, or the specific content of files. Finder On the Apple Macintosh, the graphical user interface and operating system processes through which the user interacts with the system. Multifinder allows more than one program to be executed at a time and is available on the more recent versions of MacOS. It is also a generic name for a file fmding tool that comes with the operating system. finesse In optical resonating cavities, the number of round trips a light pulse can make from one reflec- tive surface to another and back before the signal dis- appears through scattering and attenuation. Finger The name of an online information utility, based on the Finger Protocol, that allows the user to retrieve and display information about users ofa sys- tem, or the owner ofa particular account on the net- work, provided no firewalls exist to block the finger command (as a command it is spelled all in lower- case). Login and logout times may be displayed, or the length of time since the last login. If the user que- ried has particular dot files configured, such as .plan (dotplan), additional information from this file will be displayed. Users often use the .plan file to list © 2003 by CRC Press LLC philosophies, home addresses, office hours, interests, or professional credentials. See firewall. Finger Protocol A network information protocol which is an elective proposed Draft Standard of the IETF. See finger, RFC 1288. Finkel, Raphael A. Finkel is probably best known as the first disseminator of the infamous Jargon File, distributed from Stanford University in 1975. He is also the author or co-author of handbooks and numer- ous articles on networks, data structures, and com- puter algorithms. See Jargon File, The. FIPS See Federal Information Processing Standard. frrefighting Trying to fix something after the fact. Often used in a derogatory sense to indicate the frus- tration of trying to rescue a situation that would not have occurred if proper steps or prevention methods had been used in the first place. The term describes distressing, expensive catch-up or fix -up situations resulting from bad management decisions. For ex- ample, shipping a software product before it is fully tested and debugged can result in a great loss of con- fidence on the part of customers, and enormous ex- tra fire fighting expense to the company in terms of subsequent upgrades and tech support that would not have been required if the product had been properly completed before shipment. firewall A physical screen created to prevent the spread of fire. It may be a wall of heavy, fire-resis- tance materials. See wiring vault. firewall, networkA computer network security con- figuration designed to limit completely or selectively access to a system. At one time, firewalls were usu- ally implemented on a specific gateway machine, but hardware and software firewalls now are set up in a number of ways, using filters, proxies, and gateways at the circuit level. A network traffic firewall exam- ines incoming packets and selectively lets them pass through, and it may also edit outgoing traffic in or- der to protect the identities of the senders, as in some government networks. Many local area network (LAN) frrewalls are one-way, with unlimited access out of the LAN and selective access into the LAN. Systems with firewalls frequently log all activities through the point or points of entry, with or without notification. See packet filtering, proxy server. FireWire FireWire technology, also known as LLINK, is a real breakthrough for connecting a wide variety of peripheral devices to computer networks. It was developed in the mid-1990s by Apple Com- puter and quickly moved toward broader industry standardization. In 2001, the National Academy of Television Arts and Sciences (NATAS) recognized Apple's FireWire contribution to the multimedia in- dustry by awarding the company the Primetime Emmy Engineering Award. The Fire Wire serial communications data rate is fast, up to 200 Mbps when it was first released, with 400 Mbps supported soon after. FireWire cables are easy to connect and hot-swappable (they can be plugged and unplugged without rebooting the host computer). A FireWire bus can support up to 63 devices, com- pared to the seven devices commonly supported by most computer SCSI buses. The format is autocon- figuring, so it isn't necessary to set or keep track of peripheral ID numbers for the devices. Fire Wire de- vices don't need to be terminated by the user. FireWire is a good standard for a world demanding high-bandwidth multimedia applications. It's much faster than USB and supports isochronous data trans- fers, providing guaranteed bandwidth for realtime audio/video data streams. Many vendors have devel- oped PCI-format FireWire cards and software driv- ers for computers that don't have native support for Fire Wire. Cards will typically support between one ::~S~;~~~~~~~~~l~~~:~I~fs '. likely that most operating systems will soon provide native support for the FireWire (IEEE-1394x) stan- dard. Peripheral hardware vendors supporting Fire- Wire include Canon, WC, Kodak, and Sony. By Au- gust 2001, 60 GByte Fire Wire hard drives were avail- able for less than $200. In spring 2001, the 1394 Trade Association intro- duced an update to the Fire Wire standard, called 1394b. The previous speed of 400 Mbps was already ripping fast compared to previously common periph- eral bus standards, but the new standard increased this data rate even further, up to 3.2 Gbps over glass op- tical fiber media. The updated format also uses a new bus arbitration scheme, called Bus Owner Supervi- sor Selector (BOSS). It enables pipelined unidirec- tional arbitration, in parallel with data transmission. By using bilingual mode, the 1394b specification is backwardly compatible with previous versions. The new features of 1394 are available in beta mode. FIRMR Federal Information Resources Manage- ment Regulation. firmware Programmed circuitry that is semiperma- nent. Software on a disk is easily changed and rewrit- ten. Software on the circuitry of a microchip is not easily changed and rewritten. In between these are EPROMs, erasable, reprogrammable chips which can be changed with the right equipment, and which re- tain the information during a power-off. FIRST See Forum of Incident Response and Se- curity Teams. first call dateA record of the frrst time a subscriber line is used, sometimes used in billing or in settling disputes. first in, first out See FIFO. fish job slang Phrase to describe a difficult wiring installation in which the wiring has to be pulled and threaded through constricted or hard-to-reach spaces. fish tape slang A smooth-surfaced, nonconductive (e.g., steel) metal tape that is threaded through tight areas, such as a wall or cable conduit. It is then at- tached to a cable so that it can be pulled more easily back through the wiring path. See pulling eye. fishbone antenna An antenna named for its resem- blance to the ribs ofa fish because it includes a se- ries of coplanar antenna elements arranged in pairs. The fishbone antenna is used in conjunction with a balanced transmission line. 367 © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary Fisher, Yuval Author of Fractal Image Compression, which describes the current knowledge of fractal compression in down-to-Earth terms with C source code examples. See fractal transform. FITL See Fiber in the Loop. FIX Federal Internet Exchange. fIXed access unit FAU. A wireless telephony desig- nation for a wireless phone unit that is not intended to be carried around, but rather to provide wireless communications within a limited region. Thus, local wireless phone service can be installed without go- ing through a local phone provider, much like a fancy intercom unit, or it can be subscribed through an al- ternate vendor as a limited cellular or PCS seIVice. Fixed End System F-ES. Anonmobile data commu- nications system through which a mobile subscriber accesses landline network services. F- ESs typically comprise modems installed into desktop computers. See Cellular Digital Packet Data, Mobile End System. Fixed Radio Access FRA. Local telephone service based upon wireless radio technology transmitted to an antenna attached to the subscriber's premises. The concept did not catch on until it was marketed to con- sumers as plain old telephone service (POTS) with enhancements, as opposed to new wireless technol- ogy. The concept originally was more prevalent in the U.K. than the U.S., but it is beginning to influence vendors in the North American market. In typical in- stallations, the digital signal from the transceiver is converted to analog and carried to various points on the premises through the existing copper wire, but the digital signals can also be fed directly through newly installed fiber optic cables, an option that would be of interest to individuals and businesses desiring wideband high-speed services. The local loop con- cept, in which a network of about 20 base stations could serve a community of 40,000 population, is less expensive to implement and serve than current cel- lular systems and thus could serve a niche somewhere between traditional telephone and mobile telephone subscribers. fIXed satellite service FSS. One of two divisions into which Ku-band satellite broadcast services have been split. FSS operates in the 11.7 to 12.2 GHz range. The other is broadcasting satellite service (BSS). See Ku- band. Fixed Telecommunications Network Service FTNS. A category of licensed service recognized by communications authorities in Hong Kong. There are various types of services that constitute FTNS, in- cluding wireline, cable, wireless, and satellite. FTNS Operators are assigned tariffs on the basis of the spe- cific types of services they provide, such as voice or data. Changes in the provision of local FTNS were made in 1995 when the Hong Kong Telephone Company's franchise expired, and the service was licensed instead to four companies. Fixed Wireless Access FWA. In regions where the cost of installing wire line may be prohibitive, due to rough terrain or sparse population, or where regional growth outstrips wireline installation capacity, FWA provides a long-term or temporary alternative. It 368 combines radio-based phone service, in the place of the local wireline loop, with common carrier phone service. See time division multiple access, code di- vision multiple access. Fizeau interferometer See interferometer, Fizeau. FK foreign key. A designation in a key cryptography scheme. See key, encryption. FL port On a Fibre Channel network, a switch that connects to a loop. Middle priority addresses are as- signed to FL ports, giving them higher priority than N ports (node ports) and lower priority (in terms of loop control) than an end loop (NL port) endstation port. See F port. flag n. 1. A device or signal used to attract attention or to indicate the state ofa situation. In software pro- gramming and network operation, flags are fre- quently used to indicate the state of processes or vari- ables, often under changing conditions. FLAG Ltd. Fiberoptic Link Around the Globe. A commercial fiber services carrier with installations of more than 18,000 miles of fiber optic cable in- stalled worldwide. flame resistant, flame retardant A medium that is inherently resistant to catching fire or spreading flames or is treated or manufactured to increase these retardant properties. Flame resistant and retardant materials are used in many industries including con- struction, electrical installation, and clothing manu- facture. flammable A property of easily catching fire or con- tinuing to bum readily. flange A rim or rib on an object to add strength or to aid in alignment. flash v. On a phone or intercom system, to send a sig- nal through the line by pressing the switch button on the handset holder or the button designated as ajlash button. The flash button is used on some local multi- line systems to transfer a call and may be followed by the keying in of the number of the extension. flash button A button designated on a phone or in- tercom system to send a signal that is the same as pressing the switch button on the handset holder. See flash, flash hook. flash cut See hot cut. flash hook See switch hook. flash interference In television transmission and dis- play, a flash is a very brief interference, sufficient to distort the picture information. flash memory A type of nonvolatile, rewritable com- puter memory technology, developed by Intel, pro- viding an alternative to large storage devices. Since flash memory is physically compact and doesn't lose its data when the device is not in use, it has been in- corporated into PCMCIA cards for portable comput- ing applications. Flash memory is also starting to be used in portable telephone devices and digital cam- eras. See memory, PCMCIA. flash tube A bulb or tube used to create a bright, momentary burst of illumination through application ofa high-voltage pulse. One-time flash bulbs were used in older cameras; electronically activated, reusable bulbs are now common. © 2003 by CRC Press LLC flat connector Any of a large variety of electronic connectors that are basically flat, that is, wide and narrow. Within each subset of connector types (power cable connectors, data cable connectors, etc.) there are usually some that are called flat connectors due to their low profile. Flat connectors typically contain a single line of pins, pads, or holes for coupling with cables, backplanes, or components. F or portable devices, a flat connector is a small, low- resistance, narrow electronic connector. This type of connector is increasingly favored for low-power por- table device slide-in connections for use in a vari- ety of applications where quick and easy connec- tions and disconnections are desired. Examples in- clude small cards that slide in and out of data readers or small handheld devices that slide into cradles and docking bays. flat panel Any ofa number of types of display sys- tems that are narrower and flatter than traditional CRT displays. These may be special flat panel CRTs, gas plasma displays, liquid crystal displays (LCDs), or light emitting diode displays (LEDs). Flat panel dis- plays are especially favored on mobile systems, such as computer laptops. flat panel CRT A type of cathode-ray tube (CRT) color display technology in which the electron beams are aimed parallel to the front of the display device, then deflected 90 degrees onto the viewing surface. This configuration permits the construction ofa much flatter, smaller, more convenient display device. While this technology is still relatively new and ex- pensive, the bulkiness of traditional CRTs makes the flat panel CRT commercially attractive. See faceplate, fiber optic. flat plate antennaAcommercial/industrial/military satellite communications focusing antenna based on microcircuit design. It is similar to a common para- bolic antenna, except that it incorporates a series of concentric rings laid over a transparent sheet to cre- ate a lens that can be used to redirect signals. flat rate service A very common subscriber billing technique. Flat rates usually arise in services where the overhead of keeping track of many different types and quantities ofusage would cut into profits. Flat rate services are also attractive to many subscribers, as they know in advance what it will cost and don't have to watch the clock or keep track of usage. In computer network access and telephone services, flat rate billing is very common. Since users of these ser- vices vary dramatically in time of access, connect times, and types of services used while connected, it probably is more economical in the long run to as- sign average usage fees than to try to track and bill widely varying usage. Flat rates for businesses tend to exceed those for residential use by roughly a fac- tor of three, depending on the type of service. Local phone calls in many areas in North America are billed on a flat rate. In Europe and some parts ofNorth America, per-call charges are levied instead and long- distance services are usually billed on a per-call ba- sis. The newer digital cellular technologies sometimes have a flat rate billing option. flat top 1. Something with a flat surface on top, as a flat-roofed building or aircraft carrier. 2. The portion of an antenna that lies horizontal. flat top antenna An antenna that has two or more parallel, horizontally strung wires. flatbed scannerA type of desktop scanner that per- mits the object to be scanned to be placed directly on the scanning surface; the object lies flat and doesn't have to roll through a drum or other moving mecha- nism. This type of scanner is preferred for scanning books and other large or three-dimensional objects. flavor A slang term for type or model. Programmers Eif~~t:i.;~~~~i~ri;nr~r~~~~~;!~:~:~~a patibility issues. The distinction is somewhat like a 'dialect,' in languages, or a 'model' in a type of car. FLC See ferroelectric liquid crystals. FLCD ferroelectric liquid crystal display. See ferro- electric liquid crystal. FLEA memory flux logic element array memory. The whimsical acronym for a type of computer memory developed by RCA in the early 1960s. The FLEA was created photographically and was capable of storing 128 bits of information. Its processing speed was 100,000 items per second. Fleming, John Ambrose (1849-1945) An English electrical engineer who investigated the Edison ef- fect and experimented with improvements to wire- less receivers in 1904. By modifying an electron bulb so that it incorporated two electrodes, and attaching it to a radio receiving system, the radio waves could be converted to direct current (DC). Unfortunately, this new diode was not a significant improvement over previous electron tubes, but it was important in the evolution towards more sophisticated tubes that came later. The most important of these was the tri- ode in which L. de Forest took the two-element Fleming tube as the basis for the invention of the Audion, which included a controlling grid as a third element. See two-electrode vacuum tube. Fleming oscillation valve An electron tube devel- oped by J. A. Fleming, based on Edison's work with electric light bulbs. This diode tube was in essence a two element rectifier. While it did not achieve the practical utility oflater tubes, it led to the develop- ment of the triode by Lee de Forest. Fleming's rule See right-hand rule. flicker A characteristic of display devices, such as cathode-ray tubes (CRTs), in which the scanning of the screen is visible to the human eye as a light-dark flashing flicker. Flicker can result from a number of causes, including the quality of the monitor, the mode of display (interlace or noninterlace), or the speed of the screen refresh as the electron beam sweeps the screen. Generally, slower sweeps will appear to flicker more, as do interlace screen modes. Apparent flicker is eliminated on better multiscan monitors. Most individuals can comfortably watch displays that are refreshed at about 70 Hz to 80 Hz; above that level, the trade-off in cost and computing is not sufficient to justify the insignificant or 369 © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary nonexistent improvement. While flickering on screens may be uncomfortable to watch, sometimes an interlaced mode has a prac- tical purpose, as when an NTSC-compatible signal is being generated to output to video. See cathode- ray tube, frame, interlace, multiscan. flip-flop 1. Quick reversal of direction or opinion. 2. A circuit or logic state that can assume one or the other of two stable states (on/off, high/low, etc.). A trigger circuit or toggle. floating pointA mathematical representation system in which a number is expressed as a product of a bounded number (mantissa) and a power of scale fac- tor (exponent) within a number base (e.g., base 10); hence, 123.45 can be expressed as .12345 x 10 3 • Floatingpointrefers to the flexibility inherent in plac- ing the decimal point by adjusting the exponent. floating pointunit FPU. In computers, floating point math coprocessing chips are often paired with cen- tral processing units (CPU s) to carry the processing load of the math calculations, which are usually cycle- intensive, thus freeing the CPU for other tasks. floating selection In graphical user interfaces, a se- lected text or image area that can be manipulated and moved separately from its background; thus it appears to float over the other elements on the screen. Float- ing a selected region is useful for cut and paste, drag and drop, and image processing applications. flood I. To inundate, overflow, or cover a broad area all at once. 2. In scanning and printing technologies, flood lamps are often used to process plates and pro- vide illumination for the recording of images. 3. To inundate with data, often unintelligible, as an incen- diary or retaliatory action. 4. The outpour of vast quantities of digitally generated infonnation. See core dump, data mining. flooding I. Overflowing, inundating. 2. In networks, a technique of sending many identical packets through various routes so redundancy increases the chances of the data reaching its destination. 3. In net- works, a deliberate act of vandalism in which data is directed toward a system, or an email address, to fill the hard drive space or tie up the processor, to render the system useless. Users caught flooding are usu- ally denied further access to a system. See core dump, mail bombing. FLOP floating point operation. Mathematical ma- nipulation ofa floating point number. FLOPS (Float- ing Point Operations per Second) is often used to describe and compare microprocessor speeds. See MFLOP. floppy diskette, floppy disk A thin, compact, por- table, flexible, read/write, random-access data stor- age medium originally encased in a soft protective case or, later, a hard protective case. Data is stored and modified by rearranging magnetic particles on the surface of the disk and, as such, the disk should be kept away from magnetic surfaces to reduce risk of loss. Generally, magnetic media are not reliable for long-tenn storage (see superparamagnetic). floppy diskettedrive FDD. A device for reading and writing data to a floppy diskette data storage medium 370 that became more prevalent in the early 1980s. There was usually one floppy drive built into a computer and sometimes a second external drive would be available in place of a more expensive hard drive. Prior to this, most consumer machines used tape drives to store data. FLOPS floating point operations per second. Amea- sure of the speed of mathematical computations. See FLOP. flow In packet networking, a sequence ofpackets with the same source and destination addresses and other similar characteristics. The detection ofa flow by various routing and switching mechanisms can trigger flow-based processing of that sequence of packets to improve efficiency. Flow detection may also include marking the flow with a label. For ex- ample, a new virtual circuit (VC) may be set up for a packet flow, thus removing or reducing the need for routing until the end of the flow is detected. Flow processing is a means of handling high-speed data through systems not nonnally capable of very high rates of packet transmission. The bottleneck is the overhead in managing the IP datagrams associ- ated with the packets. Cut Through Routing, devel- oped by Ipsilon (a commercial switch vendor), en- ables significantly faster IP routing by detecting classes ofIP flows and processing them accordingly. When processed through a VC, the transmission can be handled by a switch without individual routing. The signaling between IP switches is handled with the General Switch Management Protocol (GSMP) and the Ipsilon Flow Management Protocol (IFMP). See General Switch Management Protocol, Ipsilon Flow Management Protocol. Flow Attribute Notification Protocol FANP. In packet-switched networks, a protocol for manage- ment of cut-through packet fOIWarding functions be- tween neighbor nodes. F ANP indicates mapping be- tween adatalink connection and a packet flow to the neighbor node, and it helps nodes manage the map- ping infonnation. This allows the bypass of the usual Internet Protocol (IP) packet processing by allowing routers to fOIWard incoming packets. See RFC 2129. flow chart A somewhat standardized diagrammatic representation of processes, procedures, conditions, and directions of traffic or information flow. Flow charts employ geometric shapes, symbols, and con- necting lines to indicate the relative importance and relationships of the concepts being illustrated. Programmers are often required by managers to pro- vide flow charts of their software designs. However, many argue that outlines and pseudocode are more useful in representing the relationships and flow within a software program than conventional flow charts because of the lack of correspondence between human interface actions and the looping and jump- ing structure of the code itself (in other words, the order and frequency with which the user interacts with the software rarely corresponds to the order and frequency of the algorithms and procedures that en- able those functions to be executed). Another factor complicating the application of traditional manage- © 2003 by CRC Press LLC ment flowcharts to the programming process is the complexity of the decision-making points in a pro- gram and the inability to predict every instance and sequence of events that the user might take in a so- phisticated program with many options (it would be like trying to chart the moves in a chess game before the game has begun). Code usually changes many, many times before the full program is developed, even when the flow rep- resentation stays the same. Programming is a rela- tively young art and many of the algorithms are still being invented as the software is being developed and cannot be known in advance, before the problem is actually solved. Imagine trying to flow chart the high school course selections for a four-year-old child without knowing anything in advance about his tal- ents, skills, and interests and then you can understand the difficulty of flow charting a software program before it is written. Thus, flow charts are best seen as tools for conveying to management and co-workers the general goals and structures of a project, but not as efficient tools for developing the individual com- ponents of the computer algorithms themselves, which must be worked out as they are encountered. FLOW-MATIC See B-O. Floyd-SteinbergA dithering algorithm, i.e., a means of creating a perceptual tone or range of tones by in- termixing colors related to those tones to create the illusion of more colors. Dithering is one way of stretching a limited palette to make it appear as though there are colors that are not actually available. Dithering works best with dots of light or color that are very small, too small for the human eye to resolve. In the Floyd-Steinberg error diffusion algorithm, the error between the approximate output value ofa pixel and the actual value ofa pixel is sequentially diffused to its near neighbors. See dithering. FLTSAT, FLTSATCOM The U.S. Naval fleet com- munications satellite system that is one of the primary U.S. satellite communications systems along with the Defense Satellite Communications System (DSCS) and the Air Force Satellite Communications (AFSATCOM). Together, the three systems comprise the Military Satellite Communications (MILSATCOM) system. Control of the systems is handled through the Air Force Satellite Control Net- work (AFSCN). FLTSATCOM was developed in the early 1970s to provide communications for seagoing vessels, air- craft, and U.S. military ground crews worldwide. In addition to Naval and Air Force communications, FLTSAT was designed to provide fast communica- tions between the U.S. President and Commanding Officers. Transmissions are received by several hundred fixed and mobile user stations on sea, air, and ground ter- minals in addition to Communication Area Master Stations (CAMS) in the U.S., Guam, and Italy. Chan- nels are allocated to the Navy, Air Force, and Com- mand. The first units were launched in the late 1970s, with additional units added to the system in the 1980s. The geographical area covered by the near-geosyn- chronous equatorial orbits ranges from about 70 de- grees north to about 70 degress south. In 1991, operational control of satellite programs was turned over to the 3D Satellite Control Squadron (3 SCS) which became the 3D Space Operations Squad- ron (3 SOPS). Then, in 1996, FLTSAT constellations were turned over from 3 SOPS to the Naval Satellite Operations Center in California. The FLTSATCOM Laboratory has a computer simu- lation of the satellite system (minus the radio fre- quency capabilities) provided by The Aerospace Cor- poration that gives a graphical representation of the satellite and its operations. When fully deployed, a FLTSAT unit resembles a trashcan with an umbrella on one end (the parabolic antenna) and rectangular, solar array' elephant ears' protruding from the central body. The FLTSAT sys- tems incorporate a number of antennas in different wave bands, including S-band, UHF, EHF, and SHF (Super High Frequency) radio frequencies and have an operational life of about five years. They weigh approximately one to two tons each and are about the size ofa large motorhome, with the solar panel ears extending to over 40 feet. It is expected that the UHF Follow-On (UFO) system will eventually supersede the FLTSAT constellation. fluorescent lampA fluorescent bulb used for lamps typically consists ofa long glass tube equipped with an electrode at each end, with specialized vapor and gases sealed inside the tube. When electricity passes through the tube, light waves are emitted, causing phosphors coated on the inside of the tube to glow. Manufactured since the late 1930s, the fluorescent lamp doesn't use a filament and provides more light than an incandescent lamp for the same amount of current. Since less current is required, the bulb emits less heat. Fluorescent lamps manufactured before 1978 may contain PCBs in the ballasts and should be disposed of according to guidelines for PCB disposal to avoid contaminating landfills and waterways. flutter 1. A rapid, repetitive, agitated back-and-forth movement; any erratic vibration or oscillation. In most systems, flutter is an undesirable characteristic that interferes with the main signal. See drift, wow. 2. Undesirable phase distortion variations that may result from more than one frequency transmitting at the same time. 3. In radio terminology, also loosely called drift and wow. flutter bridge A device to measure flutter (undesir- able variations from a constant oscillation, move- ment, or signal). It is used for testing and diagnostic purposes for various playback devices that should be playing at a constant speed, such as phonographs, tape recorders, film projectors, or disc players. flutter rate The speed at which an oscillating body moves back and forth, commonly expressed in units per second or minute. flux 1. Stream, continued flow. 2. An expression of the rate oftransfer across or through a unit area ofa given surface, per unit of time. See watt. 3. A sub- stance used to facilitate the fusing of materials, as the use of rosin in soldering or welding. 4. Magnetic lines 371 © 2003 by CRC Press LLC . Fiber Optics Illustrated Dictionary Fibre Channel Loop Community FCLC. A Cali- fornia-based organization supporting and promoting Fibre Channel technology with particular attention to mass storage in arbitrated loop topologies. The FCLC merged into the Fibre Channel Assocation as a working group in 1999. Fibre Channel Topologies point-to-point topology Direct connections between two N ports wherein. = D(C(O)/A.) As applied to biological systems, the net rate of dif- fusion ofa gas across a fluid membrance is propor- tional to (a) the difference in partial pressure, (b) to the area of the membrane, and inversely propertional to the membrane's thickness. Fick's second law describes the time-variant diffu- sion of atoms in a material for a one-dimensional sys- tem (e.g., unidirectional diffusion from aplanar sur- face) for a constant diffusion coefficient. This facili- tates approximations for various factors related to diffusion. See diffusion. FID Field Identifier, part. LLC Fiber Optics Illustrated Dictionary achieved after several failures and temporary successes, with a permanent cable installed in the mid-1860s. Instantaneous intercontinental communi- cation was now possible, a revolution that forever changed humankind's commercial and social inter- actions. After the laying of the transatlantic cable, Field be- came an advocate for the public acquisition of com- munications services. To gamer support for this con- cept, Field penned an article called "Government Te- legraphy" for the North American Review in March 1886 that states, in part: "It appears to me that the time has arrived when the Government of the United States should pur- chase, in the interest of the people, all the telegraph lines in the country