Fiber Optics Illustrated Dictionary - Part 40 pdf

Fiber Optics Illustrated Dictionary communications. This is mainly due to the prohibi- tive cost of completing the last link between the transmission pipeline and millions of individual buildings. FSO links could be established between the backbone and local drops through building-mounted eye-safe infrared laser transmitters rapidly pulsing binary onl off signals. FSO links based upon infrared lasers as the light source can transmit to about I lan, depending upon weather, at transmission rates of up to more than a gigabit/second, with the potential for higher rates as diode technology evolves. In spite of the limitations ofline-of-sight and the impact ofweather (e.g., fog) on free-space transmissions, FSO systems have a big advantage in terms of speed of installation and cost of installation and maintenance over underground cable systems. They may be particularly useful for interconnecting local area networks in different parts ofa building or industrial complex. The transmitters can be placed on windows or roofs, without the need to run cables over the parking lots or inside building walls and can transmit at speeds more than 60 times faster than wireless radio links. FSO transmission links were pioneered in the early 1970s by groups such as Bell Laboratories, who re- searched lasers and light-emitting diodes (LEDs) for FSO communications. Interest in FSO links increased in the late 1990s, with companies such as Global Crossing and Lucent Technologies testing new systems. See line of sight, Photophone. FreeBSD A Unix computer operating system de- scended from Berkeley Standard Distribution (BSD), that flourished with the development of the ARPA- NET, the forerunner to the Internet. The Computer Systems Research Group (CSRG) enhanced BSD with 32-bit addressing, virtual memory, and a fast file system supporting long filenames. They further in- troduced BSD Lite which was BSD without the li- censed AT&T code and could be freely distributed. The CSRG disbanded in 1992, and the community at large adopted BSD and developed FreeBSD. In 1994, some of the CSRG briefly came together and further developed BSD 4.4 Lite. See Berkeley Stan- dard Distribution, Unix, UNIX. freeware A category ofproduct, usually software, that may be distributed and acquired without cost. Freeware does not mean copyright free. Adeveloper has the right to retain the copyright to an original work and still distribute that work or product free of charge, keeping the right to revoke freeware privileges. Freeware is not the same as public domain software, in which the owner has given up the copyright, and it is not the same as shareware for which there is a moral obligation to pay the stipulated fee. Freeware (public domain) and shareware are two common types of freely distributable software. See public domain, shareware. freeze frameA mode ofvisual display in which only one screen-full, or cell, of an animated sequence is shown. On digital systems, it's easier to show a single frame of information; displaying a single frame on film or on a CAY laserdisc is pretty straightforward. 382 In analog systems, or those recorded with overlap of information or no firm transition from one "cell" (frame) to the next, it is more difficult, as VCR tapes and the freeze frame mode may be of limited dura- tion and quality. Some analog/digital systems will take a digital shapshot of the frame to be displayed and display it as a digital image, usually with better results than trying to display the analog image. Many videoconferencing systems don't show actual real- time motion but rather snapshot a digitized freeze frame every few seconds, to provide the illusion of seeing what is going on at the other end without seeing actual movement. Such systems are sometimes distinguished as audiographics systems. As transmission media become faster, full-motion video will become standard. frequency (symb. - f) The number ofperiodic oc- currences or oscillations in a specified unit of time. Frequency designations are used to describe the varying periodic character ofspecific regions of the electromagnetic spectrum. In electricity, frequency is the number of times a current alternates in hertz (named after Heinrich Hertz). Radio signals are usually mea- sured in kHz, or in MHz at high frequencies (above 30,000 kHz). Many older radio and electronics manu- als will describe frequency in terms of cycles per second instead of hertz, as the unit name was widely used until the 1960s. See wavelength. frequency biasAn adjustment made to a signal, such as an audio signal, that biases it in one direction or another. In practical applications, it may be a constant adjustment to a signal frequency to prevent it from reaching zero. It may also be a high-frequency addition to a signal to bring up the low-frequency sounds to reduce distortion in regions that don't record well. Too much bias can result in clipped or distorted signals, depending upon how the bias is applied. In audio recording, bias may be added to a signal to over- come flat regions in the magnetic recording medium. Playback equipment ignores the bias signal but provides a better original, provided the addition of the bias signal is carefully controlled so as not to intro- duce distortion. Different types of tape respond dif- ferently to bias. For example, common ferric oxide tape is referred to as normal bias tape. In computer sound programs, there may be utilities for adding or controlling bias in order to edit the characteristics or quality of the sound. frequency departure The degree ofvariation ofa carrier frequency or reference frequency from an expected' assigned value. Frequency Division Multiple Access FDMA. One of the simplest techniques for increasing capacity over communications channels, since the radio frequency spectrum is not unlimited. FDMA is a way of dividing up the available spectrum according to frequencies. The communications station typically assigns a unique frequency or frequency sequence to each user currently engaged in communication, and it tracks these as needed to provide many simultaneous links. This technique is used in cellular phone © 2003 by CRC Press LLC and satellite transponder systems. See Code Division Multiple Access, Complex Scheme Multiple Access, Demand Access Multiple Access, Multiple Access, Time Division Multiple Access. frequency division multiplexing FDM. A technique used to more efficiently utilize a fixed or limited amount ofbandwidth by subdividing it into narrower channels. Typically, guard bands are inserted between communications bands to reduce interference. Multiplexing can be used to increase the number or types of transmissions within a fixed medium. For example, it may be used to simultaneously transmit voice and data. George Ashley Campbell invented the electric-wave filter in 1915, a device used in FDM. FDM is still a widely used transmissions technique that is only now being superseded by other methods, such as time division multiplexing (TDM is prevalent in fiber optic communications systems). See single sideband, time division multiplexing. frequency frogging See frogging. frequency hopping In mobile communications systems, a spread spectrum technique in which frequencies are jumped during the course ofa transmission. This hopping may be done for many reasons, such as to try to fmd a cleaner or more stable signal or to try to avoid detection (sometimes used in military zones). Frequency hopping was invented by Hedy Lamarr (born Hedwig Eva Maria Kiesler) while trying to develop a secure guidance system for a torpedo, using radio signals that would not be detected and subse- quently jammed. Her collaborator, George Antheil, suggested a way to synchronize the varying frequencies with paper tape, but the synchronization system was somewhat cumbersome, and it was not until the development ofcomputer electronics that Lamarr's idea was fully implemented. Lamarr and Antheil received a patent for the technology in 1942 and it has since been extensively used in military and civilian communications systems. Unfortunately, neither Lamarr, better known for her film career, nor Antheil, received any of the compensation or credit due for the invention. See direct sequencing, multiple access, spread spectrum. frequency modulation FM. A sine-wave modulation technique widely used in broadcasting that works by varying the frequency ofa constant amplitude carrier signal with an information signal. FM radio broadcast signals typically require about 200 kilohertz ofbandwidth and are not as subject to noise and interference as amplitude modulation (AM). Many scientists insisted that frequency modulation was not possible. Edwin Armstrong thought it was and devoted a decade ofintenseresearch to the problem, ultimately proving successful. FM radio stations began broadcasting in the early 1940s. In the United States, the Federal Communications Commission (FCC) approved FM stereo broadcasting in 1961. It has approved the range from 88 to 108 MHz for FM broadcasting. In one type of telephony, a frequency-modulated carrier signal can be transmitted over wires. Frequency modulation can be used when digital data is routed through an analog system for part of the transmission. FM is also commonly used for very short range communications for cordless phones, home and business intercoms, baby monitors, short-range television se- curity systems, and burglar alarms. See amplitude modulation; Armstrong, Edwin; carrier; channel; modulation; Moonbounce. frequency shift keying FSK. A modulation tech- ~~i::~:a:~~ti~ ~~~~~~:s:,f~:da~::;~;~~ :. (zero) are coded on separate frequencies. This scheme can also be adapted to regular phone lines by assign- ing binary "1" to a tone and binary "0" (zero) to a different tone. There are other keying schemes for carrying information such as on/offkeying and phase shift keying. See frequency modulation, phase shift keying. frequency swing In frequency modulation, the dif- ference between the maximum and minimum values at a given frequency. In other words, the limits within which the oscillations range. frequently asked question( s) FAQ. A query or question-and-answer list of questions that have been asked and answered many times, so often, in fact, that some- one has taken the time to write up the question/answer and post it, usually in apublic forum on the internet. FAQs comprise an important part of the information base of the Internet, on private and public forums, chats, special interest groups (SIGs), USENET newsgroups, and Web data sites. All Inter- net users are strongly advised to read the FAQ before posting on any online forum or risk being soundly scolded or flamed by other users. See Neti- quette, RTFM. Fresnel equations Mathematical descriptions of electromagnetic wave behavior developed by Augustin Fresnel. For radiant energy incident on a dielectric medium, the equations describe the amplitude of the transmitted and reflected electric fields. In other words, when an incident wave encounters a dielectric (e.g., when sunlight travels through air and then encounters window glass or water) some of the energy is transmitted through the dielectric, some of the energy is reflected and the sum of the two energy values equals that of the incident wave. Fresnel lens An efficient optical component with multiple faceted glass, acrylic, or materials designed to prismatically refract light to produce a brightly concentrated beam. A large light assembly designed from concentric rows of glass in a Fresnel configuration can propagate light for about two dozen miles, making it highly useful for lighthouses. The shape of the beam can be controlled to some extent by the positioning of the facets. By coloring some of the facets and rotating the lens or light source, the assembly can be made to flash. Small Fresnel lenses can be used as substitutes for magnifying glasses for anumber ofapplications and 383 © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary have the advantage ofbeing very flat, compared to traditional curved optical lenses. The tradeoff is optical quality, with curved, smooth lenses providing a clearer image. A coherent light source (e.g., laser light) can be shone through a Fresnel lens to see how the refractive surfaces of the lens alter the course of the light beam. A Fresnel lens can concentrate light for use in projection systems and can be configured to provide par- allellight arrays for large-scale projection walls by concentrating and "feeding" the light to lenticular lenses. Inventors have suggested that inflatable domed or cylindrical Fresnel lenses might be useful as concentrators for supplying space or terrestrial solar power systems. Safety glasses (preferably welding glasses) should be used when installing or adjusting Fresnel lenses even if the light source is disabled, because sunlight can be concentrated sufficiently by the lens to melt metal, which means it can readily (and quickly) burn skin. See diffraction, nearfield diffraction, Ronchi grating. Fresnel Equations - ReflectancelTransmission Fresnel mathematically described the relationship between incident electromagnetic radiation interacting with a dielectric substance and the resulting reflected andtransmitted energy. He demonstrated that the sum of the energy associated with the reflected radiation (E) and the energy that continues to be transmitted through the dielectric (E) equal the en- e1ID' asso'ciated with the original incident wave (E). Fresnel regionA region around an antenna between the physical equipment and the Fraunhofer (far-field) region. The transition between the Fresnel and Fraunhofer regions can be mathematically calculated if the length of the antenna and the wavelength are known. Fresnel approximations are used to describe diffraction patterns in the Fresnel region under certain wavelength, size, and distance conditions. See Fraunhofer region. Fresnel, Augustin Jean (1788-1827) A French physicist and engineer who pioneered a transverse- wave theory of light as an explanation for the phe- nomenon of double refraction, developing Fresnel equations related to reflective and refractive pro- cesses. In 1819, Fresnel submitted his theories on diffraction to the Paris Academy. In 1822, he demon- 384 strated a faceted lens designed to refract light to concentrate a beam, a structure now widely used inlight- houses and scientific components. See Brewster, David; Fresnel lens. friction feed A feed mechanism in a machine that relies on friction or pressure to feed the sheets (paper, card stock, thin metal plates, etc.) as in aprinter, press, or photocopying machine. Friction feed devices are often made from rubbery materials to help adhere the medium to the feeder. See tractor feed. friendly name A name that is easy to recognize and remember, used in place ofcryptic or long names or codes. For example, aprinter with a computer designation of LSL2345-b may be assigned a friendly name of AdminLaser in lists of available output devices. Domain names on the Internet have been given friendly names. The computer system doesn't require a familiar name like "coolsite.com" to locate a site; a binary address is more direct. But humans prefer language to numerals or binary addresses, and so domain names have been associated with data addresses to make it easier to use FTP or Telnet protocols, or to access a site through the Web. See alias. fringe areaAregionjust outside the majortransmis- sion area of a broadcast signal where the signal is degraded and inconsistent but generally present. Sometimes those receiving signals in fringe areas can improve the quality of service, up to a point, with better antennas. fringing 1. An undesirable visual artifact, especially on cathode-ray tube (CRT) color displays, in which the electron beams are converging incorrectly so as to appear unfocused, with a fringe or edge ofcolor slightly offset. 2. A visual artifact on an object displayed in a computer paint program, in which the color of the previous background of the object (e.g., a blue sky) shows up distinctly as a halo around the edges when the object is placed on another color (e.g., a red brick wall). A defringing option to blend the edge colors is available in many paint programs, to smooth the transition in a process called anti aliasing. 3. An effect that occurs when coherent optical plane waves intersect one another and combine intensities to produce a set of spaced bright and dark regions. The fringing may be viewed or photographed depending upon the magnitude of the effect and the wavelength of the optical energy. The best results occur when the intersecting waves are of equal intensity, but this is often not the case in real life, where light tends to drop off as it continues along the line of travel. For deliberately creating fringe patterns, laser lights, with coherent monochromatic characteristics and a longer range are favored. See diffraction. FRM focus-rotation mount. Apivoting antenna-fo- cusing structure. FRND Frame Relay network device. frogging 1. An equalizing technique in which incom- ing high or low frequencies are inverted to become outgoing low or high frequencies. 2. Corruption of transmissions data in which incorrect data is inserted into or overwrites some of the expected data in a non- random way. © 2003 by CRC Press LLC front end The portion of an application or device that interacts with or is accessible to the end user. On computers, shell command lines and graphical user interfaces are the most common types of front end. In audio/video equipment, the front end consists of the knobs and dials that are within easy reach of the user. The Web has become an interactive front end to the Internet. In commercial facilities, the front end is usually a store front or reception area that provides customer services, as opposed to storage or person- nel-only work areas. In broadcast circuitry, the front end consists of the knobs and components which tune in the desired frequency. front end system Asystem that acts as an interme- diary gateway, filter, or console for a more powerful, but less user-friendly or accessible system. A desktop computer-based telecommunications server can serve as a front-end to a mainframe, sparing it for more computing-intensive tasks. An information kiosk with a simple touchscreen or touchpad input system that hooks into a more powerful network system is a type of front end for the general public. An automated teller machine (ATM) is a banking system front-end for the public. FRSE Frame Relay switching equipment. FRTE Frame Relay terminal equipment. frustum The surface of a solid cone or pyramid that would be created if the top of the cone or pyramid were cut offparallel to its base. A concept ofinterest to mathematicians, programmers, and users of 3D modeling software. FS federal standard. FSAN See Full Services Access Network. FSBS Frame Switching bearer service. See Frame Relay. FSFA nonprofit educational association supporting GNU. See Free Software Foundation. FSK See frequency shift keying. FSO 1. Foreign Service Office/Officer. A foreign af- fairs diplomatic liaison. 2. See free-space optics. FSP See File Service Protocol. FSS See fixed satellite service. FSTC See Financial Services Technology Consor- tium. FTA See Federal Telecommunications Act. FTIPFiber Transport Inside Plant. FTNS See Fixed Telecommunications Network Service. ftp The command typed at an FTP site to access an archive based on File Transfer Protocol (FTP). It is usual to type the command in lower case; however, the name ofprotocol itself is usually written in up- per case. FTP See File Transfer Protocol. FTPmailserverA mail server that facilitates the re- trieval of files from FTP archives by sending them to the user's email address. Since files on FTP sites can be text or binary, and some email addresses can- not directly accept binary files, the retrieved files may be sent as a binary file attachment. See file attachment, ftp, FTP. FTR federal telecommunications recommendation. FTS 1. file transfer support. 2. See Federal Technol- ogy Service. 3. Federal Telecommunications System. A government private telephone network. See FTS2000. FTS2000, FTS2001 A nonmandatory program of intercity telecommunications services provided to federal agencies by the U. S. General Services Admin- istration (GSA) through two networks (A & B) transmitting through fiber optic cable. Due to delays resulting from federal agencies failing to meet the 6 Dec. 2000 deadline, the project was changed from FTS2000, with Sprint and AT&T as major vendors, ~f::~:~::e~~ln~:;~~:~~ii£~lli~¥~~ '. requesting that competition be reopened (Spring 2001), alleging material changes in the contract re- quirements, which had been relaxed to ease the process of agency compliance. In response, the GSA contended that data collection requireme~ts were relaxed but service stipulations remained the same. The transition is ongoing and is expected to be fully in place by about 2005. FTSC 1. Faculty Technology Support Center. 2. See Federal Telecommunications Standards Committee. 3. See FidoNet Technical Standards Committee. 4. Foreign Trade Service Corps. FTTC Fiber to the Curb. Fiber cabling that reaches the drop near the home but does not include the drop onto or into the home. See Fiber to the Curb. FTTH See Fiber to the Home, cable modem. FTTHO Fiber to the Home Office. FTTL See Fiber to the Loop. FTTN Fiber to the Neighborhood. FUBAR fouled up beyond all recognition. Aphrase purportedly originating in military speak in World War II. Less polite versions of it fit the acronym as well. See foo. Fun fear uncertainty doubt. Asales strategy attrib- uted to Gene Amdahl, stated as "FUD is the fear, uncertainty, and doubt that ffiM sales people instill in the minds ofpotential customers who might be con- sidering [a competitor's] products." The marketing spin is that customers are safer with International Business Machines (IBM) products. fudge v. To hedge, approximate, overstate, or talk around a subject so as to try to appear to know what you are talking about, to use "bafflegab"; to cobble together so it appears as though it might work, or so that it approximately works but may not be complete or robust. fudge factor Tolerance factor, buffer, safety net. See fudge. Fujitsu Limited A large Japanese commercial con- glomerate originating in the 1920s. Fujitsu is known for a number oflarge-scale computing products, is a world leader in industrial robotics, and manufactures many consumer computer-related accessories (e.g., office-quality printers). See FACOM. Fujitsu Laboratories, Ltd.Awholly owned subsid- iary of Fujitsu Limited, founded in 1968. It is an international research laboratory which has recently 385 © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary devoted significant resources to the development of fiber optic amplifiers and wavelength Division multiplexing (WDM) technologies for highspeed communication over longhaul optical networks. Fujitsu Network Communications, Inc. A designer and manufacturer of fiber optic and broadband switching systems, and provider of telephone network management software which is marketed to ILCs, CLECs, VPNs, and cable TV companies. full duplex A system that supports simultaneous transmission and receipt at both ends of the circuit. Full duplex operation requires a balance of hardware and software protocols to enable two-way transmissions. In some systems, full duplex operation creates a digital echo in which each unit of textual information is repeated. Some systems can technically support full duplex operation but are selectively oper- ated in half duplex mode to improve the quality of the communication, as in some satellite voice systems and speakerphones. These systems have tones and sensors that coordinate the back -and- forth nature of the conversation so the transmission favors the direction in which the current user is transmitting. Systems with bandwidth limitations may work in full duplex mode for some operations (e.g., voice conversations) and then may switch to half duplex for more bandwidth-intensive operations (e.g., videoconferencing). See half duplex. full scale The full functional range over which an instrument or device operates. Full Services Access Network FSAN. A group of cooperating international telecommunications companies, including Bell Canada, BellSouth, BT, Deutsche Telecom, Dutch PTT, France Telecom, GTE, Korea Telecom, NTT, SBC, Swisscom, Telefonica, Telstra, and Telecom ltalia. FSAN shares its documentation with relevant standards bodies. One of the groups associated withFSAN is the Opti- cal Access Network (OAN). Nippon Telephone and Telegraph (NTT) and BellSouth are developing fully FSAN-compliant ATM-PON systems for 1999. See fiber to the home. function key Aconfigurable or special-purpose keyboard button. Function keys are often programmed as shortcuts to produce the same effect as typing several keys, or selecting an operation several menu items deep. Many computer keyboards have 10 or 12 function keys with a variety of uses, depending upon the currently active software. They may be located in a vertical line above the other keys in the keyboard, or they may be organized in two rows to the right or left of the keyboard. For touchtyping, the double row to the right or left of the keyboard is more practical and easier to use. Many telephones have prelabeled or configurable keys for redial, speed dialing, and other optional functions. functional specification The specification of an object or system in terms of how it will be used and/or what it specifically is designed to accomplish as an end goal. In its purest sense, a functional specification concentrates on user interaction or the task at 386 hand (e.g., punching out keyboard key caps on a production line) and does not specify the parts, process, or equipment that may be needed to create the object or system, since there are usually many different ways in which the same end result can be achieved. Thus, a functional specification for a computer would include descriptions of what a user might wish to do with the system and the means by which the user might interact with a system (visually, tactilely, auditorially, etc.) but would not specify the CPU, bus type, interface slot formats, specific model or styles of input/output devices, etc. Sometimes it is wise to turn to functional specifications when technology becomes entrenched. A functional specification is one way to spur creative inno- vation. For example, a computer mouse is a ubiqui- tous means of interacting with a graphical user interface, but is it the best way? In a functional specification, one usually asks what does one want to accomplish with the computer. If the answer is to indicate a choice or selection in a certain context in a way that is natural and comfortable for the user, then perhaps a graphical pen, data glove, or eye-scanning headset might be suggested to fulfill the functional specification, rather than a mouse. functional transparency The capability ofa system to carry out its functions in such a way that the user doesn't have to see or worry about the inner work- ings or lower-level protocols and configuration of the system. The more natural and direct the interaction, the more transparent the system. In heterogenous distributed computer networks with many different types of computers and operating systems intercom- municating, functional transparency is a situation in which the user doesn't have to worry about the type of data or the network medium or protocols used. In the earlier dialup modem days, users had to have enough technical knowledge to know how to configure terminal software to the correct baud and par- ity rates, etc. for each system to which they wanted to connect. Eventually auto baud modems added a certain degree of functional transparency by auto- matically negotiating and adjusting the data rate between the answering system and the calling system. With newer network protocols, such as email protocols on the Internet, once the initial configuration is installed, users are able to transmit a variety of types of data transparently over the system without wor- rying about compression protocols, file types, or whether the receiving system has the same param- eters, operating system, or data rate capabilities as the sending system. fundamental frequency 1. The lowest natural frequency in an oscillating system. 2. The reciprocal of the period ofa wave. 3. The frequency most effec- tive in a given situation (e.g., the one that transmits best over aparticular waveguide ). fundamental groupA group of trunks in which each local switching center is interconnected to one ofa higher order. furcation unit In fiber optics, a fiber installation and © 2003 by CRC Press LLC maintenance device that channels the individual strands ofa fanned out bundle to their desintations. A furcation unit might be used, for example, as a connection between an outdoor bundled cable and an in- door multidevice hub. fuse 1. n. A protective mechanism that reacts to break an electrical circuit when the current through the circuit exceeds a specific value. The mechanism may consist of a wire or chemical junction mounted in serial, which melts or breaks at a specified value, usually indicated with a number. Fuses are designed to break, if there is a problem, in order to protect more expensive electrical components from harm. The fuse was first patented by Thomas Edison in the early 1880s. Circuit breakers have replaced fuses in most new home electrical installations, as resetting the breaker is more convenient than replacing a fuse. See circuit breaker. 2. v. To join or blend together, usually by melting. To fuse implies a stronger or more consistent bond than does to bond (as with an adhe- sive), since there may be momentary heat or chemical alteration to create the bond. fuse alarmA type of fuse connected with an audible device or a flashing light (or both) to indicate that the fuse is blown and must be replaced. fuse blockAn insulated mounting structure for a fuse or bank of fuses. In smaller electronic devices, the block may secure a small clip that holds the fuse in place. In larger wiring installations, as in houses and offices, the fuse block may be a large metal electrical cabinet with several rows of fuse mountings. When further enclosed, it is usually called a fuse panel or fuse box. fuse cable A section of cable spliced into electrically sensitive wiring installations (e.g., aerial cables prone to lightning strikes) that differs in specifications from the main wiring. A fuse cable is any cable that can defuse an electrical surge, but tends to be a higher gauge cable than is commonly used in electrical installations. Fuse cable lengths are usually kept as short as possible due to the added attenuation intro- duced by splicing in the different cables. In fiber optics installations, which are not sensitive to electrical charges in the same sense as wired communications, fuse cables are rarely needed except where the optical components are coupled to electrical devices. fuse wire The wire inside the fuse housing that breaks when subjected to excessive current loads, breaking the circuit with the intention of protecting sensitive electronic parts. In the illustration of fuses, three different types of fuse wires can be seen, with straight wires on the three right fuses, a corrugated wire third from the left, and a flat zig-zag wire in the two left fuses. fused biconic taper FBT. A process used for manu- facturing couplers that are important in the fiber optics industry. FBT can meet the needs of wideband and ultra-wideband networks, a technology in which the coupling is crucial to providing a strong, reliable signal and can carry bidirectional signals. Multiple FBT couplers may be fused andlor cascaded in series, depending upon the network configuration. Be- cause of the FBT, the light doesn't have to leave the optical fiber medium to pass through an optical interface, which is desirable for the prevention of signal loss. FBT couplers may also be used in conjunction with other types of couplers (e.g., Mach Zehnder dB). In dense wavelength networks, other technologies are being developed to solve coupling of fiber optic components, including planar waveguide components. These are not yet as common as FBT products. See fiber optic taper. fused quartz, fused silica A glassy substance made from quartz crystals that is highly resistant to chemicals and heat. Quartz has remarkable noncorrosive and vibrational qualities that make it a valuable industrial material. See quartz. fused semiconductor In semiconductor fabrication, the materials can be subjected to heat in such a way that they cool and recrystallize on a base crystal to form a tight electronic junction. See p-n junction, semiconductor. fusion 1. A heat-induced liquid state. 2. A union of parts by applying heat or chemicals to liquify one or both of the parts (or abinding substance such as sol- der or weld) to form a permanent bond between them. 3. The union of atomic nuclei to form heavier nuclei, a process which generally requires enormous amounts of heat or pressure and can result in the re- lease ofa great amount of energy. fusion sleeve A short strip of coating for supporting and protecting a fusion splice, as in a fiber optic cable with fused joints. The term tends to be applied to protective coverings made of soft (often shrinkable) materials. Sleeves from hard materials (e.g., metal), are more often called ferrules and long "sleeve' lengths are called jackets. The term sheath seems to be somewhat generically applied to both sleeves and jackets. F or fiber optic joints, fusion sleeves are commercially available in single or ribbon (mass fusion) styles. They may be preshrunk to reduce the amount of time it takes to install and shrink the sleeve the rest of the way to get a snug fit. Preshrunk sleeves also reduce the amount of time heat must be applied to secure the sleeve, reducing the possibility of heat-related damage to the joint and extending the life of the heating element. Commercial fusion splicers require about 1.5 to 3 minutes to process a sleeve heating cycle. Sleeves may be transparent, for revealing the joint or colored for coding the joint (or the person who created the joint). Some companies will customize sleeves with code numbers, company logos, etc. on mass quantity purchases. See ferrule, fusion splice, splice guard. fusion splice A thermally or chemically fused joint where two or more sections of cable have been com- bined to provide a continuous transmission path. A soldered joint in spliced wires is a type of fusion splice, as is a thermal joint in a fiber optic cable. Even though a fusion-spliced joint has some mingling of molecules to provide a more solid connection than might be expected from oil or glue joints, it may still be fragile and require support and protection from 387 © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary knocking or bending. Asleeve and sometimes also a boot or extra support guard are typically placed over the joint for extra protection from strain and environmental damage. See fusion sleeve, fusion splicing, mechanical splice. fusion splice viewer An instrument for imaging two or more fiber optic filaments that are secured for splicing. In the field this is sometimes done with simple tools such as magnifiers, but in mobile or fixed fusion splicing labs, viewing systems of various types are built into single and mass fusion splicing machines. Viewing may be through microscopes or LCD-based video imaging systems. Most fusion splicing machines enable viewing from two angles- the X and Y axes. The viewing system enables the technician to check the joints for debris or aberrations prior to splicing, facilitates alignnment, and allows the joint to be inspected after it has been fused. In single-fiber splicing systems, it is reasonably straightforward to magnify the region of the splice to inspect the joint and make adjustments to alignment. Gauges are often incorporated into the display system to facilitate microadjustrnents. In mass fusion splicers, the problem of imaging the entire area over multiple filaments without making the viewing mechanisms prohibitively large sometimes results in tradeoffs in magnification and image clarity. Good lighting across the staging area can help compensate for reduced magnification, especially in portable splicing machines where size is a consideration. fusion splicing Ajoining of two or more components (e.g., optical fibers) through a heat or chemical process that melts together the parts to be coupled. Fu- sion splicing is a common way to connect plastics, glass, and other fabrication materials for which the heat or chemical fusing process does not substantially alter the fused materials or interfere with their signal-transmitting characteristics. Since the molecules are intermingled, a fusion splice may be superior to other bonding methods (e.g., glue or oil). In the fiber optics industry, protective sleeves are commercially available to cover splices which, depending upon the material fused, may be more fragile and subject to breakage or apt to pick up tiny particles if there are rough edges. Sleeves in different colors can be used to identify types ofsplices (or the individual who made the splice). A sleeve may have an extra strength component to support the splice and may be bonded to the splice or heat-shrunk to provide a tight fit, depending upon the application. Stan- dard sleeve sizes range from about 30 to 50 mm. While heat is commonly used to fuse optical fibers, chemical fusion through UV-cured resin compounds is possible. In the more common heat fusion process, the fibers melt away from each other as heat is applied by an electrode-generated arc, but are pushed together at the same time until the ends fuse. The heat must be applied in such a way that alignment is main- tained and there are no combustion residues intro- duced within the splice. Some devices provide control over temperature and art time so that a fiber can be prefused prior to the final fuse. It is crucial that 388 the joint be nonreflecting so that the lightguide is continuous and undistorted from one fiber joint to the next. Fusion splicing is still largely a hand-assembly and -inspection process, even with newer automatic fusion splicing devices. Fusion splicing equipment ranges from a pair of Kevlar-cutting scissors and a cable-stripping knife at the low end to sophisticated computerized inert-gas and vacuum-equipped automated systems at the high end. Manual fusion splicing takes practice, especially when using manual or semiautomatic methods. Es- sentially, the process consists of the following steps: • Strip the fiber filaments to an appropriate length. • Clean the fibers without introducing scratches. • Cleave the filament ends that are to be fused (cleanly and precisely within industry tolerances for angle and loss). • Position the fiber ends within the fusion splicing mechanism. This is usually within a groove that aligns the fibers along two or three axes. The operator may have to align the Z axis in semiautomatic or manual machines. • Clamp the fibers to maintain their aligned position. • Close the mechanism and select a program for the splice (depending upon filament materials and diameter). • Initiate the splice cycle (which takes a few seconds). • Inspect the splice locally, if the fusion splicer has built-in capabilities for testing refraction patterns and tolerances, or remove the spliced cable and inspect it with other devices (e.g., an interferometer). Fiber alignment in preparation for fusing may be manual, semiautomatic, or automatic. Most semiautomatic and automatic systems have some sort of computerized data display or ocular viewing system (e.g., similar to a microscope) to aid the technician in aligning fibers. Some systems use piezoelectric transducers to enable microalignment to more pre- cise tolerances. Multiple fused cables or filaments that are aligned in parallel proximity may not easily fit within sleeves. Fusion splice organizers with grooves to hold the cables and help keep out particles and moisture may be used instead. Aligning two fibers in three planar directions (horizontal, vertical, and depth) may not be sufficient to maximize the light-guiding properties of the fibers when spliced. Through various fabrication or doping methods, the polarizing characteristics of the fibers may negatively influence the effectiveness of the waveguide ifjoined at different angles with respect to polarity. Thus, the rotational Olientation of the fibers may have to be aligned with some of the more © 2003 by CRC Press LLC Fiber Filament Fusion Splicing Basics Times vary with the materials (glass, wire, or plas- tic), the type of splicer, and sometimes the ambient temperature and humidity. In general production work, where fast turnover is preferred, the process may take seconds or minutes, especially if splicing machines are used. With manual connections, such as fusing a connector to a fiber filament with epoxy and air-drying, the process can take as long as 18 hours. See fusion splice. Future Public Land Mobile Telecommunication System FPLMTS. A standards effort initiated in the early 1990s to create a global mobile communications system that encompasses cordless and cellular technologies. It is intended to form a basis for integrated voice, paging, and data services at rates up to 9600 bps, and perhaps up to 20 Mbps, in both connection and connectionless modes, and for videoconferencing, global positioning services (GPS), and multimedia capabilities. See Global Systems for Mobile Com- munications. future shock A state of human reaction tQ overload or too great a rate of change (as in changing technology), described in Alvin Tomer's 1970 book of the same name. In general, Tomer posits that humans, as biological/social organisms, have limitations as to how quickly they can adapt to change and contends that technological change could occur faster than they can adapt, resulting in an undesirable state of future shock. In the 1980s and 1990s, people began to be more aware of the rate of change and obsolescence char- acteristic of computer technologies, but this idea was not generally considered in the late 1960s, when Toffler was researching and writing his book. Tomer's predictions were prescient, occurring half a decade before desktop computers became generally available, and are well worth keeping in mind, in terms of our ability to adapt to the computer revolu- tion, to control its rate of change and evolution, and to assess and respond to how it affects our health and quality of life. Fuzhou The capital ofFujian a Chinese province on the southeast coast. This region is home to global leading suppliers of ADSL modems and optical communication components, including Star Network Technology Co., Ltd. tv abbrev. femtovolt (10- 15 volt). FVR flexible vocabulary recognition. A type of speech recognition in which a variety of words, not necessarily just those found in an associated database, can be processed. FVR is useful for wired and wireless telephony devices for dispensing instructions, schedules, answers to queries, and other commercial and industrial applications. FVR is an advanced type of speech recognition. Be- cause people's manners of speaking are varied, including dialects, accents, and slang, it is difficult to write algorithms to process natural speech spoken by many different people. Thus, programmers have developed a number of compromise solutions to sim- plify the interpretation process. One of these is to develop a limited vocabulary that is recognized by _ _ 4 3 2 sophisticated fusion splicing machines to maintain the polarity through the length of the path. Fusion splicing at its simplest involves splicing one fiber joint at a time. However, the demands of the marketplace for higher production rates for individual fibers orJiber ribbons with have resulted in machines called mass fusion splicers that can handle multiple joints. For the assembly of complex cable arrays such as fiber optic patch panels, certified technical services are available for outsourcing the work. The fabrication of the fiber pigtails and fusion splicing may be car- ried out at the same location and documentation on the process and technical specifications may be provided as part of the service. Costs commonly range from $20 to $50 per splice. See cladding alignment splicer, core-to-core splicer, cleave, fusion sleeve, local injection and detection, mass fusion splicer. This simplified diagram illustrates the basic steps of heat splicing two sections offiberfilaments toform asingle continuous lightguide. Fibers are cleavedand aligned in the Z direction in V-grooves or vacuum chucks (1) and then fine-aligned (2) in the X and Y directions until they are lined up core to core orclad- ding to cladding, depending upon the type of fiber and device used. A heating arc is applied across the region to be fused (3) which causes meltback as thefila- ments are warmed (4) which is compensated by mov- ing thefibers closer together at a carefully controlled speed so they fuse without gaps or undue pressure. fusion time The time it takes to complete a heat or chemically fusedjoint so it is stable enough, in terms of temperature and strength of the joint, to continue to the next step in the process or to be handled without compromising the bond. This may include a prefusing step that prepares the joint (e.g., by soften- ing the ends) in preparation for fusing. 389 © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary the software. FVR, on the other hand, overcomes this limitation in a number ofways, with larger databases and natural language processing algorithms. It may still be necessary to train a flexible vocabulary recognition program to recognize the particular speech characteristics and pronunciation of an individual speaker. FWA See Fixed Wireless Access. FX 1. In the multimedia industry, an abbreviation for effects, as in SpecialFX. 2. See Foreign Exchange. FXO Foreign Exchange Office. See Foreign Ex- change. FXS Foreign Exchange Station. See Foreign Ex- change. FYEO "For your eyes only;" another way ofsaying 390 "private" or "confidential." FYIAn abbreviation for "for your information" that is commonly used on business memos, documents, email, and postings on the Internet. FZA A data compression program developed by D. Carr (Gandalf Data Ltd.), that is derived from Lempel-Ziv (LZ), and favors high levels ofcompres- sion over central processing unit (CPU) speed and memory. FZAis based upon packet-switched network techniques to compress information into a single frame or across multiple frames. See FZA+, Lempel- Ziv. FZA+ An updated version of D. Carr's FZA data compression program. FZA+ was developed by A. Barbir. © 2003 by CRC Press LLC yr Gamma, the third letter of the Greek alphabet, used in mathematical diagrams and equations. Gamma is used to describe relativistic relations. G I. symb. conductance. See conductance. 2. abbrev. giga See giga 3. abbrev. grid (as in a vacuum tube). g force (symb. - g) A unit of force of acceleration equal to that which would occur in a falling body acted upon by gravity at the Earth's surface, 9.81 meters per second per second. F forces influence the process of crystallization in an optical fiber during the pulling stage. G Interface In Operation, Administration, Mainte- nance, and Provisioning (OAM&P), the GInterface is the user-to-computer interface of the Telecommu- nications Management Network (TMN). The G In- terface is intended to promote consistency in the user interface and to reduce errors. G Series RecommendationsA set ofITU- T-recom- mended guidelines for transmission systems and media, digital systems and networks. These are available as publications from the ITU-T for purchase, and a few may be downloadable from the Net. Some of the related general categories and G Series Recom- mendations ofparticular interest are organized into general categories at the end of this chapter. Alist of the general categories is included in the Appendix. See also I, Q, V, and X Series Recommendations. G style handset The designation for older telephone handsets having a round design on the ear- and mouthpieces. They are similar to the newer, squared- off K style handsets, and both G and K style are heavier and more substantial than some of the newer cordless or cell phone handsets which are very flat and small. See K style handset. G3Fax A facsimile machine that transmits through traditional phone networks using 1.4 standards. For Internet facsimiles based on email formats.a G3Fax device is accessed through an IFax gateway that serves as a mail transfer agent (MTA) between the Internet and the traditional phone line-based fax machine. See IFax device, TIFF-FX, RFC 2305. G-line A round, insulated wire used in microwave transmissions. G-Line A Cornell University physics resource for X-ray beam-related research. The G-Line Laboratory is organized into three experimental stations, G-I for the study of large molecule reactions, G-2 for general purposes, and G-3 for studying the growth of semiconductor films. G-Scope, G-ScanA type ofrectangular radar display in which a centralized blip is illuminated and becomes wider or narrower horizontally as the target moves nearer or farther away. Errors in aiming the radar are indicated by the horizontal and vertical placement of the blip (orpip). G.lite An International Telecommunication Union (lTD) low-cost, splitterless alternative proposal to ADSL CPE. See Asymmetric Digital Subscriber Line, UAWG. G/A ground to air communication. GIG ground to ground communication. G: Line In a network server configuration file, a global (network-wide) ban that is kept in memory until it is removed or expires. It is generally used to ban users who abuse their network privileges but may also be used to restrict access by specified domains or countries, or by servers with specified characteristics. While G: Lines usually default to a few hours, it is possible to configure them to last for months or years. Sometimes legitimate users are prevented from ac- cessing a site because aparticular domain or ISP has been "G: Lined." In this case it usually takes a con- certed effort and some negotiations to regain or retain access. G: Line queries or protests should be di- rected, in most cases, to email address abuse@domainname.com (substituting the relevant domain name). See fraud. GA go ahead. A common verbal and written communications convention that indicates that the commu- nicator is finished and the listener is welcome to pro- ceed (similar to "Roger" in radio communications). It is frequently used in question-and-answer style conferences on the Internet, particularly in moderated conferences where many people are queued to com- municate, and each one has to wait for a turn. GAB 1. Group Access Bridging, Group Audio Bridg- ing. A telephony chat or party line service in which multiple users call the same number and are connected to one another at the same time. 2. See Group Asynchronous Browsing. 391 © 2003 by CRC Press LLC . phone line-based fax machine. See IFax device, TIFF-FX, RFC 2305. G-line A round, insulated wire used in microwave transmissions. G-Line A Cornell University physics resource for X-ray beam-related research. The G-Line Laboratory is organized into three experimental stations, G-I for the study of large molecule. Fiber Optics Illustrated Dictionary communications. This is mainly due to the prohibi- tive cost of completing the last link between the transmission pipeline and millions of individual buildings. FSO links could be established between the backbone and local drops through building-mounted. useful for lighthouses. The shape of the beam can be controlled to some extent by the positioning of the facets. By coloring some of the facets and rotating the lens or light source, the assembly can be made to flash. Small Fresnel lenses can be used as substitutes for magnifying glasses for anumber ofapplications and 383 © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary have the advantage ofbeing very flat, compared to traditional curved optical