Fiber Optics Illustrated Dictionary - Part 40 pdf

FDM is still a widely used transmissions technique that is only now being superseded by other methods, such as time di-vision multiplexing TDM is prevalent in fiber optic communications

Fiber Optics Illustrated Dictionary

communications This is mainly due to the

prohibi-tive cost ofcompleting the last link between the

trans-mission pipeline and millions ofindividual 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 aboutIlan,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

of line-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

sys-tems See line of sight, Photophone

FreeBSDA 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

freewareA category of product, usually software,

that may be distributed and acquired without cost

Freeware does not mean copyright free A developer

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

privi-leges Freeware is not the same as public domain

soft-ware, 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 offreely distributable software See public

do-main, shareware

freeze frameAmode 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

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 see-ing actual movement Such systems are sometimes distinguished as audiographics systems As transmis-sion media become faster, full-motion video will be-come standard

frequency(symb - f) The number of periodic oc-currences or oscillations in a specified unit of time Frequency designations are used to describe the vary-ing periodic character of specific regions ofthe elec-tromagnetic spectrum.Inelectricity, 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 ofcycles per sec-ond instead ofhertz, as the unit name was widely used until the 1960s See wavelength

frequency biasAnadjustment made to a signal, such

as an audio signal, that biases it in one direction or another In practical applications, it may be a con-stant adjustment to a signal frequency to preventit from reaching zero.Itmay 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 sig-nals, depending upon how the bias is applied In au-dio 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 pro-vides 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 asnormal 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 departureThe degree of variation of a carrier frequency or reference frequency from an ex-pected' assigned value

Frequency Division Multiple AccessFDMA One

of the simplest techniques for increasing capacity over communications channels, since the radio fre-quency 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 simulta-neous links This technique is used in cellular phone

Multiple Access, Complex Scheme Multiple Access,

Demand Access Multiple Access, Multiple Access,

Time Division Multiple Access

frequency division multiplexing FDM Atechnique

used to more efficiently utilize a fixed or limited

amount ofbandwidth by subdividing it into narrower

channels Typically,guard bandsare inserted

be-tween 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

di-vision multiplexing (TDM is prevalent in fiber optic

communications systems) See single sideband, time

division multiplexing

frequency frogging See frogging

frequency hoppingInmobile communications

sys-tems, a spread spectrum technique in which

frequen-cies are jumped during the course of a transmission

This hopping may be done for many reasons, such

as to try to fmd a cleaner or more stable signal or to

tryto avoid detection (sometimes used in military

zones)

Frequency hopping was invented by Hedy Lamarr

(born Hedwig Eva Maria Kiesler) while trying to

de-velop 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

frequen-cies with paper tape, but the synchronization system

was somewhat cumbersome, and it was not until the

development of computer electronics that Lamarr's

idea was fully implemented Lamarr and Antheil

re-ceived 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 Asine-wave modulation

technique widely used in broadcasting that works by

varying the frequency of a constant amplitude

car-rier 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 ofintense research to the

prob-lem, ultimately proving successful FM radio stations

began broadcasting in the early 1940s.Inthe 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

rier signal can be transmitted over wires Frequency modulation can be used when digital data is routed through an analog system for part of the trans-mission

FM is also commonly used for very short range com-munications 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 ason/offkeyingandphase shift keying.See frequency modulation, phase shift keying

frequency swingInfrequency modulation, the dif-ference between the maximum and minimum values

at a given frequency.Inother words, the limits within which the oscillations range

frequently asked question(s) FAQ Aquery or ques-tion-and-answer list ofquestions that have been asked and answered many times, so often, in fact, that some-one has taken the time to write up the question/an-swer and post it, usually in a public forum on the ternet FAQs comprise an important part of the in-formation 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 be-fore 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 ampli-tude of the transmitted and reflected electric fields

Inother 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 en-ergy 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.Alarge light assembly designed from concentric rows of glass in a Fresnel configu-ration 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 as-sembly can be made to flash

Small Fresnel lenses can be used as substitutes for magnifying glasses for a number ofapplications and

Fiber Optics Illustrated Dictionary

have the advantage of being very flat, compared to

traditional curved optical lenses The tradeoff is

op-tical quality, with curved, smooth lenses providing a

clearer image

A coherent light source (e.g., laser light) can be shone

through aFresnel 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

pro-jection 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

interact-ing with a dielectric substance and the resultinteract-ing

re-flected and transmitted 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 regionAregion 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

cer-tain 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.In1819, Fresnel submitted his theories on

dif-fraction to the Paris Academy In1822, he

demon-strated a faceted lens designed to refract light to con-centrate a beam, a structure now widely usedin light-houses and scientific components See Brewster, David; Fresnel lens

friction feedA feed mechanism in a machine that relies on friction or pressure to feed the sheets (pa-per, card stock, thin metal plates, etc.) as in a printer, 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 nameA name that is easy to recognize and remember, used in place of cryptic or long names or codes For example, a printer with a computer desig-nation of LSL2345-b may be assigned a friendly name ofAdminLaserin lists of available output de-vices 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 do-main 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 areaA regionjust 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 ofservice, up to a point, with bet-ter antennas

fringing1 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 of color slightly offset 2 A visual artifact on an object dis-played 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 antialiasing

3.Aneffect 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 depend-ing upon the magnitude of the effect and the wave-length 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, la-ser lights, with coherent monochromatic character-istics and a longer range are favored See diffraction FRMfocus-rotation mount A pivoting antenna-fo-cusing structure

FRND Frame Relay network device

frogging1.Anequalizing 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 ofthe expected data in a non-random way

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.Incommercial 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 ofthe knobs and components which tune

in the desired frequency

front end systemA system that acts as an

interme-diary gateway, filter, or console for a more

power-ful, 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.Aninformation

kiosk with a simple touchscreen or touchpad input

system that hooks into a more powerful network

sys-tem 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

FRTEFrame Relay terminal equipment

frustumThe 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

FSfederal standard

FSANSee Full Services Access Network

FSBSFrame Switching bearer service See Frame

Relay

FSFA nonprofit educational association supporting

GNU See Free Software Foundation

FSKSee frequency shift keying

FSO1 Foreign Service Office/Officer Aforeign

af-fairs diplomatic liaison 2 See free-space optics

FSPSee File Service Protocol

FSSSee fixed satellite service

FSTCSee Financial Services Technology

Consor-tium

FTASee Federal Telecommunications Act

FTIPFiber Transport Inside Plant

FTNS See Fixed Telecommunications Network

Service

ftpThe command typed at an FTP site to access an

archive based on File Transfer Protocol (FTP).Itis

usual to type the command in lower case; however,

the name of protocol itself is usually written in

up-per case

FTPSee File Transfer Protocol

FTP mail serverA 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 binaryfile attachment.See file

attach-ment, ftp, FTP

FTRfederal telecommunications recommendation

ogy Service 3 Federal Telecommunications System

A government private telephone network See FTS2000

FTS2000, FTS2001A nonmandatory program of intercity telecommunications services provided to federal agencies by the U.S General Services Admin-istration (GSA) through two networks (A &B) trans-mitting through fiber optic cable Due to delays re-sulting 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,

requesting that competition be reopened (Spring 2001), alleging material changes in the contract re-quirements, which had been relaxed to ease the pro-cess of agency compliance In response, the GSA contended that data collectionrequireme~tswere re-laxed but service stipulations remained the same The transition is ongoing and is expected to be fully in place by about 2005

FTSC1 Faculty Technology Support Center 2 See Federal Telecommunications Standards Committee

3 See FidoNet Technical Standards Committee 4

Foreign Trade Service Corps

FTTCFiber 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

FTTHSee Fiber to the Home, cable modem

FTTHOFiber to the Home Office

FTTLSee Fiber to the Loop

FTTNFiber to the Neighborhood

FUBARfouled up beyond all recognition A phrase purportedly originating in military speak in World War II Less polite versions of it fit the acronym as well See foo

Funfear uncertainty doubt A sales strategy attrib-uted to Gene Amdahl, stated as "FUD is the fear, un-certainty, and doubt that ffiM sales people instill in the minds of potential customers who might be con-sidering [a competitor's] products." The marketing spin is that customers are safer with International Business Machines (IBM) products

fudgev 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 factorTolerance factor, buffer, safety net See fudge

Fujitsu LimitedA large Japanese commercial con-glomerate originating in the 1920s Fujitsu is known for a number of large-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 in-ternational research laboratory which has recently

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 Adesigner

and manufacturer of fiber optic and broadband

switching systems, and provider oftelephone 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 ofhardware

and software protocols to enable two-way

transmis-sions In some systems, full duplex operation creates

a digital echo in which each unit of textual

informa-tion is repeated Some systems can technically

sup-port 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

direc-tion 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

band-width-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

com-panies, 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 ofthe 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

key-board button Function keys are often programmed

as shortcuts to produce the same effect as typing

sev-eral keys, or selecting an operation sevsev-eral menu

items deep Many computer keyboards have 10 or 12

function keys with a variety ofuses, 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 ofthe 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 ofan

ob-ject 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

specifica-tion concentrates on user interacspecifica-tion or the task at

hand (e.g., punching out keyboard key caps on a pro-duction line) and does not specify the parts, process,

or equipment that may be needed to create the ob-ject or system, since there are usually many differ-ent ways in which the same end result can be

achieved

Thus, a functional specification for a computer would include descriptions ofwhat 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 toturnto functional specifica-tions when technology becomes entrenched Afunc-tional 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 in-terface, but is it the best way? In a functional speci-fication, one usually asks what does one want to ac-complish with the computer Ifthe answer is to indi-cate a choice or selection in a certain context in a way that is natural and comfortable for the user, then per-haps 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 ofthe system The more natural and direct the interaction, the more transparent the system.Inheterogenous dis-tributed computer networks with many different types ofcomputers 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 con-figure terminal software to the correct baud and par-ity rates, etc for each system to which they wanted

to connect Eventually autobaud modems added a certain degree of functional transparency by auto-matically negotiating and adjusting the data rate be-tween the answering system and the calling system With newer network protocols, such as email proto-cols on the Internet, once the initial configuration is installed, users are able to transmit a variety oftypes

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 fre-quency in an oscillating system 2 The reciprocal of the period of a wave 3 The frequency most effec-tive in a given situation (e.g., the one that transmits best over a particular waveguide)

fundamental group Agroup oftrunksin which each local switching center is interconnected to one of a higher order

furcation unit In fiber optics, a fiber installation and

strands of a fanned out bundle to their desintations.

A furcation unit might be used, for example, as a

con-nection between an outdoor bundled cable and an

in-door multidevice hub

fuse 1.n.Aprotective mechanism that reacts to break

an electrical circuit when the current through the

cir-cuit 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,

usu-ally 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,

usu-ally by melting Tofuseimplies a stronger or more

consistent bond than does tobond(as with an

adhe-sive), since there may be momentary heat or

chemi-cal alteration to create the bond

fuse alarm Atype 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 blockAninsulated 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

electri-cal cabinet with several rows of fuse mountings

When further enclosed, it is usually called a fuse panel

or fuse box

fuse cable Asection ofcable 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

in-stallations 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

op-tics installations, which are not sensitive to

electri-cal charges in the same sense as wired

communica-tions, 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 offuses, three

dif-ferent 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

op-tics 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

se-ries, depending upon the network configuration

Be-optical fiber medium to pass through an Be-optical in-terface, which is desirable for the prevention ofsignal loss FBT couplers may also be used in conjunction with other types ofcouplers (e.g., Mach Zehnder dB)

In dense wavelength networks, other technologies are being developed to solve coupling offiber optic com-ponents, 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 chemi-cals and heat Quartz has remarkable noncorrosive and vibrational qualities that make it a valuable in-dustrial 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 a binding substance such as sol-der or weld) to form a permanent bond between them

3 The union ofatomic nuclei to form heavier nuclei,

a process which generally requires enormous amounts of heat or pressure and can result in the re-lease of a 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 pro-tective coverings made of soft (often shrinkable) materials Sleeves from hard materials (e.g., metal), are more often calledferrules and long "sleeve' lengths are calledjackets.The termsheathseems to

be somewhat generically applied to both sleeves and jackets

For fiber optic joints, fusion sleeves are commercially available in single or ribbon (mass fusion) styles They may be preshrunk to reduce the amount oftime

it takes to install and shrink the sleeve the rest of the way to get a snug fit Preshrunk sleeves also reduce the amount oftime heat must be applied to secure the sleeve, reducing the possibility of heat-related dam-age 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 cre-ated 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 ofcable 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

Fiber Optics Illustrated Dictionary

knocking or bending A sleeve 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 viewerAninstrument 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 ofvarious types

are built into single and mass fusion splicing

ma-chines 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 angles-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

align-ment 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 splicingAjoining of two or more components

(e.g., optical fibers) through a heat or chemical

pro-cess 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

sig-nal-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,

de-pending upon the material fused, may be more

frag-ile and subject to breakage or apt to pick up tiny

par-ticles if there are rough edges Sleeves in different

colors can be used to identify types of splices (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

pro-vide 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

ap-plied 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

con-trol over temperature andarttime so that a fiber can

be prefused prior to the final fuse Itis crucial that

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 auto-mated 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 toler-ances for angle and loss)

• Position the fiber ends within the fusion splic-ing 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 po-sition

• Close the mechanism and select a program for the splice (depending upon filament materi-als 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 semiau-tomatic and ausemiau-tomatic 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 (hori-zontal, 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 if joined at different angles with respect

to polarity Thus, the rotational Olientation of the

fi-bers may have to be aligned with some of the more

Fiber Filament Fusion Splicing Basics

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 SystemFPLMTS A standards effort initiated in the early 1990s to create a global mobile communications system that encompasses cordless and cellular tech-nologies.Itis 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 videoconferenc-ing, global positioning services (GPS), and multime-dia capabilities See Global Systems for Mobile Com-munications

future shockA state of human reaction tQ overload

or too great a rate of change (as in changing technol-ogy), 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 ofcomputer 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 evolurevolu-tion, and

to assess and respond to how it affects our health and quality of life

FuzhouThe capital ofFujian a Chinese province on the southeast coast This region is home to global leading suppliers ofADSL modems and optical com-munication components, including Star Network Technology Co., Ltd

tvabbrev.femtovolt (10-15volt)

FVRflexible vocabulary recognition A type of speech recognition in which a variety of words, not necessarilyjust those found in an associated database, can be processed FVR is useful for wired and wire-less 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, in-cluding dialects, accents, and slang, it is difficult to write algorithms to process natural speech spoken by many different people Thus, programmers have de-veloped 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

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

fi-ber 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

pro-vided 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

ofheat splicing two sections offiberfilaments toform

a single continuous lightguide Fibers are cleaved and

aligned in theZdirection 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 or

clad-ding to cladclad-ding, depenclad-ding upon the type offiber and

device used A heating arc is applied across the

re-gion to befused(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 timeThe 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

with-out compromising the bond This may include a

prefusing step that prepares the joint (e.g., by

soften-ing the ends) in preparation for fussoften-ing

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

vocabu-lary 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 of saying

"private" or "confidential."

FYIAnabbreviation 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

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

GInterfaceIn Operation, Administration,

Mainte-nance, and Provisioning (OAM&P), the G Interface

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

GSeries RecommendationsA set

ofITU-T-recom-mended guidelines for transmission systems and

media, digital systems and networks These are

avail-able 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 of particular interest are organized into

general categories at the end of this chapter A list of

the general categories is included in the Appendix

See also I, Q, V, and X Series Recommendations

G style handsetThe 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 ofthe newer

cordless or cell phone handsets which are very flat

and small See K style handset

G3FaxA 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

ma-chine See IFax device, TIFF-FX, RFC 2305

G-lineA round, insulated wire used in microwave

transmissions

G-LineA Cornell University physics resource for

X-ray beam-related research The G-Line Laboratory

the study of large molecule reactions, G-2 for gen-eral purposes, and G-3 for studying the growth of semiconductor films

G-Scope, G-ScanAtype 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 AnInternational Telecommunication Union

(lTD) low-cost, splitterless alternative proposal to ADSL CPE See Asymmetric Digital Subscriber Line, UAWG

G/A ground to air communication

GIGground to ground communication

G: Line In a network server configuration file, a glo-bal (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 a particular domain or ISP has been "G: Lined." In this case it usually takes a con-certed effort and some negotiations to regain or re-tain 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

GAgo ahead Acommon verbal and written nications 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 con-ferences on the Internet, particularly in moderated conferences where many people are queued to com-municate, and each one has to wait for aturn

GAB1 Group Access Bridging, Group Audio Bridg-ing A telephony chat or party line service in which multiple users call the same number and are con-nected to one another at the same time 2 See Group Asynchronous Browsing