Fiber Optics Illustrated Dictionary - Part 36 ppsx

fanoutA device that facilitates the separation of in-dividual fibers in a fiber optic cable bundle, enabling them to be more easily handled, attached, configured, or repaired.. Fantail F

Fiber Optics Illustrated Dictionary

compress-send-decompress schemes, with the

com-pression needed only to speed transmissions, and thus

not degrading the quality ofthe original See facsimile

mode, Huffman encoding, TIFF-FX, RFC 2301,

RFC 2304, RFC 2305

facsimile mode Facsimile machines have a number

of operating modes, including various regular and

fine resolutions, and can be manipulated to send in

monochrome or grayscale, depending on the

capa-bilities of the sender and receiver, and the software

or hardware Most fax machines and fax/modems

send in Group 3 standard and fine modes, that is

203;dX;d98pixels and 203;dX;d196 pixels Other

modes have been defined (Group 3203;dX;d39I -

su-perfine; Group 4400;dX;d400 -standard), but they

are not widely supported in consumer-priced

prod-ucts Afax can be only as good as the weakest link in

the transmission If the sending fax sends in the

low-est resolution, a higher resolution receiving fax

doesn't improve the image Conversely, if the

send-ing fax uses fine resolution, but the receivsend-ing fax can

only support standard resolution, the details will still

be lost Since the orientation ofmost faxes isportrait,

and the orientation of most computer monitors is

landscape, fax/modem software usually has zoom,

pan, and rotate features to aid in viewing documents

facsimile modem, fax modem Afax modem system

consists of a fax-enabled data modem (one which

works in two modes) hooked to a computer,

some-times combined with a scanner Instead of creating a

document, printing it, feeding it through the fax

ma-chine, receiving a printed page at another destination

fax machine, and then perhaps even typing or

rescanning (and OCR-ing) the printout back into a

computer at the other end, the fax modem system

sends a digital fax directly from the software

appli-cation that created the document, to the receiving end

Or, ifa scanner is used, the system sends the scanned

file as the fax.Ifthe receiving device is a fax modem

system, rather than a fax machine, then the fax goes

directly to the computer hard drive, and no paper is

used in the transaction

Optionally, a fax machine may connect to a local

net-work so that users can be notified if a fax has been

received or even select an option to view the fax on a

computer monitor (thus providing hybrid fax

ma-chine/fax modem capabilities)

In business environments some people erroneously

use fax machines when they should be doing direct

data transfers This is a common scenario: the main

office of a corporation creates a new 80-page policy

manual and wants to distribute it to all ten branch

offices The branch offices would like an electronic

copy in order to customize it for their needs, or to

easily make corrections as directed by the main

of-fice, etc The typist types a copy, faxes 80 pages to

each of the ten branch offices; 880 pages are

gener-ated in all, the original, and the 10 branch copies Now

the typists at each branch office retype the document

into their word processors, thus duplicating the work

already done

Rather than always using a fax machine, there are

better waystodistribute some types of documents The first is a slight improvement By using a fax! modem software program to send the document di-rectly to each branch to another fax/modem program,

no paper is printed until the documents are complete

to each branch's satisfaction, and the completed cus-tomized documents can be OCR-scanned back into a word processing text file at the destination

A better solution is to send the original file, in docu-ment format, through a modem or through the Inter-net, to each branch office, where the secretaries can load the received file directly into the word proces-sor This can be accomplished by putting the file on

an FTP site, and notifying the branches that they can access the site and download the latest version of the file If different word processors are being used, the original can be saved in Microsoft Interchange For-mat (also known as RTF or Rich Text ForFor-mat), a widely supported format that can be read and saved

by all major word processing programs

The best solution to document exchange may be to have a secure centralized online document repository which can be accessed and modified dynamically by all branches through an Internet or private network connection Fax machines are a great resource for sending short documents, but they are not the best solution for all document transfers, and the Internet provides distant branches with a way to dynamically produce and maintain documents without incurring long-distance charges Integrated data, video, and voice services are increasingly offered by telecom-munications carriers; facsimile comtelecom-munications are being superseded to some degree by email attach-ments, especially PDF files See facsimile device, fac-simile fonnat, facfac-simile history, facfac-simile modes, Portable Document Format

facsimile switchAnexternal switching device that allows a single phone line to be used for more than one phone-related piece of equipment Fax switches often can also handle telephone answering machines and computer modems The fax switch is attached between the phone line plug and the various phone devices When a call comes through, the device evalu-ates the tones and decides whether it's a voice call, a modem call, or a fax call, and routes the calltothe appropriate device Unfortunately, most fax switches can't detect when a manual fax machine is going to send a fax if the call originated as a voice call If the person dials the phone manually and then wantsto switch over to a fax call after the connection is es-tablished, many fax switches can't reverttodata mode (newer ones may be switchable on receiving a par-ticular code) In spite of that limitation, it's a great tool for homes, home offices, and small businesses that can't afford extra phone lines

fade To diminish in strength, loudness, or visibility

Invideo or audio editing, fading is deliberately used

to provide transitions that are perceptually pleasing

Indata or broadcast transmissions, fade is usually an undesirable effect due to various factors such as dis-tance, loss of signal, obstructions, interference, etc Undesired fade can sometimes be reduced or

mediums, and good insulation.

fade marginSignal losses in satellite systems can

occur from scattering, absorption, and various subtle

types of interference Consequently various fade

margins are incorporated into the design of the

sys-tems, and they will vary depending on the degree of

fade expected from various sources and on the length

ofthe broadcast waves, with shorter waves generally

being more subject to fade

Fahrenheit scaleAtemperature scale that designates

32 degrees for the freezing point of water at normal

pressure and212 degrees for the

boilingpointofwa-ter at normal pressure, and other points relative to

these See centigrade scale, Celsius scale

Fahrenheit, Daniel Gabriel(1686-1736)

APolish-born German scientist who established the widely

used Fahrenheit scale Zero degrees was designated

as the temperature of a mix of ice, water, and salt,

and 90 degrees was considered to be the temperature

ofthe human body (in fact, it's closer to 98.6 degrees)

See Riimer, Ole Christensen

failsafeA designation that indicates that failure of a

system is unlikely or impossible, or that backups are

available if needed In networking, few, if any,

sys-tems are completely failsafe, but there are steps that

can be taken to prevent problems, such as the use of

surge suppressors, backup power systems, redundant

data storage or broadcast signals, etc See fault

toler-ant, redundant array of inexpensive disks

fake codeSee pseudocode

fallbackA contingency mode, plan, or operation In

communications, a designation for another speed or

mode of operations if the current mode is not

func-tioning as well as might be desired Many modems

may fall back (two words) to a slower speed if the

connect negotiation doesn't work at higher speeds

Many communications programs may fall back to

smaller packet sizes if there is a lot of noise, or other

impingements on a data file transfer In software, a

fallback (one word) may be one in which the

appli-cation or operating system goes to another mode or

another program ifsome error condition or slowdown

is detected A network may go to a fallback route if

the usual one is not available or not responding as

expected

falsing Spurious signals that accidentally are

inter-preted by a system as commands, or that are

deliber-ately introduced to fool a system, usually for

unau-thorized purposes In telephone systems, certain

situ-ations can be simulated by playing particular tone

se-quences, so the system is fooled into switching,

trans-ferring, or connecting long-distance or other types of

calls In transmissions control for satellites and other

radio-controlled devices, environmental noise, falsely

interpreted signals, etc can have major consequences

if the system thinks it's a command and acts upon it

fan 1 Fan of science fiction Since there are a large

number of software developers who are science

fic-tion fans, they have co-opted this term into many

computer-related situations, video games,

simula-tions, and virtual reality environments 2.Anactive

as heat sinks) often used to cool computers so that chips and other components are kept at optimum op-erating temperatures

FAN See flexible access network

fanfoldSee z-fold

fanoutA device that facilitates the separation of in-dividual fibers in a fiber optic cable bundle, enabling them to be more easily handled, attached, configured,

or repaired After being fanned, individual strands

may be channeled through a furcation unit for

rout-ing to its destination See furcation unit See fantail FANP See Flow Attribute Notification Protocol

Fantail Fiber Optic Wiring Bundle

A fantail wiring bundle secured at the point where

it connects to the electronic components, with con-nectingpointsfor individualfibers fanned outfor cou-pling with the appropriate connectors Individual fi-ber pigtails typically have protective caps, in prepa-ration for adding a connector, or will have a connec-tor already attached to protect the precision-cut and polished terminal point They may be color coded to facilitate the correct connections [NASAILangle photo, 1999.J

fantailA descriptive term for a wiring bundle that is secured somewhat near the point at which the wire connectors spread apart for attachment to a wiring rack, thus creating a shape that fans out from the bundled point The strap that secures the bundle aids

in holding the wires together if one or more of the wire connectors are disconnected, as they will hang

a few inches below the rack for easy location and re-attachment, ifdesired The fantail configuration also makes it easier to disconnect and reconnect the en-tire bundle of wires See fanout

FAQ See frequently asked questions

far end crosstalkFEXT When wires are packed to-gether tightly, and signals are travelling through most

or all the wires, the potential for interference from crosstalk increases Far end crosstalk is a type of in-terference originating from multiple signals travel-ling in the same direction, typically through wire pairs, as in common copper twisted-pair installations FEXT directly effects bit error rates (BERs), as it

Fiber Optics Illustrated Dictionary

cannot be cancelled as easily or as effectively as near

end crosstalk (NEXT) See near end crosstalk

farad Aunit ofcapacitance equal to one coulomb (of

electricity) divided by (a potential of) one volt

Named after Michael Faraday

faradaic Relating to an asymmetric alternating

cur-rent (AC) produced by an induction coil

faraday A measure of electrical charge transferred

in the process of electrolysis per weight of an ion, or

element, that is equal to about 96,500 international

coulombs (or 96,490 absolute coulombs) Named

af-ter Michael Faraday

Faraday cage A structure, usually mesh- and

cage-like, to isolate a person, device, or electronic system

from damage or interference from outside electrical

sources These may sometimes be seen in science

museums where electrical devices, especially large

Van de Graaff generators, are demonstrated Named

after Michael Faraday

Faraday Dark Space In a cathode discharge tube, a

region between the positive column and the negative

glow that appears dark Regions in the tube become

easier to distinguish if the pressure is lowered in a

tube that has some air in it (normally air is removed

to extend tube life and effectiveness) Then it becomes

possible to distinguish the Faraday Dark Space as a

region just outside a pale negative discharge glow,

which in turn terminates in Crookes Dark Space,

which borders the outside glow of the cathode

Named after Michael Faraday See Crookes Dark

Space

Faraday dynamo A historic electrical generator

de-veloped in 1832 by Michael Faraday

Faraday effect A basic magneto-optical effect in

which a plane of polarization of light in a magnetic

field, traveling parallel to the lines of magnetic force,

can be rotated to another plane by a transparent

iso-tropic medium Named after Michael Faraday, who

described it in 1846, this effect was studied further

three decades later by John Kerr The distinction

be-tween the Faraday effect and the Kerr

magneto-opti-cal effect is that Faraday focused his attention on a

beam that was transmitted through the magnetic

ma-terial, while Kerr focused on a beam that was reflected

off the magnetic material The Faraday effect can be

seen in a number of telecommunications

technolo-gies.In satellite communications, the plane

ofpolar-ization of radio waves traveling through the

iono-sphere rotates about the direction ofpropagation,

par-ticularly at lower frequencies See Kerr

magneto-op-tical effect

Faraday effect, acoustic The Faraday effect was

described by Michael Faraday more than 150 years

ago.Itis a basic, fundamental effect that is exhibited

in many different phenomena and is of continuing

interest to scientists, both as to its properties and its

practical applications The acoustic Faraday effect is

the acoustic analog ofFaraday's magneto-optical

ef-fect Typically, liquids do not propagate transverse

waves, but L.D Landau, in 1957, predicted that a

quantum liquid phase of 3He might exhibit transverse

sound waves under specific conditions Lee et al have

observed rotation of the polarization of transverse sound waves in superfluid 3He-B in a magnetic field, lending support to Landau's prediction See Faraday effect

Historic Faraday Electromagnet

This Faraday electromagnet, cobbled out ofavail-able materials was wound partly from Faradays

wifespel/icoat [Classic Concepls ilIusrralion.}

Faraday-Stark effect A novel effect resulting from the combination of the Faraday magneto-optical ro-tation and quantum-defined Stark effect This phe-nomenon enables an electrical field to be used to in-fluence a Faraday or magneto-optic Kerr rotation It

is a photonic effect that was discovered in the mid-1990s which, along with linear polarizers, may have applications for future high-frequency modulation devices The Faraday-Stark effect was described by Lee et al inApplied Physics in 1996, and Faraday-Stark magneto-optoelectronic (MOE) devices were patented by Lee and Heiman (U.S #5,640,021, 1997) See Faraday effect, Stark effect

Faraday, Michael (1791-1867)AnEnglish physi-cist and chemist who was apprenticed to a bookbinder

at the age of 13 He took time to read the books and

to listen to local lectures by Humphry Davy, becom-ing his laboratory assistant in 1813 Faraday went on

to conduct extensive experiments in electricity and magnetism He passed electrical currents through so-lutions and observed their effects, adding new knowl-edge to the discoveries of A Volta Faraday demon-strated that the amount of an element deposited at an electrode is proportional to the current flowing through the solution.In 1831, he demonstrated that

an electrical current can induce a current in a differ-ent circuit and made a historic differ-entry in his journal linking electricity and magnetism The following year

he constructed a basic generator, calling it adynamo.

Faraday also studied the properties of metals and glass and developed new types of optics He coined

portant investigations of inductance in electrical

cir-cuits by other scientists grew out of Faraday's work

Many electrical effects have been named after him

See Davy, Humphry

Faraday's lawsMichael Faraday investigated the

phenomena related to decomposition by galvanic

current and made some important discoveries that

have been investigated and variously stated by

suc-ceeding scientists Generally, Faraday's laws are

de-scribed as follows:

I in electrolytic decomposition, the number of

ions charged or discharged at an electrode is

pro-portional to the current passed;

2 the amounts ofdifferent substances deposited or

dissolved by the same quantity ofelectricity are

proportional to their equivalent weights;

3 when passing a constant quantity of electricity

through different electrolytes, the masses of the

ions set free at the electrodes are directly

pro-portional to the atomic weights of the ions

di-vided by their valence

Faraday called his discovery the "law ofdefinite

elec-trolytic action." It was opposed by Berzelius and

those who adhered to Volta's theory of galvanism

Through subsequent experiments, Faraday's concepts

have been refined and confirmed, and his

discover-ies are now known as Faraday's laws

Farber, DavidJ.Originally a computer consultant

to the Rand Corporation in the late 1970s, Farber later

became a cofounder of CSnet (Computer Science

Network), NSFNet, and others In 1995, he was

awarded the SIGCOMM Award for lifelong

contri-butions to his field Farber has served on the boards

ofAT&T and several other industry telecom

compa-nies, as well as the Electronic Frontier Foundation

and the Internet Society In January 2000, the

Fed-eral Communications Commission (FCC) announced

his appointment as Chief Technologist for the FCC

He is known for his online discussion list

"interest-ing People."

FARNetSee Federation ofAmerican Research

Net-works

Farnsworth, Philo Taylor(1906-1971) A

preco-cious American musician and inventor who built an

electric motor at about 12 years ofage and described

a television system to friends He is reported to have

shown a drawing of the idea to J Tolman, a teacher,

in 1922 Fortunately,Tolman later remembered the

incident and produced the drawing, or the young

Farnsworth might not have received credit for being

one ofthe earliest inventors oftelevision technology

Farnsworth kept working on the idea, submitted a

patent application in January 1927, and successfully

transmitted his first TV image in September 1927

The television patent was awarded in August 1930

(U.S #1,773,980)

The versatile inventor also developed several types

of amplifying systems, a system of pulse

transmis-sion, a projection system, a microscope, and a type

of cold cathode-ray tube (CRT), securing hundreds

be noted that biographers and Farnsworth himself credit his wife Elma "Pem" Gardener-Farnsworth as contributing significantly to the construction of his devices

In September 1983, the U.S Postal Service com-memorated the achievements ofPhilo T Farnsworth with a 20-cent stamp and first day cover and later is-sued a 33-cent portrait stamp from the Great Ameri-can Inventors series See television history

http://philotfarnsworth.com

Farnsworth Historic Imaging Tube .~.

Farnsworthsteenage drawing of his concept ofa historic television system emerged during patent dis-putes in the 1930s {Philo T Farnsworth, 1922.J

FAS 1 See facility-associated signaling 2 See frame alignment signal

fast busyA telephone busy signal that is distinctive

in that it repeats at twice the rate ofa regular busy A regular busy signal indicates the caller's phone is unavailable (it's off-hook or in use), whereas a fast busy indicates that all trunk lines are busy, and the call cannot currently be routed to the destination

Fast EthernetAversion ofEthernet enhanced to in-crease its 10 Mbps capacity up to 100 Mbps over cop-per or fiber, which brings it into the high speed net-working range along with asynchronous transfer mode (ATM) and FDDI This enhanced capability requires the upgrade of other devices such as hubs and network cards, partly because Ethernet hubs can

be cascaded, whereas Fast Ethernet hubs are stacked

Fast Ethernet is an international open IEEE standard (802.3u, 1995) used in medium-scale networks such

as campus backbones See Fast Ethernet Alliance, Gigabit Ethernet

Fast Ethernet AllianceAnopen trade association established to develop and promote Fast Ethernet technologies for existing voice-grade traditional cop-per twisted pair, founded in July 1993 A major goal

of the Alliance was to standardize 100 Mbps Ether-net technology By 1994, it had submitted

100Base-TX and 1OOBase-T4 wiring specifications for con-sideration to the IEEE for inclusion in the IEEE Fast Ethernet 1OOBase-T standard The Alliance member-ship totaled more than four dozen telecommunications

Fiber Optics Illustrated Dictionary

vendors including well-known companies such as

NCR Microelectronics, National Semiconductor, Sun

Microsystems Fast Ethernet was adopted officially

in June1995 by the IEEE 802.3 group See Fast

Ether-net

fast Fourier transform FFT See Fourier transform,

fast

Fast SCSI A means of configuring SCSI to provide

faster transmission speeds, up to 10 Mbps There have

been a number of variations on the SCSI standards

One of the more commonly implemented versions is

SCSI-2 See Small Computer System Interface for a

detailed description of SCSI technology

FastIP, Fast Internet Protocol A3Com commercial

product in whichjust the first datagrams ofthe IF

traf-fic are passed through the router and, if a direct path

is found, subsequent ones may bypass the router

us-ing Next Hop Resolution Protocol(NHRP).It is

em-bedded in local area network (LAN) adaptors and

implemented in LAN switches rather than in

Inter-net Protocol (IP) routers See IP switching

FAT 1 File Allocation Table See FAT format

2 final acceptance testing

FAD See fixed access unit

fault A defect, incorrectly functioning system,

mis-take, or accident In fiber optic cables, faults may

in-clude crystallization during fabrication, bubbles,

un-desired particles (apart from deliberate fiber doping),

misalignments, incorrect coupling or bonding,

exces-sive bends, and dispersion problems

fault isolationIn electronic circuitry or software

de-bugging, a troubleshooting strategy for isolating the

location of a problem In circuitry, it may involve

shutting down parts of the system, wiring in shunts

or bridges, or selectively stimulating particular areas

Insoftware, it may involve setting breakpoints,

print-ing debug messages, or tracprint-ing particular variables

See bridge, shunt, trace

fault threshold The level at which a system's

struc-ture or function is considered to be compromised

This may be a certain number oflost packets, a

speci-fied electrical level, a certain number of physical

flaws, or any other measures particular to a system

that affect its integrity and functioning for a

particu-lar purpose

fault tolerant A fault tolerant system is one that is

designed so if a problem occurs, the entire system or

important parts of the system will continue to

func-tion until the problem is corrected Thus, system

re-dundancy, backups, secondary routines or hardware

paths, etc can be incorporated to increase fault

toler-ance Good computer operating systems are designed

so that individual applications don't crash the system

The application itselfmay crash, or need to be "killed"

(by killing the individual processes associated with

the program), but the system can handle the crash

without affecting other programs or the general

op-erations and will clean up stray files, memory, etc

See Byzantine Generals problem, failsafe

faxcolloq facsimile See facsimile machine.

fax mode See facsimile mode

FB See framing bit

FBT See fused biconic taper

FBus Frame Transport Bus

FC 1 See feedback control 2 frame control FC- connector A relatively common coupling part for fiber optic connections that physically resembles ST- connectors, but with a friction rather than a bayo-net mount FC- connectors are used to couple single-mode fiber connections They are also available in hotmelt styles

FC-x In the Fibre Channel hierarchical model, a se-ries of services and protocols

For more detailed information, see Fibre Channel, including the Fibre Channel Layers chart

FC-O physical media, transport speeds,

re-ceivers, and transmitters are defined at this level FC-l encodings transmission encodings and

decodings FC-2 signaling a protocol for specifying

mechanisms and rules for transfering data blocks, con-trolling data flow, and error detection mechanisms FC-3 services common services for

N Ports on a node FC-4 protocols upper level protocols in

terms of channels and net-works (e.g., SCSI and ATM) that map into the system

FCASee Fibre Channel Association

FCIA See Fibre Channel Industry Association FCCSee Federal Communications Commission FCC Glossary of Telecommunications Terms See Glossary ofTelecommunications Terms, FCC FCLCSee Fibre Channel Loop Community FCS 1 See Federation ofCommunications Services

2 See Fibre Channel specifications 3 See Frame Check Sequence 4 Fraud Control System FCSI See Fibre Channel Systems Initiative FCWSeeFederal Computer Week Magazine.

FDD See floppy disk drive

FDDI See Fiber Distributed Data Interface FDM See frequency division multiplexing FDMASee frequency division multiple access FDMS See Fiber Dispersion Measurement System feature code A number or character sequence used

to activate a feature on a phone system, such as speed dialing, last number redial, etc These are more com-mon on multiline business phones than on residen-tial phones

feature connector Aconnector for coupling a periph-eral card or device to another periphperiph-eral card, such

as a video graphics adapter, so the second card can perform direct memory access (DMA) through the card's bus, without having to load the system bus The feature connector is commonly used on VESA-com-patible systems

Feature Group Switching Arrangements

feature phoneA phrase for phones that have extra

features Sometimes the features improve

function-ality (redial, speakerphone, channel, etc.), but

some-various types of long-distance carrier switching

ar-rangements that are part of the Bell Operating

Com-panies (BOC) system

Group A

Group B

Group.C

GroupD

A subscriber line connection

rather than atrunkconnection to

a local exchange carrier's

network

A trunk connection that uses an

authorization code for billing

Used in areas where it is not

practical to offer Feature Group

D (Equal Access services), such

as some older switching

systems, and independent

services

The older long-distance services

offered by local exchange

carriers to AT&T before

divestiture Mutually exclusive

with Feature Group D

Equal Access services, facilities

and signaling specifications,

established since divestiture and

implemented in the mid-1980s

Mutually exclusive with Feature

Group C

not be very useful

FEe 1.See Forwarding Equivalence Class 2 See forward error correction

FECNSee Forward Explicit Congestion Notifica-tion

Federal Communications CommissionFCC Asig-nificant U.S federal regulatory organization origi-nally created through the Communications Act of

1934, evolving from the formation ofthe Federal Ra-dio Commission (FRC) in the RaRa-dio Act of 1927 The original mandate of the FCC was to regulate the

time slots, and callsigns Since then, its jurisdiction has been broadened, reflecting the growth in telecom-munications in general The Commission is directly responsible to the U.S Congress

The FCC has a powerful role to play in the fair and equitable enactment and distribution of telecommu-nications resources in accordance with the Telecom-munications Act of 1996 It is the responsibility of the FCC to see that the Act meets its goals of open-ing the telecommunications business to anyone, and ofpromoting fair competition in the industry

The FCC now also oversees product emissions, en-suring that computing devices do not emit harmful radiation or unharmful radiation at levels that may nevertheless interfere with other radiant technologies such as radio waves

The FCC overall organization consists of a number

of commissioners, about nine offices (public affairs, plans and policy, general counsel, etc.) and six bu-reaus See Primary Divisions chart See Communi-cations Act of 1934 http://www.fcc.gov/

Primary Divisions of the Federal Communications Commission

Common Carrier (CCB) Enforcement, pricing, accounting, program planning, network

services, and wireline services

Wireless Telecommunications (WTB) Domestic wireless communications, including paging, cell

phone, PCS, and radio, excepting satellite communications

This bureau is further subdivided into Commercial Radio, Enforcement, Policy, Private Radio, Licensing, Customer Services, and Auctions divisions

Mass Media (MMB) Audio service, enforcement, policy and rules, video services,

administration, and inspections

Compliance&Information (CIB) A national call center, and infonnation resources,

management, compliance, technology, and regional offices

International International planning and negotiations, satellite and radio

communications, and general administration

Cable Services (CSB) Consumer protection and competition, engineering and

technical services, policy and rules, public outreach, management

Fiber Optics Illustrated Dictionary

Federal Communications Commission classes,

FCC classesA series of designations or ratings

ap-plied by the FCC to electronics devices These are

primarily intended to help prevent interference from

devices like computers that may affect

electromag-netic broadcast waves such as radio and television

signals Ifyou have tried to use a cordless phone near

a computer and experienced interference, you are

fa-miliar with the type ofproblem excess emissions can

create Many commercial video devices, for example,

are labeled 'For Commercial Use Only' to comply

with FCC regulations

Federal Computer Week Magazine FCW A

news-paper providing up-to-date news and product

infor-mation to U.S government computer technology

us-ers on sources and types offederal information

tech-nology (IT).Itespecially focuses on desktop,

client-server, and enterprise computing and issues of

vol-ume procurement FCW publishes online and print

editions and maintains an online archive of past

in-formation

Federal Information Processing StandardFIPS.A

set ofstandards for document processing, search, and

retrieval Examples include FIPS PUB 180-1 (secure

hash standard) and FIPS PUB 144 (digital

commu-nication performance parameters) Anumber ofFIPS

publications are based upon ANSI and CCIT

stan-dards

Federal Networking CouncilFNC The FNC

re-ports to the Federal Coordinating Committee on

Sci-ence Engineering and Technology and was chartered

by the National Science and Technology Council's

Committee on Computing, Information and

Commu-nications (CeIC) It provides a focal point and forum

for networking collaboration among U.S federal

agencies with regard to education, research,

intercom-munications, and network operations Since 1997, the

various activities of the FNC have been carried out

through the Large Scale Networking (LSN) group

http://www.filc.gov/

Federal Standard Glossary of

Telecommunica-tions TermsSee Glossary of Telecommunications

Terms, Federal Standard

Federal Technology ServiceFTS A service of the

U.S General Services Administration (GSA) that

provides infonnation technology and network

ser-vices to U.S government agencies, including its

mo-bile workforces http://www.fts.gsa.gov/

Federal Telecommunications Standards

Commit-teeFTSC AU.S government agency that promotes

the standardization of communications interfaces,

including computer networks The FTSC is chaired

Category

ClassA

ClassB

Notes

Computing devices rated for

office use and that may not be

used in the home

Computing devices rated for

home use

by the Chief of the Technology and Programs Divi-sion Through the work of its technical subcommit-tees, it is the primary telecommunications standards mechanism supporting the National Communications System (NCS) The FTSC liaises with and evaluates the development of national and international stan-dards and develops federal stanstan-dards recommenda-tions or the standards themselves in situarecommenda-tions where existing standards are unavailable or unsuitable for U.S government needs The technical subcommit-tees have specialized expertise in various fields, in-cluding mobile, wireless, and multimedia telecom-munications

Federal Telecommunications SystemFTS The in-tercommunications network used primarily by U.S government civilian agencies It includes intercon-nections to other agencies and to the public switched telephone network (PSTN)

Federation of American Research Networks FARNet An organization comprised of commercial providers, some telephone providers, and mid-level NSFNet networks that meet to discuss issues related

to these businesses and the Internet

Federation of Communications ServicesFCS.A trade association representing the mobile communi-cations industry in the British Isles FCS promotes and encourages a healthy market environment for the communications industry in the U.K and represents its members to the government and various tele-communications agencies

http://www.fcs.org.uk/

feed horn, feedhornA basic signal-capturing com-ponent in satellite receiving antennas that is mounted

at the focal point It must either be rotated to corre-spond to the polarity ofthe incoming signal (horizon-tal or vertical) or be attached to a dual coupler The focal length ofthe feed hom is dependent on the depth and diameter of the parabolic dish in which it is mounted The feed hom is attached to a signal am-plifier See antenna, low noise amplifier, microwave antenna, parabolic antenna

feedbackn. 1.Information or phenomena that are re-flected or translated and returned to the originating

or transmitting source 2.Anopinion offered in re-sponse to some preceding event or infonnation 3 Re-turned information about data that has been received

or passed through In networks, there are many feed-back mechanisms providing information data rates, congestion, traffic in the opposite direction, and the progress or success of a transmission

feedback controlFC.Ameans of controlling a sys-tem by sensing impulses or signals that are compared

to areference or desired value and responding accord-ingly For example, when humans get cold and their body temperatures drop, the nervous system senses the difference and causes the body to shiver to help

it generate sufficient heat to maintain life In a tele-phone system, if a tele-phone remains off-hook for more than a prescribed length of time, the system 'senses' the anomaly and responds with a beeping sound or message suggesting the subscriber hang up the phone

In Internet services using dynamic IP allocation, if a

oftime, the service may disconnect the subscriber in

order to make the IP number available to another

sub-scriber In robotics, feedback control is an important

means to enable a robot to sense and navigate around

its environment Thus, feedback control systems are

used throughout the telecommunications industry in

a multitude of ways to start, stop, and maintain

sys-tems in order to facilitate efficient operations See

hysteresis device

feedback signal 1 A signal that loops back around

to its source An undesirable audio or visual artifact

can occur when the same signal that is being

trans-mitted travels back through the original transmissions

media In sound systems, it commonly manifests as

a piercing, shrieking sound, as when a microphone

is located too near a speaker carrying signals from

that microphone If carefully controlled, audio

feed-back can sometimes be used to boost a weak signal

Invisual systems, feedback often manifests as ghost

images or wiggly distortions 2 An intentional

diag-nostic looped back signal In diagdiag-nostic systems,

when a signal is transmitted and then compared with

a reference when it returns (the returning signal is

the feedback signal), it is possible to evaluate the

similarities and differences between the two signals,

or the information carried on those signals

feeder cable 1.Aprimary cable, extending from a

service provider or central switching location, to a

distribution panel or end-user In large installations,

there may be a main feeder cable and branch feeder

cables 2 The cable that connects a primary

distri-bution frame with intermediate distridistri-bution frames

3 A main network backbone cable, which may have

branch feeder cables leading to the main host

com-puters 4.Aheavy duty, primary, or high bandwidth

wire or cable intended to carry the main part of

traf-fic from the transmission source to its primary dropoff

points or hosts Thus, fiber optic cables and 25-pair

cables are common feeder cables

FEFOfirst ended, first out.Apriority queuing

ar-rangement in which the first item processed, or the

first process completed, is the first to be passed on,

or further processed Thus, processes that are finished

are taken out of the queue in order to leave space or

processing time for others See FIFO, FILO, LIFO,

LILO

femto-(symb - f)An SI unit prefix for10- 15

,a very, very small amount.Indecimal, femto- is expressed

as0.000 000000000001.See atto-

FEPSee Front End Processor

FERFrame Error Rate

Fermat, Pierre de (1601-1665) AFrench lawyer,

lin-guist, and mathematician who made many

contribu-tions to our understanding of mathematics and

op-tics, in spite ofhis recreational approach to

mathemat-ics, which meant that many ofhis discoveries initially

went unpublished Fermat's principle is named after

him

Fermat's principleWhen electromagnetic radiation

travels by reflection off a surface from one point to

another, it will take the path that can be traversed in

Fermi levelA value designated for electron energy

at half the Fermi distribution function

Fermi, Enrico(1901-1954) An Italian physicist who investigated atomic physics by systematically irradi-ating the elements, work derived in part from the in-vestigations of James Chadwick

ferric oxide Ametallic compound commonly used

to coat thin tapes or platters used in magnetic stor-age media The ferric oxide molecules can be selec-tively rearranged by magnetic impulses in order to encode the desired information on the medium There are other types of coatings available for applications such as sound or video recording; the differences in various coatings can affect the quality ofthe recording

ferroelectric liquid crystalFLC Crystals that are incorporated into spatial light modulators (SLMs) in optical computing technologies They have the ca-pacity for very fast bipolar switching Surface-stabi-lized FLCs, created by suppressing the natural heli-cal structure of FLCs, are used in a number of high-resolution color display technologies, including low power microdisplays They are also suitable for use

in optical shutters The Ferroelectric Liquid Crystal Materials Research Center is located at the Univer-sity of Colorado

ferromagnetic Having the property of being very easily magnetized with high hysteresis, Le., magne-tism that changes readily with changes in the mag-netizing force See electromagnet

ferrule Asnug ring or cap encircling a tool, pipe, or wire; a short length of tubing or bushing (insulating liner) that helps to strengthen or secure ajoint or cou-pling component It is sometimes called a sleeve, though the term is usually applied to "hard" sleeves (as opposed to soft, flexible sleeves) made of sturdy materials It may include a flange

Ferrule Examples

Ferrules are the most important single component

in fiber optic connectors They come in a variety of shapes, materials, andformats They may be unflanged (bonom left) orflanged with plastic (left) or stainless steel (right), and they are commonly fabricated from zirconia (a type of corrosion and heat-resistant ce-ramic - right), though plastic ferrules (left) are now available Ferrules similar to those shown above are commonly incorporated into standardized ST- and FC-connectors.

ferrule, fiber opticIn fiber optics cable assemblies,

a ferrule is the most important structural member It

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Fiber Optics Illustrated Dictionary

surrounds, secures, and aligns the fiber filament and

supports the surrounding housing To meet the

de-mands of optical alignment of fiber lightguides,

fer-rules must be exact and should not stress or overly

bend the joint, othetwise interference from imperfect

coupling could adversely affect the angle of the light

beams or allow them to leak at the joints

Ferrules are commonly made of zirconia (a ceramic

made from a crystalline powder) or alumina

Zirco-nia is favored for its bending strength, resistance to

corrosion, hardness, and heat resistance It holds up

well in the polishing process and over time once

in-stalled More recently, plastic and opaque

glass-ce-ramic ferrules have been improved to the point where

they exhibit acceptable strength and durability for

cost-effective alternatives to zirconia for certain

ap-plications in addition to which they may not require

polishing

Commercial ferrules for fiber filaments may come

with pre-domed or pre-angled endfaces to facilitate

termination They may be semifinished blanks or

whole fmished standardized ferrules such as SC- and

LC- styles They are available with or without flanges

3M has produced a line of connectors that use a

V-groove rather than a ferrule for coupling optical

fi-bers Interferometers can be used to assess the

char-acteristics ofthe ferrule-supportedjoint See

interfer-ometer

FESFixed End System

Fessenden, Reginald Aubrey (1866-1932)A

pro-lific, Canadian-born, American inventor and radio

pioneer who was one ofthe fIrst totryto devise ways

to carry information on top of a carrier wave In the process oftrying to achieve this, he developed ahigh-frequency generator in1901 that could create radio wave, and a hot-wire barretter, which was developed into an electrolytic detector, for detecting radio waves On Christmas Eve1906,to the astonishment

of those who heard the broadcast, Fessenden suc-ceeded in transmitting voice and music, using an Alexanderson alternator, over public radio waves to the U.S east coast See barretter, carrier wave, elec-trolytic detector, radio history

FEXTSee far end crosstalk

Feynman, Richard Phillips (1918-1988) Acharis-matic, individualistic American physicist who con-tributed greatly to our understanding of physics, es-pecially in quantum electrodynamics (QED quod erat demonstrandum - that which has to be demon-strated), who developed Feynman diagrams and pro-vided insights into the theory of computing

FFTSee Fourier transform, fast

FGDC See Federal Geographic Data Committee

fiber 1 A strand, filament, or other structure with long, slender threadlike qualities 2 Colloquial for fiber optic (or optical fiber) See fiber optic

fiber bundleTwo or more fiber optic filaments held

in close proximity, either with a supporting structure

or sheathing Combining fibers in a bundle enables more light signals to be delivered to the destination

Itis not uncommon for hundreds of fiber filaments

to be contained within a single bundle as the indi-vidual filaments are very small Why use many

fi-bers instead of a fatter fiber(jiber rod)?There are a

Basic Components of a Fiber Optic Cable Bundle

filler (no fibers) tension member single cable assembly

fiber optic filament

Single Cable Assembly Bundled Cable Assembly

The basic parts ofa single multifiber cable (left) and a bundle ofmultifiber cables (right) containing four single multifiber cables, with reflectiveiprotective sheaths (cladding) and outer sheaths (e.g., armoring), as needed.

including flexibility and the capability ofsplitting off

fibers along the path as needed as for

communica-tions "drops" (local service), signs, or ambient light

fixtures

The arrangement of fibers within a bundle is related

to the purpose, length, size, weight, and philosophy

of the fabricator Often large numbers of fibers are

randomly bundled with small gaps between fibers

The gaps may be useful in providing added

flexibil-ity to the cable, or may be filled with filler materials

to provide structural cohesion to the bundle Some

bundles are loose along the running portion of the

bundle but tightly aligned at the endfaces through a

fusion joint process This facilitates coupling and

re-duces the space needed for the coupler

Bundles are sometimes carefully aligned for certain

purposes, as in a singlelightlineor an arrayed

face-plate of certain dimensions Sometimes bundles are

deliberately randomized in order to provide a

ran-domly even light source at the point where the light

exits the endfaces of the fibers in the bundle

Sometimes fibers are bundled for ease of handling

together and provide extra external insulation and armoring against the elements in bundles that are to

be laid hundreds of feet undetwater in deep oceans Bundles are also practical in situations where the de-livery of different wavelengths over the same cable

is desired See faceplate, lightline

Fiber ChannelSee Fibre Channel Standard fiber creelAdevice for spooling fiber optic filaments

to facilitate handling 1 W Hicks was one ofthe first

to spool optical fiber See creel

Fiber Dispersion Measurement SystemFDMS A fiber Bragg grating measurement system that utilizes interference phenomena to evaluate grating transmis-sion properties, developed by NASA The system is quickly able to fully characterize fiber device phase, amplitude, transmission, and reflection from either direction

Fiber Distributed Data Interface FDDI.An Ameri-can National Standards Institute (ANSI X3T12, for-merly X3T9.5) standard high-bandwidth 100 Mbps packet-switched protocol developed by the X3T9.5 committee

FDDI Architecture Standard Documents

MAC Media Access Control A network control mechanism for defining fonnats and

methods Like the PHY layer, the MAC layer is directly implementedinFDDI chips The higher LLC sublayer provides data to the MAC

PHY Physical layer Anelectronic signal encoding/decoding layer which

mediates between the higher MAC layer and the lower PMD layer

PMD Physical Medium Dependent The lowest sublayer, which specifies various physical

media such as interface connectors, cables, power sources, photodetectors, etc

SMT Station Management A node manager and bandwidth allocator The SMT is

further subdivided into connection management (CMT) which controls access, ring management (RMT) which provides diagnostic capabilities, and frame services

FDDI Basic Port Types

Mport Master port Connects two concentrators and can communicate with DASs and SASs Sport Slave port Connects single-attachment devices for interconnecting stations, or for

connecting a station to a concentrator

Aport Dual-attachment Connected to the incoming primary ring, and outgoing secondary ring

See A port dictionary entry

Bport Dual-attachment Connected to the incoming secondary ring and the outgoing primary

ring