Fiber Optics Illustrated DictionaryA sniffer is a useful system administration tool for monitoring and logging peak traffic times, network load, and possible problems.. Sniffer Network A
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A sniffer is a useful system administration tool for
monitoring and logging peak traffic times, network
load, and possible problems This information can
help an administrator tune a system to operate
effi-ciently See packet sniffer, Sniffer 5 A radio
direc-tion-finding tool for locating radio transmitters See
Ultra sniffer 6 A detective or investigative
journal-ist who sniffs out (investigates) information as
de-sired by clients or editors
Sniffer A registered trademark of Network General
Corporation The term "sniffer" has been used for
de-cades in the search and rescue and law enforcement
communities to refer to working dogs that are trained
to sniff out fugitives, lost individuals, or chemical
substances The term has also historically been used
in the radio community to refer to receiving devices
that locate the source of radio signals These
direc-tion finders help to trace signals emanating from
sources such as wildlife radio collars or radio
listen-ing devices (bugs) With the advent ofcomputer
sniff-ers, Network General Corporation has trademarked
the term in the context of software utilities and
net-work analyzers and the firm endeavors to protect this
registered trademark See Sniffer Network Analyzer
Sniffer Network Analyzer A commercial product for
analyzing local area network (LAN) traffic, first
in-troduced in 1988 by Network General Corporation
The software provides a log of traffic, a suite of
alarms, and various statistics The corporation
spe-cializes in fault and performance management
solu-tions for enterprise networks
Sniffer Technologies A commercial vendor
ofwiless monitors and network traffic analyzers and
re-porting products, including Sniffer Distributed,
Sniffer Wireless, Sniffer Optical, and others
sniffingjargon In computer networks, the process of
looking at network data for testing, diagnosis, or
un-authorized purposes Because the Internet as a whole
is a shared system, rather than a switched system
(though switched portions exist), it is relatively easy
to breach a system with software and hardware tools
provided for network testing and administration One
type of scouting sniffer for clandestine use captures
the firstfe~hundred bytes of every remote session
or file download/upload, so that the unauthorized
snoop can scan the sessions for interesting
informa-tion that might suggest a closer look
Snitzer, Elias (ca 1922- ) An electrical engineer and
professor emeritus at Rutgers University, Snitzer
demonstrated with Hicks that tiny-diameter fiber
cores could be used to transmi t light as a single mode
wavelength He authored articles on dielectric
waveguide modes in theJournal ofthe Optical
Soci-ety ofAmerica, in 1961 and coauthored
"Amplifica-tion in a Fiber Laser" inApplied Optics, in 1964 In
1990, he coauthored articles on rare earth doping of
optical fibers
Snitzer was elected to the National Academy of
En-gineering in 1979 and worked for many prominent
finns in optical technologies, including Polaroid
Cor-poration, American Optical CorCor-poration, and
Honey-well.In 1995, he became president of Photo
Refrac-tive Enterprises, Inc Snitzer is responsible for many firsts in the field of optical waveguides and develop-ment of glass, erbium, and ruby lasers See Kao, CharlesK
SNMP See Simple Network Management Protocol SNOM See scanning near-field optical microscopy snoop A testing and maintenance software tool for Solaris that enables the user to capture and inspect each packet in packet-based network traffic Ituses both the network packet filter and streams buffer modules for packet capture and displays them as re-ceived or logs them to a file It is similar to tcpdump and related to etherfind (SunOS) The snoop utility can be used to tune network variables, to detect re-transmissions, duplicate acknowledgments, and other aspects of the network configuration
snooper, snooperscope, night scope A device de-signed to enhance night vision by sending out and intercepting an infrared beam The incoming beam
is interpreted into an image that shows objects not visible to the human eye
snow An undesired aberration in a broadcast or dis-play of a video image in which there are many ran-domly distributed speckles, often white Snow can result from transmission problems, such as a weak
or drifting signal, or from display device problems,
as in a cathode-ray tube (CRT)
SNVT (pran snivit) See standard network variable type.
SOA See semiconductor optical amplifier
Societe Internationale de Telecommunications Aeronautiques SITA An international airline reser-vations and telegraphic transmissions service back-bone network established in 1983
Society for the History of Technology SHOT An interdisciplinary organization dedicated to fostering and promoting an interest in the development oftech-nology and how it affects society and culture, and to promoting scholarly study of related documents and artifacts Members include individuals, profession-als, museums, scientists, and librarians The organi-zation was formed in 1958 and is headquartered in the Department ofHistory of Science, Medicine, and Technology at Johns Hopkins University
Society of Broadcast Engineers, Inc SBE A non-profit organization providing publications, work-shops, a certification program, and liaison with im-portant regulatory agencies such as the Federal Com-munications Commission (FCC) in order to promote education, standards, and professional competency in the broadcast engineering industry The SBE was founded in 1963 and has since grown to over 100 chapters in the U.S and abroad It publishes the quar-terly journalThe SBE SIGNAL http://www.sbe.org/
Society of Cable Telecommunications Engineers Inc SCTE A U.S national nonprofit professional organization founded in 1969 The society includes over 13,000 members from around the world, repre-senting a broad spectrum of cable professionals The society provides education, certification, and stan-dards development http://www.scte.org/
Society of Motion Picture and Television Engi-neers SMPTE An international organization
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en-compass the emergence ofthe television industry The
society includes over 8500 members in 72 countries,
including engineers, technical directors, and
produc-tion/post-production professionals dedicated to
ad-vancing the theory and application ofmotion-picture
technologies SMPTE contributes to standards
devel-opment, encourages consensus-based recommended
practices (RPs), and industry engineering guidelines
(EGs)
In 1957, the society was awarded an Oscar for its
contributions to the advancement of the motion
pic-ture industry It has also received three Emmy awards
for various recording and video systems and standards
SMPTE is best known for developing SMPTE time
code methods, which are used for video editing
When video tape began to be widely used for
record-ing and editrecord-ing, a way was needed to synchronize
edits, to locate specific places on the tape, and to dub
sound to match the video sequences SMPTE began
in 1969 to develop a standard for digitally encoding
time information in terms ofhours, minutes, seconds,
and frames onto audio or video tape See MIDI time
code, SMPTE time code http://www.smpte.org/
socket1.Ameans ofproviding unique identification
to which or from which information is transmitted on
a network RFC 147 specifies a socket as a 32-bit
number; even sockets identify receiving sockets, odd
sockets identify sending sockets Each socket is
iden-tified with a process running at a known host
SOCKSAnaccess and security technology designed
to provide a framework for TCP and UDP client!
server applications to conveniently, transparently, and
securely utilize and traverse a network firewall There
have been a number of versions of SOCKS, with
RFC 1928 representing version 5 Version 5 adds
UDP and authentication capabilities, and extends
ad-dressing to accommodate the future needs ofIPv6
The protocol fits between the application layer and
the transport layer and does not provide ICMP
mes-sage-forwarding services Traversing a firewall
se-curely depends upon the various authentication and
encapsulation methods selected and used in the
ne-gotiation between the SOCKS client and server See
firewall, gateway, proxy, RFC 1928
sodium vapor lampA lamp that glows a warm
golden color, from the passage of electricity through
metallic vapors in a cylinder encased in a glass tube
Sodium vapor lamps have been used as street and
bridge lamps See mercury vapor lamp
soft copyAstored image, document, or file which is
recorded on a medium which must be accessed with
some type of technology in order to be viewed,
ma-nipulated, or displayed Soft copies commonly exist
on hard drives, floppy diskettes, tapes, CDs, and other
magnetic or optical media
soft transferAterm for an electronic monetary
trans-action which precedes the actual exchange of funds
between individuals or banking institutions.Apaper
check is a type ofsoft transfer It is a monetary
trans-action which is not finalized until the money is
with-etary transactions which are soft transferred and later
"hard transferred" from the actual bank or other fi-nancial institution, such as a credit union
SoftCardAnearly commercial product from Micro-soft, from an idea suggested by cofounder Paul Allen The SoftCard was an internal peripheral card equipped with a Z80 processor, which ran CP/M-80 from Digital Research This card, when installed in
an Apple II computer, allowed its user to install and run CP/M-compatible applications programs SoftSource Corporation/CatarraA Colorado and Bellingham-based firm that has developed a next-generation wireless mobile Personal Digital Assistant (PDA) macrobrowser that works transparently with the World Wide Web This product may define the future of mobile wireless Web browsing Recogniz-ing the improved capabilities ofnewer PDA devices, the developers, Scott Sherman, Mike McMullen, Dan Suslo, and Steve Work, created anapplica~ionengine and server technology compatible with HTML, that
is not dependent upon specialized subsets (e.g., Wire-less Application Protocol) or PDA languages char-acteristic of other microbrowsers See PDA macro-browser for an illustration See PDA micromacro-browser, Wireless Application Protocol
softwareComputer instructions stored on a medium which is reasonably portable and accessible by us-ers Actually, the distinction between hardware and software is much less clear than many people real-ize It may seem reasonable to designate everything inside the computer as hardware and everything that holds information that can be inserted into external storage read/write devices as software, but that's not really the best distinction Floppy disks and computer chips are tightly integrated hardware/software com-binations whether external or internal, so the matter
is really one of accessibility coupled with structure Since computer instructions stored on disks are eas-ily read, written, and moved, they are thought of as software Since computer instructions on computer chips are not easily read or written and not easy for a lay person to access or move, they are considered part
of the hardware
The lowest level software functions are programmed into the computer chips themselves At the hardware operations level, this software acts to start up the sys-tem, testit,bootstrap the device drivers to come online, and initiate the operating system to accept user input and output, and to otherwise communicate with the central processor Some ofthese operating instruc-tions may be read, in tum, from hard drives,
CD-ROMs, cartridges, or other storage media High level software interacts with the user through application programs
Software is created with a variety of programming, editing, debugging, compiling, interpreting, and link-ing tools in a great assortment of languages, which are general purpose or optimized for specific types ofprogramming See programming
Software& Information Industry Association SIIA A trade organization representing companies
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that create, distribute, and facilitate the use of
infor-mation in print and digital formats Evolved from an
organization originally founded in 1968, SIIA was
established through a merger of the Software
Pub-lishers Association and the Information Industry
As-sociation, in 1999 SIIA promotes the information
industry, represents its members in government
policy and regulatory affairs, and provides a business
development support network for top executives in
the field SIIA is based in Washington, D.C
http://www.siia.net/
Software Engineering Research NetworkSERN
Anengineering and research joint venture ofthe
De-partment of Computer Science and the DeDe-partment
of Electrical and Computer Engineering at the
Uni-versity of Calgary, Alberta It is sponsored by the
government of Alberta, University of Calgary,
Mo-torola, Computing Devices, and Northern Telecom
Software Publishers AssociationSPA See Software
&Information Industry Association
solar cellInthe 1940s, Bell Telephone Laboratories
developed a storage cell from thin strips of silicon
which had the characteristic of developing a charge
in the presence of light Since the silicon is not
di-rectly depleted in this process, solar cells are not
sub-ject to the limited life spans oftraditional wet anddry
cells Solar cells have since been developed and
refined in many ways and are used in many aspects
of electronics See photovoltaic
SolarisA popular 32-bit operating system from Sun Microsystems that is commercially distributed, as is their SunOS operating system and, more recently, OpenStep Solaris is multiprocessing, multithreaded, and network-friendly (using NFS), based on an open systems architecture Many large Internet Services Providers, university systems, and enterprise local area networks (LANs) run on Solaris Solaris is avail-able for various Sun SPARC, Intel-based, and Motorola-based systems
solenoidA long, cylindrical, current-carrying coil with properties similar to a bar magnet, into which
an iron bar will bedrawnwhen current is applied to the coil Solenoids are commonly used in circuit breakers which have replaced traditional fuses See electromagnet
Siimmering, Samuel Thomas von(1755-1830) A Prussian anatomist and inventor, Sommering was one
of the earliest inventors of telegraphic technology Based on the work ofF Salva, he developed an elec-trochemical wire telegraph which signaled letters and numbers through the application of current from a voltaic pile to a specific wire such that it created bubbles in an acid bath at the receiving end Each wire corresponded to a character, with the wires and frame
at each end looking very much like a threaded loom This invention, which was demonstrated to the ANSII Standards Related to SONET - Examples
T1.105.01-l995 Synchronous Optical Network
T1.105.02-1995 Synchronous Optical Network
T1.105.03-1995 Synchronous Optical Network
T1.105.03a-1995 Synchronous Optical Network
Tl.105.04-1995 Synchronous Optical Network
T1.105-1995
T1.105.05-1994
Tl.105.06-1996
T1.l05.07-1996
T1.l05.09-l996
T1.119-1994
T1.119.01-1995
Synchronous Optical Network
Synchronous Optical Network Synchronous Optical Network Synchronous Optical Network Synchronous Optical Network Synchronous Optical Network Synchronous Optical Network
Basic Description including Multiplex Structure, Rates, and Formats Automatic Protection Payload Mappings Jitter at Network Interfaces Jitter at Network Interfaces - DS 1 Jitter Data Communication Channel Protocol and Architectures
Tandem Connection Maintenance Physical Layer Specifications Sub-STS-1 Interface Rates and Formats Network Element Timing and
Synchronization Operations, Administration, Maintenance, and Provisioning - Communications OAM&P Communications Protection Switching Fragment
SONET Multiplexing Techniques
Technique
Interleaving
Single-stage interleaving
Two-stage interleaving
Type of interleaving
Interlaces individual bytes Direct byte interleaving Direct byte interleaving
Notes
Reduces overhead at receiving end STS-N signal created directly Accommodates European lTV-T rate
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STS-24 STM-8 1244.16 Mbps STS-48 STM-16 2488.32 Mbps STS-192 STM-64 9953.28 Mbps
can be transported together This is done to accom-modate broadband services such as ISDN
Following is an overview of some of the bit rate speeds for the Synchronous Transport Signal levels and how they compare to European equivalents This chart only indicates bit rates; the frame formatting for each system differs even further
SONET Interoperability ForumSIF.An organiza-tion devoted to identifying and suggesting soluorganiza-tions
to SONET interoperability issues, founded in 1994 Various workgroups work on topics such as remote login implementations and user requirements, inter-operability with specific systems (e.g., TARP), archi-tecture requirements, information models, access pro-tocols and more
The SIF findings and recommendations are published
as SIF Approved Documents Here is a small selec-tion to give an idea of the scope of the documents Most are available online; some can be obtained in paper format upon request
Focus Title Number
SIP-007-1996 Graphical User Interface
Design Principles for the Development ofOAM Graphical User Interfaces
SIP-009-1197 Remote Login
NE-NE Remote Login Implementation Requirements Specification
SIP-020-1998 Testing
IS to IS Abstract Test Suite
SIP-023-1998 Infonnation Modeling
Network View Model for Connection Management and Fault Management
NSIF-03 1-1999 Architecture
Architectures for an IP-Based DCN
NSIP-038-2000 Security
NSIF Requirements for a Centralized Security Server
Wheatstone and Morse technologies by three
de-cades Sommering improved upon Salva's design by
extending the transmission range of the device and
later collaborated with Schilling, who made some
sig-nificant contributions to early electromagnetic
teleg-raphy See Salva i Campillo, Francesc; Schilling,
Pavel; Steinheil, Karl August
sonarSonar is currently considered to be the
acro-nym for sound navigation and ranging (other phrases
have been suggested) It is essentially a technology
for generating and directing sound signals with the
intent ofanalyzing the returning echoes to determine
information about the size, shape, and relative
dis-tance of any objects encountered by the outgoing
sound waves
Sound requires a medium in which to travel.Itis, in
fact, a disturbance of a medium and, thus, sonar is
used for probing elastic media such as water and, to
a lesser extent, air (as in robotics)
SONETSynchronous Optical Network SONET is a
set of ANSI telecommunications standards which
specify a modular family ofrates and formats for
syn-chronous optical networks
SONET provides a standard operating environment
for managing high bandwidth services, and
incorpo-rates multiplexing, service mappings, and
standard-ized interfaces, so commercial vendors can develop
interconnecting technologies
SONET has been adopted by the ITU-T as the basis
for the Synchronous Digital Hierarchy (SDH)
trans-port system, and is a subset of this system SONET
is based on STS-l which is suitable for T3, and SDH
is based on STM-l, suitable for E4 transmissions
Communication between nodes, to permit control,
provisioning, administration, and security, is
accom-plished through the Synchronous Transport Signal
(STS) transmitting at a line rate of 51.84 Mbps The
STS comprises payload information and signaling
and protocol overhead Since the two ends of a
SONET transmission may vary in format and speed,
data are converted to the STS format, transmitted,
and, when received, converted into the appropriate
user format OAM&P is integrated into SONET See
detailed information in the following listings
SONET ANSI standardsA number of important
American National Standards of Committee TI
re-lated to SONET are available from ANSI and
de-scribed in the form ofabstracts on the Web See ANSI
Standards Related to SONET chart
SONET frameThe frame length is 8000 fps or 125
flsec SONET uses Synchronous Transport Signal
level 1(STS-l) as its basic signal rate of51.84 Mbps
SONET frames are organized in a row by column
structure totaling 810 bytes Transport overhead is
contained in the first three columns and is subdivided
to include section and line overhead The remaining
columns, from four to 90, are used for the
Synchro-nous Payload Envelope (SPE)
The STS-Nframe consists of frame-aligned,
byte-interleavedNSTS-l signals
TheSTS-Ncframe consists of concatenated STS-l
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Class A Payload independent functions
Required by all payload types
Class B Mapping dependent functions
Required by some payload types
Class C Application-specific functions
Class D Reservedfor future use
There are a number of ways to accomplish this, as
showninthe SONET Multiplexing Techniques chart
SONET optical interface layers SONET includes
a hierarchy of interface layers Each one builds on
the previous; from high to low, they are path layer,
Line layer, section layer, and photonic layer Individual
layers communicate to peers on the same layer and
to adjacent layers above and below
SONET path overhead In SONET, path overhead
is transported with the payload until the signal is
demultiplexed at the receiving end The path
over-head supports four classes:
SONET path terminating element PTE The PTE
is an element which multiplexes and demultiplexes
the Synchronous Transport Signal (STS) payload and
processes the path overhead as needed to originate
or access it If necessary, the PTE can also modify or
terminate it See SONET, Synchronous Transport
Signal
SONET timing In SONET networking,
synchroni-zation is accomplished by referencing a high
accu-racy clock and information from its slaves, so
syn-chronization characters between equipment nodes are
not used Due to the high data rates carried by
SONET, it is important to maintain clock accuracy
The three major timing modes supported are
exter-nal timing based on a clock, generated free
run/hold-over timing from an internal clock, and OC-N signal
line timing
SOP standard operating procedure
Sorokin, Peter P (1931- )AnAmerican physicist
who worked in collaboration with Mirek [Cevcik]
Class Functions Notes
Stevenson, Sorokin developed the first uranium la-ser, in 1960, that would set the stage for future tun-able continuous wave lasers At about the same time, Schmidt et al were developing similar technology in Germany Sorokin continued to work with laser tech-nology, developing a dye laser, demonstrated in 1966
at the IBM Laboratories with John Lankard Dye la-sers set the stage for tunable lala-sers
In 1991, Sorokin was awarded the Arthur L
Schawlow Prize in laser science See laser history sound Radiant mechanical energy produced by vi-bration, which requires a physical medium for its transmission (such as air), and is detected by hear-ing, accomplished through physical sound-detection, perception, and interpretation by the nervous system Compared to light and heat, sound waves move very slowly Human sound perception through hearing covers a frequency range from about 20 Hz to about
20 kHz, although lower, and sometimes higher fre-quencies are felt, though not heard, through vibrations
in the body Other creatures perceive broader, nar-rower, or more specific frequencies, and sound is a ubiquitous means ofspecies communication Enough
is known about the nature of sound waves to record, reproduce, and modify them, and to propagate them over great distances Humans can project unampli-fied voice through the air for a few dozen or hundred yards, depending upon atmospheric conditions Whale songs will resonate for thousands of miles through water, although whale communication dis-tances have been drastically reduced by interference from industrial shipping noise See acoustics, sonar sound spectrographAn instrument for measuring the structure of speech and displaying it visually, de-veloped in the early 1940s by Bell Laboratory re-searchers This opened the door to more objective, quantitative measures of speech, information that is
of interest not only to speech therapists, physicians, and educators, but also to developers of communi-cations technologies
sounder A sound amplification device incorporated into a communications receiver, usually a telegraph receiver, to make the code clicks audible to a human operator Sounders were invented when it was noticed
SONET Interface Layers
Path Services and path overhead mapping Transport services between path terminating
equipment (PTE) Mapping signals to line layer format
Conversion between STS and OC signals Line SPE and line mapping Transport of path layer payload and overhead
across physical medium Synchronization and multiplexing
Section STS-N and section overhead mapping Transport of STS-N across physical medium Photonic Optical conversion Transport of data across physical medium
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faster than a paper tape could print the messages A
mainline sounderwas an adaptation that allowed
vari-able adjustments without a relay See resonator
SP stream protocol See byte-stream protocol
space division multiple accessSDMA One of two
common optical multiplexing techniques which
uti-lizes an angle diversity receiver, that is, multiple
re-ceiving elements rere-ceiving from different directional
angles See wavelength-division multiple access
space-charge fieldIn electronics, an electric field
created outside the physical surface of a conductor
or semiconductor
space-to-mark transition, S-M transitionIn
tele-graphy, the momentary change when the system
re-verses polarity, or changes from an open to a closed
circuit At this point, a small amount of delay must
be taken into consideration, which can be plotted on
a timing wave The reciprocal is the mark-to-space
transition
SpacewayAcommercial constellation
ofgeostation-ary communications satellites from Hughes
Commu-nications Spaceway was formed from the merger of
the Hughes Galaxy Satellite Services and the
PanAmSat Corporation Hughes Electronics is a
sub-sidiary ofGeneral Motors Corporation Spaceway is
intended to be a global broadband communications
system with service planned for 2003
spade lug, spade tipA small, flat, notched
(some-what U-shaped) conductive connector attached to the
end of a conductive wire in order to easily secure it
to an electrical terminal by sliding the end around the
mounting screw and applying pressure via a bolt, or
by soldering Spade lugs are still common inside
small residential phone wire junction boxes, but in
large installations, punchdown blocks and modular
components are more prevalent See lug
spamslangA term widely used on the Internet to
describe annoying, unsolicited, irrelevant, illegal, or
worthless communications, usually in the form of
email orpublicpostings.It.s generally said that the
word originated as a tongue-in-cheek reference to a
Hormel meat product called Spam, which is
fre-quently pilloried and satirized in the media Whether
or not that is the case, thespamon the Internet,
espe-cially in the form of unsolicited email bulk
tion of get-rich-quick schemes and sex site
promo-tion has become a big problem due to the intrusive
way in which the spammers violate the space and
pri-vacy of recipients Not as often acknowledged is the
fact that spam causes substantial expense to ISPs, and
general annoyance and expense to users who pay for
email or extra storage space
spammingslangPosting or
emailingirrelevant.an-noying, illegal, or unsolicited opinions or promotional
materials, sometimes through anonymous mailers or
with false return email addresses
SPAN Switched Port Analyzer ACisco Systems
net-work switch feature for extending the monitoring
capabilities of existing network analyzers into a
switched Ethernet environment SPAN takes the traffic
defined SPAN port Anetwork analyzer which is at-tached to the SPAN port can monitor traffic on other compatible switched ports
spanning tree algorithmSTA Astandard technique described in IEEE 802.1 which is incorporated into bridges in computer networks For example, in Fi-ber Distributed Data Interface networks, it is incor-porated into bridges that connect the primary and sec-ondary rings The spanning tree logic can prevent duplicate bridging and allows the backup ring hub to handle bridging ifthe primary ring hub fails See Fi-ber Distributed Data Interface, Token-Ring
Spanning Tree ProtocolSTR A protocol based on IEEE 802.1 d that provides resiliency through system and link redundancy that is especially suitable for virtual local area networks (VLANs)
sparkAbrief: bright, heat discharge, often from elec-trical or friction sources Sparks are generated by spark plugs to fire up an engine or by matches or light-ers to fire up combustible substances such as wood, cardboard, or lighter fluid Unintentional sparks may
be dangerous and may occur as a result of incorrect electrical connections (shorts, crossed wires), inad-equate insulation, or contact with unintended conduc-tive substances such as water
spark coilA device incorporating an inductive mag-netic core surrounded by helical windings ofconduc-tive materials used to generate a spark The spark coil was typically used in conjunction with a condenser and vibrator (or interrupter) for telecommunications applications Spark coils are still used to ignite inter-nal combustion engines, but for many electronics applications, transfonners began to replace spark coils in the early 1900s See armature, coil, dynamo,
:~::;a~:1~~:U~I~:~~~~Ss.~~j~s::~~~;:~.
affects the behavior of the spark If the gap is too large, the spark may not jump the gap
SPARS codeSociety ofProfessional Audio Record-ing Studios A three-letter code found in compact discs which indicates the analog or digital nature of
a portion ofthe recording history For example, ADD indicates that the original recording was analog, the mixing was digital, and the mastering stage was digi-tal See compact disc
SpartanA family of satellites designed for remote sensing In 1997 an unsuccessful Spartan mission occurred when astronauts failed totumon the satel-lite before releasing it into space Initial efforts to re-trieve the satellite were unsuccessful and it was manu-ally retrieved later
In 1998, all /2-ton Spartan satellite was successfully used for capturing images of the Sun's corona from space Before the Spartan was retrieved by the crew ofthe Space ShuttleDiscoveryin November 1998, it had already beamed hundreds of images to ground controllers One ofthe interesting aspects ofthe Spar-tan 207 multipurpose satellite was a 132-pound Inflatable Antenna Experiment (IAE) that was de-ployed aboard the Space ShuttleEndeavorSTS-77
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mission The IAE, resembling a flat, stiff parachute
when inflated, was developed by JPL and L'Garde,
Inc as part ofNASA's In-Space Technology
Experi-ment Program
Spartan Remote-Sensing Satellite
The Spartan 201 satellite, one in a series
ofremote-sensing meteorological satellites, as part of a
pre-launch Crew Equipment Integration Test (CElT) in
the Kennedy Space Center (NASA image.]
The Spartan 201 is held by the Space Shuttle
Columbia'sRemote Manipulator System (RMS),
De-cember,1997,over the Pacific Ocean The RMS,
de-signed in Canada, released the satellite intofree flight.
[NASA images.]
spat 1 A unit of solid angle comprising the space
about the vertex of an angle, equal to a sphere or 41t
steradians See steradian 2 A unit of distance
his-torically used by astronomers to represent 1012meters
(terameter), now rarely used
spatial light modulator SLM A
computer-con-trolled optical or opticaVelectrical component that
controls a beam of light through spatial dimensions
through an array of optical modulators and
associ-ated detectors
Spatial light modulation can drive 2D image displays
as well as projecting 3D spatial images The effect is
more easily understood by envisioning 3D
holo-graphic images and then imagining that the image is
created in realtime with light rather than being
holo-graphically recorded in a static medium Spatial
modulators can modulate laser or metal halide light
beams to create 3D images based upon the human
characteristic of persistence of vision and, in more
sophisticated systems, the basic motion concepts of frame animation
Commercial SLMs are fairly recent and there are still many variations and experimental systems evolving
In general, however, SLMs work by sending a near-infrared or visible light pulse through various grat-ings and lenses to modulate the light, with the output pulse projected into an imaging system Ferroelec-tric or nematic liquid crystals are often used as the retarding material with synthetic fused silica as the substrate The phase of the lightwave may be modu-lated, with the intensity of the light kept constant, or the amplitude may be modulated, changing the beam intensity and the phase profile (which may be cor-rected with dual modulators connected in series, for example) Polarizing elements may be optional There are various ways to image the light beam It can drive a 2D display like a computer/television dis-play or it can be projected to a rotating 20 screen Persistence of vision makes the successive images appear as 3D objects since one image is still briefly visible while the next is formed Imaging successive frames at high speed and presenting the frames at a speed that makes it appear to the viewer as ifthere is natural motion (about 24+ frames/sec) is also pos-sible, as frame rates in the order ofover 2000 frames/ sec (which could combine imaging frames and im-plied-motion frames as the image changes over a set
of frames) can be achieved with this technology Thus, many types of effects and images are possible and people can walk around the image and see it in three dimensions at the same time
Spatial modulation technology has great possibilities for medical imaging, chemical analysis, the model-ing of neural networks, optical computmodel-ing, beam steering, spectroscopy, flat panel displays, entertain-ment, education, and volumetric computer-aided de-sign
SPECSee Standard Performance Evaluation Corpo-ration
Specialized Common Carrier decisionA decision
by the Federal Communications Commission (FCC)
in 1971 to permit competition with AT&T in the provision of specialized voice and data services Specialized Mobile RadioSMR Awell-established analog, trunked two-way radio dispatch system fa-vored by commercially dispatched passenger and cargo fleets, public safety, and local services (e.g., taxi) SMR enables a group ofradio communications users to share a common channel through a central station Allocated frequencies are in the 800- and 900-MHz ranges
In North America, more than two million users sub-scribed to SMR services, a number that was gradu-ally increasing until bandwidth bottlenecks began to impact the service In response, the Federal Commu-nications Commission (FCC) made available addi-tional radio spectrum frequencies in the 900-MHz range, in the mid-1990s, and above 860-MHz·in 1997, thus opening the door for SMR services to compete with niche areas of the cellular market
With digital technology being adapted to SMR
Trang 8Motorola developed a system called the Motorola
Integrated Radio System (MIRS) and, more recently,
Enhanced Specialized Mobile Radio (ESMR) is
catching on, which makes ESMR competitive in
some areas with cellular services While SMR
spec-trum is more limited than cellular, it can be used over
a longer range
The upgrade to digital technology has greatly
accel-erated the increase in ESMR users in North America
and Europe due to the improved quality ofthe sound
and greater variety ofservices offered See Enhanced
Specialized Mobile Radio
Specification and Design LanguageSDL.An
ITD-I-defined language for the description and
specifi-cation of the behavior of telecommunispecifi-cations
sys-tems XDL is an extension of this language
spectral spreadingSee spread spectrum clocking
spectral transmissionIn a fiber optic cable, the
ra-tio between the incoming light and the outgoing light
at the other end of a fiber cable link As light
propa-gates through the fiber filament, it is reflected towards
the cladding and back into the conducting core and
may also be reflected in certain ways by the endfaces
(points of entry and exit), and dopants or gratings
within the fiber
Whenever there are obstacles or microbends, some
of the light is absorbed or lost through the cladding
(if there are excessive bends or fractures in the
clad-ding) It may even be stopped entirely or reflect
back-wards ifthe bend radius ofthe fiber exceeds the angle
at which the light reflects in the desired general
di-rection Thus, depending upon the length ofthe cable,
its components, the degree ofbend, the wavelengths
used, fiber impurities, fiber fluctuations in density,
dopants (deliberate impurities), and grating factors,
the outgoing light is typically less than the incoming
light Thus, incoming light versus outgoing light can
be plotted with respect to wavelength for a cable with
specified properties This can be modeled with
com-puter software or tested directly with measuring
probes in installed or sample cables
spectrographAninstrument for spreading light into
its spectral components By studying the brightness
of the spectrum at each wavelength, it is possible to
study the composition and characteristics of
sub-stances through their light-emitting properties and
patterns This is widely used by astronomers
study-ing our solar system
spectrometerAninstrument that detects and records
the spectral components of light The main element
is a dispersing component for separating light rays
into their component wavelengths Other typical
com-ponents include a collimator to align the incoming
light (which may beam directly to the collimator or
come through a fiber optic probe), a prismatic
grat-ing to direct and condition the light reflected by the
dispersing element, various concentrating lenses, and
an optical detector Once detected, the signal is sent
to a display or recording device (e.g., charge coupled
device)~ndmay further be analyzed by a signal
pro-cessor Echelle spectrographs enable a larger amount
persion over shorter wavelength ranges for each or-der See echelle grating, interferometer
spectrometer, massAninstrument for detecting and recording the differences in mass-charge ratios of ionized molecules or atoms that occur when a sub-stance is stimulated by an electromagnetic force This enables molecular properties to be separated/distin-guished, which is useful for assessing the structural and chemical properties of substances
spectrophotometer Aversatile optical sensing and measurement instrument used in a variety of appli-cations from chemical analysis to high energy phys-ics research The instrument may be used for evalu-ating the existing qualities ofa substance as light en-ergy passes through it, or may be used in conjunc-tion with externally applied energy (e.g., radiaconjunc-tion)
to apply controlled influences to the sample under study Thus, the spectrophotometer measures the characteristics of a substance through its absorption
of light or the amount of light passing through the substance as compared to reference information
A spectrophotometer includes a phototube or photo-multiplier tube to convert photon energy into electri-cal energy so that the characteristics may be measured with electronic circuits and viewed with electric-based display components
When the light emitted from a sample is dispersed with a monochromator, the resulting spectral lines can
be analyzed and the results compared or combined with information from the photomultiplier tube When a monochromatic light source (e.g., laser light) strikes a substance and emits electromagnetic energy
at a different frequency from the source energy, a phenomenon called Raman scattering occurs This effect may be amplified with a photomultiplier tube
so that the wavelength difference can be used to as-sess qualities of the sample
Fiber optics are increasingly being incorporated into spectrophotometric and radiometric devices Re-flected or weak emissions may be detected with pho-tomultiplier tubes and optical filters and the function ofamonochromator may be handled by optical fibers For general reference, the diameter of commercial side-on and smaller gauge head-on photomultiplier tubes ranges from about 10 to 38 mm, with effective areas of about 3 to 34 mm Depending upon the type oftube and its intended use, spectral response is typi-cally around 160 to 185 om or 300 om at the low end ranging up to about 650 om or 850 to 900 om at the high end Afew specialized near-infrared components have a spectral response between about 400 to 1200
nm Larger gauge head-on tubes range from about 51
to 127 mm, with effective areas of about 46 to 460
mm See diffraction, phototube
spectroscopyAtechnique used by scientists to study the composition and/or characteristics ofa substance based upon an analysis of its light-emitting proper-ties Spectroscopy is useful for chemical and crys-talline structure analysis
In electronics, spectroscopy enables semiconductor components to be tested and monitored The property
Trang 9Fiber Optics Illustrated Dictionary
ofphot0reflectance can help determine electron
mo-bility; by beaming laser light of a specific frequency
into the semiconductor and influencing the dielectric
properties, the optical response in terms of the
reflec-tance coefficient may be determined
In medicine, fiber optic probes may be used in
con-junction with spectroscopes to assess the
character-istics of healthy and diseased tissues to aid in
medi-cal diagnosis
In astronomy, spectroscopy has enabled more detailed
study of stars, beyond distance and brightness
spectrum In general, a continuous sequence or range
of some property or radiant energy Many
phenom-ena are described in terms of their characteristics or
position within the spectrum ofradiant energy,
includ-ing electromagnetic, radio, sound, visible light,
spe-cific colors, etc See band allocations, radio, sound,
visible spectrum
speech recognition The process of receiving,
inter-preting, and parsing spoken words On computers,
this is often accomplished with a microphone input
device, an analog-to-digital peripheral card, and a
software program that works independently or in
con-junction with other programs such as word
proces-sors It may also include noise-canceling features that
help to separate the voice of the speaker from
ambi-ent room noise such as the hum of computers or low
conversations in the distance
Speech recognition is distinct from voice recognition
in that voice recognition is the processing of the
par-ticular characteristics of a specific voice so that it can
be recognized, such as in a security identification
system Voice recognition does not involve making
sense of the content of the message, as does speech
recognition Speech recognition systems typically
require a minimum sampling rate of about 3000
samples per second in order to reliably recognize
words Many systems sample at 8000 samples/sec
Speech recognition can be used to dictate text, give
commands, and receive information over a
commu-nications system in digital or altered form Since
speech recognition is a complex process, most
cur-rent systems are specialized to recognize a specific
limited vocabulary as spoken by a number of
speak-ers in a specified language or a general (or specific)
vocabulary as spoken by one particular speaker More
sophisticated systems can recognize and react to
sen-tences and grammatical structures Many speech
rec-ognition programs have training algorithms (speaker
adaptive algorithms) included so the software can
gradually adapt to the idiosyncrasies of a particular
speaker's prounciation and mode of expression
In the mid-1990s, speech recognition computer
soft-ware began to be reliable and inexpensive enough to
interest small businesses and individual consumers,
and its use will probably spread through a variety of
applications, perhaps adding another means of input
to standard software such as word processors and
electronic mail programs See phonemes, voice
rec-ognition
speech synthesis The reproduction ofaudible human
communication, through the use of computers There
are many different ways to create synthesized voice Sound samples of human voices uttering certain words, sounds, and syllables can be recorded as sepa-rate entities, stored digitally, and then combined and played back to create words and phrases Other schemes, such as pure digital recreation ofvoice-like sounds are also available, but tend to have a distinctly mechanical quality to them
The most famous synthesized voice in the world is probably that of Stephen Hawking, world acclaimed physicist who talks indirectly through words and phrases programmed into a computer keyboard in-stalled on his wheelchair When Mr Hawking is fin-ished composing the message, it is played to the lis-tener through a speech synthesizer
Synthesized voices are used in multimedia applica-tions, on storybook CD-ROMs, in automated tele-phonemail order and banking systems, etc See pho-neme, speech recognition, voice recognition Speech Technology and Research Laboratory STAR Adivision of SRI International which engages
in world-class research in speech technology using engineers, linguists, and computer scientists Tech-nology developed in the STAR lab is fed to Nuance Communications for commercial development for telephony applications Of particular interest to re-searchers is natural speech recognition (without the usual training to recognize a particular individual's voice) that can provide automated phone services or voice-based securities trading Other areas ofresearch include text-to-speech translation, visual information systems development, and digital encoding of audio signals
speed dialing Ameans of keying in a shorter code to represent a longer one in order to speed up the dial-ing oflong phone numbers See abbreviated dialdial-ing SPF I shortest path first 2 See stateful packet fil-tering
SPIDGS Simple PRIGS See PHIGS
SPI I Security Parameters Index 2 Service Provider Interface
SPID See Service Profile Identifier
SPIE - The International Society for Optical En-gineering SPIE is a nonprofit, international profes-sional society in Bellingham, Washington, dedicated
to advancing research, engineering, and applications
in optics, photonics, imaging, and electronics SPIE produces educational publications, sponsors confer-ences and workshops, and now also provides Web re-sources in cooperation with the Institute of Physics (lOP) http://www.SPIE.org/ http://optics.org/ spilling In a fiber optic cable assembly, light that ex-ceeds the critical angle within which total internal reflectance (TIR) is possible and thus passes through the cladding and is lost Sometimes spilling is delib-erately induced (e.g., by bending the fiber) to produce light effects at periodic intervals along the length of
a fiber In general, however, it is undesirable, result-ing in losses that occur in the power of the light sig-nal as it reflects through the fiber link See cladding SPINS See Security Protocols for Sensor Networks SPIRITS A network architecture that supports
Trang 10Telephone Network (PSTN) interacting with the
In-ternet In simple terms, it is an architecture to
sup-port popular telephone services over Internet phone
connections, such as Internet-based Caller ill, Call
Forwarding, etc The SPIRITS architecture was
sub-mitted as an Informational RFC by Slutsman et al in
June 2001
Implementation of SPIRITS services requires an
In-ternet Protocol (IP) host installed with
SPIRITS-sup-porting software and identification (e.g., PINs) for
communicating with other SPIRITS servers Once a
host is SPIRITS-enabled, a user may connect to the
Internet and register a service session and optionally
specify the session duration
The SPIRITS architecture consists of a number of
service control, service switching, client, server, and
gateway functions as well as a number of interfaces
Interface Notes
Interface A A conduit for PINT
requests/re-sponses Supports service session
subscription, registration, and
activa-tion of a SPIRITS service
Interface B Notifies the subscriber of incoming
calls and call infonnation and
sub-mits a subscriber's choice ofcall
dis-position to the SPIRITS gateway
InterfaceC Client/gateway communication The
gateway may, in turn, communicate
with the SPIRITS server or may act
as a virtual server, terminating
re-quests without relaying them
Interface D SCF to client communication,
send-ing parameters associated with the
applicable IN triggers The SCF
translates user requests into
corre-sponding actions
Interface E PINT to SCF requests
See PINT, RFC 2995, RFC 3136
splashing When using competitive operator services
for long-distance calls, ifthe caller places a call from
San Francisco to Portland and the alternate service
is based in Los Angeles, the call is said to besplashed
if the billing is determined by the distance from Los
Angeles to Portland See Operator Service Provider
splicelJ. 1 To unite or combine separate lines,
usu-ally by weaving together the individual strands 2 In
electrical splices, the joining of conducting wires to
complete or extend a circuit Care is usually taken to
match the data lines so as not to cross one type ofdata
channel with another, and bare wires are generally
covered with an insulator such as a cap, electrical
tape, or plastic shrink sleeve to prevent short circuits
or shock 3.Infiber optics, ajoint where two ends of
a fiber optic waveguide are mechanically joined or
fused to facilitate the unimpeded travel oflight across
the splicejoint See fenule, fusion splice, splice guard
splice enclosure A component for protecting spliced
are needed For example, a splice enclosure for elec-trical wires may provide extra protection against moisture, rodent chews, or electrical interference, as well as protecting from shock hazards
For fiber optic cables, a splice enclosure can help align multiple cables and provide extra protection to spliced joints so that the waveguide is not interrupted
or compromised A splice enclosure is sometimes be called a splice organizer shelforfiber organizer shelf
and may be rack mountable Asplice guardmay be used in place of a splice enclosure in some circum-stances See splice guard, splice tray
splice guard An extra support component for a fused
or mechanical joint that fits over a sleeve It is usu-ally shorter than the sleeve, in case the sleeve pro-vides color or printed code information For fiber optic cables, a splice guard is usually secured with-out heat or glue and provides extra protection against external forces that might compromise a joint, such
as side or axial pull Asplice guard is usually applied and secured with a specialized crimp tool
A splice guard is sometimes used instead of asplice enclosurein situations where only a few fibers need protection or where space is limited Commercial products usually meet relevant Bellcore GR-326-CORE specifications (humidity, dust, and thermal aging, etc.) See splice enclosure
splice tray A tray for protecting spliced cables, es-pecially for temporary storage prior to installation
When the tray is used to organize multiple spliced cables for longer periods oftime, a hardening gel may
be used to support and secure the cables See splice enclosure
splitting Aubiquitous function in computing in which
~~~~::~~;;;~~~;:~~:~~~~~~l~i.Splitting is usually used in a context where the data
will be reassembled or rejoined when it reaches its intended destination or is needed by some applica-tion See joining for a detailed explanaapplica-tion
SPNE signal processing network equipment
spoofing 1 Deceiving, covering up the identity of, impersonating, or otherwise conveying an impression
of being something else 2 A means of gaining un-authorized access to a premises or system by deceit, impersonation, or other misrepresentation
spoofing, facsimile Facsimile devices, especially the desktop models, have not traditionally been speedy machines and many are designed to time out ifno data
is received for a while (in order not to tie up phone lines) With the advent of faxing over faster packet-based network connections, facsimile delays can lead
to time-out problems in the connection that would interfere with the function ofthe fax machine Spoof-ing extends the tolerance for these delays so that the fax can finish with the machine disconnecting By padding and other methods, delays and packet 'jit-ter" can be smoothed over to spoofa realtime voice-line connection A number of vendors have access server technologies that take into account the needs