Fiber Optics Illustrated Dictionary - Part 72 potx

Fiber
Optics
Illustrated
Dictionary
and others. The OSN architecture
is
intended to fa-
cilitate the interoperability and accessibility
of
data
via industry-standard networks.
Open
Trading
Protocol
OTP. See Internet Open
Trading Protocol.
Open
Video System OVS. A regulatory distinction
for video services carried by Local Exchange Carriers
(LECs), for example, who are not recognized as lo-
cal cable service providers perFederal Communica-
tions Commission (FCC) guidelines and regulations.
Thus, a local exchange carrier (LEC) could become
an OVS operator, but was also required
to
provide
nondiscriminatory access on a portion
of
its channel
capacity to unaffiliated program providers.
By

2000,
25
OVS
operators
had
been certified to
serve
50
areas.
The mid-1990s was an important time during which
technological advances made
it
possible for a wider
range
of
types
of
providers to offer a broader range
of
telephony and cable programming options to their
subscribers. In addition to this, the Telecommunica-
tions Act
of
1996 opened the doors for
tekos
to offer
ISO/Open
Systems
Interconnection
(OSI)

Reference
Model
From bottom to top, seven layers have been defined for OS
I,
ranging from physical and data layers
through presentationand applications layers, thus following a low-level to high-level an'angementcom-
mon in many computerarchitecture models. The selection
of
the layers was based on subdivisions cho-
sen to distinguish well-defined functions and various levels
of
abstraction. In general, layers are re-
lated to services provided by the layers below. In actual implementations, the situation is a little more
complex and many variations with sublayers or lesser-used layers exist.
Layer Function Number
Purpose, Implementation
Application
Layer 7
User interfaces, applications programs, emulation, and other higher-level
software implementations.
Presentation Layer 6
Character sets, text handling. Data conversion into standard formats for
transmission over a network or conversion from the transmitted format
to something that user applications can understand. Encryption and other
means
of
data security are also handled at this layer.
Session
Layer 5
Connection and session mechanisms for facilitating intercommunication

between networks. File transfers, program sharing, data sharing, and
basic traffic direction are managed at this layer
to
provide
an
orderly
exchange
of
information (e.g., management
of
simultaneous requests
from different users that might affect data integrity).
Transport
Layer 4
Process-to-process communications, addressing, and a number
of
end-
to-end services. The data are packaged into packets
in
preparation for
transmission. Identification
is
added so that disassembled packets that
may travel different routes can be reassembled at the destination. Local
network addresses may be defined at this layer. Error handling not
already managed by lower levels may be handled here with respect
to
reliability and data integrity.
Network
Layer 3

Host-to-host communications and basic transfer units (packets), network
addressing, forwarding, and routing. Addresses may be provided by the
Network Layer
to
the Transport Layer.
Data Link
Layer 2
Activation, handshaking, interfacing, and other basic communications
intended
to
initiate, regulate, and terminate a communications session.
Common functions
at
this level include the management
of
wired
connections (modems, Ethernet, etc.) orwireless transmissions, although
the actual physical medium used
is
handled by the Physical Layer
transparently
to
the Data Link Layer. Low-level error handling, data
synchronization, and flow control are managed at this layer.
Physical
Layer I
The transmission medium, electromagnetic properties, and other
physical aspects associated with getting the signal from one place to
another such
as

cables, devices, buses, signaing, etc. The physical layer
is independent
of
the actual medium used and thus the layer model
applies equally
to
electrical voltages
in
wired lines, radio waves
in
wireless transmissions, and laser light beams
in
fiber optic cables.
702
© 2003 by CRC Press LLC
video
through
phone
lines,
to
seek
cable
franchises,
or
to
develop
wireless
cable
systems.
Together,

these
conditions
resulted
in
blurred
distinctions
between
cable
and
telephone
companies
since
many
services
were
now
being
offered
over
the
same
media.
Thus,
regulatory
authorities
were
asked
to
clarify
some

of
the
issues
and
the
FCC
Cable
Services
Bureau
became
involved
in
this
process.
On
the
other
side
of
the
equation,
in
1996
the
cable
providers
expressed
concerns
about
telcos

not
being
regulated
in
the
same
way
as
cable
companies
were
by
the
Cable
Act.
Organizations
such
as
the
National
Cable
Telecommunications
Association
argued
that
the
FCC
exceeded
its
authority

by
preventing
cable
operators
from
switching
to
become
Open
Video
Sys-
tems
(OVS)
providers,
as
defined
by
the
FCC.
In
January
2001,
the
FCC
presented
its
seventh
An-
nual
Report

on
competition
in
the
video
markets.
The
document
confinned
that
cable
TV
was
still
the
domi-
nant
video
delivery
technology,
but
with
a
declining
market
share
ofa
couple
of
percentage

points
per
year.
Cable
service
rates
increased
slightly
more
than
the
rate
of
inflation
in
general
over
the
study
period.
In-
terestingly,
it
was
found
that
few
telephone
compa-
nies

had
sought
OVS
certification
since
1996.
See
Telecommunications
Act
of
1996,
Video
Dial
Tone.
operand A
quantity
or
information
which
is
being
manipulated.
For
example,
in
mathematics,
if
you
divide
200

by
10,
then
200
is
the
operand.
In
com-
puter
algorithms,
data,
or
the
address
of
the
data
to
be
operated
upon,
are
passed
to
an
instruction
in
or-
der

for
the
instruction
to
act
upon
the
data.
operating environment
This
has
two
meanings,
de-
pending
upon
the
context.
It
is
used
in
a
limiting
con-
text
to
describe
an
operating

system
which
isn't
fully
integrated
or
fully multitasking.
It
may
be
task-
switching,
or
it
may
have
a
graphical
user
interface
on
top
of a text-based operating
system
not
fully
implemented
as
multitasking.
Many

vendors
have
claimed
multitasking
operating
systems
which
were
not
really
so.
In
its
second,
broader
context,
it
refers
to
the
environment
surrounding
an
operating
system,
that
is,
the
system,
the

software
that
runs
it,
the
periph-
erals
and
applications
that
support
it,
etc.
An
operat-
ing
environment,
in
this
broad
sense,
may
encompass
more
than
one
operating
system.
operating system
OS.

The
most
important
software
on
a
computer
is
that
which
lies
between
the
user
ap-
plications
and
the
hardware.
It's
not
possible
to
con-
trol
the
CPU,
manage
memory,
access

a
disk
drive,
send
images
to
a
monitor,
or
transmit
data
through
a
network
connection
or
modem
without
an
operating
system.
The
operating
system
handles
interrupts,
tim-
ing,
the
movement

of
data
from
one
register
to
an-
other,
and
all
the
nitty-gritty
operations
that
are
typi-
cally
not
seen
or
understood
on
a
technical
level
by
most
users.
Microcomputer
operating

systems
began
to
be
devel-
oped
in
the
1970s.
The
early
ones
were
text-based.
One
of
the
first
widely
used,
popular
operating
sys-
tems
was
CP
1M,
designed
by
Gary

Kildall.
CP
1M
was
the
forerunner
of
QDOS,
and
hence,
MS-DOS,
and
the
syntax
and
commands
are
very
similar.
LDOS,
TRS-DOS,
UltraDOS,
and
other
TRS-80
operating
systems
shared
many
common

properties
with
CP/
M.
Kildall
also
later
designed
a
multitasking
operat-
ing
system
and
a
graphical
user
environment
(GEM).
In
the
early
1980s,
Apple
created
proprietary
operat-
ing
systems
for

their
Apple
and
Macintosh
lines
of
computers, featuring the first widely distributed
graphical
operating
system
descended
from
pioneer-
ing
work
at
Xerox
PARCo
This
concept
was
so
suc-
cessful
that
it
has
since
been
adapted

by
virtually
all
subsequent vendors, including Atan,
Commodore
Amiga,
Apollo,
Sun
Microsystems,
Microsoft,
SGI,
The
X
Windows
System,
and
NeXT.
It's
difficult
to
find
a
computer
now
that
doesn't
have
a
graphical
user

interface
on
top
of,
or
in
conjunction
with
a
text
operating
system,
or
which
is
fundamentally
a
graphi-
cal
operating
system.
The
various
versions
of
Win-
dows
are
popular
on

consumer-level,
Intel-based
sys-
tems.
A
number
of
multitasking
systems
were
developed
in
the
late
1970s
and
early
1980s,
but
the
first
widely
distributed commercially successful preemptive
multitasking
operating
system
on
a
microcomputer
was

AmigaOS,
introduced
in
1985.
Most
of
the
work-
station
level
computers
had
multitasking
operating
systems
by
the
early
or
mid-1980s,
and
the
other
ven-
dors
began
to
follow
this
lead

in
the
late
1980s,
most
notably
OS/2
(Operating
System
2),
originally
devel-
oped
jointly
by
IBM
and
Microsoft.
Many
other
op-
erating
systems
released
around
this
time
were
task-
switching

rather
than
fully
multitasking.
Microsoft
Windows
has
since
become
widespread
on
personal
computers,
with
Windows
NT,
originating
out
of
the
OS/2
collaboration,
used
on
many
server
systems.
Unix
is
one

of
the
most
robust, earliest,
and
most
important
operating
systems.
A
high
proportion
of
institutional
computing
operations,
much
scientific
research,
and
many
Internet
hosts
run
on
Unix
sys-
tems.
Unix
is

freely
distributable,
powerful,
flexible,
dependable,
well-supported,
and
runs
on
most
com-
puters.
Linux
is
a
popular
implementation
of
Unix
(as
is
BSD),
available
from
a
number
of
commercial
and
free

distribution
sources.
Along
with
Apache,
a
freely
distributable
server
software,
Unix!
Apache
systems
are
used
by
thousands
ofInternet
Services
Providers
to
provide
gateways
to
the
Internet
through
the
Web.
An

operating
system
runs
a
computer,
and
comput-
ers
are
increasingly
delegated
control
tasks
beyond
those
humans
can
handle
alone
or
in
cooperation
with
one
another.
Navigational
aids
on
aircraft
are

a
good
example.
Fighter jets
traveling
at
hundreds
of
miles
per
hour
move
too
quickly
for
the human
nervous
system
to
react
in
time
to
control
every
aspect
of
the
plane's
behavior,

so
computerized
systems
handle
many
functions
on
the
pilot's
behalf.
Extrapolate
that
type
of
control
to
appliances,
houses,
security
sys-
tems,
currency
exchange,
intelligent
vehicle
systems,
and
every
aspect
of

human
society
that
will
someday
be
controlled
by
computers
through
a
24-hour
Inter-
net
connection
to
all
the
other
computers
in
the
world.
Given
this
broader
outlook
on
our
probable

future,
703
© 2003 by CRC Press LLC
Fiber
Optics
Illustrated
Dictionary
the
importance
of
carefully
choosing
a
reliable
oper-
ating
system
cannot
be
overemphasized.
Buying
the
cheapest system
or
the
most popular system,
or
passively
allowing
the

choices
to
be
made
by
profit-
based
corporations
is,
in
the
long
run,
a
more
far-
reaching
decision
than
selecting
a
President
or
other
political
leader.
Why?
Because
a
President

who
does
abadjob
can
be
voted
out.
An
operating
system
that
does
a
bad
job
cannot
be
disabled
if
it
has
been
del-
egated important tasks such
as
running medical
equipment,
automated
transportations
systems,

or
en-
vironmental
controls.
Once
a
fighter
plane
has
been
designed
with
a
dependency
upon
computer
control,
you
can'tjust tumoff
the
software
in
mid-flight.
Simi-
larly,
if5
or
10
years
from

now
a family's
financial
transactions,
medical
prescriptions,
education,
and
travel
arrangements
are
handled
by
a
computer
op-
erating
system
through
the
Internet,
it
may
no
longer
be
possible
to
tum off
the

computer
at
will.
That
bears
thought
and
forethought and suggests that open
source
operating
systems
coexisting
with
commer-
cial
products
can
help
maintain
balance.
See
BSD,
Linux,
Mac
OS
X,
Microsoft
Windows,
NeXTStep,
OS/2,

Solaris,
SunOS,
Unix,
UNIX.
operational load
1.
The
full
power
requirement
ofa
facility,
which
may
be
expressed
in
terms
of
averages
or
maximums.
2.
The
administrative
and
personnel
requirements of
an
organization

when
in
full
op-
eration.
operatorAn
individual
with
system
access
privileges
hierarchically
higher
or
more
powerful
than
general
users.
A
telephone
operator
can
manage
calls
and
ac-
cess
services
and

control
mechanisms
that
are
not
ac-
cessible
by
regular
phone
subscribers.
A
chat
room
operator
can
include
or
exclude
specific
users
or
set
other
restrictions
or
standards
of
use.
A

system
op-
erator
has
access
to
monitors,
security
devices,
soft-
ware programs,
and
other computer operations
mechanisms
not
available
to
regular
users.
operator, telephone An
individual
who
handles
the
routing
of
calls
from
callers
to

callees
and
provides
a
variety
of
types
of
assistance
such
as
directory
assis-
tance,
long-distance
procedures,
billing
options,
etc.
Many
of
these
processes
have
now
been
automated,
but
in
the

early
days,
the
telephone
operator
had
com-
plete
responsibility
for
connecting,
monitoring,
and
disconnecting
calls
through
manual
patchcords.
He
or
she
was
also
implicitly
expected
to
provide
emo-
tional
support,

emergency
information,
local
news
and
gossip,
and
business
tips.
In
fact,
the
position
of
the
phone
operator
included
so
much
power
(over
connections
to
alternate
business
options)
and
infor-
mation

that
a direct
dial
system
was
invented
ex-
pressly
to
bypass
the
operator!
Later switchboard
systems
required
a
higher
level
of
concentration
and
expertise
as
many
more
lines
would
be
serviced
and

the
switchboards
included
lights
to
indicate
connec-
tions
and
incoming
calls,
switches,
cards
for
record-
ing
toll
calls,
and
more.
While
the
names
of
the
very
first
telephone
opera-
tors

have
probably been lost
to
history, George
Willard
Coy
is
generally
credited
as
the
first
telephone
704
operator
and
Emma
Nutt
as
the
first
female
telephone
operator.
Nutt
was
instated
following
the
relative

fail-
ure
of
male
telegraph
operators
to
adapt
to
the
task
of
courteously
handling
customer
voice
calls.
Nutt
apparently moved
from
a telegraph office
to
the
phone
exchange
in
Boston,
hired
in
September

1878
by
A.
Graham
Bell.
She
was
paid
asalary of
$1
0per
month
for
a
54-hour
work
week
(minus
lunch).
This
was
a
year
of
great
expansion,
during
which
the
New

England
Telephone
Company
was
formed
to
sellli-
censes
to
telephone
company
operators
in
the
New
England
area.
Ms.
Nutt
apparently
could
remember
every
number
in
the
directory.
Preferred
Voice
has

created a synthesized voice
speech
attendant
for
delivery
of
information
services
named
EMMA
in
honor
of
Ms.
Nutt.
Records
are
spotty,
but
a
small
selection of
notable
first
telephone operators
for
their
regions
prior
to

about
1913
is
shown
in
the
Selection
of
Pioneering
"First"
Telephone
Operators
chart.
See
Call
Girls,
Strowger
switch,
switchboard,
telephone
history.
Historic
Telephone
Switchboard & Operator
A telephone operator staffing thefirst switchboard
in Idaho Springs, Colorado,
wearing
a headset.
Manual switchboards still exist on islands, in remote
areas, and in many undeveloped nationas. In North

America. the main telephone system operates with
high-speeddigital switching circuits. {Denver Public
Library Collection; copyright expired
bydate.}
operator-assisted call
Any
phone
call
in
which
the
caller
contacts
the
operator
to
handle
some
part
of
the
transaction
or
connection,
rather
than
direct
dialing.
There
are

usually
surcharges
associated
with
opera-
tor-assisted
calls.
operatorconsole, computer
In
computer
networks,
a
console
is
a
computer
terminal
which
allows
access
to
management
and
administrative
functions
that
monitor
and
control
the

network.
Common
operations
carried
out
on
the
console
include
user
password
as-
signments,
new
user
account
allocations,
virtual
con-
figuration
of
devices
and
the
network
topology,
selVer
configuration,
etc.
Often

the
operator
console
is
in
a
© 2003 by CRC Press LLC
separate
room
for
security reasons
and,
at
the
very
least,
is
password
protected
to
prevent unauthorized
users,
or
well-meaning
but
uninformed
users
from
accessing
lower

level
system
functions
that
could
in-
terrupt
the
functioning
of
the
network.
operator
console, phone
In
telephony,
the
main
console of a multiline
phone
system.
The
operator
console
often
is
programmable
and
may
include a

hands-
free
earphone
set.
Operator Service Provider
OSP.
Previously called
Alternate
Operator
Services.
Acompetitive provider
of operator-assisted long-distance calls, especially
third-party
billing,
collect,
etc.,
which
usually
leases
the
services
of existing
phone
networks.
Large
ho-
tels
sometimes
provide
AOS

services
to
hotel
guests
for
a
premium.
See
splashing.
OPRE
Operations
Order
Review.
Ops
Abbreviation
for
operations, operators,
opera-
tor
services,
and
system
operators.
This
is
a particu-
larly
common
abbreviation
on

Internet chat
systems,
where the operators (ops) or channel operators
.
(chops,
chanops)
enforce
accepted behavior
on
chat
channels.
See
operator.
OPS
off-premises
station.
optical amplifier A
type
of
device
used
as
a
cable
repeater
on
fiber
optic
transmission
lines,

which
func-
tions
without
converting
the
optical
signal.
Early
ver-
sions
were
based
on
semiconductor
lasers.
Most
are
now
erbium-doped
fiber
amplifiers
(EDFAs),
that
is,
directly
doped
silica
fibers,
with

the
principal
param-
eters
defined
by
atomic
composition.
optical attenuator A coupling
component,
usually
ofa standardized
type
(e.g.,
FC-
connector)
that
at-
tenuates
the
energy
of
the
passing
optical
signal
by
a
certain
amount.

OAs
are
compact,
low-power
com-
ponents
available
in
fixed,
variable,
and
computer-
controlled
models.
Multiple
OAs
may
be
combined
into
multichannel
arrays
to
meet
the
needs
of
com-
plex
networks.

Thus,
a
fixed
or
variable
amount
of
loss
is
intention-
ally
induced
in
the
received
optical
signal
to
adjust
the
signal
to
the desired level. This
is
useful
for
switching,
gain
tilt,
modulation,

and
power
control.
optical
burst
switching
OBS.
A mechanism pro-
posed
in
1999
by
Chunming
Qiao
and
Myungsik
Yoo
for
managing
bursty network
traffic
on
the
Internet.
The
research,
supported
in
part
by

a
National
Science
Foundation
(NSF)
grant,
is
intended
to
streamline
network
switching
in
anticipation ofhigh-speed
end-
to-end optical networks of
the
future.
The
system
combines aspects of optical circuit switching
and
packet/cell
switching.
While
transition technologies
are
expected
to
combine

optical
networks
with
elec-
trical
switching,
at
some
point
there
may
be
second
generation all-optical networks
that
can
be
estab-
lished
as
a
layer
beneath
Internet Protocol
(IP).
OBS
anticipates
this
evolution
in

technology.
Many
broadband
transmissions
are
inherently
bursty
(e.g.,
multimedia),
as
apparently
are
large
numbers
ofself-similar
traffic
streams.
Thus,
a
system
more
efficient
for
this
situation
than
optical circuit
switch-
ing
was

sought.
The
researchers
have
observed that
apacket
can
be
sent
along
with
the
header,
to
reduce
setup
time
and
overhead,
but that
this
approach
has
limitations
as
well.
In
OBS,
a control packet
is

trans-
mitted
to
set
up
a
connection,
followed
by
a
data
burst
before
the
connection acknowledgment
is
received,
essentially
a
one-way
reservation
system.
In
addition,
data
burst buffering
at
intermediate
nodes
is

elimi-
nated,
reducing
the
wait
for
processing of control
packets.
Signaling
is
out-of-band.
See
Just-Enough-
Time,
Optical-Label
Switching.
optical bypass
In
a Fiber Distributed
Data
Interface
(FDDI)
token-passing network, port
adaptors
can
be
equipped
with
optical bypass switches
to

avoid
seg-
mentation
which
might
occur
if
there
is
a
failure
in
the
system
and
a station
is
temporarily
eliminated.
Normally,
optical signals pass through
the
bypass
switch
uninterrupted,
but
ifa
station
fails
and

is
elimi-
nated
from
the
ring,
the
optical
bypass
can
reroute
the
signal
back
onto
aring before
the
signal
reaches
the
failed
station,
thus
providing
fault
tolerance
for
the
system.
The

optical
bypass
switch
is
attached
to
the
FDDI
port
adaptors
between
the
attachment station
and
token-
passing
ring.
See
A
port,
dual
attachment
station.
optical
carrier
OC.
1.
In
general, a signal carried
over

optical media
that
is
intended
to
provide
con-
trol
signals, information, or other signal
data.
Com-
monly
lasers
are
used
to
provide carrier
signals
that
may
be
given
information content
through
electro-
optical modulators (e.g., a quadrature amplitude
modulator).
See
carrier, modulation.
2.

A
series
of
optical network transport levels defined
in
conjunc-
tion
with
SONET.
See
SONET
Optical
Carrier
Trans-
port
Levels
chart.
optical channel
data
unitODV. Aunit of
data
in
an
optical transmission network. In
an
ITVT
G.709
optical transport
network,
for

example,
ODV
over-
head
resides
in
columns
1
through
14
of
three
rows
of
the
frame.
It
provides
connection
monitoring,
path
supervision,
and
client
signal
adaptation.
optical characterrecognition
OCR.
A
software

pro-
cess,
or
combination ofhardware scanning
devices
and
software,
which
evaluates
marks
on
a
page
and
determines
whether
they
have
the
predefined
char-
acteristics oftext,
symbols,
and
images,
depending
upon
the
software.
Most

OCR
programs
use
acombination ofintelligent
algorithms
and
character tables
to
process
marks.
These
marks
are
typically
text
and
character
symbols,
although
some
programs
will
also
recognize
math-
ematical
and
logical
symbols
if

these
are
added
to
the
program dictionary
or
the user dictionary.
Some
programs
can
automatically discern
columns
oftext
and
images,
and
divide
the
page
up
appropriately,
handling
the
regions
separately.
Once
the
document
has

been
"recognized,'
the
characters
and
symbols
are
converted
to
a
common
format,
such
as
ASCn
or
one
of the many flavors
of
extended ASCII, and
stored
as
a
file
that
can
be
further edited
with
a text

editor,
word
processor,
or
desktop publishing pro-
gram.
In
its
strictest
sense,
OCR
just recognizes
the
characters;
software
which
handles
images
as
well
is
705
rrg

.
.
:.".:.:.~
.•
'.:.~;

,
:)1
;:~:
© 2003 by CRC Press LLC
Fiber
Optics
Illustrated
Dictionary
called
optical
document
recognition.
However,
most
OCR
applications
these
days
have
some
document
processing
and
image
recognition
functions,
so
the
phrase
is

used
broadly
here.
Most
of
the
early
work
on
pattern matching
algo-
rithms
used
in
character
recognition
was
done
in
the
late
1950s
and
the
early
1960s.
By
1963,
ffiM
had

a
system
that
could
recognize
Roman
and
Cyrillic
char-
acters
at
the
rate
of
about
50
words
per
minute,
the
speed ofa
moderately
competent
typist,
and
faster
than
most
typists
can

type
information with
many
numerals.
See
optical
document
recognition,
scanner.
Sample
Optical Choppers
Optical choppers range from simple, regular pat-
terns, to combinations
of
two or more blades (top
right). High-precision choppers
may
have hundreds
or thousands
of
chopping segments (upper left).
opticalchopperA
component
for
interrupting
a
beam
of
light,
often

at
very
fast
speeds.
Chopping
can
be
accomplished
with
shutters,
tuning
forks,
rotary
discs/
blades,
or
etched
crystalline
plates.
Applications
for
choppers
range
from
special lighting
and
art
effects
to
highly-precise scientific applications

and
experi-
ments.
Scientific
choppers
typically
have
a
data
in-
terface
to
a
display
component
or
computer.
Tuning
fork
choppers
are
intended
to
be
used
at
a
spe-
cific
frequency

and
have
small
apertures
at
high
fre-
quencies,
compared
to
rotary
choppers.
Despite
the
frequency
and
aperture
limitations,
tuning
forks
are
robust
and
have
many
applications
and
can
be
used

in
a
wide
range
of
operating
conditions.
Disc
or
rotary
choppers
resemble
pinwheels
in
the
sense
that
they
have
divided
segments
rotating
around
a
central
axis
like
a
rotary
fan.

Most
are
mounted
with
ball
bearings,
but
some
are
available
with
magnetic
suspension.
Choppers
can
be
fabricated
as
high
precision instru-
ments
with highly
accurate
divisions
in
the
chopping
segments
and
carefully

controlled
rotational
axes
and
speeds.
The
number
of
"slots"
on
a chopper
may
range
from
2
to
2000+
and
some
choppers
provide
variable
speeds
for
the
rotations
of
the
wheels.
It

is
also
possible
to
design
chopper
blades
to
chop
more.
than
one
frequency
at
a
time
by
having
two
sets
of
slots
in
the
same
wheel.
It
may
be
possible

to
option-
ally
phase-lock
the
chopper
to
an
internal
clock
or
to
auser-supplied
external
clock.
A
monochomator
for
dispersing light
waves
may
be
coupled directly
to
choppers
with
an
appropriate
coupling
head.

Choppers
may
consist of
coated
gels
or
glass
or
one
or more blades, depending upon the application.
When
there
are
two
blades,
one
may
be
fixed
while
the
other rotates.
The
alignment
of
the
blades
deter-
mines
whether

a
beam
is
passed
or
blocked.
The
beam
need
not
be
completely
blocked.
With
a
general
pur-
pose
scientific
chopper
with
just
two
blades,
it
is
pos-
sible
to
have chopping frequencies ranging

from
about
4
to
5000
Hz.
With
a
gel
chopper,
different
types
or
colors
of
coatings
may
selectively
pass
or
chop
certain
frequencies.
Piezoelectric
choppers
are
small
enough
to
fit

on
a
chip
for
use
in
integrated
circuits.
In
conjunction
with
a collimated laser
source,
they
may
be
used
as
com-
pact
optical
sensors.
SONET Optical
Carrier
(OC-) Transport Levels
Carrier
Rate
(Mbps)
08-3
08-1 08-0

OC-l
51.84
1 28
672
OC-3
155.52 3
84 2016
OC-9
466.56
9 252 6048
OC-12
622.08
12
336 8064
OC-18
933.12
18
504
12096
OC-24
1244.16
24
672
16128
OC-36
1866.24 36
1008
24192
OC-48
2488.32

48
1344
32256
OC-96
4976.64
96 2688 64512
OC-192 9953.28
192 5376 129024
706
© 2003 by CRC Press LLC
Choppers
are
usually described
in
terms
of
their
op-
erational frequencies. Disc choppers with inter-
changeable
blades
and
rotational
speeds
can
support
many
applications.
See
knife-edge

focusing,
Ronchi
grating.
Piezoelectric Semiconductor Chopper
In thequest.{oreversmallercomponents, piezoelec-
tric choppers have been developed, such as the one
illustrated here, designed
by
H.
Tohiyoshi.
Incident light (A) encounters a chopper plate
(B)
madefrom anisotropically etched Z-cut quartz, with
chopper slits perpendicular (normal) to the surface
of
the component. Light
passing
through the slits ac-
tivate photosensitive detectors
(C).
optical combiner
In
general fiber
optics
terms,
any
system
for
aggregating optical cables
in

adjacent
waveguides
or
for
combining
two
or
more
optical
sig-
nals
for
transmission through a single waveguide.
Optical
cables
are
typically aggregrated
to
facilitate
installation
and
maintenance. Optical signals are
combined
for
a variety
of
reasons. Transmission
through
a
single

rather than multiplewaveguides
can
be
cost-effective. Broadcast services available
to
all
service subscribers
may
be
combined with targeted
services requested
by
individual
users
at
appropriate
points
in
the
network.
Combined signals
may
be
use-
ful
for
research purposes
for
studying optical effi-
ciency,

interactions,
and
various sources
of
loss.
As
a
fiber
optic
network component,
the
term
more
specifically
refers
to
devices that
combine
or
com-
bine
and
regenerate combined optical signals with a
minimum
of
loss
and
interference
in
the

coupling/
combining process. Combiners
may
be
passive or
actively integrated with switching mechanisms.
An
arrayed
waveguide
grating
(AWG)
can
combine
(
or
separate) multiple wavelengths.
An
active self-
switching combiner,
as
an
example, takes signals
from
two
or
more
ports
and
physically couples
them

so
they
are
proximate, then phase-shifts
the
signals
through
optical
amplifiers
and
brings
them
together
in
a combined
signal.
See
multiplexing.
optical combiner, projection A projection surface
or
component that
combines
a projected
image
with
other functions, images,
or
physical environments.
For example,
in

military jets,
the
windshield may
serve
as
a transparent viewing window
as
well
as
a
projection surface
for
certain cockpit status
displays.
The
same
concept
is
applied
to
head-worn
optical
dis-
play systems,
some
ofwhich
have
small
transparent
screens

that enable
the
viewer
to
see
ahead
while
at
the
same
time
viewing a small projected
image
(in
some
systems,
the
image
may
pass through
the
com-
biner
to
be
projected
on
the
viewer's
retina).

Combiner projection technologies are useful any-
where
information
needs
to
be
superimposed
on
a
transparent surface
so
that
the
viewer
can
see
both
the
projected
image
and
the environment behind
the
projected image. Thus, they could
be
used with a
video
camera
to
project

an
image
of
the
area
behind
a viewer
so
the
viewer could
see
front
and
back
at
the
same
time
or they could project status
informa-
tion
over a video
image
or real-life environment.
In
terms
of
innovative networking possibilities, they
could
project a

Web
page coupled with a
GPS
reader
that
shows
a
map
and
local landmarks
at
the
specific
site
at
which aperson
is
standing with a body-worn
computer linked
to
the
Internet.
Optical Communications Demonstrator
OCD.
A
NASAlJPL
laser-based extraterrestrial communica-
tion
system capable oftransmitting
at

speeds
up
to
~~~p~~l:tJe~~eurct~~?~y~~~u~;f:::o~~~:rr~~
III
flector,
which
controls
the
orientation
of
a
Q-switched
diode-pumped laser communicating
in
the
downlink
direction.
The
ground station detects
the
light signal
using
silicon avalanche photodiodes.
This
is
seen
as
apossible alternative
to

radio
wave
communications
that
are
more
apt
to
be
distorted
due
to
Doppler shift
effects.
See
Laser Communications Demonstration
System.
optical computer A type
of
processing hardware
based
on
photons rather
than
electrons.
This
is
a
more
experimental

technology than
is
usedwith traditional
computers,
but
it
has
possible
advantages,
particularly
in
speed
and
resistance
to
interference over current
technologies,
and
may
become
more
prevalent
in
the
future.
optical connectorsConnectors specially
designed
to
couple
fiber optic cable junctions

so
they interfere
as
little
as
possible with
the
path
of
the
optical
beams
passing through
the
connectors.
The
connectors
are
usually used
at
points
where
the
fibers
connect
with
routing
or
switching circuitry, or with
the

optical
in-
terface
to
the
system itself. Optical connections
have
to
be
well-engineered,
as
they must handle
very
pre-
cise
beams
and
paths,
and
often must maintain
the
proximity
and
orientation
of
a bundle
of
optical
fi-
bers. Connectors for blown fiber installations are

easier
to
install
and
maintain than a number ofother
types
of
fiber attachments.
See
blown
fiber.
optical core
The
light-carrying central region
of
a
fiber
optic filament, commonly
made
from
silica
and
germania.
optical coupler
See
coupler.
707
© 2003 by CRC Press LLC
Fiber
Optics

Illustrated
Dictionary
optical coupler module
OCM.
A
component
that
provides
functions
in
conjunction
with
coupled
fiber
optic
cables
such
as
branching/joining,
multiplexing/
demultiplexing,
and
filtering.
OCMs
are
often
modu-
lar
and
may

be
customized
for
operating
wavelength
and
the
size
and
number
of
fiber
filament.
optical
cross
connect
OXC.
Optical
connection
com-
ponents
of
telecommunications
carrier
networks
that
help
operators
manage
the

larger
amounts
of
band-
width
enabled
by
newer
capacity-increasing
tech-
nologies.
OXCs
began
to
become
generally
available
in
the
late
1990s.
OXCs
can
facilitate
network
administration
by
en-
abling
a

network
to
be
more
readily
reconfigured
or
restored
using
optical
switches.
OXCs
can
handle
data
streams
in
the
terabit
ranges
and
work
with
a
range
of
wavelengths
and
bit
rates,

making
it
easier
to
quickly
effect
rerouting.
Currently
OXC
compo-
nents
are
part
of
the
optical
portion
of
mixed
wire
and
optical fiber networks, but
as
the
optical market
grows,
demand
for
OXCs
will

likely
increase.
See
lambda
switching.
optical detectorA
substance
or
circuit
which
detects
and
converts
electromagnetic
waves
in
the
form
of
optical
waves.
Solar
panels
contain
substances
that
allow
the
conversion
of

light
into
electricity,
which
are
widely
used
in
the
satellite
industry
to
provide
power
for
telemetry
adjustment
of
orbits.
See
solar
panel.
optical
disc
Any
ofa
number
of
technologies
used

to
store
digital
data
which
is
subsequently
accessed
by
light,
usually
a laser
beam
pickup.
The
informa-
tion
on
an
optical
disc
is
commonly
stored
in
a
series
of
pits,
that

is,
indentations
in
a
metal
disc
coated
with
a
plastic
substrate.
The
placement,
size,
and
proxim-
ity
of
these
pits
is
defined
in
part
for
the
specifica-
tion
for
the

type
of
optical
technology.
Newer
tech-
nologies have been developed
to
increase the
information
capacity
of a
disc,
as
in
digital
video-
discs
(DVDs)
that
are
slightly
thicker,
to
bring
the
disc
closer
to
the

laser
pickup,
with
slightly
smaller,
tighter
pits.
Compact
discs,
videodiscs,
PhotoCDs,
and
DVDs
are
popular
forms
of
audio
and
visual
stor-
age
media.
Optical
discs
are
also
used
for
computer

data
storage,
particularly
for
backups.
optical
document
recognition
ODR.
A
software
pro-
cess
or
combination
of
hardware
scanning
devices
and
software,
which
evaluates
the
various
elements
on
a
page
to

determine
whether
they
are
distinguish-
able
as
text,
images,
symbols,
or
lines,
and
identifies
them
accordingly.
The
ODR
in
its
simplest
sense
does
not
interpret
the
text
into
characters;
it

merely
iden-
tifies
page
layout
elements:
images,
columns,
page
numbers,
text,
etc.
However,
in
commercial
products,
it
is
commonly
combined
with
optical
character
rec-
ognition
(OCR)
capabilities
in
order
to

optically
iden-
tify
and
interpret
areas
that
are
text
into
characters
that
can
be
edited
with
a
word
processor,
text
editor,
or
desktop
publishing
program.
ODR
is
a
somewhat
more

complex
process
than
OCR;
together
they
com-
prise
powerful
tools
which
are
a
part
of
image
docu-
ment
management
and
processing.
708
ODR
is
particularly
valuable
for
converting
archived
image

information
(e.g.,
microfiche)
into
documents
that
can
be
desktop
published,
or
archived
in
data-
bases
for
faster
and
more
efficient search
and
re-
trieval.
See
image
document
management,
optical
character
recognition,

scanner.
optical
eye
pattern measurement procedure
An
optical
fiber
test
procedure
standardized
within
TW
EIA-526,
developed
by
the
Optical
Fiber
Communi-
cations
System
subcommittee.
It
describes
param-
eters
for
measuring
the
repetitive

temporal
charac-
teristics
of a
two-level
intensity-modulated optical
waveform
at
an
optical
interface.
Rise
time,
fall
time,
overshoot,
and
extinction
ratio
may
be
determined
from
the
measured
eye
pattern.
The
waveform
itself

may
be
tested
against
a
reference
waveform
mask
to
determine
standards
compliance.
optical fiber A
flexible,
light-conducting,
filamen-
tous
plastic
or
glass
medium
used
for
optical
signal
transmissions.
Optical
fiber
is
typically

from
2
to
125
J.lm
thick,
and
is
capable
of
carrying
a
variety
of
high-
speed,
wide
bandwidth
transmissions
with
relatively
low
loss,
when
correctly
installed.
Unlike
wire,
fiber
is

not
subject
to
electromagnetic
interference
or
most
of
the
types
of
radiant
eavesdropping
techniques
that
can
be
used
on
wire.
This
has
made
it
very
popular
for
backbone,
hazardous
area,

and
multimedia
instal-
lations.
It
also
does
not
present
the
same
potential
fire
hazard
as
wire
electrical
cables.
Two
common
types
of
optical
fiber
include
step-in-
dex
fibers
and
graded-index

fibers.
Step-index
fibers
have
two
layers:
a
lower
refractive
outer
cladding
layer
and
an
inner
core
with
a
high
refractive
index.
Graded-index
fibers
also
are
less
refractive
toward
the
outer

edge,
but
rather
than
being
two
layers
sand-
wiched
together,
as
in
the
step-index
fibers,
the
re-
fractivity
in
the
material
overall
decreases
gradually
in
relation
to
its
distance
from

the
innermost
point
of
the
cylinder.
Fiber
can
be
bundled
without
the
electrical interfer-
ence
common
to
bundled
wires;
a
group
of
fibers
works
together
to
provide
greater
capacity.
Single-
mode

fiber
transmissions,
in
which
the
signal
can
only
follow
one
path through
the
filament,
can
travel
greater
distances
without
repeaters.
See
multimode
optical
fiber,
single
mode
optical
fiber.
optical fiber cable
See
fiber

optic
cable.
optical fiber ribbon A bundled
fiber
assembly
in
which
individual
fibers
are
laid
side-by-side
to
form
a
flat
ribbon
or
strip.
This
is
convenient
if
they
are
to
be
installed
in
narrow

areas
such
as
inside
walls
or
under
carpeting.
This
way
of
arranging
fibers
is
less
common
than
bundling
them
into
a
cylindrical
shape.
optical handwriting
recognition
OHR
A
specialized
form
of character

recognition
designed
to
separate
joined
shapes
and
recognize
variations
ofparticular
letters,
in
addition
to
other
generalized
optical
char-
acter
recognition
(OCR)
functions.
Most
OHR
sys-
tems
have
to
be
trained

to
recognize
a
particular
style
of
handwriting,
since
there
is
so
much
variation
in
the
letter
forms
in
the
way
different
people
write.
optical insertion
loss
OIL.
The
coupling-associated
© 2003 by CRC Press LLC
Number Line Rate Frame Rate Speed

kbps kHz
In
commercial implementations,
OTUs
are
built into
SONEr optical transport platforms.
writable optical storage technology, incorporated
in
1992.
OSTA
develops technology "roadmaps," sta-
tistical illustrations of optical storage progress
and
trends,
to
define compatible product classes. It
is
not
a standards-development organization per
se,
but
it
develops
specifications and provides input
to
other
organizations regarding practical implementations
of
optical storage standards.

In
July 2001,
OSTA
an-
nounced the development and approval of a new
specification
for
organizing compressed
audio
files
on
optical disc, called MultiAudio.
The
intent
is
to
ensure
that discs with compressed audio
files
(e.g.,
MP3)
are
as
straightforward
and
standard
Red
Book
CDs.
The

format
specifies a table ofcontents
access
mechanism for
CD
and
DVD
playlists
and
media
playback.
See
MultiAudio, MultiPlay.
/>optical time domain reflectometer
OTDR.
An
in-
strument for reflecting light through a fiber optic
waveguide
to
determine loss
and
integrity of
the
fi-
ber light
path.
OTDR measurements
may
be

uni-
or
bidirectional. Unidirectional measurements
may
be
misleading
if
there
are
diameter differences
from
one
fiber
joint
to
the
next.
However,
if
the
light will
be
traveling only
in
one
direction
and
the
OTDR
is

mea-
sured
in
the
same
direction, this may
be
sufficient.
If
the
light
is
being alternately transmitted
in
two
di-
rections along
the
fiber
optic path, bidirectional
av-
eraging (taking measurements
from
each
end
of
the
fiber
path) will provide more complete
data

for
as-
sessing
the
lightguide.
See
bidirectional averaging.
optical
transport
network
OTN.
As
defined
in
ITU
G Series Recommendation G.709,
OTN
is
an
inter-
face
that
builds
upon
previous
SDH
and
SONET
tech-
nologies

to
provide layered network services, but
improves
upon previous technologies with better
op-
tical
channel management in
the
optical
domain
and
forward
error correction
(FEC)
to
increase
the
dis-
tance over which data signals can be transmitted.
G.709
standardizes the management
of
optical chan-
nels
(wavelengths) without conversion
to
electrical
through
newer bubble
and

micro-electromechanical
systems
(MEMS)
technologies.
See
optical transport
unit.
optical
transport
unit
OTU.
In
the
ITU-T
G.709
framing
structure, a
frame
in
which each
row
con-
tains
16
forward
error control
(FEC)
blocks of
16-
byte

interleaved
codecs
for
atotal
of
4 x
16
=
64
FEC
blocks.
Currently
three
line
and
frame
rates
are
de-
fined.
48.971
ms
12.191
ms
3.035
ms
2,666,057.143 20.420
10,709,225.316 82.027
43,018,413.559 329.489
OTUI

OTU2
OTU3
loss
occurring
at
joints where optical transmission
cables
are
connected
into
ports.
The
loss
is
due
to
a
number of
factors,
including
the
quality
of
the
cable
assembly,
the
diameter
and
type

offiber
(some
are
more
subject
to
loss
than
others),
the
snugness of
the
fit,
the
amount
ofstrain associated
with
the
connec-
tion,
and
the
ambient
environment.
In
product litera-
ture,
low
optical
insertion

loss
typically refers
to
the
precision of
the
fit
and
resistence
to
strain
in
the
joint
between
the
connector
and
the
port.
There
is
some-
times
atradeoff
between
ease
of
use
and

reconnection
and
loss.
OpticalInternetworking Forum
OIP.
An
open
trade
organization fostering
the
global development
and
deployment
ofinteroperable optical data switching
and
routing technologies. Membership includes ser-
vice
providers, equipment manufacturers,
and
end
users.
/>optical label switching
See
optical-label switching.
optical modulation depth
OMD.
An
expression
of
the

degree
ofmodulation
in
an
optical data transmis-
sion
system.
OMD
is
usually expressed
in
microme-
ters
as
apercentage per channel (e.g.,
4%
or
20%)
at
a specified
frequency
range.
The
OMD
may
have
to
meet
certain standards (e.g.,
SONET).

Fiber
optic
CATV
transmitting
components
may
have
controls
for
operator adjustment ofOMD. Poor
ad-
justment
can
result
in
reflections
or
clipping.
See
modulation.
optical network unit
ONU.
A device
for
connect-
ing
auser
with
a
fiber

optic
network.
The
ONU
creates
aphysical link
and
conversion services,
if
necessary,
between
the
central
office optical wavelength
and
the
home
or office optical wavelength, which
may
be
different
frequencies.
Anumber of
ONUs
are
typically aggregated
at
a
host
digital

terminal.
Groups
of
host digital terminals
are
similarly aggregated
at
a control tenninal, located
at
the
central
office
of
the
local exchange.
In
spring
2002,
companies such
as
Salira began
of-
fering multiple-customer
ONUs
so
that individual
units
for
each
customer

were
no
longer necessary.
optical scanner
See
optical character recognition,
scanner.
Optical Society
of
Japan
OS1.
Founded
in
1952
as
a division of
the
Japan Society
of
Applied Physics
(JSAP),
it
is
now
the
biggest division of
JSAP
with
almost
2000

members.
OSJ
publishes
the
Japanese
Journal
of
Optics
and
the
Optical
Review.
It
provides
educational
support,
technical working groups,
and
conferences
for
its
members
and
sponsors anumber
of
awards
for
excellence
in
the

field
of
optics.
/>-e.
shtml
opticalspectrum analyzer
OSA.
A
desktop
diagnos-
tic
instrument
for
measuring
the
power
of
a light
sig-
nal
at
each
of
its
emitted frequencies.
It
incorporates
a diffraction grating
to
split out

the
wavelengths
(in
much
the
same
way a prism splits white light into
its
constituent colors)
and
measures
the
power level of
each
wavelength.
See
reflectometer,
tracer.
OpticalStorage TechnologyAssociation
OSTA.
An
international
trade
association promoting
the
use of
709
© 2003 by CRC Press LLC
Fiber
Optics

Illustrated
Dictionary
In
"digital
wrapper"
implementations
as
introduced
by
Lucent
Technologies,
data
is
encapsulated
in
an
optical
transport
unit
frame
similar
to
a
SONET
pro-
tocol
frame
so
that
any

type
of
network
traffic
(ATM,
IP,
etc.)
may
be
handled
and
forwarded
over
existing
SONEr
networks.
The
OTU
provides
FEC
informa-
tion
at
the
end
of
the
frame
to
ensure

the
suitability
of
the
optical
signal
for
high-speed
transmission.
optical-label switching
OLS.
A
network
switching
system
developed
under
the
direction
ofSJ.
Ben
Yoo
through
a
DARPA
ITO-sponsored
research
project.
It
was

first
proposed
by
Yoo
in
1997
and
developed
independently
at
around
the
same
time
as
Multi-
protocol
Label
Switching
(MPLS).
OLS
is
a
means
of
implementing
packet-switching
protocols
over
optical

media.
OLS
is
a
scalable
ul-
tra-low-latency
multiprotocol
optical
routing/switch-
ing
system that shares
some
characteristics with
MPLS.
Underlying
OLS
is
the
packet-switching
fab-
ric
comprising
rapidly
tunable
wavelength
conversion
capabilities
and
scalable

arrayed-waveguide
grating.
OLS
is
built
upon
this
with
a
forward
look
to
next
generation
all-optical
Intemetworks.
OLS
routing
uses
an
optical
header
with
a
label
in
the
header
to
determine

the
packet
forwarding.
The
data
are
held
in
the
fiber
path
while
the
header
is
ex-
amined
and
may
be
replaced
for
the
next
leg
in
the
transmission
path.
OLS

project
goals
as
of
2000
included
router
con-
nectivity
in
excess
of
1024
x
1024
and
aggregate
switching
bandwidth
of
almost
a peta-bits-per-sec-
ond.
The
multi
protocol
optical
routing
is
intended

to
be
interoperable with circuit-, burst-, flow-,
and
packet-switched networks.
See
label switching,
Multiprotocol
Label
Switching,
optical
burst
switch-
ing.
OQPSK
offset
quadrature
phase
shift
keying.
See
quadrature
phase
shift
keying.
Orange Book A
set
of
standards
for

Compact
Disc
readable
(write
once)
optical
media.
The
previous
Red
and
Yellow
Book
standards
established
the
ba-
sic
standards
for
recording
audio
and
computer
data
to
a
Compact
Disc.
The

Orange
Book
extended
these
capabilities
to
enable
multisession
recordings
to
be
created
(though
they
are
not
recommended
as
mas-
ters).
Red
and
Yellow
Book
data
can
be
combined
on
one

disc
in
whatever
order
is
desired.
See
Blue
Book.
ORB
See
Object
Request
Broker.
ORBCOMM
Orbital
Communications.
orbit
The
path
described
by
a
moving
body
in
more-
or-less
stable
balance

with
the
gravity of
the
body
being
orbited
so
that
it
continues
in
that
path
for
a
significant
period
of
time
(usually
at
least
a
few
hours
or
days,
although
orbits

ofartificial satellites
can
last
for
years
in
a
stable
orbit).
The
Earth
is
in
orbit
around
the
Sun,
and
the
Moon
is
in
orbit
around
the
Earth.
When
the
balance
is

lost and the orbit becomes
smaller
as
the
orbiting
body
is
drawn
inward,
it
is
said
that
the
orbit
is
decaying.
Many
types
of
orbits
(or-
bits
at
different
heights,
with
differently
shaped
paths)

are
used
in
telecommunications with artificial
sat-
ellites.
710
Early
communications satellite
orbits
tended
to
be
circular or
low
and
somewhat
flatly elliptical
(and
tended
to
decay
quickly).
Communications were
hin-
dered
by
the
necessity oflocating
the

orbiting
satel-
lite
and
keeping
it
in
range
before
it
passed
around
to
the
other
side
of
the
Earth.
Later satellites
were
put
into
higher,
more
stable
orbits,
which
were
often

geo-
stationary;
that
is,
the
orbit
was
synchronized
with
the
movement
of
the
Earth
so
that
the
location
of
the
satellite
was
roughly
above
the
same
location
at
all
times.

The
amount
by
which
an
orbit
deviates
from
a
circle
is
referred
to
as
its
eccentricity.
See
geostation-
ary,
satellite.
Elliptical Orbit
Satellite orbits tend
to
be
circular or
more
flatly el-
liptical, and may
be
further controlledso that the sat-

ellite spends agreaterpart
of
the orbitover
ocean
or
land
masses,
depending
upon
whether it
is
serving
marine or terrestrial communications
needs.
The
orbits
are
often described
in
terms
of
their dis-
tancefrom the
Earth
as
low,
medium,
and
high
Earth

orbits
(LEO,
MEO
I
HEO).
Geostationary orbits
are
a
type
of
high
Earth orbit
in
which
the
satellitesmove-
ment
is
paced
such
that it
remains
in
the
same posi-
tion
relative
to
the
Earth.

Orbital
Sciences Corporation
Commercial
devel-
opers
of
global satellite communications services.
Orbital
Sciences
is
a
space
and
information
systems
company
which
designs,
manufactures,
and
markets
space-related infrastructures and products. See
OrbLink.
OrbLink
A
global
broadband
commercial
satellite
communications

network
being
developed
by
Orbital
Sciences
Corporation
for
deployment
around
2002.
The
designers
intend
to
use
the
newest
technology
to
construct
broadband
services that
can
be
offered
at
lower prices
than
existing services. OrbLink

is
based
on
seven
medium
Earth
orbit (MEO) satellites
orbiting
at
9000
kIn
in
an
equatorial
orbit,
transmit-
ting
in
extremely
high
frequency
radio
bands.
Ser-
vices
will
include
digital
voice,
data

videoconferenc-
ing,
computer
networking,
imaging,
and
other
broad-
band
applications.
Pending Federal Communications Commission
(FCC)
approval,
intersatellite
communications
will
be
at
65.0
to
71.0
GHz
at
speeds
up
to
15
Gbps,
sup-
porting

high-capacity
intercontinental
trunking.
Two-
way
digital
connections
will
be
between
37.5
to
38.5
GHz
and 47.7
and
48.7
GHz
bands
up
to
about
1.5
Mbps.
The
seven satellites, plus
one
spare,
are
based

on
© 2003 by CRC Press LLC
Orbital's
STARBus,
a
small,
lightweight,
geostationary
technology, acquired through a purchase
of
CTA
Incorporated's
space
system
business.
Each
satellite
will
support
100
spot
beams.
As
an
economic
note
on
the
dynamics
of

new
telecommunications
tech-
nologies,
the
total
cost
ofbuilding
and
deploying
the
orbital
network,
according
to
Orbital
Sciences,
com-
pares
to
the
cost
ofinstalling
two
transatlantic
fiber
cables,
which
provide
only

about
10%
of
the
trunk-
ing
capacity
of
the
proposed satellite
system.
OrckitCommunicationsA
developer
and
manufac-
turer of
high-speed
local
loop
communications
sys-
tems
and
participant
in
a
number
of
network
standards

working
groups.
Orckit
partners
with
Fujitsu
Network
Communications,
Inc.
order
entry
The
inputting, usually
by
voice
or
key-
board,
ofa
customer
request
for
aproduct
or
service.
On
the
World
Wide
Web,

Web
forms
are
often
avail-
able
for
customers
to
put
in
their
own
order
entry.
These
Web
applications
are
often
in
the
form
of
shop-
ping
carts
in
which
the

customer browses various
Web
pages
and
enters
each
product desired
into
the
shopping
cart
(order
batch).
The
order
is
typically
pre-
processed
by
a
CGI
and
then
sent
to
the
appropriate
order
fulfillment

personnel
for
shipping
and
billing.
Other
automated
systems
allow
customers
to
carry
out
a
complete
ordering transaction
over
atouchtone
phone
by
using
the
keypad
to
enter
codes
and
digits.
See
Automatic

Call
Distribution.
Organization
of
American States
OAS.
The
OAS
Web
site provides information on the group.
/>OrganizationallyUnique Identifier
OUI.
A
globally
unique
24-bit Ethernet address identifier
for
LAN
s
and
MANs
managed
and
assigned
by
the
IEEE
Reg-
istration
Authority

online
or
by
phone.
The
OUI
is
assigned
as
athree-octet
field
in
the
SubNetwork
At-
tachment
Point
(SNAP)
header,
identifying
an
orga-
nization
which
further creates
unique
six
octet
num-
bers.

Together
they
constitute a distinct
Media
Ac-
cess
Control
(MAC)
address
or
Ethernet
address.
See
Ethernet,
IEEE,
Token-Ring.
originate/answer
On
acomputer
data
modem,
when
the
user
wants
to
dial
out
to
connect

to
another
com-
puter,
a bulletin
board,
or
an
Internet
access
point,
the
commands
for
controlling
the
phone
line
and
di-
aling
the
desired
number
come
from
the
originating
modem.
"Originate mode" sets

up
a sequence of
events
which
checks
for
a
dial
tone,
dials,
and
hand-
shakes
with
the
receiving
modem
to
establish
the
con-
nection
rate
and
protocol (or
hangs
up
if
the
line

is
busy
or
is
dropped).
The
receiving
modem
is
set
to
"answer
mode'
so
it
detects
an
incoming call,
an-
swers
it,
and
participates
in
the
rate
and
protocol
ne-
gotiation. Most

of
this is automatically handled
through
a
terminal
software
program,
but
it
may
be
necessary
to
set
originate or
answer
through
menu
selections,
or
direct
commands
through
the
software
to
the
terminal
program.
originate restriction A secwity or specialized

use
restriction
on
a
phone
line
which
causes
it
to
work
only
for
incoming
calls.
Outgoing
calls
are
blocked.
This
restriction
is
sometimes
set
on
phones
adjacent
to
public
areas

to
prevent people
from
monopolizing
or
misusing
a
phone
line.
Sometimes
the
originate
re-
striction applies only
to
long-distance
calls
or
calls
outside
aprivate
branch
exchange.
In
some
circumstances,
the
local
phone
company

will
partially disconnect a
line
by setting
an
originate
re-
striction
if
the
subscriber
is
behind
in
the
payment
of
the
phone
bill.
After paying
the
bill,
it
is
usually
nec-
essary
to
request restoration of

full
service,
as
it
is
seldom
done
automatically.
originator
Initiator, caller, inventor, introducer,
founder.
The
person,
entity,
device,
or
station
that
first
communicates
a
message
or
starts
an
action
or
pro-
cess.
Orion A broadband

data
satellite service provider
aiming
at
international
common
carriers
and
indi-
vidual
companies.
ortho-correction
In
satellite
imaging,
acorrectional
adjustment
for
distortion resulting
from
t~rrain.
orthogonal frequency division multiplex
OFDM.
Amulticarriermodulation system
which
is
similar
to
discrete
multitone

in
that
it
utilizes Fourier
transforms
of data blocks.
OFDM
is
suitable
for
Digital
Sub-
scriber
Line
(DSL)
services.
See
Digital Subscriber
Line,
discrete
multi
tone.
OS X
See
Mac
OS
X.
OS/2 Operating System/2. International Business
Machines' 32-bit preemptive multitasking
text

and
object-oriented graphical operating system targeted
for
Intel-based microcomputers
in
the
late
1980s.
It
was
originally developed
for
IBM
by
both
IBM
and
Microsoft Corporation,
and
version
1.0
was
released
in
1987
to
succeed
MS-DOS.
When
an

upgrade
to
OS/2
was
well
under
way,
Microsoft pulled
out
to
concentrate
on
their
own
operating
system
in
com-
petition
with
IBM.
Many
of
the
same
concepts
that
were
part of
OS/2

were
incorporated
into
Microsoft
Windows
NT,
which
was
marketed
as
a
direct
com-
petitor
to
OS/2.
In
1991,
ffiM released
OS/2
version
2.0.
Version
2.1
added
support
for
multimedia
and
Windows

3.1
ap-
plications.
OS/2
had
some
commercial
success
in
the
early
and
mid-1990s,
but
by
1996,
through
aggres-
sive
advertising
and
bundling programs,
Windows
was
better known
and
more widespread
in
North
America.

In
spite of
this,
there
are
many
strong
sup-
porters of
OS/2,
including a worldwide
network
of
Team
OS/2
Groups.
It
is
still a popular choice
in
Western
Europe
and
Canada.
Team
OS/2
information
for
OS/2
users

is
available
at
their
Web
site.
See
Team
OS/2.
OS/2 SMP
OS/2
Symmetric
Multiprocessing.
This
version ofIBM's
OS/2
supports
systems
with
mul-
tiple
processors,
making
it
suitable
for
Internet
ser-
vices,
graphics,

and
corporate applications, particu-
larly
those
which
operate
as
various
types
of
resource
servers
in
a networked environment.
See
OS/2.
OS/2
Warp
Operating
System/2
Warp.
By
version 3
ofmM's
OS/2
operating
system,
their
operating
sys-

tem
product
was
called
OS/2
Warp.
The
Warp
ver-
sion
added
increased support
for
various peripheral
711
© 2003 by CRC Press LLC