<s>
A	O
passive	B-Architecture
optical	I-Architecture
network	I-Architecture
(	O
PON	O
)	O
is	O
a	O
fiber-optic	B-Architecture
telecommunications	O
technology	O
for	O
delivering	O
broadband	B-General_Concept
network	O
access	O
to	O
end-customers	O
.	O
</s>
<s>
Its	O
architecture	O
implements	O
a	O
point-to-multipoint	O
topology	O
in	O
which	O
a	O
single	O
optical	B-Architecture
fiber	I-Architecture
serves	O
multiple	O
endpoints	O
by	O
using	O
unpowered	O
(	O
passive	O
)	O
fiber	B-Protocol
optic	I-Protocol
splitters	I-Protocol
to	O
divide	O
the	O
fiber	O
bandwidth	O
among	O
the	O
endpoints	O
.	O
</s>
<s>
Passive	B-Architecture
optical	I-Architecture
networks	I-Architecture
are	O
often	O
referred	O
to	O
as	O
the	O
last	B-Protocol
mile	I-Protocol
between	O
an	O
Internet	O
service	O
provider	O
(	O
ISP	O
)	O
and	O
its	O
customers	O
.	O
</s>
<s>
A	O
passive	B-Architecture
optical	I-Architecture
network	I-Architecture
consists	O
of	O
an	O
optical	B-Protocol
line	I-Protocol
terminal	I-Protocol
(	O
OLT	O
)	O
at	O
the	O
service	O
provider	O
's	O
central	O
office	O
(	O
hub	O
)	O
,	O
passive	O
(	O
non-power-consuming	O
)	O
optical	O
splitters	O
,	O
and	O
a	O
number	O
of	O
optical	O
network	O
units	O
(	O
ONUs	O
)	O
or	O
optical	O
network	O
terminals	O
(	O
ONTs	O
)	O
,	O
which	O
are	O
near	O
end	O
users	O
.	O
</s>
<s>
A	O
passive	B-Architecture
optical	I-Architecture
network	I-Architecture
is	O
a	O
form	O
of	O
fiber-optic	B-Architecture
access	O
network	O
.	O
</s>
<s>
In	O
most	O
cases	O
,	O
downstream	O
signals	O
are	O
broadcast	B-Operating_System
to	O
all	O
premises	O
sharing	O
multiple	O
fibers	O
.	O
</s>
<s>
Upstream	O
signals	O
are	O
combined	O
using	O
a	O
multiple	O
access	O
protocol	O
,	O
usually	O
time-division	B-Protocol
multiple	O
access	O
(	O
TDMA	O
)	O
.	O
</s>
<s>
Passive	B-Architecture
optical	I-Architecture
networks	I-Architecture
were	O
first	O
proposed	O
by	O
British	O
Telecommunications	O
in	O
1987	O
.	O
</s>
<s>
The	O
Society	O
of	O
Cable	O
Telecommunications	O
Engineers	O
(	O
SCTE	O
)	O
also	O
specified	O
radio	B-Device
frequency	I-Device
over	I-Device
glass	I-Device
for	O
carrying	O
signals	O
over	O
a	O
passive	B-Architecture
optical	I-Architecture
network	I-Architecture
.	O
</s>
<s>
Starting	O
in	O
1995	O
,	O
work	O
on	O
fiber	B-Architecture
to	I-Architecture
the	I-Architecture
home	I-Architecture
architectures	O
was	O
done	O
by	O
the	O
Full	O
Service	O
Access	O
Network	O
(	O
FSAN	O
)	O
working	O
group	O
,	O
formed	O
by	O
major	O
telecommunications	O
service	O
providers	O
and	O
system	O
vendors	O
.	O
</s>
<s>
The	O
older	O
ITU-T	O
G.983	O
standard	O
was	O
based	O
on	O
Asynchronous	O
Transfer	O
Mode	O
(	O
ATM	O
)	O
,	O
and	O
has	O
therefore	O
been	O
referred	O
to	O
as	O
APON	B-Architecture
(	O
ATM	B-Architecture
PON	I-Architecture
)	O
.	O
</s>
<s>
Further	O
improvements	O
to	O
the	O
original	O
APON	B-Architecture
standard	O
–	O
as	O
well	O
as	O
the	O
gradual	O
falling	O
out	O
of	O
favor	O
of	O
ATM	O
as	O
a	O
protocol	O
–	O
led	O
to	O
the	O
full	O
,	O
final	O
version	O
of	O
ITU-T	O
G.983	O
being	O
referred	O
to	O
more	O
often	O
as	O
broadband	B-Architecture
PON	I-Architecture
,	O
or	O
BPON	O
.	O
</s>
<s>
A	O
typical	O
APON/BPON	O
provides	O
622	O
megabits	O
per	O
second	O
(	O
Mbit/s	O
)	O
(	O
OC-12	O
)	O
of	O
downstream	O
bandwidth	O
and	O
155	O
Mbit/s	O
(	O
OC-3	O
)	O
of	O
upstream	O
traffic	O
,	O
although	O
the	O
standard	O
accommodates	O
higher	O
rates	O
.	O
</s>
<s>
The	O
ITU-T	O
G.984	O
Gigabit-capable	O
Passive	B-Architecture
Optical	I-Architecture
Networks	I-Architecture
(	O
GPON	B-Architecture
,	O
G-PON	O
)	O
standard	O
represented	O
an	O
increase	O
,	O
compared	O
to	O
BPON	O
,	O
in	O
both	O
the	O
total	O
bandwidth	O
and	O
bandwidth	O
efficiency	O
through	O
the	O
use	O
of	O
larger	O
,	O
variable-length	O
packets	O
.	O
</s>
<s>
GPON	B-Architecture
Encapsulation	O
Method	O
(	O
GEM	O
)	O
allows	O
very	O
efficient	O
packaging	O
of	O
user	O
traffic	O
with	O
frame	O
segmentation	O
.	O
</s>
<s>
By	O
mid-2008	O
,	O
Verizon	B-Application
had	O
installed	O
over	O
800,000	O
lines	O
.	O
</s>
<s>
GPON	B-Architecture
networks	O
have	O
now	O
been	O
deployed	O
in	O
numerous	O
networks	O
across	O
the	O
globe	O
,	O
and	O
the	O
trends	O
indicate	O
higher	O
growth	O
in	O
GPON	B-Architecture
than	O
other	O
PON	O
technologies	O
.	O
</s>
<s>
G.987	O
defined	O
10G-PON	B-Protocol
with	O
10	O
Gbit/s	O
downstream	O
and	O
2.5	O
Gbit/s	O
upstream	O
–	O
framing	O
is	O
"	O
G-PON	O
like	O
"	O
and	O
designed	O
to	O
coexist	O
with	O
GPON	B-Architecture
devices	O
on	O
the	O
same	O
network	O
.	O
</s>
<s>
Developed	O
in	O
2009	O
by	O
Cable	O
Manufacturing	O
Business	O
to	O
meet	O
SIPRNet	O
requirements	O
of	O
the	O
US	O
Air	O
Force	O
,	O
secure	O
passive	B-Architecture
optical	I-Architecture
network	I-Architecture
(	O
SPON	O
)	O
integrates	O
gigabit	B-Architecture
passive	I-Architecture
optical	I-Architecture
network	I-Architecture
(	O
GPON	B-Architecture
)	O
technology	O
and	O
protective	O
distribution	O
system	O
(	O
PDS	O
)	O
.	O
</s>
<s>
GPON	B-Architecture
used	O
in	O
Fiber	B-Architecture
to	I-Architecture
the	I-Architecture
x	I-Architecture
deployments	O
may	O
face	O
vulnerability	O
to	O
Denial-of-service	O
attack	O
via	O
optical	O
signal	O
injections	O
,	O
unresolved	O
based	O
on	O
current	O
commercially	O
available	O
technologies	O
.	O
</s>
<s>
In	O
2004	O
,	O
the	O
Ethernet	B-Architecture
PON	I-Architecture
(	O
EPON	O
or	O
GEPON	B-Protocol
)	O
standard	O
802.3ah-2004	O
was	O
ratified	O
as	O
part	O
of	O
the	O
Ethernet	B-Protocol
in	I-Protocol
the	I-Protocol
first	I-Protocol
mile	I-Protocol
project	O
of	O
the	O
IEEE	O
802.3	O
.	O
</s>
<s>
EPON	O
is	O
a	O
"	O
short	O
haul	O
"	O
network	O
using	O
ethernet	O
packets	O
,	O
fiber	B-Architecture
optic	I-Architecture
cables	O
,	O
and	O
single	O
protocol	O
layer	O
.	O
</s>
<s>
10Gbit/s	O
EPON	O
or	O
10G-EPON	B-Protocol
was	O
ratified	O
as	O
an	O
amendment	O
IEEE	O
802.3av	B-Protocol
to	O
IEEE	O
802.3	O
.	O
</s>
<s>
10G-EPON	B-Protocol
supports	O
10/1Gbit/s	O
.	O
</s>
<s>
The	O
downstream	O
wavelength	B-Algorithm
plan	I-Algorithm
support	O
simultaneous	O
operation	O
of	O
10Gbit/s	O
on	O
one	O
wavelength	O
and	O
1Gbit/s	O
on	O
a	O
separate	O
wavelength	O
for	O
the	O
operation	O
of	O
IEEE	O
802.3av	B-Protocol
and	O
IEEE	B-Protocol
802.3ah	I-Protocol
on	O
the	O
same	O
PON	O
concurrently	O
.	O
</s>
<s>
The	O
upstream	O
channel	O
can	O
support	O
simultaneous	O
operation	O
of	O
IEEE	O
802.3av	B-Protocol
and	O
1Gbit/s	O
802.3ah	B-Protocol
simultaneously	O
on	O
a	O
single	O
shared	O
(	O
1310nm	O
)	O
channel	O
.	O
</s>
<s>
EPON	O
is	O
also	O
the	O
foundation	O
for	O
cable	O
operators’	O
business	O
services	O
as	O
part	O
of	O
the	O
DOCSIS	B-Protocol
Provisioning	O
of	O
EPON	O
(	O
DPoE	O
)	O
specifications	O
.	O
</s>
<s>
This	O
technology	O
connects	O
seamlessly	O
with	O
any	O
type	O
of	O
IP-based	O
or	O
packetized	O
communications	O
,	O
and	O
,	O
thanks	O
to	O
the	O
ubiquity	O
of	O
Ethernet	O
installations	O
in	O
homes	O
,	O
workplaces	O
,	O
and	O
elsewhere	O
,	O
EPON	O
is	O
generally	O
very	O
inexpensive	O
to	O
implement	O
.	O
</s>
<s>
A	O
PON	O
takes	O
advantage	O
of	O
wavelength-division	B-Architecture
multiplexing	I-Architecture
(	O
WDM	O
)	O
,	O
using	O
one	O
wavelength	O
for	O
downstream	O
traffic	O
and	O
another	O
for	O
upstream	O
traffic	O
on	O
a	O
single	O
mode	O
fiber	O
(	O
ITU-T	O
G.652	O
)	O
.	O
</s>
<s>
BPON	O
,	O
EPON	O
,	O
GEPON	B-Protocol
,	O
and	O
GPON	B-Architecture
have	O
the	O
same	O
basic	O
wavelength	B-Algorithm
plan	I-Algorithm
and	O
use	O
the	O
1490	O
nanometer	O
(	O
nm	O
)	O
wavelength	O
for	O
downstream	O
traffic	O
and	O
1310nm	O
wavelength	O
for	O
upstream	O
traffic	O
.	O
</s>
<s>
As	O
with	O
bit	O
rate	O
,	O
the	O
standards	O
describe	O
several	O
optical	B-Protocol
power	I-Protocol
budgets	I-Protocol
,	O
most	O
common	O
is	O
28	O
dB	O
of	O
loss	O
budget	O
for	O
both	O
BPON	O
and	O
GPON	B-Architecture
,	O
but	O
products	O
have	O
been	O
announced	O
using	O
less	O
expensive	O
optics	O
as	O
well	O
.	O
</s>
<s>
Forward	B-Error_Name
error	I-Error_Name
correction	I-Error_Name
(	O
FEC	O
)	O
may	O
provide	O
for	O
another	O
2	O
–	O
3dB	O
of	O
loss	O
budget	O
on	O
GPON	B-Architecture
systems	O
.	O
</s>
<s>
Although	O
both	O
the	O
GPON	B-Architecture
and	O
EPON	O
protocols	O
permit	O
large	O
split	O
ratios	O
(	O
up	O
to	O
128	O
subscribers	O
for	O
GPON	B-Architecture
,	O
up	O
to	O
32,768	O
for	O
EPON	O
)	O
,	O
in	O
practice	O
most	O
PONs	O
are	O
deployed	O
with	O
a	O
split	O
ratio	O
of	O
1:32	O
or	O
smaller	O
.	O
</s>
<s>
A	O
PON	O
consists	O
of	O
a	O
central	O
office	O
node	O
,	O
called	O
an	O
optical	B-Protocol
line	I-Protocol
terminal	I-Protocol
(	O
OLT	O
)	O
,	O
one	O
or	O
more	O
user	O
nodes	O
,	O
called	O
optical	O
network	O
units	O
(	O
ONUs	O
)	O
or	O
optical	O
network	O
terminals	O
(	O
ONTs	O
)	O
,	O
and	O
the	O
fibers	O
and	O
splitters	O
between	O
them	O
,	O
called	O
the	O
optical	O
distribution	O
network	O
(	O
ODN	O
)	O
.	O
</s>
<s>
In	O
multiple-tenant	O
units	O
,	O
the	O
ONU	O
may	O
be	O
bridged	O
to	O
a	O
customer	O
premises	O
device	O
within	O
the	O
individual	O
dwelling	O
unit	O
using	O
technologies	O
such	O
as	O
Ethernet	O
over	O
twisted	O
pair	O
,	O
G.hn	B-General_Concept
(	O
a	O
high-speed	O
ITU-T	O
standard	O
that	O
can	O
operate	O
over	O
any	O
existing	O
home	O
wiring	O
-	O
power	B-Device
lines	I-Device
,	O
phone	O
lines	O
and	O
coaxial	B-Protocol
cables	I-Protocol
)	O
or	O
DSL	O
.	O
</s>
<s>
An	O
OLT	O
provides	O
the	O
interface	O
between	O
a	O
PON	O
and	O
a	O
service	O
provider	O
's	O
core	B-General_Concept
network	I-General_Concept
.	O
</s>
<s>
IP	B-Protocol
traffic	O
over	O
Fast	B-Protocol
Ethernet	I-Protocol
,	O
Gigabit	O
Ethernet	O
,	O
or	O
10	O
Gigabit	O
Ethernet	O
;	O
</s>
<s>
Standard	O
TDM	B-Protocol
interfaces	O
such	O
as	O
SDH/SONET	B-Protocol
;	O
</s>
<s>
These	O
services	O
can	O
include	O
voice	O
(	O
plain	O
old	O
telephone	O
service	O
(	O
POTS	O
)	O
or	O
voice	B-Application
over	I-Application
IP	I-Application
(	O
VoIP	B-Application
)	O
)	O
,	O
data	O
(	O
typically	O
Ethernet	O
or	O
V.35	O
)	O
,	O
video	O
,	O
and/or	O
telemetry	O
(	O
TTL	O
,	O
ECL	O
,	O
RS530	O
,	O
etc	O
.	O
)	O
</s>
<s>
The	O
OLT	O
measures	O
delay	O
and	O
sets	O
a	O
register	O
in	O
each	O
ONU	O
via	O
PLOAM	O
(	O
physical	B-Application
layer	I-Application
operations	O
,	O
administrations	O
and	O
maintenance	O
)	O
messages	O
to	O
equalize	O
its	O
delay	O
with	O
respect	O
to	O
all	O
of	O
the	O
other	O
ONUs	O
on	O
the	O
PON	O
.	O
</s>
<s>
DS1	B-Protocol
and	O
some	O
classes	O
of	O
data	O
service	O
may	O
also	O
require	O
constant	O
upstream	O
bit	O
rate	O
.	O
</s>
<s>
Through	O
dynamic	B-Protocol
bandwidth	I-Protocol
allocation	I-Protocol
(	O
DBA	O
)	O
,	O
a	O
PON	O
can	O
be	O
oversubscribed	O
for	O
upstream	O
traffic	O
,	O
according	O
to	O
the	O
traffic	O
engineering	O
concepts	O
of	O
statistical	B-Algorithm
multiplexing	I-Algorithm
.	O
</s>
<s>
In	O
GPON	B-Architecture
there	O
are	O
two	O
forms	O
of	O
DBA	O
,	O
status-reporting	O
(	O
SR	O
)	O
and	O
non-status	O
reporting	O
(	O
NSR	O
)	O
.	O
</s>
<s>
EPON	O
systems	O
use	O
a	O
DBA	O
mechanism	O
equivalent	O
to	O
GPON	B-Architecture
's	O
SR	O
DBA	O
solution	O
.	O
</s>
<s>
APON/BPON	O
,	O
EPON	O
and	O
GPON	B-Architecture
have	O
been	O
widely	O
deployed	O
.	O
</s>
<s>
As	O
of	O
2015	O
,	O
GPON	B-Architecture
had	O
a	O
smaller	O
market	O
share	O
,	O
but	O
is	O
anticipated	O
to	O
reach	O
$10.5	O
billion	O
US	O
dollars	O
by	O
2020	O
.	O
</s>
<s>
For	O
TDM-PON	O
,	O
a	O
passive	O
optical	O
splitter	O
is	O
used	O
in	O
the	O
optical	O
distribution	O
network	O
.	O
</s>
<s>
In	O
the	O
upstream	O
direction	O
,	O
each	O
ONU	O
(	O
optical	O
network	O
units	O
)	O
or	O
ONT	O
(	O
optical	O
network	O
terminal	O
)	O
burst	O
transmits	O
for	O
an	O
assigned	O
time-slot	O
(	O
multiplexed	B-Architecture
in	O
the	O
time	O
domain	O
)	O
.	O
</s>
<s>
Data	B-Protocol
Over	I-Protocol
Cable	I-Protocol
Service	I-Protocol
Interface	I-Protocol
Specification	I-Protocol
(	O
DOCSIS	B-Protocol
)	O
Provisioning	O
of	O
Ethernet	O
Passive	B-Architecture
Optical	I-Architecture
Network	I-Architecture
,	O
or	O
DPoE	O
,	O
is	O
a	O
set	O
of	O
Cable	O
Television	O
Laboratory	O
specifications	O
that	O
implement	O
the	O
DOCSIS	B-Protocol
service	O
layer	O
interface	O
on	O
existing	O
Ethernet	B-Architecture
PON	I-Architecture
(	O
EPON	O
,	O
GEPON	B-Protocol
or	O
10G-EPON	B-Protocol
)	O
Media	B-Protocol
Access	I-Protocol
Control	I-Protocol
(	O
MAC	O
)	O
and	O
Physical	B-Application
layer	I-Application
(	O
PHY	O
)	O
standards	O
.	O
</s>
<s>
In	O
short	O
it	O
implements	O
the	O
DOCSIS	B-Protocol
Operations	O
Administration	O
Maintenance	O
and	O
Provisioning	O
(	O
OAMP	O
)	O
functionality	O
on	O
existing	O
EPON	O
equipment	O
.	O
</s>
<s>
It	O
makes	O
the	O
EPON	O
OLT	O
look	O
and	O
act	O
like	O
a	O
DOCSIS	B-Protocol
Cable	I-Protocol
Modem	I-Protocol
Termination	O
Systems	O
(	O
CMTS	O
)	O
platform	O
(	O
which	O
is	O
called	O
a	O
DPoE	O
System	O
in	O
DPoE	O
terminology	O
)	O
.	O
</s>
<s>
In	O
addition	O
to	O
offering	O
the	O
same	O
IP	B-Protocol
service	O
capabilities	O
as	O
a	O
CMTS	O
,	O
DPoE	O
supports	O
Metro	O
Ethernet	O
Forum	O
(	O
MEF	O
)	O
9	O
and	O
14	O
services	O
for	O
the	O
delivery	O
of	O
Ethernet	O
services	O
for	O
business	O
customers	O
.	O
</s>
<s>
Radio	B-Device
frequency	I-Device
over	I-Device
glass	I-Device
(	O
RFoG	B-Device
)	O
is	O
a	O
type	O
of	O
passive	B-Architecture
optical	I-Architecture
network	I-Architecture
that	O
transports	O
RF	O
signals	O
that	O
were	O
formerly	O
transported	O
over	O
copper	O
(	O
principally	O
over	O
a	O
hybrid	B-Architecture
fibre-coaxial	I-Architecture
cable	O
)	O
over	O
PON	O
.	O
</s>
<s>
In	O
the	O
forward	O
direction	O
RFoG	B-Device
is	O
either	O
a	O
stand-alone	O
P2MP	O
system	O
or	O
an	O
optical	O
overlay	O
for	O
existing	O
PON	O
such	O
as	O
GEPON/EPON	O
.	O
</s>
<s>
The	O
overlay	O
for	O
RFoG	B-Device
is	O
based	O
on	O
wavelength-division	B-Architecture
multiplexing	I-Architecture
(	O
WDM	O
)	O
—	O
the	O
passive	O
combination	O
of	O
wavelengths	O
on	O
a	O
single	O
strand	O
of	O
glass	O
.	O
</s>
<s>
RFoG	B-Device
offers	O
backwards	O
compatibility	O
with	O
existing	O
RF	O
modulation	O
technology	O
,	O
but	O
offers	O
no	O
additional	O
bandwidth	O
for	O
RF	O
based	O
services	O
.	O
</s>
<s>
Although	O
not	O
yet	O
completed	O
,	O
the	O
RFoG	B-Device
standard	O
is	O
actually	O
a	O
collection	O
of	O
standardized	O
options	O
which	O
are	O
not	O
compatible	O
with	O
each	O
other	O
(	O
they	O
cannot	O
be	O
mixed	O
on	O
the	O
same	O
PON	O
)	O
.	O
</s>
<s>
This	O
technology	O
is	O
targeted	O
towards	O
Cable	O
TV	O
operators	O
and	O
their	O
existing	O
HFC	B-Architecture
networks	I-Architecture
.	O
</s>
<s>
Wavelength-Division	B-Architecture
Multiplexing	I-Architecture
PON	O
,	O
or	O
WDM-PON	O
,	O
is	O
a	O
non-standard	O
type	O
of	O
passive	B-Architecture
optical	I-Architecture
networking	I-Architecture
,	O
being	O
developed	O
by	O
some	O
companies	O
.	O
</s>
<s>
Alternatively	O
the	O
wavelengths	O
can	O
be	O
used	O
collectively	O
through	O
statistical	B-Algorithm
multiplexing	I-Algorithm
to	O
provide	O
efficient	O
wavelength	O
utilization	O
and	O
lower	O
delays	O
experienced	O
by	O
the	O
ONUs	O
.	O
</s>
<s>
Advantages	O
:	O
The	O
MAC	B-Protocol
layer	I-Protocol
is	O
simplified	O
because	O
the	O
P2P	O
connections	O
between	O
OLT	O
and	O
ONUs	O
are	O
realized	O
in	O
wavelength	O
domain	O
,	O
so	O
no	O
P2MP	O
media	B-Protocol
access	I-Protocol
control	I-Protocol
is	O
needed	O
.	O
</s>
<s>
Time	O
-	O
and	O
wavelength-division	B-Architecture
multiplexed	I-Architecture
passive	B-Architecture
optical	I-Architecture
network	I-Architecture
(	O
TWDM-PON	O
)	O
is	O
a	O
primary	O
solution	O
for	O
the	O
next-generation	O
passive	B-Architecture
optical	I-Architecture
network	I-Architecture
stage	O
2	O
(	O
NG-PON2	B-Protocol
)	O
by	O
the	O
full	O
service	O
access	O
network	O
(	O
FSAN	O
)	O
in	O
April	O
2012	O
.	O
</s>
<s>
TWDM-PON	O
coexists	O
with	O
commercially	O
deployed	O
Gigabit	B-Architecture
PON	I-Architecture
(	O
G-PON	O
)	O
and	O
10	O
Gigabit	B-Architecture
PON	I-Architecture
(	O
XG-PON	B-Protocol
)	O
systems	O
.	O
</s>
<s>
For	O
the	O
downstream	O
transmission	O
,	O
the	O
OLT	O
broadcasts	B-Operating_System
optical	O
signal	O
to	O
all	O
the	O
ONUs	O
in	O
continuous	O
mode	O
(	O
CM	O
)	O
,	O
that	O
is	O
,	O
the	O
downstream	O
channel	O
always	O
has	O
optical	O
data	O
signal	O
.	O
</s>
<s>
The	O
given	O
ONU	O
only	O
transmits	O
optical	O
packet	O
when	O
it	O
is	O
allocated	O
a	O
time	O
slot	O
and	O
it	O
needs	O
to	O
transmit	O
,	O
and	O
all	O
the	O
ONUs	O
share	O
the	O
upstream	O
channel	O
in	O
the	O
time-division	B-Protocol
multiplexing	I-Protocol
(	O
TDM	B-Protocol
)	O
mode	O
.	O
</s>
<s>
In	O
order	O
to	O
compensate	O
the	O
phase	O
variation	O
and	O
amplitude	O
variation	O
in	O
a	O
short	O
time	O
(	O
for	O
example	O
within	O
40	O
ns	O
for	O
GPON	B-Architecture
)	O
,	O
burst	O
mode	O
clock	O
and	O
data	O
recovery	O
(	O
BM-CDR	O
)	O
and	O
burst	O
mode	O
amplifier	O
(	O
for	O
example	O
burst	O
mode	O
TIA	O
)	O
need	O
to	O
be	O
employed	O
,	O
respectively	O
.	O
</s>
<s>
Passive	B-Architecture
optical	I-Architecture
networks	I-Architecture
do	O
not	O
use	O
electrically	O
powered	O
components	O
to	O
split	O
the	O
signal	O
.	O
</s>
<s>
For	O
example	O
,	O
due	O
to	O
the	O
absence	O
of	O
switching	O
,	O
each	O
signal	O
leaving	O
the	O
central	O
office	O
must	O
be	O
broadcast	B-Operating_System
to	O
all	O
users	O
served	O
by	O
that	O
splitter	O
(	O
including	O
to	O
those	O
for	O
whom	O
the	O
signal	O
is	O
not	O
intended	O
)	O
.	O
</s>
<s>
In	O
addition	O
,	O
since	O
splitters	O
have	O
no	O
buffering	O
,	O
each	O
individual	O
optical	O
network	O
terminal	O
must	O
be	O
coordinated	O
in	O
a	O
multiplexing	B-Architecture
scheme	O
to	O
prevent	O
signals	O
sent	O
by	O
customers	O
from	O
colliding	O
with	O
each	O
other	O
.	O
</s>
<s>
Two	O
types	O
of	O
multiplexing	B-Architecture
are	O
possible	O
for	O
achieving	O
this	O
:	O
wavelength-division	B-Architecture
multiplexing	I-Architecture
and	O
time-division	B-Protocol
multiplexing	I-Protocol
.	O
</s>
<s>
With	O
wavelength-division	B-Architecture
multiplexing	I-Architecture
,	O
each	O
customer	O
transmits	O
their	O
signal	O
using	O
a	O
unique	O
wavelength	O
.	O
</s>
<s>
With	O
time-division	B-Protocol
multiplexing	I-Protocol
(	O
TDM	B-Protocol
)	O
,	O
the	O
customers	O
"	O
take	O
turns	O
"	O
transmitting	O
information	O
.	O
</s>
<s>
TDM	B-Protocol
equipment	O
has	O
been	O
on	O
the	O
market	O
longest	O
.	O
</s>
<s>
Passive	B-Architecture
optical	I-Architecture
networks	I-Architecture
have	O
both	O
advantages	O
and	O
disadvantages	O
over	O
active	O
networks	O
.	O
</s>
<s>
They	O
also	O
allow	O
for	O
analog	O
broadcasts	B-Operating_System
,	O
which	O
can	O
simplify	O
the	O
delivery	O
of	O
analog	O
television	O
.	O
</s>
<s>
However	O
,	O
because	O
each	O
signal	O
must	O
be	O
pushed	O
out	O
to	O
everyone	O
served	O
by	O
the	O
splitter	O
(	O
rather	O
than	O
to	O
just	O
a	O
single	O
switching	O
device	O
)	O
,	O
the	O
central	O
office	O
must	O
be	O
equipped	O
with	O
a	O
particularly	O
powerful	O
piece	O
of	O
transmitting	O
equipment	O
called	O
an	O
optical	B-Protocol
line	I-Protocol
terminal	I-Protocol
(	O
OLT	O
)	O
.	O
</s>
<s>
The	O
drivers	O
behind	O
the	O
modern	O
passive	B-Architecture
optical	I-Architecture
network	I-Architecture
are	O
high	O
reliability	O
,	O
low	O
cost	O
,	O
and	O
passive	O
functionality	O
.	O
</s>
<s>
These	O
components	O
are	O
used	O
in	O
interoffice	O
,	O
loop	O
feeder	O
,	O
Fiber	B-Architecture
In	I-Architecture
The	I-Architecture
Loop	I-Architecture
(	O
FITL	B-Architecture
)	O
,	O
Hybrid	B-Architecture
Fiber-Coaxial	I-Architecture
Cable	I-Architecture
(	O
HFC	O
)	O
,	O
Synchronous	B-Protocol
Optical	I-Protocol
Network	I-Protocol
(	O
SONET	B-Protocol
)	O
,	O
and	O
Synchronous	B-Protocol
Digital	I-Protocol
Hierarchy	I-Protocol
(	O
SDH	O
)	O
systems	O
;	O
and	O
other	O
telecommunications	O
networks	O
employing	O
optical	O
communications	O
systems	O
that	O
utilize	O
Optical	B-Architecture
Fiber	I-Architecture
Amplifiers	O
(	O
OFAs	O
)	O
and	O
Dense	O
Wavelength-Division	O
Multiplexer	O
(	O
DWDM	O
)	O
systems	O
.	O
</s>
<s>
A	O
fiber	B-Device
optic	I-Device
filter	I-Device
is	O
a	O
component	O
with	O
two	O
or	O
more	O
ports	O
that	O
provides	O
wavelength	O
sensitive	O
loss	O
,	O
isolation	O
and/or	O
return	O
loss	O
.	O
</s>
<s>
Fiber	B-Device
optic	I-Device
filters	I-Device
are	O
in-line	O
,	O
wavelength	O
selective	O
,	O
components	O
that	O
allow	O
a	O
specific	O
range	O
of	O
wavelengths	O
to	O
pass	O
through	O
(	O
or	O
reflect	O
)	O
with	O
low	O
attenuation	O
for	O
classification	O
of	O
filter	O
types	O
.	O
</s>
