<s>
In	O
telecommunications	O
,	O
radio	B-Device
frequency	I-Device
over	I-Device
glass	I-Device
(	O
RFoG	B-Device
)	O
is	O
a	O
deep-fiber	O
network	O
design	O
in	O
which	O
the	O
coax	O
portion	O
of	O
the	O
hybrid	B-Architecture
fiber	I-Architecture
coax	I-Architecture
(	O
HFC	B-Architecture
)	O
network	O
is	O
replaced	O
by	O
a	O
single-fiber	O
passive	B-Architecture
optical	I-Architecture
network	I-Architecture
(	O
PON	O
)	O
.	O
</s>
<s>
Using	O
1590/1610nm	O
for	O
the	O
return	O
path	O
allows	O
the	O
fiber	B-Architecture
infrastructure	I-Architecture
to	O
support	O
both	O
RFoG	B-Device
and	O
a	O
standards-based	O
PON	O
simultaneously	O
,	O
operating	O
with	O
1490nm	O
downstream	O
and	O
1310nm	O
return-path	O
wavelengths	O
.	O
</s>
<s>
RFoG	B-Device
delivers	O
the	O
same	O
services	O
as	O
an	O
RF/DOCSIS/HFC	O
network	O
,	O
with	O
the	O
added	O
benefit	O
of	O
improved	O
noise	O
performance	O
and	O
increased	O
usable	O
RF	O
spectrum	O
in	O
both	O
the	O
downstream	O
and	O
return-path	O
directions	O
.	O
</s>
<s>
Both	O
RFoG	B-Device
and	O
HFC	B-Architecture
systems	O
can	O
concurrently	O
operate	O
out	O
of	O
the	O
same	O
headend/hub	O
,	O
making	O
RFoG	B-Device
a	O
good	O
solution	O
for	O
node-splitting	O
and	O
capacity	O
increases	O
on	O
an	O
existing	O
network	O
.	O
</s>
<s>
RFoG	B-Device
allows	O
service	O
providers	O
to	O
continue	O
to	O
leverage	O
traditional	O
HFC	B-Architecture
equipment	O
and	O
back-office	O
applications	O
with	O
the	O
new	O
FTTP	B-Architecture
deployments	O
.	O
</s>
<s>
Cable	O
operators	O
can	O
continue	O
to	O
rely	O
on	O
the	O
existing	O
provisioning	O
and	O
billing	O
systems	O
,	O
cable	B-Device
modem	I-Device
termination	I-Device
system	I-Device
(	O
CMTS	B-Device
)	O
platforms	O
,	O
headend	O
equipment	O
,	O
set-top	O
boxes	O
,	O
conditional	O
access	O
technology	O
and	O
cable	O
modems	O
while	O
gaining	O
benefits	O
inherent	O
with	O
RFoG	B-Device
and	O
FTTx	B-Architecture
.	O
</s>
<s>
RFoG	B-Device
provides	O
several	O
benefits	O
over	O
traditional	O
network	O
architecture	O
:	O
</s>
<s>
More	O
upstream	O
bandwidth	O
;	O
RFoG	B-Device
's	O
improved	O
noise	O
characteristics	O
allow	O
for	O
the	O
use	O
of	O
the	O
full	O
5	O
–	O
42MHz	O
return-path	O
spectrum	O
.	O
</s>
<s>
Additionally	O
,	O
higher-performance	O
RFoG	B-Device
systems	O
not	O
only	O
support	O
DOCSIS	B-Protocol
3.0	I-Protocol
with	O
bonding	O
,	O
but	O
also	O
enable	O
64	O
quadrature	B-Device
amplitude	I-Device
modulation	I-Device
(	O
QAM	B-Device
)	O
upstream	O
transmission	O
in	O
a	O
DOCSIS	B-Protocol
3.0	I-Protocol
bonded	O
channel	O
,	O
dramatically	O
increasing	O
return-path	O
bandwidth	O
.	O
</s>
<s>
Improved	O
operational	O
expenses	O
;	O
RFoG	B-Device
brings	O
the	O
benefits	O
of	O
a	O
passive	O
fiber	O
topology	O
.	O
</s>
<s>
Both	O
cost	O
savings	O
and	O
increased	O
capacity	O
for	O
new	O
services	O
(	O
revenue	O
generating	O
and/or	O
competitive	O
positioning	O
)	O
are	O
driving	O
the	O
acceptance	O
of	O
RFoG	B-Device
as	O
a	O
cost-effective	O
step	O
on	O
the	O
path	O
towards	O
a	O
100-percent	O
PON-based	O
access	O
network	O
.	O
</s>
<s>
As	O
with	O
an	O
HFC	B-Architecture
architecture	O
,	O
video	O
controllers	O
and	O
data-networking	O
services	O
are	O
fed	O
through	O
a	O
CMTS/edge	O
router	O
.	O
</s>
<s>
These	O
electrical	O
signals	O
are	O
then	O
converted	O
to	O
optical	O
ones	O
,	O
and	O
transported	O
via	O
a	O
1550nm	O
wavelength	O
through	O
a	O
wavelength-division	B-Architecture
multiplexing	I-Architecture
(	O
WDM	O
)	O
platform	O
and	O
a	O
passive	O
splitter	O
to	O
a	O
fiber-optic	O
micro-node	O
located	O
at	O
the	O
customer	O
premises	O
.	O
</s>
<s>
The	O
fiber-optic	O
micro-nodes	O
–	O
which	O
are	O
also	O
referred	O
to	O
as	O
RFoG	B-Device
optical-networking	O
units	O
(	O
R-ONUs	O
)	O
–	O
terminate	O
the	O
fiber	O
connection	O
and	O
convert	O
traffic	O
for	O
delivery	O
over	O
the	O
in-home	O
network	O
.	O
</s>
<s>
The	O
return	O
path	O
for	O
voice	O
,	O
data	O
,	O
and	O
video	O
traffic	O
is	O
over	O
a	O
1310	O
or	O
1590/1610nm	O
wavelength	O
to	O
a	O
return	O
path	O
receiver	O
,	O
which	O
converts	O
the	O
optical	O
signal	O
to	O
RF	O
and	O
feeds	O
it	O
back	O
into	O
the	O
CMTS	B-Device
and	O
video	O
controller	O
.	O
</s>
<s>
Although	O
RFoG	B-Device
is	O
providing	O
a	O
capacity	O
increase	O
,	O
one	O
undesired	O
effect	O
of	O
the	O
system	O
is	O
that	O
more	O
than	O
one	O
R-ONU	O
can	O
have	O
the	O
optical	O
return	O
path	O
activated	O
at	O
the	O
same	O
time	O
and	O
on	O
the	O
same	O
wavelength	O
(	O
for	O
instance	O
,	O
one	O
R-ONU	O
falsely	O
triggered	O
by	O
ingress	O
)	O
;	O
thus	O
,	O
an	O
optical	O
collision	O
may	O
occur	O
(	O
optical	O
beating	O
)	O
.	O
</s>
<s>
This	O
is	O
done	O
in	O
place	O
of	O
the	O
same	O
function	O
traditionally	O
performed	O
back	O
at	O
the	O
higher-level	O
serving	O
area	O
nodes	O
in	O
the	O
HFC	B-Architecture
network	I-Architecture
.	O
</s>
<s>
When	O
the	O
network	O
is	O
upgraded	O
,	O
the	O
RFoG	B-Device
elements	O
can	O
remain	O
in	O
place	O
while	O
the	O
provider	O
rolls	O
out	O
the	O
necessary	O
components	O
(	O
OLTs	O
and	O
ONTs	O
)	O
for	O
a	O
full	O
PON	O
implementation	O
.	O
</s>
<s>
The	O
Society	O
of	O
Cable	O
and	O
Telecommunications	O
Engineers	O
(	O
SCTE	O
)	O
has	O
approved	O
SCTE	O
174	O
2010	O
,	O
the	O
standards	O
for	O
RFoG	B-Device
.	O
</s>
<s>
Many	O
have	O
tried	O
the	O
technology	O
,	O
and	O
some	O
have	O
begun	O
to	O
deploy	O
RFoG	B-Device
.	O
</s>
