<s>
NG-PON2	B-Protocol
(	O
also	O
known	O
as	O
TWDM-PON	O
)	O
,	O
Next-Generation	O
Passive	B-Architecture
Optical	I-Architecture
Network	I-Architecture
2	O
is	O
a	O
2015	O
telecommunications	O
network	O
standard	O
for	O
a	O
passive	B-Architecture
optical	I-Architecture
network	I-Architecture
(	O
PON	O
)	O
.	O
</s>
<s>
A	O
passive	B-Architecture
optical	I-Architecture
network	I-Architecture
is	O
a	O
last	O
mile	O
,	O
fibre-to-the-x	B-Architecture
telecommunications	O
network	O
that	O
broadcasts	O
data	O
through	O
fibre	O
optic	O
cables	O
.	O
</s>
<s>
NG-PON2	B-Protocol
is	O
compatible	O
with	O
existing	O
PON	O
fibre	O
by	O
replacing	O
optical	O
line	O
terminal	O
(	O
OLT	O
)	O
at	O
the	O
central	O
office	O
,	O
and	O
the	O
optical	O
network	O
unit	O
(	O
ONU	O
)	O
near	O
each	O
end-user	O
.	O
</s>
<s>
From	O
2019	O
until	O
2021	O
a	O
series	O
of	O
new	O
Recommendations	O
under	O
the	O
header	O
Higher	O
Speed	O
PON	O
(	O
G.9804	O
series	O
)	O
was	O
released	O
intended	O
as	O
successors	O
to	O
NG-PON2	B-Protocol
.	O
</s>
<s>
The	O
architecture	O
calls	O
for	O
time	O
-	O
and	O
wavelength-division	B-Architecture
multiplexing	I-Architecture
(	O
TWDM	O
)	O
in	O
the	O
upstream	O
and	O
downstream	O
directions	O
.	O
</s>
<s>
Wavelength-division	B-Architecture
multiplexing	I-Architecture
is	O
provided	O
in	O
the	O
downstream	O
direction	O
by	O
combining	O
light	O
from	O
four	O
fixed	O
wavelength	O
OLT	O
lasers	O
with	O
a	O
wavelength	O
mux	O
.	O
</s>
<s>
Time-division	B-Protocol
multiplexing	I-Protocol
is	O
provided	O
in	O
the	O
upstream	O
direction	O
through	O
the	O
use	O
of	O
burst	O
lasers	O
at	O
each	O
ONU	O
.	O
</s>
<s>
Each	O
upstream/downstream	O
wavelength	O
is	O
capable	O
of	O
providing	O
up	O
to	O
10	O
Gbit/s	O
symmetric	O
bandwidth	O
to	O
each	O
subscriber	O
if	O
the	O
channel	O
is	O
not	O
time-division	B-Protocol
multiplexed	O
between	O
several	O
ONUs	O
.	O
</s>
<s>
With	O
wavelength-division	B-Architecture
multiplexing	I-Architecture
on	O
four	O
available	O
wavelengths	O
,	O
NG-PON2	B-Protocol
can	O
provide	O
up	O
to	O
40	O
Gbit/s	O
throughput	O
to	O
the	O
entire	O
optical	O
network	O
.	O
</s>
<s>
NG-PON2	B-Protocol
was	O
designed	O
to	O
include	O
backwards-compatibility	O
,	O
or	O
coexistence	O
,	O
with	O
previous	O
architectures	O
to	O
ease	O
deployment	O
into	O
existing	O
optical	O
distribution	O
networks	O
.	O
</s>
<s>
Wavelengths	O
were	O
specifically	O
chosen	O
to	O
avoid	O
interference	O
with	O
GPON	B-Architecture
,	O
10G-PON	B-Protocol
,	O
RF	B-Device
Video	I-Device
,	O
and	O
OTDR	O
measurements	O
.	O
</s>
<s>
Additionally	O
,	O
a	O
mux/demux	O
used	O
to	O
combine	O
and	O
separate	O
the	O
NG-PON2	B-Protocol
wavelength	O
channels	O
at	O
the	O
OLT	O
can	O
be	O
designed	O
with	O
a	O
coexistence	O
element	O
to	O
isolate	O
legacy	O
wavelengths	O
.	O
</s>
