<s>
25	B-Protocol
Gigabit	I-Protocol
Ethernet	I-Protocol
and	O
50	B-Protocol
Gigabit	I-Protocol
Ethernet	I-Protocol
are	O
standards	O
for	O
Ethernet	O
connectivity	O
in	O
a	O
datacenter	B-Operating_System
environment	O
,	O
developed	O
by	O
IEEE	O
802.3	O
task	O
forces	O
and	O
and	O
are	O
available	O
from	O
multiple	O
vendors	O
.	O
</s>
<s>
802.3ba	B-Protocol
and	O
IEEE	O
Std	O
.	O
</s>
<s>
On	O
June	O
30	O
,	O
2016	O
,	O
the	O
IEEE	O
802.3by	B-Protocol
standard	O
was	O
approved	O
by	O
The	O
IEEE-SA	O
Standards	O
Board	O
.	O
</s>
<s>
On	O
April	O
6	O
,	O
2020	O
,	O
25	B-Protocol
Gigabit	I-Protocol
Ethernet	I-Protocol
Consortium	O
has	O
rebranded	O
to	O
Ethernet	B-Protocol
Technology	I-Protocol
Consortium	I-Protocol
,	O
and	O
it	O
announces	O
800	O
Gigabit	O
Ethernet	O
(	O
GbE	O
)	O
specification	O
.	O
</s>
<s>
On	O
June	O
4	O
,	O
2020	O
,	O
the	O
IEEE	O
approved	O
IEEE	O
802.3ca	O
which	O
allows	O
for	O
symmetric	O
or	O
asymmetric	O
operation	O
with	O
downstream	O
speeds	O
of	O
25	O
or	O
50Gbit/s	O
,	O
and	O
upstream	O
speeds	O
of	O
10	O
,	O
25	O
,	O
or	O
50Gbit/s	O
over	O
passive	B-Architecture
optical	I-Architecture
networks	I-Architecture
.	O
</s>
<s>
The	O
IEEE	O
802.3by	B-Protocol
standard	O
uses	O
technology	O
defined	O
for	O
100	B-Protocol
Gigabit	I-Protocol
Ethernet	I-Protocol
implemented	O
as	O
four	O
25-Gbit/s	O
lanes	O
(	O
IEEE	B-Protocol
802.3bj	I-Protocol
)	O
.	O
</s>
<s>
The	O
IEEE	O
802.3by	B-Protocol
standard	O
defines	O
several	O
single-lane	O
variations	O
.	O
</s>
<s>
25GBASE-T	O
,	O
a	O
25-Gbit/s	O
standard	O
over	B-Protocol
twisted	I-Protocol
pair	I-Protocol
,	O
was	O
approved	O
alongside	O
40GBASE-T	O
within	O
IEEE	B-Protocol
802.3bq	I-Protocol
.	O
</s>
<s>
802.3cd	O
also	O
defines	O
an	O
RS-FEC	O
for	O
forward	B-Error_Name
error	I-Error_Name
correction	I-Error_Name
in	O
Clause	O
134	O
which	O
after	O
FEC	B-Error_Name
encoding	O
gives	O
a	O
data	O
rate	O
of	O
53.125Gbit/s	O
.	O
</s>
<s>
It	O
is	O
not	O
possible	O
to	O
transmit	O
53.125Gbit/s	O
over	O
an	O
electrical	O
interface	O
while	O
maintaining	O
suitable	O
signal	O
integrity	O
so	O
four-level	O
pulse-amplitude	B-Device
modulation	I-Device
(	O
PAM4	B-Device
)	O
is	O
used	O
to	O
map	O
pairs	O
of	O
bits	O
into	O
a	O
single	O
symbol	O
.	O
</s>
<s>
PAM4	B-Device
encoding	O
for	O
50G	O
Ethernet	O
is	O
defined	O
in	O
Clause	O
135	O
of	O
the	O
802.3	O
standard	O
.	O
</s>
<s>
Name	O
Standard	O
Status	O
Media	O
Connector	O
TransceiverModule	O
Reachin	O
m	O
#( 	O
⇆	O
)	O
#( 	O
→	O
)	O
#( 	O
→	O
)	O
Notes	O
colspan	O
=	O
"	O
11	O
"	O
(	O
CL135B/C	O
)	O
0.25	O
2	O
N/A	O
2	O
PCBs	O
;	O
Line	B-Protocol
code	I-Protocol
:	O
NRZ	B-Protocol
(	O
no	O
FEC	B-Error_Name
)	O
Line	O
rate	O
:	O
2x	O
25.78125	O
GBd	O
=	O
51.5625	O
GBd	O
(	O
CL135D/E	O
)	O
0.25	O
2	O
N/A	O
2	O
PCBs	O
;	O
Line	B-Protocol
code	I-Protocol
:	O
NRZ	B-Protocol
(	O
FEC	B-Error_Name
encoded	O
)	O
Line	O
rate	O
:	O
2x	O
26.5625	O
GBd	O
=	O
53.1250	O
GBd	O
(	O
CL135F/G	O
)	O
0.25	O
1	O
N/A	O
1	O
PCBs	O
(	O
CL133/137	O
)	O
1	O
1	O
N/A	O
1	O
PCBs	O
;	O
total	O
channel	O
insertion	O
loss	O
≤	O
30	O
dB	O
at	O
half	O
sampling	O
rate	O
=	O
13.28125	O
GHz	O
(	O
Nyquist	O
)	O
.	O
</s>
<s>
,	O
25	B-Protocol
Gigabit	I-Protocol
Ethernet	I-Protocol
equipment	O
is	O
available	O
on	O
the	O
market	O
using	O
the	O
SFP28	B-Protocol
and	O
QSFP28	B-Protocol
transceiver	O
form	O
factors	O
.	O
</s>
<s>
Direct	O
attach	O
SFP28-to-SFP28	O
copper	O
cables	O
in	O
1-	O
,	O
2-	O
,	O
3	O
-	O
and	O
5-meter	O
lengths	O
are	O
available	O
from	O
several	O
manufacturers	O
,	O
and	O
optical	O
transceiver	O
manufacturers	O
have	O
announced	O
1310nm	O
"	O
LR	O
"	O
optics	O
intended	O
for	O
reach	O
distances	O
of	O
2	O
to	O
10km	O
over	O
two	O
strands	O
of	O
standard	O
singlemode	B-Device
fiber	I-Device
,	O
similar	O
to	O
existing	O
10GBASE-LR	O
optics	O
,	O
as	O
well	O
as	O
850nm	O
"	O
SR	O
"	O
optics	O
intended	O
for	O
short	O
reach	O
distances	O
of	O
100m	O
over	O
two	O
strands	O
of	O
OM4	B-Device
multimode	B-Device
fiber	I-Device
,	O
similar	O
to	O
existing	O
10GBASE-SR	O
optics	O
.	O
</s>
