CDRs will be used as glue within boxes
•
There is no economic justification for redesigning these modules
and
ICs, especially the several
-
times
-
respun
CDR chips within, for the low
volumes of HSE in the first few years
–
Should share volume with 10GE
•
Some link types will have multiple 10G modules at one end
•
Therefore the 10G signals must be at the 10G line rate, and have
the
characteristics of a 10GBASE
-
R signal (statistically balanced etc)
–
Will pass correctly through a XFP or SFP+ module
•
Therefore the FEC must be in band
–
e.g. KR FEC ~1dB gain, to 7% FEC for ~3dBo gain
–
Payload might be ~9.3 G
"bit"
/s/lane for 10G lanes
•
Compare WAN PHY rate: 9.58464*64/66 ~9.2942 G"b"/s
–
What's a "
bit
": these payload numbers are somewhat squishy because
there is non
-
information (idles, preamble, FCS,...) in an Ethernet stream,
that could be removed if wished
•
25G line rate should be exactly 10 / 4 * 10.3125 GBd
–
Allowing simple 10:4 gearbox
•
Use gapped clock concept to keep the MAC speed at 100G or 40G, a
s
for lane markers
–
Some idles can be removed using an RS Deficit Idle Count