All of this
raises the following
question: If this is so hard to measure, how much impact can it really
have in
the real world? Why not back the BER requirement off to 10e-10?
Regards,
Jugnu
I agree with Howard.
It is impractical and expensive to
test for very low BERs - the specs should be such that the power budget
is
capable of achieving BER =1e-15, yet the testing can be some kind of
accelerated BER at lower value that is derived from the curve
interpolation.
However,
the as with any extrapolation of testing results one has to be careful,
so in
this case it will be manufacturers' responsibility to guarantee the
BER=1e-15.
Regards,
Petar Pepeljugoski
IBM Research
P.O.Box 218
(mail)
1101 Kitchawan Road,
Rte. 134 (shipping)
Yorktown Heights,
NY 10598
e-mail: petarp@xxxxxxxxxx
phone: (914)-945-3761
fax: (914)-945-4134
For the 100
Mbps EFM fiber optic links
(100BASE-LX10 and 100BASE-BX10)
we specified
a BER requirement of 1E-12, consistent with the
BER requirement
for gigabit
links. We recognized that this would be
impractical to test in a
production
environment, so we defined a means to extrapolate a
BER of 1E-12
by testing
to a BER of 1E-10 with an additional 1 dB of
attenuation. See
58.3.2 and
58.4.2.
Howard
Frazier
Broadcom
Corporation
From: Roger Merel
[mailto:roger@xxxxxxxxxxx]
Sent: Monday, August 28, 2006 1:54 PM
To: STDS-802-3-HSSG@xxxxxxxxxxxxxxxxx
Subject: Re: [HSSG] BER Objective
David,
Prior to 10G, the BER
standard (for
optical communications) was set at 1E-10 (155M-2.5G). At 10G, the BER
standard was revised to 1E-12. For unamplified links, the difference
between 1E-12 and 1E-15 is only a difference of 1dB in power delivered
to the
PD. However, the larger issue is one of margin and testability (as the
duration required to reliably verify 1E-15 for 10G is impractical as a
factory
test on every unit) especially since we’d want to spec worst case
product
distribution at worst case path loss (cable+connector loss) and at EOL
with
margin. Thus in reality, all products ship at BOL from the factory
with a
BER of 1E-15 and in fact nearly all will continue to deliver 1E-15 for
their
entire life under their actual operating conditions and with their
actual cable
losses.
Thus, if by “design
target”, you mean a worst case-worst case with margin to be assured at
EOL on every factory unit, then this is overkill. I might be willing
to
entertain a 1E-13 BER as this would imply that same number of errors
per second
(on an absolute basis; irrespective of the number of bits being passed;
this
takes the same time in the factory as verifying 1E-12 at 10G although
this is in
fact a real cost burden which adversely product economics); however,
this would
not substantially change the reality of the link budget. It would make
for a sensible policy for the continued future of bit error rate specs
(should
their be future “Still-Higher-Speed” SG’s).
-Roger
From: Martin, David
(CAR:Q840)
Sent: Friday, August 25, 2006 12:22 PM
To: STDS-802-3-HSSG@xxxxxxxxxxxxxxxxx
Subject: BER Objective
During
the discussion on Reach Objectives there didn’t appear to be any
mention
of corresponding BER.
Recall
the comments from the floor during the July meeting CFI, regarding how
10GigE
has been used more as infrastructure rather than as typical end user
NICs. And
that the application expectation for 100GigE would be similar.
Based
on that view, I’d suggest a BER design target of (at least) 1E-15. That
has been the defacto expectation from most carriers since the
introduction of
OC-192 systems.
The
need for strong FEC (e.g., G.709 RS), lighter FEC (e.g., BCH-3), or
none at all
would then depend on various factors, like the optical technology
chosen for
each of the target link lengths.
...Dave
David
W. Martin
Nortel Networks
dwmartin@xxxxxxxxxx
+1 613 765 2901 (esn 395)
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