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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