| Thread Links | Date Links | ||||
|---|---|---|---|---|---|
| Thread Prev | Thread Next | Thread Index | Date Prev | Date Next | Date Index |
|
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) 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 |