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RE: Question regarding Min/Max consecutive bit strings


For LX4 (the WWDM LAN Phy), the longest run is 5.
For any of the xR Phys (the serial LAN Phys), the longest run is 66 though
that run has a very low probability (very low = it would happen about once
in 3800 years which). This is because the payload of the 66 bit is scrambled
but there will always be a transition at the sync header of the block.

For any of the WAN Phys, the whole Sonet frame payload is scrambled.
Therefore, the only guaranteed transitions are in the A1/A2s at the start of
the Sonet frame. I suspect that if one examined the Sonet scrambling
polynomial output, one would find out that there is no positioning of it
that would cancel out all the sync header transitions. However, the primary
limiting factor on runs in that environment is probably statistical. Very
long runs are possible but with infinitesimal probability.


-----Original Message-----
From: Gerry Pepenella [mailto:gjp@xxxxxxxxxx]
Sent: Monday, December 11, 2000 6:34 AM
To: HSSG (E-mail)
Subject: Question regarding Min/Max consecutive bit strings

Please forgive what is probably a simple question, but with all of the
various operating modes, scrambling patterns, FEC codes and test patterns,
does someone have a definitive view of how many consecutive 1s or 0s can be
seen on the fiber?

Thanks for the help,
Gerry Pepenella