[EFM] Split Ratios
It is eaiser to manufacture a 1x8, 1x16, 1x32 etc because every split in the
tree is an even split. (i.e. 50/50). If we had to make a 1x10, then some
of the splits would have to be uneven i.e. 60/40 or 70/30. While this is
possible and there are 1x10 and 1x12 splitters available they are non
standard.
Ketan Gadkari
Alloptic Inc.
-----Original Message-----
From: mike.obrien@xxxxxxxxxxxx [mailto:mike.obrien@xxxxxxxxxxxx]
Sent: Thursday, July 19, 2001 10:24 AM
To: david.m.horne@xxxxxxxxx
Cc: stds-802-3-efm@ieee.org
Subject: RE: [EFM] RE: EPON TDMA
Hi David,
The split ratio's are powers of two because the splitters are made
by cascading 1x2 (actually 2x2) splitters.
-----Original Message-----
From: Horne, David M [mailto:david.m.horne@xxxxxxxxx]
Sent: Wednesday, July 18, 2001 9:03 PM
To: 'Roy Bynum'; glen.kramer@xxxxxxxxxxxx
Cc: stds-802-3-efm@ieee.org
Subject: RE: [EFM] RE: EPON TDMA
Where did the often-cited split ratios of 16 and 32 come from, anyway? It
seems an argument can be made for holding off on finalizing the split ratio
choice until the TDMA scheme is better defined and quantified. That way, it
can be better matched (disaggregated and reaggregated) to Ethernet pipes on
the ends of the EFM segment, and be easier to hand off to multiple service
providers in a PoP. End-to-end Ethernet is the goal, after all.
For example, a split ratio of 8 may be a better match for 100Mbps dedicated
(logical) connections, once the actual TDMA overhead and guard bands are
known. Compared to 16:1, the cost of the extra feeder fiber (cost of 2
fibers split across 16 subs rather than 1 fiber split across 16) may be
offset by the more compatible handoff logistics. For long drop fibers, with
two 8:1's, the drops will be relatively shorter than a single 16-way split
to the same endpoints. This may even offset the extra feeder fiber. But,
there's no reason to stick with powers of 8 (that I can think of off hand)
unless they make something easier. Maybe 10 or 12 or... are attractive after
more details are agreed to.