My point was that the APL should try to be broader
than an nx10G sublayer (at least architecturally) because there are applications
that could take advantage of higher speed links, especially over time. Try to
get more mileage out of the sublayer.
I wasn't proposing that 802.3 get involved in
any WAN links - it was just an example of how economics skew in
All that you say about dispersion is true but 25G
dispersion would be 2.5 times better than 40G. Beauty is in the eye of the
----- Original Message -----
Sent: Wednesday, August 09, 2006 7:56
Subject: Re: [HSSG] Topics for
I agree that there is a cost to consuming wavelengths,
and they should be used wisely. But a system that has been engineered to
support 10G rates cannot necessarily step up to higher speeds, even if
optically compatible with the existing DWDM grid and power levels. The
SM fiber's dispersion limited distance drops as the square of the bit rate.
For example, for externally modulated sources, if the dispersion limited
distance is 60 km at 10Gb/s, then at 25 Gb/s it will be less than 10km.
So channels that exceed this distance would need to be dispersion
compensated. Were you thinking that the higher rates would be used
only on shorter channels, or were you thinking of dispersion
compensation technologies as work-arounds? If the former, then consider
how it impacts the objectives. If the latter, it opens up a whole set of
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|Re: [HSSG] Topics for
I would expand on the statement:
"Carrier want to leverage their
existing DWDM layer which mean
baudrate in the 9.95-12.5 Gig".
are two layers at which compatibility with existing DWDM systems can
achieved: the electrical layer (which this statement implies) and
photonic layer. Compatibility at the photonic layer means
with existing DWDM wavelengths, optical filters, power
leveling, etc. on
the same fiber. Is is likely that 25G (+7% FEC) NRZ
optical signals are
compatible with many existing 10G NRZ DWDM systems.
There is a premium to
using many wavelengths in these systems and a 4x25G
channel might well be
cheaper and more wavelength efficient (as measured by
Such details are probably beyond the
scope of the SG but I think it is
important to architect below the MAC to
allow link speeds faster than 10G
within the APL which make sense in
certain markets and will become more
economic and widespread over
> I have listed dilemma we
> - Implementing 100 Gig in the near term means
> - Implementing 100Gig in few years the right answer might be
> - Carrier want to leverage their existing DWDM layer which
> baudrate in the 9.95-12.5 Gig - If LAG implemented why not allow
n to be 4?
> - Operation with different width
> - Backward
compatibility XAUI, LX4 ?
> - Greatest bandwidth demands (100+Gig) are
on VSR links <50 m but
> the longer reach >10Km may be able to
live with 4x10Gig.
> All these means we should either define
some sort of scalable
> architecture or just define LAG method and do
not define any PMDs!
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