Hi Everyone,
I apologize
for the late input on this thread, but I feel it is important to
highlight that linear and limiting are not the only options here. A
retimed interface has already proven its ability to meet multiple
distance objectives (including 300m over OM3), along with having
numerous other benefits including having the highest margin of all
three interfaces as shown in latchman_01_0108.pdf.
I think that
we should avoid dictating specific implementations, and strive for
architectural flexibility when writing this standard. The 10GbE
standard did a reasonably good job at this since numerous architectures
have evolved over time while maintaining overall standards compliance.
It is however important to establish overall market needs to ensure
that the standard appropriately satisfies them.
Best Regards,
Ryan
Jonathan
I suggest you compare the PHY price premium for linear and limiting
SFP+.
No one is proposing LRM like linear interface, we have proposed SLI
"simple
linear interface". Every 8 Gig FC port which supports copper cables
will have
a 3 tap DFE, since most SerDes must have at least 1 tap DFE to
compensate for
8" of FR4 after the limited receiver going to a 3 tap DFE has not been
a burden.
I agree low cost is archived by using a known low cost technology, but
lowest cost is
achieved only if your are open minded and you explore the possibilities
not limit yourself
to the 20 years interface concept. 1000Base-T is a clear vivid example
how complex
DSP was successfully applied to solve a very complex problem, currently
at equal power
to the optics but with significantly lower cost than optics.
Thanks,
Ali
Jonathan King wrote:
Sure, adding
dollars and watts to the link can buy margin, but highest margin does
not equate to lowest cost or best suitability for high volume adoption,
(otherwise wouldn't we be using trans-oceanic terminal equipment for SR
apps. ?)
lowest cost
is achieved by choosing known low cost technologies to meet 90+% of the
application market and ensuring any application spec doesn't try to
squeeze the technology to its limits.
Jonathan King
Finisar Corp
1389 Moffet Park Drive
Sunnyvale,
CA 94089
ph: 1 408 400 1057
cell: 1 408 368
3071
e-mail:
jonathan.king@finisar.com
cube C127
-----Original
Message-----
From: Brad Booth [mailto:bbooth@AMCC.COM]
Sent: Tuesday, March
25, 2008 7:28 AM
To:
STDS-802-3-HSSG@LISTSERV.IEEE.ORG
Subject: Re: [802.3BA]
Longer OM3 Reach Objective
That's
definitely one way it can be interpreted. There is some apples and
oranges comparison going on there, and I'm not sure how the VG got
added to the 802.3 mix. ;-)
But with
optics, I would agree that the tougher choices haven't always been
made, even when the writing was on the wall. The biggest complaint
with 10GbE was all the possible port types (thank you WAN interface
sublayer). The 10GBASE-SR PHY is doing well in the market though, and
that's partially due to the fact that it is the only 850nm wavelength
PHY for that space. Interestingly enough though, implementations can
be achieved with either linear or limiting components. And, if you put
a linear at one end and a limiting at the other, they will
communicate.
That's what
I do like about Ali's proposal. He has shown that it is possible to do
300m of MMF with an linear approach. That indicates to the task force
there is more margin in a linear approach than in a limiting approach;
therefore, having more margin to play with, the linear approach with a
100m MMF reach should be able to become the lowest cost solution for
the largest volume of the MMF market. That's a huge benefit. Rather
than trying to pushing the limits and slowing the adoption curve, there
is an implementation option which should make 100G MMF up to 100m a
fiscally viable option.
Thanks,
Brad