Re: 10 Gigabit EMI
Jonathan,
You have brought up an interesting observation that I have made about the
10Gb telephony vendor's "boxes". They tend to put the copper electronics as
close to the backplane as possible, including the optical transceiver. A
very short patch cable is then brought to the front of the "box" and through
an angle aperture. All of this is covered with fully enclosed metal case
that also doubles as heat a heat sink. This may be major overkill for
10GbE, but it shows how serious the existing 10Gb vendors take what you have
expressed as a concern. As such, this would tend to validate your statement
and question:
"Up to Gig E, we have had the luxury (admittedly, with a fair amount of
pain)
of having a "convenience based, user friendly" box design. With 10 Gig,
have
we finally hit the wall?"
Thank you,
Roy Bynum
----- Original Message -----
From: Jonathan Thatcher <Jonathan.Thatcher@xxxxxxxxxxxxxxxxxxxx>
To: 'HSSG_reflector' <stds-802-3-hssg@xxxxxxxx>
Sent: Wednesday, March 15, 2000 2:59 PM
Subject: 10 Gigabit EMI
> In the world of EMI, my personal experience is that the problems are a
> combination of religion, black magic, and some practical experience (with
a
> little knowledge of Maxwell's equations thrown in). Historically, it has
> been very difficult to get "experts" to step up to the plate because
> invariably there are problems in the actual implementations that the
> "experts" simply can't explain. This is not a dig on the experts, just a
> point on the extreme difficulty of the problem.
>
> It is my opinion that the coding will be an important, but second order
> effect. My opinion is that the rise times are a second order effect. My
> opinion is that the actual bit rate is a second order effect. I know, I
> know. You can bring me Maxwell's equations and show me the math that
> demonstrate the direct relationship between these parameters and the
> emissions.
>
> But, in the end, it is the holes is the system that matter!!! It is the
> little antennas built into the boxes. It is the phase array of optical
> transceivers.
>
> Most transceiver companies will claim that the majority of the noise that
> radiates from the nose of the optical transceiver is generated inside the
> system, not inside the transceiver. The new "small form factor"
> transceivers, with ~1/2 the aperture size of the SC, are not inherently
> going to solve the EMI problem at 10 Gig.
>
> In short, from an implementation perspective, we have a very fundamental
> problem: the way we design systems today as racks of modules with arrays
of
> optical transceivers poking out through the EMI enclosure may simply not
> hack it.
>
> Up to Gig E, we have had the luxury (admittedly, with a fair amount of
pain)
> of having a "convenience based, user friendly" box design. With 10 Gig,
have
> we finally hit the wall?
>
> jonathan
>
> Jonathan Thatcher
> Chair, IEEE 802.3ae (10 Gigabit Ethernet)
> Director of Engineering, World Wide Packets
> PO BOX 141719, Suite B; 12720 E. Nora, Spokane, WA 99214
> 509-242-9000 X228; Fax 509-242-9001; jonathan@xxxxxxxxxxxxxxxxxxxx
>