RE: 8b/10b and EMI
I believe so. The 1000Base-CX is a copper cable which always gave me
unpleasant feeling. Very often, we have to test several times with
improvement to pass EMI certification.
The shield of a copper cable is not perfect, which is serving attenuation,
but not stopping leaking. Therefore, I agree, if one has high back ground
noise level, the additional 6 dB can give you trouble.
I would stay on fiber cable products.
Edward S. Chang
NetWorth Technologies, Inc.
[mailto:owner-stds-802-3-hssg@xxxxxxxx]On Behalf Of DOVE,DANIEL J
Sent: Friday, March 17, 2000 12:48 PM
Subject: RE: 8b/10b and EMI
> From: Edward Chang [mailto:edward.chang@xxxxxxxxxxxxxxxx]
> Tom, Rick and all:
> So far, in the real industry-wide installations, no one has
> the 8B/10B IDLE
> EMI problem. Furthermore, no one has proved that 8B/10B
> IDLE signals will
> cause EMI problem for 10 GbE in an enclosed environment.
Actually, I believe that there were some significant problems
getting 1000BASE-CX to meet FCC requirements and the first FC
optics also had trouble. Spreading the spectrum helps a lot.
I did some analysis for Gig E where I looked at the peak spectral
components of the IDLE sequence as opposed to a random stream and
the 1.25GHz component was substantially higher for IDLE than for
random data. I believe it was 6-8dB higher.