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RE: IEEE 802.3 Requirements


I agree with your statement completely.  If we decide to support the entire
installed base of MM fiber, we will need to either "over-engineer" the PHY to
work almost all the time, find simple way to qualify the link, or establish some
sort of auto-negotiation so the link comes up at 1 Gbps if the fiber cannot
support 10 Gbps.

We cannot rely on trial and error.  If DMD raises its hoary head again,
customers will balk at early adoption.

Bruce Tolley
Manager, Business Development
3Com Corp
voice: 408-326-5950
internet: bruce_tolley@xxxxxxxx

"Michael M. Salzman" <msalzman@xxxxxxx> on 05/19/99 02:31:46 AM

Please respond to msalzman@xxxxxxxxxx

Sent by:  "Michael M. Salzman" <msalzman@xxxxxxx>

To:   stds-802-3-hssg@xxxxxxxxxxxxxxxxxx
cc:    (Bruce Tolley/HQ/3Com)
Subject:  RE: IEEE 802.3 Requirements

Hi Bruce, Ed, et al,

My experience is that on average no installer tests fiber for any thing
other than connectivity.  To imagine that these fellows will carefully
follow some timeconsuming and deliberate procedure to check out the cable is
wishful thinking.  You are right that DMD is an innate 'feature' of most
installed base fibers.  The ethernet community only recently discovered its
ubiquity and impact.  Nevertheless we can expect the vast unwashed masses to
blithely ignore any special handling and testing requirements untill their
installation fails to come up and then they will search for causes.

In the case of 10 Gig, due to its novelty and likely expense, I think we can
lay down new standards for fiber to support it, and customers would go along
with the concept.  For those stubborn souls who insist on deploying the
technology on existing fiber, I think the 10GEA can develop recommended test
procedures and recommended equipment sets, and perhaps work with BICSI to
develop a "gigabit technician" certification program.   If we do not address
this prosaic aspect of our industry we are doomed to seeing more trial and
error installations.


> -----Original Message-----
> From: owner-stds-802-3-hssg@xxxxxxxxxxxxxxxxxx
>  Behalf Of Chang,
> Edward S
> Sent: Monday, May 17, 1999 06:36
> To: Bruce_Tolley@xxxxxxxx; Chang, Edward S
> Cc: Thomas Dineen; stds-802-3-hssg@xxxxxxxxxxxxxxxxxx
> Subject: RE: IEEE 802.3 Requirements
> Bruce:
> The 62.5 um fibers have been used for over 15 or 20 years.
> However, we just
> started paying attention to the DMD fibers two years ago.  Because of the
> small DMD population, industry did not paying attention to it.
> In fact, the
> DMD fibers have been with us since the graded index fibers were
> introduced.
> DMD fibers are defected parts like any other products having
> defected parts.
> In the past, the MM fibers, particularly 62.5 fibers, were only used with
> LED sources over-filing the fibers, which is hardly capable of creating a
> DMD results except low bandwidth.  It was until GbE requiring laser over
> 62.5 um fiber, the DMD has not been identified as a detrimental
> problem.
> The fiber vendors do not characterize "DMD" as one of the parameters in
> their commercial specification due to its very small, negligible
> population.
> As a result, no one really pays attention to verify it, unless an
> experienced engineer is purposely looking for DMD fibers.  Some time, just
> to identify DMD fibers from the waveforms is not a simple job.
> Ed Chang
> Unisys Corporation
> Edward.Chang@xxxxxxxxxx
> ----Original Message-----
> From: Bruce_Tolley@xxxxxxxx [mailto:Bruce_Tolley@xxxxxxxx]
> Sent: Friday, May 14, 1999 5:29 PM
> To: Chang, Edward S
> Cc: Thomas Dineen; stds-802-3-hssg@xxxxxxxxxxxxxxxxxx
> Subject: RE: IEEE 802.3 Requirements
> Ed:
> As far as I know, hardly any "DMD fibers" have been identified to date.
> Bruce