RE: [SI-LIST] : FCAL DB9 cable shield

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From: Knighten, Jim L (JK100005@exchange.SanDiegoCA.NCR.COM)
Date: Tue Nov 16 1999 - 17:40:52 PST


Contrary to popular opinion, fiber optics is not inherently EMI, ESD and RFI
proof. This is one of the modern myths of technology.

While it is true that optical fibers do not emit EM radiation, the
electronics that drive these modern high speed optical links are usually
particularly noisy. The fiber optic connector is often a vehicle for this
noise to get out. This is one of the major EMI compliance issues for
systems that use fiber optic links.

Part of the problem is that fiber optic circuits and connectors are
sometimes designed in a careless manner because people have bought in to the
myth.

Jim
________________________________________________________
Dr. Jim Knighten e-mail: Jim.Knighten@SanDiegoCA.NCR.com
<mailto:Jim.Knighten@SanDiego.NCR.com>
Senior Consulting Engineer
NCR
17095 Via del Campo
San Diego, CA 92127 http://www.ncr.com <http://www.ncr.com>
Tel: 858-485-2537
Fax: 858-485-3788

***** Notice the Area Code change from 619 *****

                -----Original Message-----
                From: Farrokh Mottahedin
[mailto:Farrokh.Mottahedin@quantum.com]
                Sent: Tuesday, November 16, 1999 5:06 PM
                To: 'si-list@silab.eng.sun.com'
                Subject: RE: [SI-LIST] : FCAL DB9 cable shield

                Copper media is generally used for "inside-the-box" and
other applications
                much shorter than 30 meters. For box-to-box and longer
distances, fiber
                optic media is used which is inherently EMI,ESD, and RFI
proof.

                Farrokh Mottahedin

                Quantum Corp.
                500 McCarthy Blvd.
                Milpitas, CA 95035

                -----Original Message-----
                From: Tom gandy [mailto:tgandy@ind-catalyst.com]
                Sent: Tuesday, November 16, 1999 3:21 PM
                To: si-list@silab.eng.sun.com
                Subject: RE: [SI-LIST] : FCAL DB9 cable shield

                Wouldn't this cause nasty galvanic currents through the
shield if the two
                pieces of equipment, attached by the cable with the DB9s,
were, say, on two
                different phases of a three phase power feed to a building.

                Am I missing something?

                thanks

                Tom Gandy
                Industrial Catalyst

>Fibre Channel DB9 Cables from Amphenol and W.L. Gore (with
and without
>built-in equalizer) short the shield to the plug housing on
both ends.
>
>
>Farrokh Mottahedin
>
>Quantum Corp.
>500 McCarthy Blvd.
>Milpitas, CA 95035
>

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