Re: Equalization
Fotec is well along in development of a field tester based on
FOTP-204.The prototype will be available soon for evaluation. When it's
ready, we'll be looking for guinea pigs...
Regards, Jim
Gair Brown wrote:
>
> Howard,
>
> I am under the impression that a few of the fiber optic test companies
> are working on these. If any of those folks are following this, perhaps
> they can speak up.
>
> Gair
>
> Howard Frazier wrote:
> >
> > Gair,
> >
> > Where can I buy a handy-dandy RML test unit?
> >
> > Howard Frazier
> > Cisco Systems, Inc.
>
> Gair Brown wrote:
> >
> > Mike,
> >
> > But we can say "Any fibers in the installed base which meet the RML
> > bandwidth spec, will show enhanced system performance when coupled with
> > a transciever that meets the encircled flux spec."
> >
> > A lot of folks will be willing to check out their installed fibers with
> > a handy dandy RML test unit to see what fibers they can upgrade. Folks
> > do twisted pair checks all the time. Much more cost effective than
> > pulling in a new cable.
> >
> > So....
> >
> > Perhaps a compromise for 10G would be to only guarantee performance for
> > "installed base" fibers which meet the RML requirements.
> >
> > Gair
> >
> > "Hackert, Michael J" wrote:
> > >
> > > Jack,
> > >
> > > I think I need to clarify exactly what the TIA FO-2.2.1 results mean especially to the installed base.
> > >
> > > What was concluded at the end of the validation experiment is that if fiber (in particular 62.5 um fiber), which has an enhanced restricted mode launch (RML) bandwidth, is combined with a transceiver, which has a consistently restricted launch as measured by its encircled flux, are combined, improved system performance can be achieved. My issue is with the installed base. Unless the fiber is characterized for its RML bandwidth and shown to have the increased bandwidth, there are no guarantees that the RML bandwidth will increase (although most of the time it will). Since Ethernet is based on worst case, unless the RML bandwidth is tested and shown to increase, the installed base of 62.5 um (50 um) fiber can only be counted on to give the 160 or 200 MHz-km (400 or 500 MHz-km) it was specified against.
> > >
> > > With that said, although I am not an expert on the subject, I can see no reason why equalization will not work. I would bet that in the next five years, equalization or similar electronic enhancements will be implemented for multimode.
> > >
> > > mike
> > >
> > > > ----------
> > > > From: Jack Jewell[SMTP:jljewell@xxxxxxxxxxxxx]
> > > > Sent: Thursday, July 20, 2000 2:01 PM
> > > > To: 'Edward Chang'; Jay Hoge
> > > > Cc: stds-802-3-hssg@xxxxxxxx
> > > > Subject: RE: Equalization
> > > >
> > > >
> > > > Ed/Jay,
> > > >
> > > > We don't have "a lot of time to play around" on "interesting research
> > > > projects."
> > > >
> > > > The TIA FO2.2.1 effort addresses 2 issues in worst case MMF. 1) The
> > > > specification of 75% or more of the light within a 15um radius improves the
> > > > modal bandwidth. 2) The specification of less than 25% within a 5um radius
> > > > limits the effect of defects present in the center of the fiber (much as the
> > > > offset patch cord does for 1310nm where the defects have much more severe
> > > > effects). These 2 conditions improve the modal bandwidth of "worst-case"
> > > > MMF from 160MHz-km to 385MHz-km with a very high degree of confidence. Link
> > > > simulations indicate that a 385MHz-km modal bandwidth fiber will support a
> > > > 850nm serial link with a reach of 65-75 meters. Also, the link simulations
> > > > indicate 10Gig serial transmission can go over 100m when the modal bandwidth
> > > > reaches ~650-700MHz-km (not 800MHz-km as in Ed's email). Thus it only
> > > > requires about 5dB of equalization gain and the TIA-FO2.2.1-specified launch
> > > > to reach 100m over worst-case 62.5um fiber with an 850nm serial link. This
> > > > modest gain is rendered even more reasonable by the fact that the restricted
> > > > launch helps to avoid the fiber-center defects.
> > > >
> > > > The 5dB value was determined via the Pisi column in the link simulator. At
> > > > 100m for a 385MHz-km fiber, the Pisi was less than 5dB in excess of the
> > > > "acceptable" 3.0-3.6dB. Thus improvement of the Pisi by 5dB brings the isi
> > > > back to an acceptable level.
> > > >
> > > > Do we agree on the above as a reasonable means for estimating the
> > > > equalization gain?
> > > >
> > > > Regards,
> > > > Jack
> > > >
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--
Jim Hayes fotec,inc./Fiber U
jeh@xxxxxxxxx 151 mystic ave.
http://www.fotec.com/ medford,ma 02155
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