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RE: Equalization


A multimode fiber carries numerous modes, or solutions to Maxwell's
Equations, if you will. Modes of a multimode fiber couple energy
among each other due to a variety of factors, including temperature
and vibrations affecting the alignment of interconnections and
transmit assembly. Also, the output of a laser can exhibit changes
in the energy distribution of its modes. It stands to reason that
the problem will be less severe if you restrict the launch to a
small subgroup of modes. If I understood Gair correctly, he was
pointing out that techniques like Encircled Flux launch reduce this
time-variance sufficiently to allow us to approximate the impulse
response as time-invariant. I haven't seen the evidence, but it
seems reasonable, so I accept his point.



> -----Original Message-----
> From: owner-stds-802-3-hssg@xxxxxxxx
> [mailto:owner-stds-802-3-hssg@xxxxxxxx]On Behalf Of Larry Rennie
> Sent: Friday, July 21, 2000 2:02 PM
> To: Gair Brown; Edward Chang
> Cc: HSSG
> Subject: Re: Equalization
> I am also a bit confused regarding the time variance of the fiber
> characteristics.  What is their about the fiber that makes the
> chracteristics time variant?  Vipul, you too had an
> e-mail that said the
> fiber was time-variant.
> Regards,
> Larry Rennie
> ----- Original Message -----
> From: Gair Brown <gdbrown@xxxxxxxxxxxxx>
> To: Edward Chang <edward.chang@xxxxxxxxxxxxxxxx>
> Cc: HSSG <stds-802-3-hssg@xxxxxxxx>
> Sent: Friday, July 21, 2000 1:56 PM
> Subject: Re: Equalization
> >
> > Ed,
> >
> > You need to talk to some of the participants of the
> FO-2.2.1 round
> > robins.  I suspect that some of the participants do
> have data that
> > contains phase information.
> >
> > On a different note.  I believe that the fiber response
> is relatively
> > invariant with respect to time.  There is variation
> between different
> > fibers, but for fibers selected using the RML
> requirements the variation
> > should be manageable.
> >
> > Gair
> >
> >