RE: Equalization
Edward:
I agree with you that it is important to analyze the
cause and nature of DMD. It would still be very useful to
make some time domain waveforms which demonstrate
this effect available to this group. It will be interesting
to see what portion of this effect is deterministic and hence
corrected using some signal processing. As long as this effect
is deterministic the fact that DMD is completely different from
one fibre to the next only means that it requires adaptive signal
processing to combat it.
best regards,
Kishore
> -----Original Message-----
> From: owner-stds-802-3-hssg@xxxxxxxx
> [mailto:owner-stds-802-3-hssg@xxxxxxxx]On Behalf Of Edward Chang
> Sent: Friday, July 21, 2000 7:57 AM
> To: Kishore Kota; Jonathan Thatcher; vipul.bhatt@xxxxxxxxxxx; HSSG
> Cc: Vivek Telang
> Subject: RE: Equalization
>
>
>
> Kishore:
>
> The debate on the screen is not the theory or validity of equalization
> technique, which has been proved on the copper of known media application.
>
> The debate here is the fiber frequency response characteristics with
> complicated DMD factor. The DMD characteristics of the fiber is not
> determined yet.
>
> As ordinary approaches, we should define the problem (fiber bandwidth
> related to DMD) first, then we can chose the tools. There are
> many variety
> of tools available.
>
> The eye pattern ISI, or amplitude reduction is not frequency response at
> all. For a linear BW media, copper, the frequency response is
> defined, and
> given by vendor. You can design an equalizer without any test all. Fiber
> is quite different.
>
>
> Regards,
>
> Edward S. Chang
> NetWorth Technologies, Inc.
> EChang@xxxxxxxxxxxxxxxx
> Tel: (610)292-2870
> Fax: (610)292-2872
>
>
> -----Original Message-----
> From: owner-stds-802-3-hssg@xxxxxxxx
> [mailto:owner-stds-802-3-hssg@xxxxxxxx]On Behalf Of Kishore Kota
> Sent: Friday, July 21, 2000 12:10 AM
> To: Jonathan Thatcher; vipul.bhatt@xxxxxxxxxxx; HSSG
> Cc: Vivek Telang
> Subject: RE: Equalization
>
>
>
>
> Jonathan,
>
> If you are interested in the potential for signal processing techniques
> to mitigate the interference effects in optical links, it will be very
> useful for this group to collect some data. Specifically, if this group
> would collect receiver sample data at atleast 2X (preferably 4X)
> the baud rate, it would facilitate a lot of analysis. A number of signal
> processing people who have been monitoring this group (including yours
> truly) would be willing to calculate the potential benefit of any
> equalization techniques and present the data on this reflector and at
> the next meeting.
>
> Since I have seen numerous eye diagrams presented to this
> group, it should be possible to use the same lab setup and
> a digitizing oscilloscope to collect this data. For this data to
> be useful,
> the transmitted bits should be random and at least a few thousand baud
> intervals of samples to allow extraction of the necessary parameters. The
> sampling could be completely asynchronous as long as the sample rate is at
> least twice the baudrate. Given this data, it is relatively
> straightforward
> for those in the signal processing field to calculate the effectiveness of
> equalization techniques. Numerous techniques are available to
> combat linear
> and certain types of non-linear deterministic effects. The random effects,
> if any, would take more work (and more data).
>
> Any volunteers?
>
> -Kishore
>
> ______________________________
>
> Kishore Kota
> Cicada Semiconductor Inc.
> 811 Barton Springs Road, Suite 550
> Austin, Texas 78704
>
> 512-327-3500 x104 voice
> 512-327-3550 fax
> kkota@xxxxxxxxxxxxxxx
> http://www.cicada-semi.com
> ______________________________
>
>
>
> > -----Original Message-----
> > From: owner-stds-802-3-hssg@xxxxxxxx
> > [mailto:owner-stds-802-3-hssg@xxxxxxxx]On Behalf Of Jonathan Thatcher
> > Sent: Thursday, July 20, 2000 7:51 PM
> > To: 'vipul.bhatt@xxxxxxxxxxx'; HSSG
> > Subject: RE: Equalization
> >
> >
> >
> > Vipul,
> >
> > Not a punishment, just something I've been noodling over and
> > wasn't sure if
> > we were ready to ask.
> >
> > Specifically, I have been curious about the potential for the
> DMD response
> > (assumes no launch control) to be non-deterministic. In short,
> > what happens
> > to that thing we used to call "modal noise" in a DMD-sensitive system?
> >
> > It seems likely that a simple experiment could be created if one
> > had a BERT,
> > Scope, LX transceiver, and a spool of the "bad DMD fiber" to see if the
> > general shape of the pulse into the Rx would change under
> various types of
> > "abuse." I'm not talking about dynamic changes like wrapping it around a
> > mandrel or anything that would not be "typical" in an installed
> > infrastructure. Just fiber blowing in the wind, the temperature
> of the Tx
> > changing... stuff like that.
> >
> > Now, you could argue that these types of things would be "random"
> > in nature.
> > Even so, if the response of the system to these changes is significantly
> > non-linear, then the effect could end up unmanageable. I hope otherwise.
> >
> > jonathan
> >
>
>