Re: Wide Area Networking for the Rest of US - the debate on BER and other issues
- To: Rohit Sharma <RSharma@xxxxxxxxxxxxxxxxxxx>
- Subject: Re: Wide Area Networking for the Rest of US - the debate on BER and other issues
- From: "Mike Dudek" <mdudek@xxxxxxxxxxxx>
- Date: Fri, 04 Jun 1999 12:28:11 -0600
- CC: "'stds-802-3-hssg@xxxxxxxx'" <stds-802-3-hssg@xxxxxxxx>
- References: <B123A833D5BDD1119776006008AE250B650911@xxxxxxxxxxxxxxxxxxxxxxxx>
- Sender: owner-stds-802-3-hssg@xxxxxxxxxxxxxxxxxx
I agree that the "knob" may not be very useful. 10e-12 to 10e-10 is actually
approx 1dB difference in optical power in the absence of error floors. The best
use of the "knob" would probably be to allow longer link distances if the error
rate requirement is lower. ie within the committee produce a table of link
length versus error rate for the same Rx and Tx performance. The other option
would be to create multiple categories of Rx/Tx specifications. I don't think
this is a good idea unless cost savings are significant which I don't think they
will be. In this scenario with different Rx/Tx specifications manufacturer's
and users will have to keep the various options separated and ensure that both
ends of a link use the higher grade parts when a low error rate is required.
Rohit Sharma wrote:
> Its hard to see whether such a "knob" would do anything for optical gear
> (Tx, Rx, amps) under operation. I agree with Drew that the most one can
> gain is looser specs on the design end...
> Also, remember that the difference between a 10^-12 and 10^-10 BER is merely
> a few dB at best (in absence of floors) if you look at the 'waterfall' BER
> curves. Once the Tx, Rx, amps are designed (and installed) for a certain
> BER objective, operating them for a worse BER (e.g. reducing the launch
> power at the transmitter) doesn't result in cost savings.... so the "knob"
> is fairly static in any case.
> Optical Networks
> > -----Original Message-----
> > From: Drew Perkins [mailto:drew.perkins@xxxxxxxxxxxx]
> > Sent: Friday, June 04, 1999 10:24 AM
> > To: 'bill.st.arnaud@xxxxxxxxxx'; 'Larry Miller';
> > 'stds-802-3-hssg@xxxxxxxx'
> > Subject: RE: Wide Area Networking for the Rest of US - the
> > debate on BER
> > a nd other issues
> > Bill,
> > I concur completely with your analysis of BER vs. RED.
> > But I still
> > don't believe that a BER "knob" would be very useful to anyone. BER is
> > really a side-effect of controlling something else, so you
> > really can't
> > control BER directly. The other things that could be
> > controlled include:
> > output launch power, loss (distance) between transmitter and receiver,
> > receiver sensitivity, bit rate, and probably a few other
> > things. Some of
> > these things, such as output launch power or receiver sensitivity, are
> > controllable at the time equipment is designed. Thus I don't
> > see these as a
> > "knob" so much as simply a looser spec. Other things, such as loss
> > (distance) between are in the direct control of the end-user, but are
> > fairly static. I don't see these as "knobs" either.
> > How are you defining "knob"? Is it a setting that can be controlled by
> > network management? Is it a design parameter that can be
> > controlled by the
> > equipment designer? The network designer?
> > Drew
> > ---------------------------------------------------------
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