AW: AW: 1550nm Serial PMD Question
Hi,
The jitter has nothing to do with optical muxing. You can always use a bad
electrical signal in WDM environment, however to really doing some more than
only point to point links the Ethernet (the "electrical" part as jitter and
clock tolerance) have also take into account that you are may need to
regenerate and for this this spec is not suited. Here it should be noted
that for our experience the CDR modules for Ethernet clock tolerance of
+/-100ppm are currently not less expensive but generate higher cost than the
SONET specified version. So in this respect the Ethernet is of more
expensive nature and I do not understand your point for the "low cost
Ethernet".
The second aspect are the optical parameters. The Ethernet is currently
specified in a way that no easy verification if an receive signal is in spec
is possible. Something like this is not in line with the goal for ensuring
interworking and low operation cost and in the past the operators have
insisted on simple operation as operation cost is the main part of their
expenses. So in this respect the 10GE interface spec as currently written
will be a cost driver. In addition there is one small issue with
availability of components as if you look around the market you find no
single transponder supporting the specs as written in the current draft (At
least I searched around and did not find a single unit fulfilling that
parameter set). There are of course a lot of marketing slides around in the
world but on verifiable technical details there is a big gap . (May be
fulfilling more demanding specs will lower cost but normally it is just the
other way around.) This is valid already for the current spec.
For WDM interworking something in addition is needed. You where mentioning
the ITU grid. So at least what you need is a transmitter wavelength as
specified in the
If you want to connect the interface as currently specked connected to a
WDM system you are limited to the power budget Including mux and demux as
given by the interface. In this case you have to note that there will be a
penalty in addition due to Xtalk at the de- mux. This penalty however is
difficult to be considered as the power specifications in 10 GE are not
precisely given. This situation will be worse in case of optical amplifiers
which are normally required and used in WDM. In case of this the optical
specs have to be amended anyway as the current specification will lead to
unknown optical performance when using optical amplification. If an optical
spec that would allow WDM interworking would be developed it will not be
different from a similar SDH spec in this respect.
It should be noted that the only transversal compatible WDM spec is
currently in G.959.1 while everything else on WDM is longitudinal
compatible. So if you want to have transversal compatible optical WDM
interface specifications you should use this G.959.1 and you are done. If
you will do something different it is just different, not standard, but not
automatically cheaper.
Regards Juergen
> ----------
> Von: Roy Bynum[SMTP:rabynum@mindspring.com]
> Gesendet: Samstag, 5. Mai 2001 01:09
> An: Rahn, Juergen (Juergen); stds-802-3-hssg@ieee.org; 'Marshall
> Eisenberg'
> Betreff: Re: AW: 1550nm Serial PMD Question
>
>
> Rahn,
>
> It might be noted that the jitter specification that the ITU is applying
> is
> to allow all signals to be multiplexed at the electrical level, not just
> the optical level. No one in ITU has considered an "optical multiplexing
> only" jitter specification. Using the "Class B" regenerator specification
>
> with a plezio-isosynchronous timing instead of a full isosynchronous and a
>
> relaxed timing specification would allow non-TDM multiplexed optical
> services and non-"digital wrapper" DWDM wavelength services. The larger
> vendors are attempting to maintain their dominance and high margins for
> transmission equipment. I expect that ITU is very upset about 802.3ae
> being a non-electrical multiplexable optical channel.
>
> Thank you,
> Roy Bynum
>
> At 09:37 AM 5/4/01 +0200, Rahn, Juergen (Juergen) wrote:
>
> >Hi,
> >The spec is indeed not in line to the "ITU Grid". However it should be
> >noted that beside this small pree condition of supporting particular
> >wavelength there are a lot further specs required that are not at all in
> the
> >Ethernet document. This means this interface in the current spec is not
> >suited for direct WDM also. For WDM you would in this case require a real
> >SDH/SONET interface. In this respect it should also be noted that one
> reason
> >(beside the optical parameters that do not support effective
> transmission)
> >is the way the jitter is specified as this prevents the cascadability of
> 3 R
> >regens which are needed in WDM networks of larger dimensions.
> >Regards Juergen Rahn
> >
> > > ----------
> > > Von: Marshall Eisenberg[SMTP:marshall@foundrynet.com]
> > > Gesendet: Mittwoch, 2. Mai 2001 16:39
> > > An: stds-802-3-hssg@ieee.org
> > > Betreff: 1550nm Serial PMD Question
> > >
> > >
> > > All,
> > > A while back there were rumors that the 1550nm Serial PMD would be ITU
> > > Grid
> > > Spec compliant, making it DWDM 'ready' I've downloaded draft D3.0
> and
> > > cannot find any references or further notations. Can anyone shed any
> > > light
> > > on this or point out the relevant section in the draft?
> > >
> > > Regards,
> > >
> > > Marshall Eisenberg
> > > Director of product marketing
> > > Foundry Networks Inc.
> > > 2100 Gold Street
> > > P.O. Box 649100
> > > San Jose, CA 95164-9100
> > > (408) 586-1754 direct
> > > (408) 586-1900 fax
> > > (408) 398-0014 mobile
> > >
> > >
>