Re: [802.3BA] MMF Extended Reach conference call reminder
Brad,
I think what Ali is saying is that if one had the same transceiver
specifications that we had in 802.3ae, one could support 300m on OM3
parallel fibers. The problem is that most VCSEL manufacturers cannot
maintain those same VCSEL specifications on a 4x arrays or a 10x arrays.
My problem is that they have gone too far in the relaxation of the 802.3
ae specs so that we now cannot support anything longer than 100m on OM3
and even if we were to provide a higher performance fiber, we can't get
additional length because we are dispersion limited.
I don't think Ali's proposal to ref Cl 52 is really practical nor do I
think the current 802.3ba baseline is really practical; the practical
answer lies somewhere in between the transmitter spec in 802.3ae and the
baseline proposal in 802.3ba.
Cheers,
Steve
-----Original Message-----
From: Brad Booth [mailto:bbooth@xxxxxxxx]
Sent: Wednesday, July 23, 2008 2:46 PM
To: STDS-802-3-HSSG@xxxxxxxxxxxxxxxxx
Subject: Re: [802.3BA] MMF Extended Reach conference call reminder
Ali,
Hopefully you can help me understand something related to what you said.
I agree it would be possible for XR to use the existing specifications
in Clause 52 as a baseline for doing 300m on OM3.
What I don't understand, and I hope you can clarify, is that the 300m on
OM3 in Clause 52 was based upon a single wavelength on two strands of
MMF; are you implying the re-use of that 300m of OM3 fiber currently
being used for 10GBASE-SR?
A WDM approach would permit re-use of the existing installation, but so
far the task force approach being taken is parallel fiber. As far as
the MMF reach objectives are concerned, there is no legacy cabling
infrastructure.
I apologize if I've missed some of the discussion related to this point,
but it seems that extended reach requires a new cabling infrastructure
and therefore needs to meet the 5 Criteria if the task force is going to
put any serious effort into it. If it was a case of saying "add EDC and
get an extra x meters" or "the next generation MMF can go x more
meters", then that seems like a simpler effort which can be handled by
an annex. If this is about creating a whole new PMD, then the task
force needs buy into it with an objective.
Just my thoughts on this.
Thanks,
Brad
-----Original Message-----
From: Ali Ghiasi [mailto:aghiasi@xxxxxxxxxxxx]
Sent: Wednesday, July 23, 2008 12:39 PM
To: STDS-802-3-HSSG@xxxxxxxxxxxxxxxxx
Subject: Re: [802.3BA] MMF Extended Reach conference call reminder
Alessandro/John
Looking at some of the email trails related to XR several people
suggested for application longer than 100 m just use SMF. I absolutely
agree with the approach of using SMF for >100m if you could shove the
SMF module into the MMF QSFP cage.
We had several constructive discussion toward a resoluAlessandro/John
Looking at some of the email trails related to XR several people
suggested for application longer than 100 m just use SMF. I absolutely
agree with the approach of using SMF for >100m if you could shove the
SMF module into the MMF QSFP cage.
We had several constructive discussion toward a resolution for MMF XR
last week with 5 option on the table:
- Tighter transmitter specifications
- CDR outside the module
- CDR inside the module
- Simple EDC (2 tap DFE) ghiasi_01_0108 was replaced with
dudek_01_0708
- Optional FEC
- FEC always encode (John P withdraw this proposal)
At the meeting it was stated CDR in the module will be least invasive
and would not require defining a 2nd PMD. There is no guarantee if you
put CDR in the module the TX or RX jitter will improve, we have to
define a new PMD with full set of TP2 and TP3 specifications.
If we do not want to define a new PMD for XR the obvious solution would
be to reference
802.3 CL 52 single optical specifications for SR4/SR10, it already
defines 300 m on OM3 fiber!
Thanks,
Ali
Alessandro Barbieri (abarbier) wrote:
> Colleagues,
> as proposed during the Ad-Hoc report by John Petrilla at the TF
meeting in Denver
(http://grouper.ieee.org/groups/802/3/ba/public/jul08/petrilla_02_0708.p
df), we are planning another conference call this Thursday, July 24th
8.30am pacific, to continue the selection process among the remaining
proposals on the table (internal CDR, enhanced TX spec and light-weight
EDC) and to discuss the best way to add XR to the standard.
>
> Below are the bridge information.
>
> Anyone wishing to present, please follow the guidelines described on
the Procedure for Presenters web page:
> http://www.ieee802.org/3/hssg/public/presentproc.html
>
> If you are planning to participate to the teleconference please take a
moment to read the IEEE patent policy available here:
> http://standards.ieee.org/board/pat/pat-slideset.ppt.
>
> Thanks,
> Alessandro
>
>
>
> ************************
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