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Re: [HSSG] 40G MAC Rate Discussion

Pat and anyone else that wants to chime in,
I've been following the HSSG emails and I do not understand the
advantage of using fiber ribbon for spans as long as 100 meters. 
The quotes that I've received for fiber ribbon per meter are quite
expensive. With today's edge emitting DFBs and modern optical multiplex
and de-multiplex we can supply the transmitter, receiver, and single
mode fiber at a cost less than the 100m cost of the ribbon (unless the
ribbon folks are quoting very high cost for some unknown reason).

-----Original Message-----
From: Pat Thaler [mailto:pthaler@BROADCOM.COM] 
Sent: Wednesday, April 11, 2007 1:58 PM
Subject: Re: [HSSG] 40G MAC Rate Discussion


Everyone proposing 40 Gig (or at least all those that I have had contact
with) is proposing 4 lanes using the same PCS as most 10x10G proposals:
10GBASE-R - therefore 64b/66b encoded. I expect any exposed serial
electrical interface would also be 10GBASE-R based - again similar to
many of the 100 G proposals but 4 wide instead of 10 wide. 

My preference would also be to use the same multiplexing mechanism for
distributing the traffic to the lanes for both 100 Gig and 40 Gig. There
are at least a couple of proposals out there for multiplexing and I see
no reason why they couldn't be used for both speeds.

Given that the market is data center, I think a parallel optical
interface could be appropriate which would allow using an existing 10
Gig optical PHY as is though I don't think we have gotten to discussions
yet of that vs. wavelength multiplexed.


-----Original Message-----
From: Marcus Duelk [mailto:duelk@ALCATEL-LUCENT.COM] 
Sent: Friday, April 06, 2007 7:18 AM
Subject: Re: [HSSG] 40G MAC Rate Discussion

Hi everyone,

I have a question regarding a possible PCS implementation of 40GbE. To
my knowledge the block code is chosen according to the PMD
configuration, i.e. a 4-lane PMD will most likely use a different PCS
than a 10l-lane PMD or a serial PMD.

For 40GbE we have been arguing that the prime candidate would be 4x10G.
Looking at 10GBase-LX4 I could imagine that the PCS of choice is 8B/10B.
This would, however, result in 12.5 Gb/s per lane. Is that a reasonable
assumption or are there any reasons that 4x10G could use the same PCS as
10x10G (e.g. 64b/66b) ?


Marcus Duelk
Bell Labs / Alcatel-Lucent
Crawford Hill HOH R-237
791 Holmdel-Keyport Road
Holmdel, NJ 07733, USA
fon +1 (732) 888-7086
fax +1 (732) 888-7074