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Re: Feliz Haridad

Patrick Gilliland wrote:
> Rich,
> The weather is really starting to get cold here.
> They are going to find me with my fingers frozen
> to the keyboard.  It's 10 degrees F outside.  I
> have some comments.  See below for details.
> >> illustrate the greater availability of power at 1300nm.  The
> >> accessible power level at 1300nm is greater than at 850nm by
> >> an order of magnitude.  This would help in overcoming the SNR
> >> degradations occasioned by MAS.
> >
> >I agree. This is the well known 1300 vs. 850 nm tradeoff, but has nothing
> > to do with MAS.
> -------------------------------------------------
> >From my point of view it has a lot to do with MAS.
> MAS is the reason behind any SNR degradation at the
> transmitter.  With 1300nm, there is room below the
> laser safety limit to increase transmit power and
> therefore offset the SNR degradation occasioned by
> MAS.
> ---------------------------------------------------

Increasing transmitter power in an unconstrained manner in for a multi-level
system which modulates the intensity of the laser to correct only for SNR lost
at the transmitter would saturate the receiver. This is not a good thing for a
MAS system. This would result in an optical compression penalty and would likely
INCREASE rather than DECREASE SNR, specifically for the highest intensity level
at the receiver. My PAM5x4 proposal is independent of laser wavelength.   

> >I have no clue as to what you mean by PAM10 if it doesn't mean 10 levels,
> >please explain.
> ------------------------------------------------
> Yes. By PAM10 I do mean 10 levels.  It would
> be one way to cram an additional bit into the
> baud rate.  However, I introduced the PAM10
> example as an illustration of the additional
> transmitter power available at 1300nm over 850nm.
> I do not advocate the use of MAS at this time.
> I believe there are numerous difficulties which
> have yet to be overcome.  If the technical challenges
> to MAS can be overcome, I reserve the right to change
> my opinion.
> -----------------------------------------------------

You have a right to your opinions and your own proposals as I do mine. My MAS
proposal is based on 5 levels (PAM5x4). I do not advocate using 10 levels for
MAS just as you wouldn't advocate using 2600 nm lasers (i.e. 2 times 1300 nm).
Please don't add to the confusion. My PAM5x4 is a complete 10 GbE PHY proposal
with all interfaces, coding, O/E support, etc. defined. Unless you're going to
propose a 10 level PAM system, please drop this idea to keep this MAS thread on

> >My PAM5x4 MAS proposal uses a single laser. The x4 stands for 4 Baud intervals
> >per byte. I think I'm beginning to understand your confusion and concern with
> >laser safety. The answer is that this is independent of MAS.
> ----------------------------------------------------------
> At the risk of beating this horse again, I am assuming
> you mean 4x1.25Gbaud in your reference to 4 baud per byte.
> I will admit my understanding of your HARI/MAS proposal has
> metamorphosized over the weeks of this thread.  Part of the
> reason for this is some perceived inconsistencies in your
> statements, and/or at minimum, terminology.


You really need to review proposals before you comment on them. My PAM5x4
proposal in question is located at:
I've spent a lot of time working on this proposal and presenting it to the HSSG,
If I'm not mistaken, I don't believe that you were ever present at a 10 GbE HSSG
meeting. It is clear in the MAS proposal as well as this thread, that the MAS
Signaling rate is 5 GBaud, not 1.25 Gbaud. This means that I'm sending a symbol
5,000,0000,000 times per second. The symbol sent is a 5 level symbol containing
approximately 2.3 bits. 4 of these PAM5 symbols are used to represent one byte.
The overhead of 2.3 x 4 = 9.22 - 8 = 1.22 bits is used to transport a Forward
Error Correcting (FEC) code which is used to increase effective SNR at the
receiver. I call the code PAM5x4, per the customary labeling of a code to
represent the encoding of one byte of MAC data. 
> In a proposal I have open in front of me entitled
> "Multilevel Serial PMD Update" you refer to a serial line
> rate of 2.5GHz.  In the proposal you seem to be emphasizing
> the rate reducing features of MAS.  Above you mention a 5.5GHz
> rate.  It is also possible your proposal has evolved.  I might
> be reading from the wrong sheet of music.  I hope this is what
> you call "Maui".  I can only assure you I am not smoking it.

Are your sure? I can't see you from here :-)
You have the correct proposal in front of you.
2.5 GHz is the fastest effective symbol rate and corresponds to 5 GBaud.
5.5 GHz is the proposed laser bandwidth using the formula ~1.1x Baud. 
Where is the confusion?
> I do not agree that MAS and laser safety are independent for
> the case of the 850nm lasers I cited in my previous posting
> which I have left in below.

I believe that you'll need to make a better case for a dependency because I blew
your previous case out of the water above.

> ----------------------------------------------------------------
> I believe your proposal must address the entire system including
> the transceiver, optical link budget, and laser safety in
> order to have a complete proposal.  Your 5.5GHz figure for
> the transmitter bandwidth is much closer to the truth for
> a real multimode optical link.  The dispersive nature of the
> multimode fiber often can be compensated for by a small pre-
> emphasis and the link length may be extended.
> ---------------------------------------------

I've already addressed many of these issues and will continue to fill out the
MAS proposal in the coming weeks and months as presentations to P802.3ae. If you
have a specific question about my PAM5x4 proposal or MAS in general, please
don't be bashful. However, don't be alarmed if my answer is different to that
you would expect in a traditional binary signaled transceiver design.

Pre-emphasis (at the transmitter) or receiver equalization is equally applicable
to multi-level systems. Equalization is the rule, rather than the exception in
most non-binary signaled systems. 

> >> The following picture illustrates what I have been suggesting
> >> as an alternative which makes some sense.  It helps define the
> >> question of where to partition a little better.
> >>
> >> +--------+ XGMII +-------------+
> >> |        +------->             | Hari,  +------+       +-- -----+
> >> |        |   .   |          E S| |S (E) |       | Trans- |
> >> |10 GbE  |   .   | 10 GbE   n e+-------->e (n) |       | ceiver | Medium
> >> |        |  36   |          D r+-------->r (D) |1 line | Module |
> >> +--------|       |             |        |      |-------|        |
> >> |  MAC   |   .   | PCS/PMA  e D+-------->D (e) | 10Gb  |  (PMD) | 1 fiber
> >> |        |   .   |          c e+-------->e (c) |       |        |
> >> |        |   .   |            s| FR-4   |s     |       |        |
> >> |        +------->             | Trace  +------+       +--------+
> >> +--------+ short +-------------+ <=20"
> >>
> >> Figure 1 - Recommended partitioning of a transceiver module.
> >>
> >> +--------------+
> >> |              |               +-----+        +--------+
> >> |           E S|     Hari      |S (E)|        | Trans- |
> >> |  10 GbE   n e+--------------->e (n)| 1 line | ceiver |   Med2um
> >> |           D r+--------------->r (D)|--------| Module +------------>
> >> |  MAC/PHY  e D+--------------->D (e)| 10Gb   |(PMD)   | 1 fiber
> >> |           c e+--------------->e (c)|        |        |
> >> |             s|   FR-4 PCB    |s    |        |        |
> >> |              |    Traces     +-----+        +--------+
> >> +--------------+     <=20"
> >>
> >> Figure 2 - Preferred partitioning of Hari and Integrated MAC/PHY Chip
> >>             within a 10 GbE Device
> >>
> >
> >Now I understand. You actually agree with Hari as a Protocol (MAC) to PMD
> >interface! You are merely focusing on only one of the 4 PMDs I was illustrating,
> >the Serial PMD. My point all along is that Hari is the "best" interface back to
> >the MAC/PHY. Besides that, you're figures 1 and 2 have the following
> >disadvantages with respect to mine (above)
> -----------------------------------------------------------
> Actually I do not agree or disagree with HARI as a protocol
> (MAC) interface.  I disagree with HARI as a PMD interface
> because it anticipates multi-level or multi-color PMD options.
> HARI is unnecessary as a PMD interface for the serial case.

The pictures above are YOURS not MINE!!! You show no alternative other than Hari
as a MAC interface.

Please follow the developments of the 10 GbE HSSG. Most HSSG proposals to date
which include the very high-speed SerDes/EnDec that you show are associated only
with a specific PMD type, Serial, and are considered to be part of the PMD. PMD
is NOT synonymous with transceiver module. A Serial PMD may include a
Hari interface, high speed mux/demux/CDR, and a transceiver module. The jitter
budget at the PMD, and extended to the remote PMD, must be sufficiently large to
make the link work. Hari helps greatly to addresses this latter requirement.
Please see the following Kauai proposals for illustrations of a 10 GbE PMD:,
pages 22,23,
pages 2,3,
page 3

If your intention is to supply pluggable 10 GbE Serial transceiver modules to
the industry and expect these to work in a 10 GbE link at 10-12.5 Gbps (encoded)
please show me how you're going to meet the following 10 GbE system

1) Link jitter budget
2) EMI
3) Interface to the MAC if it's not Hari
> -----------------------------------------------------------
> >1) More elements in the path, specifically in your (semi) Integrated MAC/PHY case
> >2) High speed signals not contained within the transceiver module running
> >around on the board create huge EMI problems
> >3) What technology do you plan to implement your Hari-to-10Gb chip in? How
> >much power does it consume?
> >4) Significant jitter between the Serdes to PMD connection. This is the same on
> >both side and leave the medium with very little jitter budget to play with.
> >
> >My Serial PMD simply has your 1 line interface within the PMD.
> -----------------------------------------------------------
> If one insists on HARI as the parallel-serial technology of
> choice, then 1-4 above are not dependent on where we choose
> to partition the system.
> -----------------------------------------------------------

The items above are ABSOLUTELY dependent on Hari being the ONLY interface
between the eventual integrated MAC/PHY and PMD as shown in my prior figure 2,
as well as your figure 2 above when the high-speed SerDes/Endec is considered to
be part of the PMD. 
> Best Wishes,
> Pat Gilliland
> patgil@xxxxxxxxxxx


Best Regards,

Richard Taborek Sr.         Tel: 408-330-0488 or 408-370-9233       
Chief Technology Officer                   Cell: 408-832-3957
nSerial Corporation             Email: rtaborek@xxxxxxxxxxxxx  
2500-5 Augustine Dr.           Alt email: rtaborek@xxxxxxxxxx 
Santa Clara, CA 95054