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Re: MAS vs. WWDM vs. Serial TDM

Hi Brian,

I apologize if I came on too strongly with my reply to your note, but I
felt that mission of the HSSG was being compromised. At the March '99
Call for Interest, 4 categories of schemes for 10 Gbps transport were
presented. These included:

1) Serial TDM
3) Parallel Optics
4) MAS

The initial meeting of the HSSG is only a short three weeks away. I'd
like to encourage others to bring in alternative schemes as well as
variations on the existing schemes. The HSSG needs to diverge a bit and
ensure that all relevant technologies are adequately investigated before
it starts to converge on one or more solutions for inclusion into a 10

We at Transcendata have been performing substantial research on prior
MAS schemes, especially those applicable to optical communication links.
We have identified several experts in this field and have reviewed
research work in this area. On the copper and wireless side, most
commercial high-speed communications links utilize MAS in one form or
another. However, I'm unaware of any commercial products or major work
on MAS optical communication links. 

One notable exception in the Cable TV industry which uses analog optical
communications for cable TV distribution. The advantage of analog
optical links is that RF or microwave signal can be directly modulated
onto an optical carrier for transport without having to demodulate and
remodulate. However, due to the nature of analog signals or subcarriers,
the requirements on the optical link, in terms of signal-to-noise ratio
and linearity, are much more stringent than digital optical links.

The Transcendata MAS scheme uses substantially different modulation than
that used by cable TV style analog optical communications systems. I
believe that signal-to-noise ratios and linearity aspects and
requirements cannot be compared between the two systems. One of the key
objectives and benefits of the MAS proposal to enable the use of
inexpensive electro-optical components to transport more data at a lower

I anyone knows of any existing research or commercial products in the
area of MAS optical communication links not having to due with analog
optical cable TV systems, please post that information to this


Brian Lemoff wrote: 
>I did not mean to rule out MAS as a solution for either long-haul or
>LAN.  I wholeheartedly agree that it is much too soon to be making
>decisions on 10GbE PHY.  Earlier MAS schemes have required very
>low-noise lasers and have been very restrictive on power budget.  The
>Transcendata proposal is very new, and if it really does everything that
>is claimed, without imposing expensive requirements on the
>opto-electronics, then it may very well be a good choice for 10GbE (and
>many other applications as well).  I look forward to learning more about
>it in the coming months.
>-Brian Lemoff


Best Regards,

Richard Taborek Sr.    Tel: 650 210 8800 x101 or 408 370 9233       
Principal Architect         Fax: 650 940 1898 or 408 374 3645
Transcendata, Inc.           Email: rtaborek@xxxxxxxxxxxxxxxx 
1029 Corporation Way     
Palo Alto, CA 94303-4305    Alt email: rtaborek@xxxxxxxxxxxxx