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Re: WWDM vs. 10Gb/s serial


What is the effect on the receiver when using a scrambled code instead
of a DC balanced code like 8B/10B? Is this a good tradeoff? 

Another alternative is to choose an alternate, more efficient,
transmission code for TDM schemes including serial TDM, WWDM, and
Parallel Optics to lower Baud requirements.

MAS encodes data as analog waveforms. I am currently planning on adding
"overhead" in terms of multiple symbols for some data codes in order to
provide a modicum of analog signal DC balance. A MAS DC balance
requirement must be offset by an increase in frequency and/or #analog
levels per Baud. If DC balance is not required, system cost can be
reduced for all schemes.

How does scrabmling handle the transport of special codes required to
denote information like Start/End of Packet, Idle, Error codes, etc? I
believe that 10 GbE Ethernet will require the transport of a handful of
these special codes in addition to all 256 data codes representing 8
bits of data.


>Paul A. Bottorff wrote:
>I certainly agree that the PHY must provide fast failure detection (<10
>msec). In addition, it would be nice if the PHY layer could inform the
>transmitting end of failures.
>10 GigE has a broad range of uses for both LAN and WAN applications. The
>design tradeoffs for photonics in the WAN and LAN are different. In the WAN
>a major component of cost is the optical reach. The data which I've seen
>indicates that transmission frequency very significantly affects reach. To
>get the lowest cost solutions 10 GigE should move away form group codes
>systems like 8/10 into scrambler code systems. Scrambling provides an NRZ
>efficient line encode giving 10 gigabits of data at 10 gigabaud.
>Paul A. Bottorff
>Director Switching Architecture, Bay Architecture Lab
>Nortel Networks, Inc


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