Re: Supporting Installed Fibre
In order to support the installed fiber the baud rate at the optical
fiber must be of the order of the bandwidth of the fiber. The latest
proposal of Transcendata in Montreal uses a baud rate of 5 Gbaud/sec.
Hence, although it gets rid of the 4-WDM optical muxes it would
appear to be more difficult to use with the installed fiber (unless
it is limited to shorter links).
All the proposals that want to maximize the reuse of the installed
optical fiber use in one way or another WWDM optical muxes. These
proposals presently are (I apologize if I forgot one):
1) PAM-5 + scrambling at 1.25 Gbaud/sec using 4-WDM
2) PAM-2 + scrambling at 2.5 Gbaud/sec using 4-WDM
3) PAM-2 + 8b/10b at 3.125 Gbaud/sec using 4-WDM
I am not an expert in pricing curves, but it seems to me that the most
expensive item in the link is installing new fiber.
Jaime E. Kardontchik
San Jose, CA 95131
> The alternative to WWDM is probably a multi-level coding scheme (dibits or
> quadbits per baud), which will reduce the baud rate to a managable
> frequency. Transcendata is working on such a system. Others may be looking
> at alternative coding schemes as well.
> The disadvantage of this approach is that the IC's become very complex.
> Reletive to WWDM, this is also the charm, as the IC's will be subject to
> Moore's law, while the passive optics, plus 4X the number of devices, IC's
> etc. of WWDM will probably not.
> It seems unlikely to me that the H-P WWDM will conform to the pricing curve
> your customers expect. I think waiting a little while before we make a
> comittment might yield a scheme which better meets your customers