[c-nsp] ONSs, DWDM SFPs, and the 3560/3750E

[Justin Shore]

Many thanks for the reply, Michael.

Michael K. Smith - Adhost wrote:
> The filters are put in place between your 15454 and your one-pair uplink.  So, something like this:
> 
> 15454 -> Lambda 1  \
> 	-> Lambda 2   -> Filter (muxes wavelengths) -> outbound fiber
> 	-> Lambda 3  /
> 
> And then same in reverse.  So if you have 3 Lambdas, you will have 3 fiber connections into the filter from 15454 on separate wavelengths and the output will be on one set of fibers for transport.

So, if I'm understanding correctly what you wrote and what I've been 
researching today, essentially the xponder card acts as a switch and 
uses the 10G interfaces for one of 3 L2 design scenarios (outlined in 
the line below).  No DWDM is happening yet but instead we're using the 
xponder card as a 20 port GigE switch with 10G uplinks.  Would that be a 
fair statement?

Then, if we have multiple xponder cards we could take their output and 
stuff them into muxes (15216 for example), thus introducing the benefits 
of DWDM.  Is that correct?  Or we could just carry the xponder 10G links 
around the network without DWDM and add the DWDM gear when out bandwidth 
approaches the 10G mark.  Am I on track or in the ditch?

Can the output from DWDM SFPs in regular switches be used as input 
straight into the filters?  Not that I have a use for this right now 
(unless the 3560E-12D gained support for DWDM SFPs) but it would still 
be interesting.

> I didn't read it that way.  Here's the quote I'm referring to that indicates you can plug basically anything into it on the distribution side.
> 
> "The 20 client ports can be equipped with different Gigabit Ethernet SFPs: SX, LX, ZX, coarse wavelength-division multiplexing (CWDM), DWDM, or electrical (RJ45). Figure 2 shows a Layer 2 logical scheme, and Figure 3 shows a Layer 1 physical scheme."

I think what our SE was getting at was the use of DWDM SFPs with the 
filters directly.  I'm reading the doc the same as you and that's the 
only way it seems to make any sense.

> I would get some Cisco pre-sales support for your design, particularly since it sounds like you're a little thin on the optical engineering side.  There are other considerations that they can help with (do you need the filters, loss budget calculations, amplifiers, etc.).  I have found their optical teams are pretty good and, if you tell them exactly what you're trying to do they should be able to come up with a design for you.

Well, we do have an SE working with us.  He's an optical specialist and 
good to work with.  His time is very limited unfortunately.  Saying that 
my DWDM knowledge is a little thin is being generous. :-)  I have some 
concepts but no applicable experience.  Perhaps I can find some good 
training on the PEL site.

> If you don't have it already, you should have good OTDR data on your fiber runs because there are different optics that you will use depending on how far (from a db-loss perspective) you have to go on the two shots.

I haven't gotten the guys to run the links through their OTDR yet.  One 
path is about 10k and the other is around 20k I believe.  I'm already 
using the fiber we'll be using for single-strand GigE links.  The telco 
techs terminate all our own fiber so repairs shouldn't be a big problem. 
  They usually do a really good job so I'm not expecting major problems.

Thanks for the input.  I've gotten some great suggestions here.  DWDM, 
while it's not a difficult to grasp concept, it's definitely a learning 
curve when you're trying to learn it by seeing how a particular vendor 
implemented all the various aspects of it.  It's mind bending at times.

Thanks
  Justin