[c-nsp] itu/c DWDM

Mikael Abrahamsson swmike at swm.pp.se
Tue Feb 10 17:36:48 EST 2009

On Tue, 10 Feb 2009, Marlon Duksa wrote:

> Hi - can anyone explain  difference between 'tunable optics' and DWDM
> capable cards on Cisco routers (7600, 12K and CRS), or is this the same?

Yes, that is the same.

> Also, can in essence a  4-10GE-ITU/C  (4x10G C-band DWDM PLIM on CRS) do the
> same thing as SPA-1x10GE-L-ITUC (1x10G C-Band spa) on 12K (port capacity put
> aside)?

It's my understanding that they can.

> Does this mean that I can have a single physical port (on a DWDM enabled
> 7600/12K/CRS cards/PLIMs) carrying traffic at various speeds over
> different wavelengths(BW totaling 10G for example for a 10G physical port)?
> For example, I can create  one channel with oc-12 speed over one wavelength,
> another channel with oc-48 speed on another channel and then bind those
> channels to a sub-interface? Is this how this is done?

No, it's single wavelength at any given time, and it's 10G only, and it's 
single point to point link over that single DWDM wave. You can of course 
have multiple ports in your router and thus achieve multiple waves, but 
each port only outputs single wave.

> With  IPoDWDM optical integration they talk about eliminating transponders,
> but I'm not sure what those transponders would do anyway, before they drop
> traffic to an (RO)ADM?

A DWDM transponder converts your 1310nm light into C-band single 
wavelength light and might add Forward Error Correction (FEC), plus 
supplies the people who run the DWDM with an administrative interface to 
monitor, both the DWDM side and the local tributary side.

With the above router linecards you basically put the transponder into the 
router so the router outputs the C-band light and does FEC, and then you 
put this light via a variable attenuator into the DWDM system without any 
further Optical-Electrical-Optical conversion.

Mikael Abrahamsson    email: swmike at swm.pp.se

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