The value of electrical switching on a DWDM system

Thinking back on this, this was a fairly obvious observation, but I thought I'd mention something that I find to be very cool. I knew the theory of why this was so cool, but it was driven home by a real-world example that I ran through early this morning.

Level3 provisioned the MAGPI wave to show up on the second channel in the first bundle of 10 lambdas in New York, but on the first channel in Philadelphia. At first, I was a bit worried because I had some engineers pre-wire this particular lambda to the 3rd channel on the DWDM plan in New York. But then I realized I was thinking like a traditional DWDM groupie from the 90s. So, I took off my flannel shirt, turned down the Soundgarden and really got to thinking from a slightly less flanneled, yet still Pearl Jam'ed 2007 perspective. :-)

In a conventional DWDM system, a signal that's placed on a transponder card (translating your router's ethernet or SONET signal into something that can be multiplexed with other signals) is hard-wired to a particular DWDM lambda. Changing that lambda required changing a transponder card out to a different model- for those systems that were around before tunable DWDM optics- or at least changing the fiber run between the mux-demux card and a tunable card (for those later systems that do have tunable optics) The whole theory of having tunable optics really gets stuck on having to fix that jumper to the mux/demux card and you lose some of the dynamicism that's so heavily touted along with it.

So, back to the Infineras. Since the signal is electrically regenerated at each node, switching the lambdas around (and switching the client signals around) is a piece of cake. On the New York Internet2-owned DWDM ring, I have a client signal coming into port 2 from Level3 at 111 8th Avenue. I wired the 32 Avenue of the Americas node's client interface up to port 3. Instead of having to re-wire the 32AoA side to dump the signal out on port 2, I can simply create the circuit between ports 2 and ports 3 and be done with it. There's essentially a complete decoupling of port 2 and channel 2. The two have nothing to do with each other.

I knew you could do this on the lambdas that crossed the backplane between different fiber directions, and I suppose I figured I would be able to do it within a particular card, but it just dawned on me just how powerful that feature really is from a real-world operational standpoint. This saves us from having to move jumpers and allows us to bring circuits up really fast. Theory is great, but when you start using it, the value just pops off the screen.