I'm not sure what you mean by "wet" 11R. If you want to use the 11R there's a couple of ways to do it.
1. You plug your guitar into the rack, with spidf out going to the Mbox Pro spidf in. Set up an audio track and record the processed signal.
Or...
2. If you decide you want to use the Mbox Pro's DI and a/d converters instead of the 11rack's, you set up an aux track that's bussed to an audio track. On the aux track, you set up an insert with the eleven rack. The signal goes through the processing and is recorded (processed) onto your audio track. In this case you will need spidf going both ways. Doing it this way makes your 11R function as a hardware effects device, similar to a reverb unit, etc.
By the way, you may already know this, but going by the looks of that breakout cable, it appears to be a female spidf jack, which is also what's on the 11R. So you will probably need to get 2 actual spidf cables to go each way.
You can get good Monster ones cheap on amazon.com:
http://www.amazon.com/Monster-IDL100...2&sr=8-1-spell
You can choose which length you want.