So you're using the 2:1 splitter to input two signals from two different devices into a single input. Correct? Obviously, you won't be doing this simultaneously, but rather to save the hassle of plug/unplugging connectors. Right?
I've seen reference in a forum or two about optical splitters run 1:2 degrading the signal enough that it causes problems for both recording devices. Most of the splitters you'll find don't amplify the signal, simply split it in half - hence, the problems. I'd guess for your purposes - 2:1 as an input selector device - it would work fine. They're pretty cheap, why not give it a go.