My receiver has only one available digital audio input that is still available to use. I would like to have 2 different outputs going to this one input. Is there an optical splitter or something like that that would work for this ?
For the price and functionality, you can't beat this: http://cgi.ebay.com/DIGITAL-OPTICAL...hZ017QQcategoryZ64594QQtcZphotoQQcmdZViewItem (and that's the merchant from whom I purchased the 2 I own). It's a passive splitter/joiner, so there's no manual or remote switching necessary. I use mine as a joiner: I have my XBox 360 and a DVD player going through it to one input on my receiver. Only one device at a time can be live, or it's my understanding the sound will get fouled up (makes sense as it's passive). You can also use it as a splitter to take one source to two outputs. Mine has performed flawlessly as a joiner (as you're suggesting). I've never used it as a splitter.
If you need something where both components will be live at the same time (I can't think off hand of such an application, but I'm sure someone can), then you need a true switcher. This company has some well known components: http://www.ramelectronics.net/html/comp-vid-sw.html#spdif
rca coax can transport 5.1 audio, optical can transport 7.1 +. If u are just using 5.1 audio, no need for optical transport.
I use one like this http://www.impactacoustics.com/product.asp?cat_id=1002&sku=28734
Bought one on E-Bay for $12. Looks different but works great.