Audio Aero MK II BNC Output to Mac Digital input?

I 've been slowly moving my discs to computer PC, however it occured to me suddenly that my disc spinner in the Audio Aero ought to be able to output a better signal than the built in drive on the computer. Considering the costs involved, it had better! Problem: How do you connect the AA digital output connector (BNC) to the Apple G5 tower digital input, which is TOSLINK. I've surfed all over the web and can't find a solution. Any ideas?

Thanks!