ADAT, optical input and Garageband

I have an old ADAT tape machine and some recorded tracks on tape. I was wondering if I can import my ADAT tracks to Garageband via the optical input on my iMac. ADAT can send 8 simultaneous tracks over lightpipe, Garageband can record up to 8 simultaneous. How can I get Garageband and my iMac to recognize the ADAT and it's 8 track sources? Is this even possible?