I can not find any info on the optical part of the board and why it is so big.

I will say that i know little about electronics but if you already have SPDIF Coax would not be possible to just use a SHARP GP1F32T Toslink transmitter, This converts SPDIF to optical and is little bigger than a toslink connector.

Here is a link to a fake sound blaster and on card that users it.

http://members.ozemail.com.au/~atrac/

C.