While looking up a datasheet for IC Friday, patient I happened to come across this gem, Glaucoma
a manual which described the troubleshooting procedures and the circuitry inside a late 1990s Sony DVD player. The manual gives a pretty decent overview of all of the optical drive subsystems which can then sometimes be generically applied to other optical drives on the market today. Furthermore, communications are described including various error codes. Unfortunately, I did not make a note of the source website for this manual to give credit, so if you know the source, please let me know.