Some drives are already optical. I believe it's called fiber channel, and some high end hard drives use it. It is compatible with SCSI and can be used over copper cables, or over optical cables. Apparently it offers something like 1gbit per second bandwidth, and devices can be up to 6 miles away. Blows my mind. I'm not sure if you could find a short length optical cable/controller on the cheap for a science project through...? Pricewatch is showing roughly $100 for a controller, another $120 or so for optical cabling. I saw some drives on pricewatch for about $30 or so...I am not sure if it is a misprint, but pretty cheap for an 18gb 10k RPM drive.
Or, it would be cool to compare high end disk technologies.... If you could find an old 8088 or 286 PC with an MFM hard drive, then compare it to a modern machine with ATA133, then serial ATA, then to UW SCSI, then to fiber channel. Sheeot, that's my idea. Yea. Maybe do a comparison between two drives: same cache, same RPM, same specs except have one using fiber channel with appropriate optical cable/controller and the other using a standard UW SCSI.
-ben