Optical is based on using light for signalling across optical fiber. The light source might be LED or laser.
Serial is, generally, copper based. It's an old technology where electrical signally, in sequence (the serial), is used. "Serial" was used, as a term, to separate it from using multiple wires, concurrently, for signaling, sometimes call "Parallel". Another method was to do more complex signally, sometimes using analog (rather than digital - see modem) signally across a medium with a broad bandwidth.
Modern Ethernet, FE and gigabit Ethernet, technically, for pretty much the same basic technology, although each of those generations supporting 10x the capacity of the prior generation. They too are actually, more or less, serial (usually much faster than the old "serial"), usually on copper, might be on fiber. However, older Ethernet, on copper medium, didn't use the same copper wiring generally used today (which also, BTW, "better" copper is needed to support higher bandwidth ["speed"] copper too).
For major transitions in copper Ethernet you might want to Wiki 10Base-2, 10Base-5 and 10Base-T, followed by Cat-3, Cat-4, Cat-5, Cat-5E, Cat-6, Cat-6A and Cat-7.
The prior only scratches the surface. I.e. many aspects of Ethernet not mentioned along with there are many in optical and "serial" too.
