The X Drive.

How does an X drive work, it doesn't matter, you are not writing a technical manual. For a story all you need is the rules it works by and a name. Most technology is black box technology to the people that use it, they only understand the rules.  Use the name of the inventor that leaves no hint as to how it works. FTL drives are pure fiction, so just like a magic system all you need is steadfast rules about how they work and they will still feel consistent and scientific. 

If you want examples try wikipedia, https://en.wikipedia.org/wiki/Category:Faster-than-light_travel_in_fiction, this is not the place for that.