For all the rumours surrounding players the club could bring in, Carayol had been off the radar, even though Steve Evans had earlier confirmed they were in the market for a winger.
The 27-year-old has joined until the end of the season, report the club's official website.
This increases the club's options in an area they are light, but also make life a lot harder for summer signing Jordan Botaka.
The Democratic Republic of Congo international has found the Championship tough going since arriving from Dutch side Excelsior on deadline day.
He has made only two starts, and seven substitute appearances, since joining, with no goals or assists contributed.
Lately he has not even been on the bench, with head coach Steve Evans unimpressed with what he has been unable to offer so far, in admittedly little game time.
Carayol's addition makes his first team chances even tougher, although he may yet get a chance to show what he can do in the FA Cup against Rotherham, if Evans elects to rotate the side and bring him in. If he does, Botaka simply has to take his chance.