The Northern Ireland midfielder, 27, had a nightmare six-month stint at Craven Cottage in 2007-08 before joining Rangers.
He said: "It was a difficult period for the club and we just missed relegation that season. A lot of new players came in and it took time to gel.
"I had not played a lot of football for the previous six months, so it was a difficult spell for me too. I do not know what sort of reception I will get from the Fulham fans and I am not bothered. I have nothing to prove to anyone.
"It is always nice to score against your old team, so I would love to get one."