The 19-year-old, who joined the Cottagers in August 2011 after two seasons at Chelsea, missed the first half of this season with a knee injury after impressing in pre-season.
He is now fit again and expressed his delight at signing a new deal, which will keep him at Craven Cottage until 2016 and also has the option of a further year.
"It's nice to hear that the manager rates me," said the Portuguese youth international. "I think he likes the way I play but I need to keep working hard and trying to impress him. He's given me a lot of confidence.
"I feel much better, I feel fit. It was very frustrating to be injured. I'm a young player and I was involved with the first team in pre-season and had done well, but then picked up this injury. But everything is good now.
"I went with the squad to Newcastle (for Sunday's Premier League game) which was a good experience for me. I didn't get on the bench but hopefully I will in the future.
"I'd love to play before the end of the season but we will have to see. If I'm given the opportunity I will take it. I'm ready if the manager wants me."