The striker has attracted enquiries from Tottenham since the end of last season.
But Dembele told fulhamfc.com: "Personally, my expectations will be even higher and I want to play a greater part for the team. Playing for Fulham against the big teams and world class players excites me.
"We will be playing in the UEFA Europa League too, and that is something that I am really looking forward to. I know that the Club did very well in that competition a few years back and I know we would all like to be successful again.
"It's an early start for us, but we have to look at the positives - it is fantastic that this Club will be playing in Europe for a second time in three seasons. Fulham played some of Europe's top teams last time, and it would be great to experience nights like that myself.
"I'm looking forward to the challenge."