Chelsea boss Jose Mourinho values Belgium playmaker Eden Hazard at £200m after reported interest from Real Madrid.
Alan Pardew is weighing up chasing a big-name summer signing to boost Crystal Palace's profile.
The 18-year-old arrives at Craven Cottage on a free transfer and will be part of the Fulham development squad that will compete in the Barclays Under-21 Premier League.
Plumain represented France at Under-16 level and he made 22 appearances for Lens in the French second division last season, scoring one goal.
He has signed a contract with Martin Jol's team until June 30 2016, with the option of extending the deal for another year.