The 22-year-old, who joined Fulham's academy in 2009, has played four times for the Cottagers and spent a month on loan at Accrington last season.
The Finn also had spells on loan with Maidenhead United, Cambridge United and Finnish Premier League side FC Lahti.
The 6ft 5in goalkeeper has represented Finland at several youth levels and made his senior debut in 2013.
Find all the latest football transfers on our dedicated page.
Stevenage have signed Finland goalkeeper Jesse Joronen on a six-month loan from Championship side Fulham.