The Swedish stopper has impressed in the Eredivisie this season and has scored three goals in 24 appearances.
Reports suggest he has been watched by Newcastle in recent weeks with a view to a potential summer move.
UEFA Champions League quarter-finalists Schalke have also been tracking the 25-year-old, who joined NEC from Landskrona in 2005.
Olsson's agent Martin Dahlin: "It's no secret that there is interest from England and Germany."