The winger has previously spent loan spells at Lorient, Real Betis, Olympiacos and Villarreal, but spent last season in Arsenal's first-team.
Campbell played 30 times for Arsenal in the 2015-16 campaign, scoring four goals, but this clearly was not enough to persuade Wenger to keep the Costa Rican.
The 24-year-old has made 176 career appearances, scoring 22 goals. The Sporting loanee also has 63 caps for Costa Rica, having scored 11 goals for his country.