Ju joined the Club from AS Monaco in August.
The South Korea captain, who played in both the 2006 and 2010 World Cups, scored 25 times in 91 appearances during three seasons in Ligue 1.
Upon completing the deal to bring the 26-year-old to Emirates Stadium, Arsène Wenger said: “We are delighted to have signed Ju. He will add true quality to our attacking forces and will be a valuable addition to the squad.”
