He is currently working alongside head coach Ugo Mola, the former French full-back. He spent three seasons playing at Castres, captaining the club in 2000 before returning to Ulster to see out his playing career which was unfortunately cut short due to injury.
Commenting on Barker's transfer, Ulster Rugby Chief Executive Michael Reid said: "Tim has been a wonderful servant to Ulster Rugby and I have no doubt that his move to France will be a thoroughly enriching experience, both in terms of his rugby career and the opportunity to immerse himself in a new way of life in an area steeped in rugby. He takes with him our very best wishes for his future."
Barker returned to Ulster at the start of the 2006/07 season after a stint with the Glasgow Warriors and his current Ulster contract was set to expire at the end of the current season.