The Senegal international has signed for Albion on a one year loan deal from the French side.
"Alassane has got a good record in French football and was the subject of a big bid from another French club a couple of seasons ago," Baggies boss Gary Megson told the club's official website.
"Neil Clement's position is one we need competition and cover for so we're really pleased to have got Alassane on a year's loan."