Briggs, who was capped by England at Under-21s and Saxons level, made 104 appearances for Sale before moving to Bourgoin in France in 2011.
However Briggs is relishing his return to the Aviva Premiership with the Exiles.
The 27-year-old hooker told the club's official site: "It's going to be a big challenge, but I like that. It's a chance to help a club grow.
"London Welsh is a club which wants to push forward and they showed that with the fight they put in to go up. I'd heard good things about Lyn [Jones] and they play some pretty attractive rugby.
"The Premiership's tough for teams who've been there for ten years, so for a team coming up it's always going to be hard, but having seen how hard the boys are working and the way they want to play, I think we'll surprise a few people.
"Bourgoin was amazing, I loved it. I was made to feel very welcome and it was a great experience. Being in a different culture and learning a new language has helped me to grow and I think that will help me back in the Premiership, and in turn London Welsh."