the 27-year-old hooker made 104 appearances for Sale and was also capped by the England Saxons.
"It's going to be a big challenge, but I like that. It's a chance to help a club grow," said Briggs.
"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."