Bigby was signed Tuesday. The team waived fullback Dorson Boyce to clear a spot on the roster.
Bigby spent six seasons with Green Bay and was the full-time starter from 2007 to 2009. His best season came in 2007, when he recorded career-highs in tackles, interceptions and passes defended. He played just 20 games in 2008 and '09 due to injuries.
Last year, Bigby played in just four regular-season games and made only six tackles after having ankle surgery at the beginning of training camp, but did have one tackle in the Super Bowl against Pittsburgh.