Caldwell's last appearance in emerald green came in 2009 against Canada but he will be looking to give Ireland coach Declan Kidney food for thought in Bath's Heineken Cup clash against reigning European champions Leinster on Sunday.
"This is just what I needed, a change of scenery," Caldwell, who has been capped twice, told the Irish Independent.
"I still have ambitions to play for Ireland, I'll always have that ambition. It's a big week for me on a personal level to perform in front of whoever is watching. Hopefully I can bring a good game and people can look at me again.
"The move has brought the best out of me as a player and I'm playing good rugby. The coaches are happy. It's a good place to be right now for me.
"Some people can stay at the one club and they're successful doing that. For others, though, it can feel like treading water and sometimes you have to bite the bullet and make the move for the good of your career.
"There were a few factors behind the move. Things had gone stale for me at Ulster. I wasn't performing as well as I had been."