Manager Nigel Clough has been looking for a keeper and speculation has been about for days that it would be Fielding who filled the gap.
"It is a real coup for us to bring Frank in, as he is currently the first-choice England Under-21 goalkeeper and has been sought after by quite a few clubs," Clough told the club's official website.
"He is a goalkeeper we have had our eye on for some time and we tried to bring him in last season, but the deal did not materialise.
"He has developed further since then and we are pleased we have been able to bring him in because we required some cover after Stephen picked up an injury.
"Blackburn and Sam Allardyce have been extremely helpful and we are grateful for their assistance."