The 32-year-old has penned a two-year deal with the Corsican outfit after terminating the final year of his deal with Lille.
"It was sorted out in a few days," said Orsoni.
"We quickly found an agreement with the player and his agent, and we agreed terms with Lille too.
"As we are used to do, we didn't pay any transfer fee. Otherwise we could have not bought him."