"At times, I thought I was going to die in there," he told me earlier this year. "I told God I didn't think I'd make it out alive."
Olivera, 48, was one of 75 dissidents, journalists and others arrested in March 2003 in a government crackdown on dissent.
While in Guantanamo, he said he faced "roaches, rats, clouds of mosquitoes" and "water full of mud."
"The food I ate was for pigs. Sometimes it was rotten."
Olivera was released on medical parole in December 2004. As part of his conditional release, he said he is not allowed to travel outside Havana or attend public demonstrations.
Olivera's supporters have published short books containing his poems and short stories. And English PEN and other organizations have rallied behind Olivera, who vows to continue writing, despite the risk he could be sent back to prison.
"I can't live without writing," he said. "It's part of my life. It would be traumatic for me to stop writing."