Conor McRedmond (28) from Tullamore, Co Offaly, maintains that a taxi driver created a story about him and Rebecca Blake (29) from Surrey, England, acting inappropriately after a row over a cab fare.
Mr McRedmond's father Christy said today he is 100pc sure that his son is innocent.
"It's a laugh. That's what it is. I know he's innocent. He is not locked up. I don't know what'll happen but we'll see," he said.
"Conor is working away there, he was back to work this morning."
A close friend of the welder told the Herald today that he will do everything possible to prove his innocence, adding: "There is no evidence at all. They did DNA tests and they found nothing.
"Basically what happened was that Conor had been in Dubai for a while and knew his way around.
"But the driver thought he was a tourist and was trying to take him for a ride. There was a row over the fare and next thing the driver pulled over by some cops who arrested Conor for not having a drinking licence.
"They put him in jail for five days and then they threw this charge at him."
Yesterday Conor was sentenced to three months in jail after being convicted of "breach of honour" with "consent" and committing "an indecent act in a taxi".
Mr McRedmond and Ms Blake were both ordered to carry out their term in Dubai's tough Central Prison which is home to around 4,000 criminals, including vicious drug dealers.
His pal said: "I spoke with him afterwards and he was in good spirits. He is still out and he is going to appeal it. But the appeal won't be heard until January 22 so he's stuck there for Christmas. They've taken his passport."
Mr McRedmond and Ms Blake, a recruitment consultant, have also been told that they will be deported and must each pay a €635 fine.
They were arrested on May 4 after meeting just hours earlier in a hotel bar.
The court heard written statements from a taxi driver and a policeman that contained allegations against the couple.
Neither witness gave evidence in person to the court.
Pakistani taxi driver Qaiser Khan (29) claimed that he spotted Ms Blake in the rear view mirror with her top off, straddling Mr McRedmond and "making the sounds of a woman having sex".
He pulled over when he spotted a police patrol car and summonsed Emirati policeman Abdullah Obaid Khamis.
Mr Obaid Khamis alleged in a written statement that he caught Mr McRedmond with his trousers down having sex with Ms Blake, whom he claimed was naked at the time.
This was totally denied by both parties.