Andrew Carter was sentenced to six years and eight months in prison for five counts of penetrative sex, at Bradford Crown Court, in March 2018.
A Sexual Harm Prevention Order prohibited him indefinitely from making any direct, or indirect, contact, with the girl, who was aged 14 at the time, said prosecutor Louise Gallagher.
He made 29 telephone calls and wrote several letters, between May 25, 2018, and June 17, 2018, in a bid to arrange contact with the girl, who cannot be named for legal reasons.
"His determined intervention would have caused her serious harm if he succeeded," Ms Gallagher said.
The court heard Carter became increasingly frustrated as he tried to arrange for the girl to receive an online birthday card.
By June 22, when he wasn't getting his way, he threatened to blackmail one of the people he contacted, the court heard.
Kenneth Green, mitigating, said Carter was due to be released on licence in June 2021.
"He expressed remorse and regret and said that his head was in the wrong frame of mind," Mr Green said. "He had just received an 80 month sentence.
"He was under the impression that if the victim chose to contact him he would not be in breach of the order. No actual harm was caused to the victim."
Carter, 50, currently of HMP Moorland, pleaded guilty to the breach of a Sexual Harm Prevention Order.
On Wednesday, Judge Keir Monteith QC sentenced him to 16 months in custody, which will be added to his current sentence.
He told Carter that if he had succeeded in his plan he woud have caused an “unimaginable detrimental impact on his victim.”
"You were persistent, there was a degree of sophistication to get around the order,” the judge told him. “There was a clear risk of serious harm to your victim.
“It's a serious matter and it deserves its own punishment.”