He later admitted they had been away together and had sex and that he had bought her gifts such as underwear, jewellery and clothes.
He originally pleaded guilty at Southern Derbyshire Magistrates’ Court last month but a court order prevented Derbyshire Live from naming the school.
At the sentencing, the prosecution applied to the court to prevent the media from naming the school where Fidler worked.
However, our reporter successfully counter-argued to Judge Steven Coupland that naming Belper School and Sixth Form Centre as his place of work was in the public interest.
Dismissing the prosecution application and handing Fidler a 22-month jail term, Judge Coupland said: “You had been a teacher for more than a quarter of a century and head of music for a number of years.
“You were in a position of responsibility and knew what the rules were about sexual contact with pupils.
“Your teacher’s ethos must have told you about that.”
“You should have taken steps to distance yourself from her but instead you moved closer,” said the judge.
“She gave no victim statement but the reality is the damage this has caused her is impossible to quantify.”
Leanne Summers, prosecuting, said Fidler, of Johnson Drive, Heanor, had worked at Belper School since 1993 and had been head of music since 2002.
Fidler was dismissed from his role in December 2018 following an internal investigation.
Miss Summers said: “After being dismissed, a colleague was looking in the defendant’s office drawers and found a memory stick which contained pictures of the victim topless and in her underwear.
“He was arrested and candid, saying the lines had become blurred and that they were seeing each other three times a week.
“He said she had stayed over at his home, they had been away together that he had bought her gifts such as jewellery, clothes and underwear.”
Miss Summers said that, as part of the police investigation, Fidler’s phone had been seized and it was discovered he had been Googling whether what he and the victim were doing was illegal or not.
She said the victim was interviewed by the police and admitted she and Fidler had been involved in a sexual relationship.
At Southern Derbyshire Magistrates’ Court in July, Fidler pleaded guilty to one count of sexual activity with a girl while in a position of trust and one count of possessing 13 indecent images of the victim – 10 pictures and three videos.