The teenager has been granted interim name suppression pending a hearing in February.
The victim, whose identity is also suppressed, gave evidence that he entered a competition last year which he won.
When he failed to hear back about the prize he called the promoter and was told somebody using his name had been in contact.
Judge Chris McGuire said yesterday that when police searched the defendant's home in relation to the competition, they found a 'stalker file' containing 24 sexually explicit stories written by the defendant about himself, the victim and the victim's sister.
The house photographs and floor plan was also found, and underwear belonging to the complainant was found in the defendant's bag.
Evidence about what police found had been suppressed until yesterday.
The court was told the defendant was dealt with by the courts last year for that matter and was discharged without conviction and had received counselling.
In May this year the victim received nine Facebook friend requests from someone in the name of a person unknown to him.
Judge McGuire said evidence of the nine requests had not been resolved but there was certainly a request sent and a further eight requests could have been sent by the computer programme.
The date of birth and an email contact on the profile were linked to the defendant.
In his victim impact statement, the victim said he was scared and stressed worrying about whether the defendant would insert himself into his life again.
He feared for his safety and was concerned about his emails being intercepted.
The victim's father, in his victim impact statement, said this was not simply cyber-bullying but "prolonged perverted obsession''.
"Can we really be confident that his obsession has stopped?'' the victim's father said in his statement.
Judge McGuire described the defendant's actions as utterly unhealthy and criminal.
The judge said he found aspects of the pre-sentence report troubling.
The defendant had a new justification for what he had done which included concern over the victim's Facebook profile being fake and that he did not want to be implicated.
Judge McGuire said the defendant had positioned himself as the victim and had spoken of the horrendous process he had gone through.
The defendant had expressed some remorse but minimal insight into his offending. He had said a rehabilitative sentence would be wasteful.
His lawyer, Brian Foote, yesterday argued for final name suppression as his client had no previous convictions and the risk to the defendant's mental health outweighed public interest.
Judge McGuire said the issues surrounding name suppression concerned him a lot.
"This sort of offence absolutely relies on covert activity so, if you like, the mischief that surrounds this sort of offence makes it one where identification of the offender is actually quite a significant, important matter.''
Judge McGuire said he needed more information before he could decide whether final name suppression should be granted.
"It is highly regrettable that the dialogue that was requested by myself between the probation officer and the registered clinical psychologist did not take place.''
The issue of final name suppression will be determined at a hearing on February 16.
