A Sydney man who blackmailed women into having sex and sending him explicit photos before and after he became a NSW police officer is facing a long stint behind bars.

Vaughan Mark Hildebrand has admitted 44 offences committed over a decade, involving 15 victims - four of whom he forced into having sexual intercourse.

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The 30-year-old appeared for sentencing in the NSW District Court on Thursday, when Judge Robyn Tupman spent hours outlining some of his crimes and imposing some jail terms.

Vaughan Mark Hildebrand. Credit: 7NEWS

They involved forcing women to perform oral sex on him, intimidation, stalking, threatening to share explicit images with a victim's family, friends or colleagues, and a web of deception using fake identities on social media.

The judge will continue the "complicated and complex" sentencing on Friday before imposing his total and non-parole terms.

He had pleaded guilty to 11 counts of having sexual intercourse without consent, 10 of using a carriage service to menace or harass a person, and one of using a carriage service to solicit child pornography.

He also pleaded guilty to a count of wilful misconduct in public office, two of dealing with identification information with the intention of committing an offence, and one of possessing a prohibited weapon without authority.

Vaughan Mark Hildebrand. Credit: 7NEWS

Hildebrand, who became a police officer in 2011 and was not caught until 2017, also asked the judge to take into account another 18 offences.

Judge Tupman said his first offence occurred in 2007, when the victim was a teenager.

From when he was 18, he forced her to perform oral sex by threatening to send nude images of her to her family and friends, and later to her boss.

He "was already acting callously and in a manipulative way", the judge said.

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His persistent abuse of her for years involved escalating behaviour including intimidation and menacing her by playing with knives and describing how he hunted and killed pigs.

At one stage after he became a police officer, she came to him for advice about a relative's arrest and he forced her into sex again by either saying he would help through his contacts or get "him put away".

Chevron Right Icon 'Hi, I'm back, do you think you can hide from me'

He told a second young victim that someone in the neighbourhood had been boasting about installing a secret camera and getting naked images of her.

Hildebrand then used an assumed identity and befriended her online, demanding pictures of her naked, claiming people were watching her through her bedroom.

When she blocked that identity, he created another one, saying: "Hi, I'm back, do you think you can hide from me".

She confided in Hildebrand about these demands, unaware that he was the perpetrator.

He used the same tactic with other victims he was acquainted with, contacting them using false identities while using details he knew about them from his personal knowledge.