James Anthony Gwynne, 31, admitted sending explicit messages referencing fantasies of incest and bestiality to users of an encrypted social media app.
He pleaded guilty to six charges including the transmission and soliciting of child-abuse material, engaging with someone under 16 outside Australia for the purposes of sexual activity, and using a carriage service in an offensive manner.
In chats from February to April 2022, the officer shared a naked photo of himself holding his genitals next to his police shirt and discussed fantasies of what he would do to young girls, people's daughters and their dogs.
These chats included claims he would take the virginity of his future daughters.
Gwynne denied he had a persistent sexual interest in children, telling a court he was looking for a "cheap wank".
"My fantasies are pretty f***ed up and I've never told anyone because I will go to jail," he wrote to one user on an anonymous messaging app.
One of the people he chatted with in April 2022 was a US investigator, posing as a 15-year-old.
Gwynne was arrested later that month and has been suspended from the police force, instead working as a traffic controller.
He previously told Campbelltown District Court he had been looking for "a cheap way to get my rocks off".
After reading media reports covering his case, he felt disgusted and a "worthless human".
"I'm embarrassed and ashamed," he said.
Gwynne was investigated in 2019 and again in 2021 for breaching the police social media policy by posting Tinder profile pictures of himself in full uniform.
Crown prosecutor David Jordan said he leveraged his status as a police officer to create a "cloak of trust" behind which he and the people he communicated with could continue to talk.
"Daddy's not going to do anything to risk his job and go to jail, like share your pics," Gwynne said in one message.
"You are safe with daddy if you want to show your face."
While the then-police officer never acted on his "graphic and highly depraved" fantasies, the conversations ran the risk of normalising the discussion of child abuse online, Judge Tanya Smith said on Tuesday.
"He was trading off his status as a police officer in an attempt to create a safe space," she said.
A psychologist diagnosed Gwynne with zoophilia, a sexual interest in animals, and autism, but did not find that he had an interest in young children.
Judge Smith imposed a prison term of two years and three months. Gwynne will be eligible for release after 12 months, with conditions.
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National Sexual Abuse and Redress Support Service 1800 211 028
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