A traffic controller allegedly told a 14-year-old girl she was "a baby" before sending her sexually explicit images of himself.

Mostapha Alameddine is accused of attempting to groom a teenager for sex during a graphic conversation conducted in an online chatroom in May.

But the 40-year-old was unaware that the person replying to his messages was in fact a police officer posing as a teenage girl.

When told the person he was communicating with was 14 years old, Alameddine escalated the situation, police claim.

"Lol, you a baby, but it's cool, we're just chatting," Alameddine allegedly wrote.

He was arrested on Wednesday during an early morning raid on a home in Merrylands, in Sydney's west, and charged with three child grooming offences and possessing a prohibited drug.

Alameddine applied for release on Wednesday afternoon when he appeared in bail court from police custody.

His lawyer Hisham Karnib argued it had been a "spur-of-the-moment" conversation without any planning or premeditation.

"The offending lasted just over one hour, so it wasn't the type of offending ... where the applicant had the opportunity to really rationalise and think about what he was doing," he said.

Mr Karnib noted that his client has no criminal record and is the sole breadwinner for his family, which includes his elderly parents.

But the police prosecutor opposed bail, highlighting the sustained level of grooming and the extremely serious nature of the alleged offending.

After learning the teen's age, Alameddine is accused of escalating the graphic nature of the conversation by sending a photo of his genitals and asking for one in return.

Acting Judge Estelle Hawdon said the photos would have been "very confronting" for a 14-year-old to receive.

Although she recognised there was no actual harm done because the 'teen' was an officer, the judge raised concerns about the alleged behaviour.

"This is a brazen offence," she said.

She dismissed the bail application and adjourned the case for two months.

1800 RESPECT (1800 737 732)

National Sexual Abuse and Redress Support Service 1800 211 028