Kenneth Dymond, 37, also made contact with a 15-year-old girl over the internet.
Lincoln Crown Court heard that more than 500 images were recovered from Dymond's computers and phones after a raid on his home in August 2015.
He was also placed on the sex offenders' register for 10 years.
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Dymond of Magna Mile, Ludford, Lincolnshire, was serving as an detective constable in the Met's Specialist Crime and Operations Command at the time of the offences.
Stephen Kemp, prosecuting told the court that the internet search history on Dymond's computers "identified various terms which indicated searches for material of a paedophilic nature".
Mr Kemp added: "There were extracts of a Skype conversation recovered from a laptop which appeared to be from a 15-year-old girl's brother calling the defendant a paedophile.
"That person threatened he would go to the police if the defendant did not delete his sister's profile."
Reka Hollos, defending, said Dymond suffered from chronic depression and had undergone counselling for his addiction to pornography.
"He is very remorseful for what he has done," she said.
Judge Michael Heath, passing sentence, told him: "As a serving police officer you ought to know that children are grievously abused so that this material, this utter filth, can be put out there on the internet for people to view it.
"I cannot suspend the sentence in a case such as this."
A detective serving with the Metropolitan Police has been jailed after admitting downloading hundreds of pornographic images of children.