Christopher Parkes' youngest victim was just a few weeks old when he abused her, the Crown Prosecution Service said.
The 48-year-old, of Birmingham, committed the offences between January 2019 and August 2020.
His offending came to light when the oldest victim, a 14-year-old girl, told her mother that she had been assaulted by Parkes and that he had started "blackmailing" her, asking for sexual activity.
The girl’s mother reported the incident to police which led to other victims being discovered.
When police raided his property, they found images of some of the abuse including that of the very young children on the paedophile's phone.
Parkes initially denied the charges but changed his plea after overwhelming evidence was presented to him.
He was jailed for 17 years and three months at Birmingham Crown Court after admitting 11 different counts of child sex offences.
Parkes pleaded guilty to three counts of sexual assault of a child under 13, two counts of sexual activity with a child, two counts of assault of a child under 13 by penetration, one count of voyeurism and three counts of making indecent images of a child.
He will now be on the sex offenders’ register indefinitely.
Julia McSorley, senior crown prosecutor, said: “This was a distressing case and our thoughts are with the young victims and their families.
"Christopher Parkes is an extremely dangerous man with a perverted sexual interest in very young children, including a baby and a toddler.
"It is rightly so that he has received a lengthy prison sentence which reflects the seriousness of his offending.
"He will now be in prison where he can no longer be a danger to other children.”