The man, who cannot be identified to protect the anonymity of the victim, was also sentenced on two counts of sexual assault at Belfast Crown Court.
Stealth rape is the removal of or not using a condom during sex without a sexual partner's consent. The victim has urged other women who may be in the same situation to come forward to police.
The former officer was convicted of the four offences at the end of a trial in April. The court heard on Friday he was dismissed by the PSNI in May.
During sentencing, judge Paul Ramsey KC described it as a highly unusual case. He said the defendant and the victim had been living together for several years, but had become estranged.
The judge said police attended their home in 2020 following a report of a domestic disturbance. The victim subsequently made a number of allegations of sexual assault.
The court heard the first rape occurred in March 2007 when the defendant refused to stop during sexual intercourse after being asked by the victim. The second rape occurred between April and May 2017 when the victim agreed to have sex only if he wore a condom. She then saw the condom on the floor during intercourse.
He was also convicted of sexual assaults in December 2017 and May to June 2018. The judge said the defendant continues to maintain his innocence.
Judge Ramsey said medical reports indicated the defendant had been exposed to life-threatening incidents through his work and had been diagnosed with post-traumatic stress disorder.
The judge then referred to a statement provided to court by the victim who had said the defendant's "appetite for sex was insatiable". He said the victim felt she had been re-victimised by the trial process, which she described as "embarrassing and harrowing".
The defendant was sentenced to five years, with half the sentence to be served in custody. He will also be placed on the sex offenders' register for life.
PSNI detective superintendent Lindsay Fisher said: "This man's disgraceful actions fell far below the standard we expect from our officers and staff.
"Once his offending came to light, he was arrested, suspended and subsequently dismissed by the police service. Today, our thoughts are with the brave woman in this case who has assisted us in our investigations. I commend her courage in taking the brave step to come forward.
"Today we send another strong message that there is no place for this behaviour in policing and we are dedicated to relentlessly pursuing perpetrators and bringing them to justice, no matter who they are."
A statement from the victim said: "I wish to thank my family and friends for the unwavering support you have given me throughout this entire process.
"I also want to thank Women's Aid for the support, comfort and reassurance they have provided.
"Lastly, I want to thank the investigating officer within the police service, and all those who contributed to the police investigation, for the empathy and swiftness in which my case was dealt with.
"I urge anyone else who has suffered similarly to take confidence from my journey and to reach out and tell someone about it, knowing you will be treated with the utmost respect and sensitivity.
"If you have experienced any form of sexual abuse contact police on 101, or in an emergency call 999."