That followed a four-year spell in Belfast, and O'Connor revealed that it was good to be home again under new Ulster boss Mark Anscombe.
He said: "It feels like I've been away a bit longer than a season but not too much has changed.
"There are a few new faces, but most of the backroom staff has stayed the same, and pre-season is just as tough.
"The decision to come back really came when Ian Humphreys decided to move to London Irish.
"They needed someone to fill in that position and although I had another year left on my contract at Connacht they were happy to let me go. Dan Parks was obviously arriving there so it made sense for me to return to my home club.
"It's a great opportunity for me. I know Paddy Jackson has taken his chances very well and stepped up in the second part of last season.
"He will be seen as first choice but we will get an equal chance to stake a claim for the fly-half spot."
Having spent the majority of his first spell at Ulster battling with Humphreys for the first-choice fly-half jersey, O'Connor admits the move away did him good.
But having sampled the life in Galway and worked with former Irish fly-half Elwood, he insists he has come back a much better player.
He added: "It was a good experience for me to get away for a year. Before I left a lot of people were saying that the only way to improve was to get more game time.
"I got that opportunity in Connacht and it did me a lot of good, it gave me a lot of confidence being first choice.
"I've definitely got more game awareness than when I left, and that's something I'll be looking to show at Ravenhill.
"We're ambitious going into the new season with Mark Anscombe in charge who is settling in well. The guys have really taken to him well and he's come in here with some fresh ideas."
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