Back in October, the German club defeated the Hoops 2-0 at home in the Europa League.
Poulsen - who is valued at €17.8 million (£15.91m) by the CIES Football Observatory - has praised Celtic, and the comments of the 24-year-old Denmark international forward will make fans of the Scottish giants proud.
Poulsen told The Scottish Sun: "We have played all the teams in the Bundesliga for the past two seasons and we know how they play and what their weak points are. With Celtic it was different.
“When you meet an opponent like Celtic in Glasgow for the first time in Europe, there were new challenges that we needed to face first. And sometimes it doesn't work out so well and that's what happened.”
Europa League progress
Celtic are going strong in the Scottish Premiership and could also progress to the knockout rounds of the Europa League.
Brendan Rodgers's side will take on RB Salzburg at Celtic Park in the Europa League next week.
The Hoops are second in Group B with nine points from five matches, six points behind Salzburg - who have already won the group - and three points clear of third-placed Leipzig.
A draw next week will be enough for Celtic to progress to the knockout rounds of the Europa League this season.