Career
Ahlsen started as a midfielder, but was later re-educated as a forward defender. He was known for his long-shots. Ahlsen started his career at the senior level with Fredrikstad FK in the middle of the 1970s.
In 1987, he transferred to South.K. Brann where he played for six seasons, a part from a short loan period to German Fortuna Düsseldorf.
Ahlsen became an iconic figure in South.K. Brann. He was looked upon as a saviour because he put a stop to the "elevator era" in South.K. Brann.
He finished his career back in Fredrikstad, where he is now the assistant coach. He made his debut for the Norwegian national team in 1983 and earned 54 caps, scoring three goals.