Koppel began working for Georg Jensen in 1945 and remained with the company for over 30 years. He created some of the company's most iconic designs, including the famous "Pyramid" cutlery series, which won the gold medal at the Milan Triennale in 1954.
His designs are characterized by a use of organic, flowing forms, as well as great attention to detail and functionality. Koppel was also known for his minimalist approach, which won him international recognition.
In addition to his work for Georg Jensen, Koppel also worked on projects for other companies, as well as public installations and exhibitions. He died in 1981, leaving behind a lasting legacy as one of Denmark's most influential designers.