Two degrees in Electronic and Mechanical Engineering from the Catholic University of Leuven (Belgium) in 1967, and subsequently received ME and Ph.D. degrees from Carleton University, Ottawa, in 1968 and 1970 respectively.
From 1970 to 1973, he was involved in research into power semiconductors at the Brown Boveri research center in Baden, Switzerland.
J. Cornu joined the Belgian subsidiary of ITT, Bell Telephone, in 1973 as Design Center Manager, and was responsible for LSI Design and Development. In 1983, he became General Manager of the newly formed components company Mietec, jointly owned by Bell Telephone and the Flemish Government. In 1984, he was appointed General Manager of Bell Telephone and member of its Board of Directors.
In March 1987, just after the creation of Alcatel, he was named Vice President and Group Executive, Public Network Systems. On January 1, 1988 he assumed the additional responsibility of Executive Vice President, Business Development, Technical and Operations for the whole Alcatel group and was named member of the Board of Management. On January 1, 1990 he was also appointed President of the Alcatel Network Systems Group.
On July 17, 1995, he was appointed Chief Operating Officer of Alcatel Telecom and member of the Alcatel Executive Committee.