Résumé
A strong edge colouring of a graph $G$ is a proper edge colouring such that every path of length 3 uses three colours. In this paper, we prove that every subcubic graph with maximum average degree strictly less than $\frac{15}{7}$ (resp. $\frac{27}{11}$, $\frac{13}{5}$, $\frac{36}{13}$) can be strong edge coloured with six (resp. seven, eight, nine) colours.