  We present Fourier analysis at 490\,nm for 87 Cepheid light curves in the bar
of the Large Magellanic Cloud. The photometry has be obtained through the EROS
project whose main purpose is the search for baryonic dark matter in the
Galactic halo. The very high quality of the photometry and the good phase
coverage enable us to obtain accurate Fourier decomposition of the ligh curves.
As a consequence we confirm that the so-called s-Cepheids are overtone
pulsators and represent about 30 $\%$ of our sample, whereas the Classical
Cepheids are fundamental pulsators. We have identified a number of features in
plots of amplitude ratios and phase differences versus period. These features
are usually related to resonances between different pulsation modes. If we
accept that Fourier decomposition techniques applied to light curves yield
positions for the centres of resonances, then it seems that resonances occur in
LMC Cepheids at the same period as in Galactic Cepheids for fundamental
pulsators, whereas they appear to be at shorter periods for overtone pulsators.
