  We are interested in the time asymptotic location of the level sets of
solutions to Fisher-KPP reaction-diffusion equations with fractional diffusion
in periodic media. We show that the speed of propagation is exponential in
time, with a precise exponent depending on a periodic principal eigenvalue, and
that it does not depend on the space direction. This is in contrast with the
Freidlin-G\"artner formula for the standard Laplacian.
