  We present, experimentally and numerically, the observation of
Fermi-Pasta-Ulam recurrence induced by breather solitons in a high-Q SiN
microresonator. Breather solitons can be excited by increasing the pump power
at a relatively small pump phase detuning in microresonators. Out of phase
power evolution is observed for groups of comb lines around the center of the
spectrum compared to groups of lines in the spectral wings. The evolution of
the power spectrum is not symmetric with respect to the spectrum center.
Numerical simulations based on the generalized Lugiato-Lefever equation are in
good agreement with the experimental results and unveil the role of stimulated
Raman scattering in the symmetry breaking of the power spectrum evolution. Our
results shows that optical microresonators can be exploited as a powerful
platform for the exploration of soliton dynamics.
