  In Ref. [Parra-Rivas at al., 2013], using the Swift-Hohenberg equation, we
introduced a mechanism that allows to generate oscillatory and excitable
soliton dynamics. This mechanism was based on a competition between a pinning
force at inhomogeneities and a pulling force due to drift. Here, we study the
effect of such inhomogeneities and drift on temporal solitons and Kerr
frequency combs in fiber cavities and microresonators, described by the
Lugiato-Lefever equation with periodic boundary conditions. We demonstrate that
for low values of the frequency detuning the competition between
inhomogeneities and drift leads to similar dynamics at the defect location,
confirming the generality of the mechanism. The intrinsic periodic nature of
ring cavities and microresonators introduces, however, some interesting
differences in the final global states. For higher values of the detuning we
observe that the dynamics is no longer described by the same mechanism and it
is considerably more complex.
