  Based on the connection between the spectral form factor and the probability
to return, the origin of the $1/f^\alpha$-noise in fully chaotic and fully
integrable systems is traced to the quantum interference between invariant
manifolds of the classical dynamics and the dimensionality of those invariant
manifolds. This connection and the order-to-chaos transition are analyzed in
terms of the statistics of Floquet's quasienergies of a classically chaotic
driving non-linear system. An immediate prediction of the connection
established here is that in the presence of decoherence, the spectral exponent
$\alpha$ takes the same value, $\alpha=2$, for both, fully chaotic and fully
integrable systems.
