Generation of 1/f noise in locked systems working in nonlinear mode

Properties of the phase fluctuations of a nonlinear oscillator were investi gated. The multiscale aspect of synchronization is experimentally confirmed with the observation of lockings at any rational ratio. This global proper ty of synchronization is associated with a local one by the study of the ph ase locked loop (PLL) under nonlinear conditions. We show that the disconti nuity between the locking and the free-run state is characterized by the pr esence of slow temporal variations that induce a low frequency spectrum. An experimental verification of the increase of fluctuations confirms the cla ssical results, which associate 1/f noise to nonlinearity, autosimilarity a nd regularity, represented here by the synchronization.