Noisy precursors in one-dimensional patterns

Noisy pattern precursors have been observed experimentally in a Kerr-like slice subjected to one-dimensional (1D) optical feedback. These noise-induced patterns appear below threshold and anticipate the characteristics of the incoming patterns. In our 1D system, precursors are rolls with an undefined spatial phase which wanders erratically and locks spatially when crossing the threshold. Phase localization allows for a criterion to define the threshold in presence of noise. The experimental observations are well reproduced by the standard model of the Kerr slice medium with optical feedback when Langevin noise terms are included.