A method, system and non-linear optical storage medium are presented for use in at least reading data in the medium. The technique utilizes a first function corresponding to an effect of data recording in the medium and a second function corresponding to an effect of reading the recorded data, where each of the first and second functions is a function of at least a power profile of applied interacting radiation in a respective one of the recording and reading events and a duration of said event. These data is utilized to select a certain operating mode defined by ranges of said power and duration parameters during the reading process corresponding to a non-degenerate relation between the first and second functions.