We demonstrate a self-organizing system based on photorefrac (cid: 173) tive ring oscillators. We employ the system in two ways that can both be thought of as feature extractors; one acts on a set of images exposed repeatedly to the system strictly as a linear feature extractor, and the other serves as a signal demultiplex (cid: 173) er for fiber optic communications. Both systems implement unsupervised competitive learning embedded within the mode interaction dynamics between the modes of a set of ring oscilla (cid: 173) tors. After a training period, the modes of the rings become as (cid: 173) sociated with frequencies within the incoming data stream.