Abstract
The periodic structures show interesting optical properties. In addition to the temporal behavior, light propagation is a spatial phenomenon and therefore it associates three dimensions x, y (transversal) and z (propagation) in a physical harmony. Periodicity presents a spatial or a temporal link in the four-dimensional space (x,y,z,t). Thus, three main situations of periodic structures are distinguished. Periodicity may be imposed on the transversal plane (x,y), on the longitudinal axis (z) or on the time axis (t). In this work we show how all of these situations have direct interesting applications in fiber based telecommunications.