Optical delay lines based on optical filters

Optical delay lines have some important applications, notably in optical co mmunication systems and in phased arrays. These devices are based on the co ncept of optical group delay, which, in turn, call be understood as the pro perty of an optical filter. Optical filters are well-understood devices and , in particular, their dispersive properties determine the group delay resp onse,We review these dispersive properties and point out some of the inhere nt tradeoffs involved in generating large group delay Fiber Bragg gratings and recent results on optical all-pass filters are used as examples.