A method, apparatus and system for aligning frames in which an Optical Network Unit (ONU) receives a frame comprising frame delimitation information and synchronization-related information; performs a first verification based on a comparison of the frame delimitation information and a fixed pattern; performs a second verification based on a comparison of the synchronization-related information and a value associated with synchronization-related information in a previously received frame; proceeds to a synchronization state if both the first verification and the second verification are successful; and returns to a hunt state if either the first verification or the second verification fails.