Abstract: The communication device is connected with a plurality of user-side devices via a splitter. The communication device includes a matching means for performing matching to determine whether each of a burst delimiter, positioned at a start position of frame data which is a synchronization target in a burst optical signal transmitted from each of the user-side devices, and sync pattern data, positioned from the beginning of the burst optical signal to the burst delimiter in the burst optical signal, matches a predetermined pattern. The communication device also includes a synchronization means for, if matching of the sync pattern data and matching of the burst delimiter by the matching means succeeded, performing synchronization of the frame data on the basis of the position of the burst delimiter in the burst optical signal. The matching means performs matching of the burst delimiter after successful matching of the sync pattern data.

Abstract: The object of the present invention is to provide an IP multicast service system which can design an independent multicast group system in each network on the center side and the subscriber-side. In an IP multicast service system according to the present invention including: a center-side network configured by a plurality of multicast servers; and a subscriber-side network configured by a plurality of IP-STBs (Internet Protocol-Set Top Boxes) for receiving a multicast packet transmitted from the multicast servers and reproducing the multicast packet as an image, a group design on the basis of an independent group address system on the center-side network and on the subscriber-side network can be made by converting a group address of the multicast packet transmitted and received between the center-side network and the subscriber-side network.

Abstract: A PON (Passive Optical Network) system, which is installed in an access network for connecting a user terminal to a network and can improve the utilization efficiency of the network, is provided. The PON system comprises an OLT (Optical Line Terminal) and at least one ONU (Optical Network Unit), and the OLT connects with the network and the ONU accommodates a user terminal and connected to the OLT via an optical fiber. A logical link generation or deletion condition table and a logical link identifier management table are provided for allocating logical links to be used between the OLT and the ONU. The logical link generation or deletion condition table defines generation or deletion conditions of logical link depending on the traffic (or service) class indicated by contents of a packet passing through the PON system.