Abstract: In an extensive distribution system with no delay guarantee network used as a relay network, an influence of a fluctuation of a communication delay time is avoided to conduct a high-precision time synchronization. First and second delay control devices installed in junctions between communication networks and a relay network, respectively, have functions of retaining first and second time information, and setting a first relay network passing time of a first communication signal directed from a time dissemination device toward a time receiving device through a relay network, and a second relay network passing time of a second communication signal directed from the time receiving device toward the time dissemination device, respectively. In measurement of communication delay time of the first communication network and the second communication network prior to time synchronization, the first and second relay network passing times are unified in advance to exclude uncertainty of the communication time.

Abstract: In an extensive distribution system with no delay guarantee network used as a relay network, an influence of a fluctuation of a communication delay time is avoided to conduct a high-precision time synchronization. First and second delay control devices installed in junctions between communication networks and a relay network, respectively, have functions of retaining first and second time information, and setting a first relay network passing time of a first communication signal directed from a time dissemination device toward a time receiving device through a relay network, and a second relay network passing time of a second communication signal directed from the time receiving device toward the time dissemination device, respectively. In measurement of communication delay time of the first communication network and the second communication network prior to time synchronization, the first and second relay network passing times are unified in advance to exclude uncertainty of the communication time.

Abstract: In a PON system having a station side apparatus (OLT) and plural home side apparatuses (ONUs), the station side apparatus includes an uplink frame transfer processing part controlling frame transfer from the home side apparatus to the station side apparatus, a transfer database managing the destination of frame transfer from the station side apparatus to the plural home side apparatuses, a statistical counter part counting transfer data amount for each user, and a user usage state management part managing the user usage situation. The user usage state management part determines the user usage situation (used/unused) based on the state monitoring result of any one or all of parts described above, switches the operation of the uplink frame transfer control part depending on the usage situation and adjusts DBA control frame amount between the station side apparatus and the home side apparatus.