Abstract: In a communication system using a PON, time synchronization of a slave device such as a base station is realized with respect to a master device such as an L2SW or the base station. Time information acquired by a GPS satellite is corrected by ranging information of a discovery function of an OLT so as to be reflected on time information of each ONU. A propagation delay from the L2SW to the OLT is obtained with the use of a delay estimation mechanism, a propagation delay from the OLT to the ONU which is obtained by ranging is added to obtain a propagation delay from the L2SW to the ONU. The obtained propagation delay from the L2SW to the ONU is added to the transmitted time stamp value whereby a time stamp value received at a base station or femtocell side becomes a time into which the propagation delay to the ONU is incorporated, and absolute values of clock timers can be synchronized with each other.

Abstract: In a communication system using a PON, time synchronization of a slave device such as a base station is realized with respect to a master device such as an L2SW or the base station. Time information acquired by a GPS satellite is corrected by ranging information of a discovery function of an OLT so as to be reflected on time information of each ONU. A propagation delay from the L2SW to the OLT is obtained with the use of a delay estimation mechanism, a propagation delay from the OLT to the ONU which is obtained by ranging is added to obtain a propagation delay from the L2SW to the ONU. The obtained propagation delay from the L2SW to the ONU is added to the transmitted time stamp value whereby a time stamp value received at a base station or femtocell side becomes a time into which the propagation delay to the ONU is incorporated, and absolute values of clock timers can be synchronized with each other.

Abstract: In the case where, in a WDM-PON system, a high-output optical signal or a pseudo signal for illegal access by a hostile user, or an optical signal with a wavelength which is not assigned from an OLT is input to an ONU-side optical fiber, the quality of communications for other users is possibly affected and a receiver on the station side is possibly destroyed. By providing an optical blocking unit at a position near an ONU-side optical splitter of an optical branching unit, in the case where input of an extraordinary optical signal is detected, an optical route into which the extraordinary optical signal is input is blocked, so that the input of the extraordinary optical signal to an OLT and optical lines shared by plural users can be preliminarily blocked.