| 摘要 |
PROBLEM TO BE SOLVED: To obtain the redundancy changeover system for an optical subscriber interface in which mis-recognition of a line activation control signal is not caused when no optical signal is present so as not to give any effect onto the service in operation. SOLUTION: A branch device 15 transits forcibly by itself a frame synchronization state into a hunting state in comformity with an optical subscriber line frame timing 24 with a forced stop signal 14 from an active system optical subscriber line interface section 21. Furthermore, when the frame synchronization of the branch device 15 reaches the hunting state, an optical subscriber line interface section 22 of the active system changed from the standby system matches a timing when an optical signal output is started. Thus, the branch device 15 does not receive a no optical signal, extracts correctly the line activation control signal to attain redundancy changeover of the optical subscriber line interface without giving any effect on the service in operation. |
