| 摘要 |
PURPOSE:To eliminate the transmission fault based on the changeover of an optical transmission terminal station by constituting a switch circuit that the switching operation is started only in the timing when the part from the start of switching to its end is included completely during the stop period of optical transmission based on the AND between detecting signals of a switching start enable timing detection circuit. CONSTITUTION:Optical transmission terminal stations 12A, 12B duplicated normally are operated by identical optical inputs divided into two by an optical branching filter 5 and the data is transmitted by allowing a switch circuit 22 to select an optical output of either optical transmission terminal station. When the stop of continuity of the optical transmission over a time required for the operation of the switch circuit depending on the content of optical reception of the optical transmission terminal stations 12A, 12B is detected at the point of time of optical transmission stop by switch start enable timing detection circuits 13A, 13B, it is expected that the switching operation of the switch circuit 22 is finished while the optical transmission is stopped even when the switch circuit 22 starts the switching operation and the output using the output logic as logical 1 is transmitted to an AND circuit 14 during the expected time. Thus, while the output logic of the AND circuit 14 is logical 1, even when the switch circuit 22 starts the switching operation, the switching is finished until the next start of optical transmission. |
