| 摘要 |
PROBLEM TO BE SOLVED: To build up a passive double star PDS method optical communication system where the installation investment cost is suppressed and a communication service with high reliability is served in an optical line concentrator in the PDS method communication system and a changeover method of active system/ standby system. SOLUTION: The optical line concentrator 1 where many user devices are connected via an optical transmission line 22 and an optical star coupler 23, is provided with two optical transmission systems 2, 3 that transmit an optical signal to the optical star coupler 23 and with changeover means 4-8 that switch an active system transmission line to a standby system transmission line for the optical transmission lines 25, 26 between each of the two optical transmission systems 2, 3 and the optical star coupler 23. |
