| 摘要 |
PURPOSE:To prevent any fault at one part from being propagated to the entire system while securing reliability and further to house the system even in a user equipment provided with just one pair of a transmitter and a receiver by providing a mutual connecting means for mutually connecting two pairs of transmitting/receiving means and two pairs of light joining/branching means at a center equipment. CONSTITUTION:Since two pairs of photocouplers (mutual connecting means) 4-0 and 4-1 are used between optical star couplers 1a-0, 1b-0, 1a-1 and 1b-1 and a center equipment 2, the '0' system transmitting/receiving means of the center equipment 2 is connected with the '0' system and '1' system transmitting/receiving means of user equipments 3z-3k and 3n, and the '1' system transmitting means of the center equipment 2 is connected with the '0' system and '1' system transmitting/receiving means of the user equipments 31-3k and 3n. Thus, the fault of a part common for the respective user equipments 31-3k and 3n is distinguished from the fault of a part individual for the respective user equipments 31-3k and 3n, and an active system can be individually switched to a spare system within a required range. Therefore, the range to be affected by hit or the like with switching can be suppressed at a minimum. |
