| 摘要 |
PURPOSE:To simplify the extension or the removal of nodes in an optical bus by constituting a branch coupling rate between anode and an optical bus so as to be controlled and setting the branching coupling rate of a branching coupler with no node connecting thereto to be smaller than the branching coupling rate of the branching coupler with a node connecting thereto. CONSTITUTION:The branching coupling rate of branching couplers 8a-8d is changed by a control voltage applied to external control terminals 11a-11h and set to a prescribed value. Then a control voltage from the branch coupling rate control means sets the branching coupling rate between the node and the optical bus of the branching coupler 8b where nodes 13a-13c (13) are not connected so as to be smaller than that of branching couplers 8a, 8c, 8d where a node 13 is connected. Thus, the transmission loss of the branching coupler 8b where nodes 13a-13c (13) are not connected is very small. Thus, lots of the branching couplers 8a-8d are inserted in the optical bus and the node 13 is connected as necessary to simplify the extension and the removal of the node 13 in the optical bus. |
