| 摘要 |
PURPOSE:To switch an active optical fiber line to a new switching line without interrupting communication state by providing two 1X2 variable branch couplers per one connecting point to two switching points of an active line and varying the branch ratio. CONSTITUTION:A couple of 1X2 variable optical branching couplers 20, 21, 22, 23 are provided at switching points A, B in an active line before switching work. Moreover, a couple of branch side optical fibers 25a, 25b and 31a, 31b are connected respectively to a couple of branch side optical fibers 27a, 27b and 29a, 29b respectively by the couplers 21, 22. Then the branch ratio of each coupler is made variable and the line consists of the coupler 20, a tenttive switching line 13 and the coupler 22 or the like at first and the switching and constitution of the line by the couplers 20, 21, a main switching line and the couplers 22, 23 are implemented by six processes. Thus, the branch ratio is made variable without interrupting the normal state in the site of changeover to prevent rapid change in the optical signal level, then the out of synchronism due to the change in the optical signal level is not caused in comparison with the fixed branch ratio to attain changeover. |
