| 摘要 |
PURPOSE:To make it possible to reduce the number of transmission lines, constituting each terminal station, down to one and also to halve needed switches in an exchange in number by changing transmission over to reception, or vice versa in each terminal station by using a branching filter. CONSTITUTION:Each of terminal stations 1-4 is provided with branching filter 8, filter 9 of which allows light of waveform lambda1 to pass through and reflects that of waveform lambda2. One transmission line 7 from terminal stations 1-4 is used and the number of switches 6 in exchange 5 is halved. When terminal station 4 communicates with terminal station 2, switch 10 is connected as shown by solid lines and light emission source 11 emits light of lambda1, which reaches terminal station 2 after piercing filter 9. A light signal of lambda2 transmitted from terminal station 2, on the other hand, is reflected by filter 9 and reaches photodetector 12. Next, when terminal stations 1-3 communicate with terminal station 4, switch 10 of terminal station 4 is left connected as it is as shown broken lines and a light signal of lambda1 transmitted from terminal stations 1-3 reaches photodetector 12 and terminal station 4 sends the signal of lambda2 from light emission source 13. |
