| 摘要 |
<p>PURPOSE:To maintain communication even when an optical transmission line itself has been disconnected, by making each wave supervisory station have a folding function, by folding by an optical signal of the other wavelength when an optical signal of one wavelength between 2 kinds of wavelength has been cut off. CONSTITUTION:When an optical signal of wavelength lambda1 has been stopped, a control signal is outputted from an input signal cut-off detecting circuit 18', and a switch 20 is switched to the side of B' from A'. Accordingly, an optical signal of wavelength lambda2 from an optical transmission line 3' is converted to an electric signal, and after that, the prescribed processing is executed by a data inserting an branching circuit 17 it is converted to an optical signal of wavelength lambda1 by an electric signal/electric signal converting circuit 9 through the switch 20, and is folded to the transmission line 3' again. On the other hand, in case the optical signal of wavelength lambda2 has been stopped, a switch 19 is switched to the side of B from A by a control signal 23, and the same operation as above is executed. In this way, communication can be maintained even if the optical transmission line has been disconnected, and reliability of the transmission system is raised.</p> |
