Protection in mixed optical wdm systems

摘要: Devices (13.1, 31.1) communicate with each other on a wavelength channel using specific signals working WDM fiber (21) having parallel protection (23). An SDH system (13.S, 31.S) uses one of the fibers as fibres pair and has separate fibre (37) constituting that protecting for SDH-system. To provide an unambiguous or predictable behaviour case being cut RETs (29.1, ..., 29.S) have two modes. In first mode RET will be always carry traffic when input power is high enough. second they not automatically turn again after it lost signal thereupon returned. The can then manually restarted some suitable delay. Then sequence events unambiguously defined. For break fibre, loose its signal, off, immediately again. Thereby there enough time scheme SDH-system to carried out. thus path, i.e., now working, former fibre.