The optical switching equipment is basically configured as a single configuration without protection as a basic unit and to split the optical signal into one signal passing through the equipment and the other signal to be added and dropped in the equipment and execute the adding and dropping process in a redundant portion. The optical transport network is configured to locate a plurality of optical switching equipments and optical transmission routes so as to allow the optical signals processed in the equipment for adding the optical signals to pass through the different optical transmission routes and equipments respectively. The optical signal allowed to pass through the equipment is processed in the single configuration portion of the equipment. The setting of the routes of the optical switching equipment and the optical transmission route makes it possible for the overall optical transport network to transmit the redundant optical signal.