Abstract: The invention refers to a method and an arrangement for signaling in a network comprising nodes (A, B) provided with optical ports (2, 3). The optical ports have logic for signal loss detection and activation of optical output power or modulation control. The invention utilizes the logic for signal loss detection of transmis sion of information. Especially, the invention is utilized for transmission of topological information when ports and nodes are connected. According to the invention the information is transmitted by turning off and turning on the optical output power or modulation of the transmitting node. A port turned off provides an optical power or modulation below a threshold value, which corresponds to a logical level and a port turned on provides an optical power or modulation over a threshold value, which corresponds to another logical level. Nodes and ports can be connected in accordance with the method.

Abstract: A method and a device in a cross-connector node in an optical network for error propagation and signal path protection including supervision of incoming signal on input port, switching off of output port at loss of signal, alteratively switching so that output port is connected to signal source being part of protected path, and restart respective reconnection at detection of recurred signal.