Patent ID: RE42095

Claim:
A method for transmitting useful optical signals, comprising the steps of: providing an optical transmission device between a first transceiver and a second transceiver, the first transceiver including at least one of a first signal source and a first signal sink, the second transceiver including at least one of a second signal source and a second signal sink, the optical transmission device including at least one normal segment and at least one alternative segment, the at least one normal segment and the at least one alternative segment running parallel; intercoupling the at least one normal segment, the at least one alterative segment, the first transceiver and the second transceiver via at least two coupling nodes; generating, receiving and recognizing optical test signals section by section via at least four test signal nodes, the optical test signals being in addition to the useful optical signals and including at least a first of the optical test signals, a second of the optical test signals and a third of the optical test signals, the third one including the optical test signals that are not of the first one and not of the second one, the at least four test signal nodes including at least two test signal nodes and at least two additional test signal nodes, the at least two test signal nodes being arranged at ends of the at least one normal segment, the at least two additional test signal nodes being arranged at ends of the at least one alternative segment; transmitting the optical test signals via the optical transmission device; detecting a disturbance of the optical transmission device by receiving the third one via a test signal node of the at least four test signal nodes; and switching over between the at least one normal segment and the at least one alternative segment via the at least two coupling nodes, wherein the step of switching over between the at least one normal segment and the at least one alternative segment includes the step of switching over from a particular normal segment to a particular alternative segment via a particular coupling node, the particular coupling node being coupled to a closest test signal node of the particular normal segment via a control unit, and wherein the step of switching over from the particular normal segment to the particular alternative segment occurs when, before receiving the optical test signal of the third one, the closest signal node of the particular normal segment receives the optical test signal of the first one.