An optical connection path surveillance device for a transparent optical network includes analysis means (80, 81) adapted to detect node signatures carried by an optical signal in transit at a point of said network, each node signature including information uniquely associated with a switching node of the network. The analysis means include calculation means (81) adapted to determine a number of hops from said detected node signatures and error detection means (81) adapted to compare said number of hops to a predetermined threshold in order to detect a routing error in relation to said optical signal if said threshold is exceeded. In one embodiment, a surveillance device detects looped paths on the basis of the detected node signatures.