Abstract: A communications network is described comprising a cable and a remote test unit being coupled to the cable. Optical data signals are transmitted with a first wavelength on the cable. The remote test unit is adapted to transmit optical test signals as well as optical result messages with a second wavelength to the cable.

Abstract: Mapping of a network topology, comprising a plurality of elements with one or more interconnections between the plurality of elements, is accomplished by representing the plurality of elements in a first matrix dimension, and representing the one or more interconnections in a second matrix dimension. A group of elements can be represented in a third matrix dimension. Instead of representing a connecting device for connecting groups of elements in the first matrix dimension, the connecting device can be represented in the second matrix dimension. The mapping can be used for providing a graphical representation of the network topology. In one embodiment, the plurality of elements is represented by parallel lines in the first matrix dimension, and/or the one or more interconnections by parallel lines are represented in the second matrix dimension.