The fiber network refers to the network connected by fiber links, whose topology is called the fiber topology. The fiber network is constructed over the physical network, but its topology may
differ from the original physical topology. A lightpath is a wavelengthchannel from the source node
to the destination node in the fiber network used to transport the service traffic.
Therefore, lightpaths are built over the fiber links and the fiber links are con-structed over the physical links (cables).