Regenerator placement algorithms for connection establishment in all-optical networks

In wavelength-routed all-optical networks, signals are transmitted on a direct optical path, or a lightpath, in a single-hop manner without opto-electronic/electro-optic (OE/EO) conversion at intermediate nodes. However, due to the physical constraints of optical elements such as ASE noise and crosstalk, signals can be degraded on a long path. To establish a connection under such impairments, the optical signal may need to be regenerated at intermediate nodes, dividing a lightpath into two or more fragments. However, since signal regeneration at intermediate nodes requires additional network resources, the selection of these nodes should be made carefully to minimise blocking of other lightpaths. The problem of establishing a lightpath in a multihop manner under physical constraints is considered. The authors provide both minimal-cost and heuristic algorithms for locating signal regeneration nodes (SRNs). For a minimal-cost algorithm, the problem is formulated using dynamic programming (DP) such that blocking of other lightpaths due to the lack of transmitters/receivers (TXs/RXs) and wavelengths is minimised throughout the network. The blocking performances of the algorithms are compared with several other algorithms in a ring network