Regenerator Placement and Waveband Routing in Optical Networks with Impairment Constraints

Waveband networks allow multiple lightpaths to be aggregated and routed as wavebands, resulting in fewer switch ports. In an impairment-aware waveband network, a lightpath needs to be electronically regenerated before its signal to noise ratio reaches an unacceptable level. However, when a lightpath in a waveband needs to be regenerated, the entire waveband needs to be demultiplexed into wavelengths, resulting in additional wavelength ports at a node. Regenerator placement in a waveband network should be done so as to facilitate banding of lightpaths and to reduce the total cost of switch ports in the network. We formulate the regenerator placement problem in an impairment-constrained waveband network as an integer linear program (ILP). We propose three heuristics and show that the performance of the proposed band-aware reachability graph heuristic yields solutions that are close to the ILP for small networks. We also study the performance of the heuristics on larger networks with respect to the cost of optical switch ports and electronic regenerators.