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 compare the performance of the heuristics with an ILP for a small size network. Results demonstrate that the proposed band-aware reachability graph heuristic yields solution that are very close to the ILP. We study the performance of the heuristics on larger networks and study their effectiveness in reducing the combined cost of optical switch ports and electronic regenerators.