Cost-effective and reliable multi-period optical network planning comparing capacity and topology upgrades

This paper investigates cost-effective and reliable multi-period planning of optical networks. To meet the expected demand increase, three planning optimization approaches are proposed and compared: spatial division multiplexing using the C-band (SDM-CB), ultra-wideband transmission in the C + L bands (UWB-MB), and topology upgrade (TopUp-CB). Each approach is evaluated through an integer linear programming formulation based on a cost model that considers the costs of lightpaths, fiber deployment, and link installation under two reliability requirements: 1 + 1 demand protection and minimal bit error rate (BER) for signal transmission. Simulation results on the Nobel Germany and NSFNET topologies reveal critical trade-offs between cost and resource utilization to prevent blocking. For Nobel Germany, UWB-MB requires 50% fewer fibers than SDM-CB but is 5% more expensive under high L-band transceiver costs. For NSFNET, when a lower transmission BER is required, the planning costs increase up to 150% compared to a higher BER value, while TopUp-CB can reduce the costs by up to 35% and 25% through the optimal addition of new links compared to SDM-CB and UWB-MB, respectively. These findings provide actionable guidelines for network operators to select the most suitable planning strategies under varying cost, capacity, and reliability constraints.