Launch Power Control for Digital Subcarrier Equalization in Filterless Optical Networks

This paper investigates the advantages of exploiting launch power control in point-to-multipoint (P2MP) transceivers when deployed in filterless horseshoe optical networks. In order to realize simple and cost-effective optical nodes, 2-by-2 optical couplers can be used in these networks, resulting in a filterless architecture that avoids the deployment of expensive wavelength selective switches (WSSs). Optical amplifiers can be deployed as needed to compensate for losses. However, if P2MP transceivers are used, in the upstream direction the receiver can only tolerate up to a certain difference between the power levels of the incoming signals. Meeting this limit may demand additional amplifiers to be used in the transmission paths. Leveraging the ability to control the launch power of each transmitter in the upstream direction can mitigate the need to deploy additional amplifiers. This work proposes a mathematical framework to minimize the number of optical amplifiers required in filterless horseshoe networks fitted with P2MP transceivers with launch power control. The results support the benefits of having launch power control in the transceivers to reduce the number of optical amplifiers required when exploiting $\mathbf{P} 2 \mathrm{MP}$ connectivity in the optical domain.