Reverse power feeding (RPF) is a technology being standardized by ETSI[1] and the Broadband Forum in 2020.
The DPU includes typically a DSL access multiplexer (DSLAM) that can support up to 24 users and an optical network terminator (ONT), which connects the DPU to a central office (CO) where the optical line terminator (OLT) is located.
RPF is a critical technology for the upgrade of VDSL2 subscribers to the new G.fast standard, which has a maximum range (at high speeds) of 250m.
Given that only a small number of subscribers is located at a radius of 250m from a DPU, the number of DPUs required to deploy G.fast infrastructure greatly increases, compared to VDSL2 and older xDSL technologies.
This important difference comes from the fact that PoE was defined with enterprise networks in mind (where the maker of the powered device (PD) needs to interoperate with any power sourcing equipment (PSE)), while RPF is defined for networks that are closed by nature, deployed by a service provider.