Design concept and characteristics of a power supply for optical network units in FTTH systems

This paper describes the design concept and characteristics of a power supply for optical network units in Fiber To The Home (FTTH) systems. Powering architectures of local powering, network powering and power hub powering are compared in terms of cost and maintainability. A local powering architecture is selected for an ONU power supply because it is the most cost-effective overall compared with the others. The local power supply is mainly composed of a rectifier, DC-DC converters, a ringer, and batteries. A battery deterioration test function is important for the local power supply because battery lifetime varies depending on ambient temperature, discharge history, and charging conditions, and it is shorter than other electrical components used in ONU. Supplying power using alternative batteries is also necessary because the capacity of batteries installed in the power supply is limited. These functions and electrical characteristics are checked using an experimental power supply with Ni-Cd batteries.