The increasing demand for faster broadband access requires the development of next-generation Passive Optical Networks (PONs) operating at very high bit rates (e.g. 40 Gb/s). On the same time, energy efficiency in Information and Communication Technology (ICT) infrastructure has become a very important topic. In this paper, several proposed solutions for future high-speed PONs, such as coherent and incoherent multilevel signaling, wavelength-multiplexed On-Off Keying (OOK) and Orthogonal Frequency Division Multiplexing (OFDM), are examined with regards to the energy consumption of the system, with results indicating that the necessary bit rates can be provided without sacrificing energy efficiency
