  This paper proposes a novel scheme which can efficiently reduce the energy
consumption of Optical Line Terminals (OLTs) in Time Division Multiplexing
(TDM) Passive Optical Networks (PONs) such as EPON and GPON. Currently, OLTs
consume a significant amount of energy in PON, which is one of the major FTTx
technologies. To be environmentally friendly, it is desirable to reduce energy
consumption of OLT as much as possible; such requirement becomes even more
urgent as OLT keeps increasing its provisioning data rate, and higher data rate
provisioning usually implies higher energy consumption. In this paper, we
propose a novel energy-efficient OLT structure which guarantees services of end
users with the smallest number of power-on OLT line cards. More specifically,
we adapt the number of power-on OLT line cards to the real-time incoming
traffic. Also, in order to avoid service disruption resulted by powering off
OLT line cards, proper optical switches are equipped in OLT to dynamically
configure the communications between OLT line cards and ONUs.
