8. An apparatus for controlling transmission in an Ethernet passive optical network (EPON) which includes an Optical Line Terminal (OLT) and at least one Optical Network Unit (ONU), wherein an ONU implements a data-link layer and a physical layer, the apparatus comprising: a receiving mechanism configured to receive, at the physical layer of an ONU, a word which is communicated from the data-link layer of the ONU, wherein the word may be a data word or an idle word; a delay mechanism configured to delay, at the physical layer in the ONU, the word for a pre-determined amount of time before allowing the word to be transmitted by a transmitter, thereby providing time for turning the transmitter on or off; and a control mechanism configured to turn the transmitter at the physical layer in the ONU on or off based on the current state of the transmitter and content of the received words without data-link layer sending a control signal across multiple sublayers to the physical layer in the ONU.
8. An apparatus for controlling transmission in an Ethernet passive optical network (EPON) which includes an Optical Line Terminal (OLT) and at least one Optical Network Unit (ONU), wherein an ONU implements a data-link layer and a physical layer, the apparatus comprising: a receiving mechanism configured to receive, at the physical layer of an ONU, a word which is communicated from the data-link layer of the ONU, wherein the word may be a data word or an idle word; a delay mechanism configured to delay, at the physical layer in the ONU, the word for a pre-determined amount of time before allowing the word to be transmitted by a transmitter, thereby providing time for turning the transmitter on or off; and a control mechanism configured to turn the transmitter at the physical layer in the ONU on or off based on the current state of the transmitter and content of the received words without data-link layer sending a control signal across multiple sublayers to the physical layer in the ONU. 9. The apparatus of claim 8 , wherein while turning the transmitter on or off based on the content of the received words, the control mechanism is configured to turn on the transmitter if the transmitter is currently powered off and if the received word is a data word.