Patent ID: 8290369

Claim:
An optical access system, comprising: an Optical Network Terminal; and an Optical Line Terminal connected to the Optical Network Terminal and a network, wherein the Optical Line Terminal comprises: a first receiving unit that receives time-division multiplexed signals from a single terminal within the network at a constant period, a first transmitting unit that transmits each of subsets of the time-division multiplexed signals from the single terminal within the network to the Optical Network Terminal within a respective one of a plurality of first periodic frames, wherein each of the first periodic frames has a same fixed length, and a firsts scheduler that schedules transmission of a ranging signal for measuring a distance between the Optical Line Terminal and the Optical Network Terminal such that the ranging signal is transmitted after transmission of a first subset of the time-division multiplexed signals has begun, wherein the first transmitting unit: transmits the ranging signal at a first fixed timing within a second periodic frame, wherein the second periodic frame is composed of a fixed number of first periodic frames, and transmits the subsets of the time-division multiplexed signals at a second fixed timing within the second periodic frame, wherein the transmission of the subsets of the time-division multiplexed signals is not overlapped with the transmission of the ranging signal.