A method of handling upstream data transmissions in a passive optical network includes determining signal power levels of a plurality of optical network units (ONUs); and scheduling transmissions of upstream data bursts of the plurality of ONUs by, assigning each of the upstream data bursts to one of two or more data burst groups based on the determined signal power levels, and selecting time intervals during which the upstream data bursts are transmitted in accordance with the two or more data burst groups such that the two or more data burst groups are scheduled to be transmitted sequentially.