A passive optical network system includes an optical line terminator (OLT) configured to detect signal strength and a phase of a burst-mode uplink signal from each of optical network units (ONUs) to control the ONUs so as to equalize signal strengths of signals received from the ONUs and configured to control the ONUs so as to adjust a phase of each of the signals received from the ONUs, and the ONUs are each configured to control signal strength and phase of an burst-mode uplink signal and transmit a resultant burst-mode uplink signal under control of the OLT.