Passive optical network systems

A passive optical network system comprising an optical line terminator (OLT) and a plurality of optical network units (ONUs),

• wherein the OLT comprises:
• a power measurer configured to measure signal strength of an electrical signal converted from a burst-mode uplink optical signal received in each of channels allocated to the ONUs in a test mode;
• a phase detector configured to detect phase of the electrical signal obtained by conversion for each of the ONUs in the test mode;
• and
• a remote transmission signal controller configured to determine reference signal strength on the basis of signal strength measured for each of the ONUs, and create and transmit a signal strength control message for control of signal strength of each of the ONUs according to the reference signal strength, and a phase control message for synchronization on the basis of a phase detected for each of the ONUs in units of ONUs, and
• the ONU comprises:
• a control message receiver configured to receive the signal strength control message and the phase control message from the OLT,
• a signal strength controller configured to control signal strength of the burst-mode uplink optical signal to be changed according to the received signal strength control message;
• and
• a phase controller configured to control a delay according to the received phase control message so as to adjust a phase of the burst-mode uplink optical signal.