There is a need to recover an ONU from a sleep state for communication with the PON before a specified sleep cancel time in a short period of time without degrading the band use efficiency. An OLT manages an electric state of each ONU connected to a PON. When at least one ONU is in sleep mode, the OLT transmits a grant to allocate a band for a sleep cancel report to the ONU. When the sleep-mode ONU requires communication, the ONU transmits the sleep cancel report to the OLT using the band for the sleep cancel report. When receiving the sleep cancel report, the OLT changes the managed ONU to a normal state and resumes the communication with the PON.