Initial status (O1)
The ONU in this status has just powered on and is still in LOS / LOF.Once a downstream is received, the LOS and LOF are eliminated, and the ONU moves to the standby status (O2).
Standby status (O2)
The ONU of this status has received the downstream, waiting to receive the network parameters.When the ONU receives the Upstream_Overhead message, it performs the relevant configuration (e. g., demarcation character, power mode, preset equilibrium delay) and transfers to the serial number status (O3).
Serial Number status (O3)
The OLT sends Serial-Number Request messages to all the ONU in that status to discover the new ONU as well as their serial number.When the OLT finds a new ONU, the ONU waits for the OLT to give it an ONU-ID.OLT pass through The Assign_ONU-ID message refers to the ONU-ID match.After ONU obtains ONU-ID, it transfers to ranging status (O4).
Ranging status (O4)
Different ONU sending signals should remain synchronized when they reach the OLT, so that each ONU needs an equilibrium delay, and this parameter is measured in the ranging status.The ONU receives the Ranging_Time message and moves to the running status (O5).
Running status (O5)
The ONU in this status can send uplink data and PLOAM messages under the control of the OLT, and the ONU in this status can also establish other connections as required.When the ranging is successful, all the ONU are sent according to their respective equilibrium time delay signal to keep the uplink frame synchronized.The signals sent by the different ONU will reach the OLT separately, but each signal appears exactly where it should appear in the uplink frame.Pause the ONU in operation: During normal operation, the OLT may cause the ONU to pause the signal to obtain the serial number of the other ONU or distance the other ONU.OLT stops licensing all uplink bandwidth for a time, ONU works the normal way, and does not receive the authorization, creating a quiet period, so OLT causes all ONU to pause the signal.
POPUP Status (O6)
This status is entered when the ONU in the operation status (O5) detects a LOS or a LOF.In this status, the ONU immediately stops sending the signal, so that the OLT will detect the LOS alarm for the ONU.When an ODN fiber is interrupted, many ONU will enter this state, considering the network reliability, in one of the following ways:
If protection inversion is enabled, all ONU will inverted to the backup fiber.At this point, all ONU will resagain, and this OLT sends a Broadcast POPUP message to notify all ONU to enter the ranging status (O4).
If there is no protection inversion but the ONU has internal protection capability, the OLT sends a Directed POPUP message to notify the ONU to enter the running status (O5).When the ONU enters the O5 status, the OLT needs to detect the ONU first and then Restore the business of the ONU.If the ONU does not recover from the LOS or LOF, the ONU will not receive the Broadcast POPUP message or Directed POPUP message, and after the TO2 time, the ONU enters the initial status (O1).
Emergency Stop State (O7)
When the ONU receives a Disable_Serial_Number message with the “Disable” option, the ONU enters an emergency stop state (O7) and turns off the laser.In the O7 state, the ONU is prohibited from sending signals.If the ONU does not successfully enter the O7 state, and the OLT can continue to receive signals from the ONU, the OLT generates a Dfi alarm.When the ONU fails, the OLT sends a Disable_Serial_Number message with the Enable ” option to activate the ONU.ONU receives the message and enters standby (O2) and all parameters (including serial number and ONU-ID) are re-checked.