An Optical Line Terminal, OLT, comprising: a Passive Optical Network, PON, communications interface; one or more data processing apparatus; and one or more memory devices, wherein the one or more data processing apparatus execute instructions that cause the one or more data processing apparatus to perform operations comprising: broadcasting a message over an optical network; receiving, from an Optical Network Unit, ONU, a response to the message; transmitting, to the ONU, activation parameters specifying that the OLT supports multiple different Forward Error Correction, FEC, code lengths when FEC is activated; receiving, from the ONU, a set of FEC code lengths supported by the ONU and performance measures collected by the ONU; selecting, from among the FEC code lengths supported by the ONU, one or more appropriate FEC code lengths for communications between the ONU and the OLT based on the performance measures collected by the ONU and performance measures collected by the OLT; and configuring the ONU to utilize the appropriate FEC code length, wherein broadcast messages transmitted by the OLT use a longer FEC code length than unicast messages transmitted to at least one of the ONUs that are registered with the OLT. a Passive Optical Network, PON, communications interface; one or more data processing apparatus; and one or more memory devices, wherein the one or more data processing apparatus execute instructions that cause the one or more data processing apparatus to perform operations comprising: broadcasting a message over an optical network; receiving, from an Optical Network Unit, ONU, a response to the message; transmitting, to the ONU, activation parameters specifying that the OLT supports multiple different Forward Error Correction, FEC, code lengths when FEC is activated; receiving, from the ONU, a set of FEC code lengths supported by the ONU and performance measures collected by the ONU; selecting, from among the FEC code lengths supported by the ONU, one or more appropriate FEC code lengths for communications between the ONU and the OLT based on the performance measures collected by the ONU and performance measures collected by the OLT; and configuring the ONU to utilize the appropriate FEC code length, wherein broadcast messages transmitted by the OLT use a longer FEC code length than unicast messages transmitted to at least one of the ONUs that are registered with the OLT. broadcasting a message over an optical network; receiving, from an Optical Network Unit, ONU, a response to the message; transmitting, to the ONU, activation parameters specifying that the OLT supports multiple different Forward Error Correction, FEC, code lengths when FEC is activated; receiving, from the ONU, a set of FEC code lengths supported by the ONU and performance measures collected by the ONU; selecting, from among the FEC code lengths supported by the ONU, one or more appropriate FEC code lengths for communications between the ONU and the OLT based on the performance measures collected by the ONU and performance measures collected by the OLT; and configuring the ONU to utilize the appropriate FEC code length, wherein broadcast messages transmitted by the OLT use a longer FEC code length than unicast messages transmitted to at least one of the ONUs that are registered with the OLT.