Operators can use Forward Error Correction (FEC) on some ports to improve either the transmission reliability or reach, or both. FEC must always be used on some interface types while it is optional for other interface types. Also, some interface types allow more than one type of FEC. No matter what the setting of the FEC attributes, the transmitter and the receiver must have the same configuration, or the link will not work. The setting of FEC on a specific port is dependent on the interface type and the specific optical transceiver in use. Contact your Nokia representative for information about the options based on the transceiver in use.