An optical transmitter and receiver has stored in advance therein FEC techniques and applicable conditions for applying the FEC techniques to a counterpart optical transmitter and receiver. The optical transmitter and receiver measures a state of receiving data transmitted from the counterpart optical transmitter and receiver, determines an applicable condition satisfying the measured data reception state from among the stored applicable conditions, and selects a FEC technique stored in association with the applicable condition determined as satisfying. The optical transmitter and receiver then notifies the counterpart optical transmitter and receiver of the selected FEC technique.