Patent ID: 8811821

Claim:
An optical transmitter comprising: a selection circuit that selects signal components on sides of maximum and minimum values in a multivalued electrical signal for modulation of a transmitting signal as a low-frequency superimposed part, the multivalued electrical signal having three or more values including the maximum and minimum values and an intermediate amplitude value; a signal processing circuit that generates a multivalued electrical signal from a combination of a superimposed signal obtained by superimposing a low-frequency wave on the low-frequency superimposed part and a signal having a plurality of intermediate amplitude values on which the low-frequency wave is not superimposed; an optical modulator that modulates a carrier light on the basis of the multivalued electrical signal generated by the signal processing circuit; and an amplitude control circuit that controls a reference amplitude value or amplitude of the multivalued electrical signal on the basis of low-frequency components contained in a modulated optical signal modulated by the optical modulator.