Optical transmitter

An optical transmitter for converting an input data series which is an input electrical signal into an optical multi-level signal and for outputting the optical multi-level signal, comprising:

• a look-up table in which data for executing optical multi-level modulation is stored and from which first modulation data and second modulation data are output based on the input data series;
• a first D/A converter which converts the first modulation data by D/A conversion to generate a first multi-level signal;
• a second D/A converter which converts the second modulation data by D/A conversion to generate a second multi-level signal;
• and
• a dual-electrode MZ modulator which comprises a first phase modulator for modulating light from a light source in accordance with the first multi-level signal and a second phase modulator for modulating light from the light source in accordance with the second multi-level signal, and which combines an optical signal from the first phase modulator and an optical signal from the second phase modulator to output the optical multi-level signal.