| 摘要 |
PROBLEM TO BE SOLVED: To perform phase shift control at the time when generating a multi-value QAM signal parallel-using electrical front-end dispersion compensation by digital signal processing.SOLUTION: An optical transmitter comprises: a first optical modulator changing a phase and intensity of continuous wave light on the basis of first data; a second optical modulator changing a phase and intensity of the continuous wave light on the basis of second data; a phase shifter phase-shifting output light of the second optical modulator; an optical coupler multiplexing output light of the first optical modulator and output light of the phase shifter; first dither signal application means for superposing a first dither signal on a first bias voltage extinguishing the output light of the first optical modulator when the first data is at zero level; second dither signal application means for superposing a second dither signal orthogonal to the first dither signal on a second bias voltage extinguishing the output light the second optical modulator when the second data is at zero level; and phase amount correction means for correcting a phase shift amount so that a result of synchronously detecting a signal indicating a light power of the output light of the optical coupler by using a frequency double the first dither signal becomes zero. |
