| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical transmitter and the like that are able to prevent deterioration in transmission characteristics in polarization multiplex transmission by optimizing the modulation amplitude of a polarization modulator without observing the polarization state of output of the polarization modulator by means of an optical element such as a polarizer.SOLUTION: A polarization modulator 103 performs polarization modulation of a phase modulation light phase modulated by a RZ-BPSK or CSRZ-BPSK scheme in a data modulator 102. An optical band-pass filter 104 limits the band of polarization modulation light that is obtained by polarization modulation and switches between two polarization states alternately. An envelope detector 107 performs envelope detection of voltage generated by photoelectric conversion of the band-limited polarization modulation light by a photoelectric converter 106. A controller 108 discriminates the modulation amplitude of the polarization modulator 103 when the envelope detected voltage value becomes the minimum, and performs control to the modulation amplitude to make the modulation amplitude of the polarization modulator 103 constant. |
