| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical modulator for generating an optical signal having a modulation code transmission speed exceeding the band limit of a digital analog converter.SOLUTION: In an optical modulator, a digital IC separates a digital modulation signal into a digital signal having high frequency side components and a digital signal having low frequency side components, and outputs the digital signal having the low frequency side components and the digital signal of the high frequency side components which are subjected to frequency downward conversion. A digital analog converter converts the digital signal of the low frequency side components and the digital signal of the frequency-downward-converted high frequency side components into first and second analog signals. An electrical signal combining unit subjects the second analog signal to frequency upward conversion to generate a frequency-downward-converted first analog signal having the same frequency band as the digital signal of the high frequency components, and adds the frequency-downward-converted first analog signal and the first analog signal, and outputs the added signals as an analog modulation signal to the optical modulator. |
