| 摘要 |
PROBLEM TO BE SOLVED: To obtain a stable RZ optical signal by making an electric signal always follow up an optimal bias point without having an influence on bias control in the other light intensity modulator even when a drift occurs on a transmission characteristic of one light intensity modulator. SOLUTION: Based on an electric signal from a photo-diode 5, 1st and 2nd bias control circuits 61, 62 generate optimal bias voltages, and supply them to 1st and 2nd light intensity modulators 2a, 2b, respectively, and also generate 1st and 2nd modulation signal 15a, 15b for a data modulator 7 and a clock modulator 8, to modulate the amplitudes of the outputs of the data modulator 7 and the clock modulator 8, respectively. |
