| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide a bias controlling device of an LN modulator having neither deterioration of quality nor deviation from the optimum point in modulated light while the characteristic of a conventional technology that an element having low speed corresponding to a low frequency sine wave may be used as a photo diode and the photo diode is not affected by power change is maintained, and to provide an optical modulation device using the bias controlling device. <P>SOLUTION: A low frequency signal generator 10 outputs a sine wave 30 having a lower frequency as compared with the frequency of an input signal 34. A tr and tf variable means 13 outputs a modulation signal 35 formed by changing the rising tr and the falling tf of the input signal 34 according to the sine wave 30. The LN modulator 2 modulates the inputted light by the modulation signal 35. A photoelectric transducer 4 transduces light 23 from the LN modulator 2 branched by a light branching means 3 into an electric signal and a synchronous detector circuit 11 receives the electric signal and extracts a low frequency component. A controlling means 12 controls bias voltage of the LN modulator 2 so that output of the synchronous detector circuit 11 is made zero. <P>COPYRIGHT: (C)2005,JPO&NCIPI</p> |
