| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical intensity modulation apparatus that prepares no table of operating conditions in advance, does not know the input wavelength during operation, and yet can operate adaptively to operating conditions without allowing its modulation characteristics to vary even when operation conditions vary over time.SOLUTION: An optical intensity modulation apparatus that uses a differentially driven Mach-Zehnder modulator in which two optical waveguides have a characteristic that the phase difference between the two optical waveguides varies non-linearly relative to applied voltage comprises: the Mach-Zehnder modulator in which a first data signal voltage over which a first modulation electrode bias voltage is superposed is applied to a first modulation electrode, a data signal voltage, reverse in phase to the first data signal voltage, over which a second modulation electrode bias voltage is superposed is applied to a second modulation electrode, and a phase difference adjusting electrode, separately from the modulation electrodes, for adjusting the phase difference of a Mach-Zehnder interferometer is included; and an automatic operating point control circuit which comprises a minute modulation signal superposing circuit, a light branching circuit, a minute modulation signal detecting circuit, and a phase difference adjusting electrode control circuit. |
