| 摘要 |
PROBLEM TO BE SOLVED: To provide a broad band frequency modulator capable of keeping characteristics constant independently of an environmental change such as temperature and of the aged deterioration of components. SOLUTION: This broad band frequency modulator having to laser beam sources whose oscillated wavelength changes with a drive current, a differential modulation means 60 that applies modulation signals of opposite polarity to the two laser beam sources as drive currents, and a photocoupler 30 that combines lights from the two laser beam sources, is provided with a photoelectric conversion means 40 that applies photoelectric conversion to the combined light, a variable optical attenuator 80 that electrically controls attenuation of the light from one or both of the two laser light sources, an extract means 90 that extracts a signal component that is intensity-modulated as the modulation signal from the photoelectrically converted signal, and an attenuation control means 95 that controls the variable optical attenuator 80 so as to minimize the amplitude of the extracted signal components. |
