| 摘要 |
<p>PROBLEM TO BE SOLVED: To increase the degree of modulation of a pilot tone which never generates high-level tertiary distortion and to obtain high efficiency of a voltage stabilizing loop for a bias by making it possible to use an amplifier in a band limited to the band of a modulated signal. SOLUTION: An optical modulator 7 supplies a 1st and a 2nd modulated light signal which are complementary to each other and two outputs of the modulator 7 are connected to an optical coupler 10 having branches for supplying parts of the modulated light signals and connected to an optical receiver 19. In response to the frequencies of the 1st and 2nd analog modulated light signals, a 1st and a 2nd electric control signal are generated. A driving circuit of the modulator 7 includes a circuit generating an electric pilot signal of 2nd frequency which is a half as high as a 1st frequency and added to an electric modulated signal, a converting circuit generating a signal which is proportional to the amplitude difference between the 1st and 2nd electric control signals and continuously converted, and a bias circuit which can generate a bias signal in response to the control signals.</p> |
