| 摘要 |
PURPOSE:To prevent lowering of light emission efficiency and restriction of transmission zone of optical fibers even when center frequency is enlarged by using a voltage control oscillator having high center frequency and making frequency conversion afterward. CONSTITUTION:The output center frequency f0 of the voltage control oscillator 3 is made as high as, for instance 100-200MHz, and DELTAf is selected to 4-5MHz as before to reduce distortion without increasing noises. Frequency-modulated signals of high f are led to a frequenct convertor 13 according to analog signals inputted from an input terminal 1 by the voltage control oscillator 3. On the other hand, a signal of frequency fL lower than frequency fO outptted from a local oscillator 12 by 20-30MHz is led to the frequency converter 13. A frequency-modulated signal of center frequency (fO-fL) is obtained from the converter 13. This is inputted to a light emission element driving circuit 4 to make a light emission element 5 emit light. |
