| 摘要 |
PURPOSE:To easily and correctly compensate the FM modulation sensitivity depending on the frequency dependency and to ensure the characteristic of a transmission signal by modulating in advance the transmission signal, changing the drive current of a semiconductor laser by a minute quantity and modulating the frequency of light and transmitting the resulting light. CONSTITUTION:A transmission signal 1 is modulated by a modulator 4 with the output 3 of a carrier oscillator 2, the frequency characteristic is corrected by a correction circuit 5, the current of a semiconductor laser 6 is changed by a minute quantity in a range where the luminance modulation component of an output light is negligible. The modulated light is led to an optical receiver 101 via a transmission medium 8. The received light 9 mixed with the output light 11 of the semiconductor laser 10 with a frequency equal to the oscillated frequency of the laser 6 in an optical transmitter 100 by a mixer 12, the result is fed to a photoelectric conversion element 13, in which the beat component is detected and fed to a demodulator 15 via an FM demodulator 14 where the original signal is regenerated. |
