| 摘要 |
PURPOSE:To reduce the generation of noises and distortion in an alalog frequency multiplex optical transmitter by holding the modulation degree of a semiconductor laser constant by applying a signal and an output having the opposite amplitude characteristics to its waveform to the semiconductor laser together. CONSTITUTION:When a signal havng a waveform (e) obtained by multiplexing two TV signal waves having carrier frequencies f1 and f2 in the VHF band is applied to a terminal 7, part of the signal is detected by a detecting circuit 9 to generate a signal as shown by (f). The output (g) of an oscillating circuit 8 is modulated at an amplitude modulating circuit 10 by an inversion signal (f) to obtain an output (h), which is mixed with a signal having a waveform (e), thereby applying the resulting signal to a semicondutor laser driving part 4. The semiconductor laser driving part 4 adds a bias current IB to the waveforms (e) and (h) to obtain a constant amplitude waveform, and then applies it to a semiconductor laser 1, so the modulation degree of the semiconductor laser 1 is constant, reducing the generation of noises and distortion. |
