| 摘要 |
<p>PURPOSE:To output an FSK light signal with a small waveform distortion by causing a unipolar original signal to be bipolar, superimposing a bias current, and outputting a light signal to be direct-modulated. CONSTITUTION:A unipolar original signal 1 is inputted to an AMI(Alternate Mark Inversion) encoder 2, and outputted as a bipolar signal 3. The bipolar signal 3 is superimposed on a bias current 4 by a superimposing device 5. Such a superimposed signal 6 is injected to a semiconductor laser 7, and a bipolar FSK(Frequency Shift Keying) light signal 8 is outputted. Namely, when the original signal 1 is AMI-encoded, the power density spectrum of the signal can be centralized to an area in which the frequency characteristic of the FM response of the semiconductor laser 7 is flat. Thus, the distortion of the FSK light signal can be widely reduced.</p> |
