| 摘要 |
PURPOSE:To obtain an optical transmission circuit capable of detecting the abnormity of the waveform of an optical output by adding newly a waveform discriminating circuit deciding a level of a monitor waveform at a level change point of an input signal of a drive circuit. CONSTITUTION:When a high level state of an output transmission waveform of a flip-flop 10 is normal, a waveform fault detection signal 12 is obtained as a normal detection level, that is, a high level and when a waveform fault is caused, the signal 12 is obtained as a waveform abnormity detection level, that is, a low level. The above is obtained similarly at a flip-flop 14 and the level after a prescribed time elapses from the leading/trailing of the monitor waveform is compared with a reference voltage, then a waveform abnormity over a short time is detected. In using a modulation circuit 13, the quantity (pulse width fault) of distortion of the monitor waveform 9 is detected. Since the change point of the timing waveform 11 has a width by applying frequency or phase modulation to an input signal 1 of a drive circuit at the modulation circuit 13, the quantity of waveform distortion in the monitor waveform 9 is detected by selecting the modulation properly. |
