| 摘要 |
PURPOSE:To enable suppression of the effect of any mode hop without the need to use a longitudinal multimode semiconductor laser or a severe temperature regulator, by calculating a value representing the relationship between the output from a front photodetector and the output from a rear photodetector, and differentiating the obtained value. CONSTITUTION:When mode hop occurs as a result of a change in the ambient temperature of a laser diode 2, a difference is produced between the change in power of the back light detected by a photodiode 3 and the change in power of the front light detected by a photodiode 4, so that there is also a change in the output of a difference detector circuit 5. In consequence, differentiation pulses are led out to the output terminal of a differentiating circuit 6, and positive and negative pulses are respectively taken by Schmitt trigger circuits 7, 8. A pulse signal is led out to the output terminal of an OR circuit 9 only during a period of time (temperature range) when mode hop occurs. Accordingly, this pulse signal is used as an alarm signal or an optical communication inhibiting signal in the case where optical communication is carried out. |
