| 摘要 |
PURPOSE:To make the level of an optically transmitting wave invariable depending on the signal mark ratio of an input transmission signal even when the detected voltage of the optical transmission wave has errors. CONSTITUTION:The pulse current S22 which is obtained by converting an input transmission signal S21 by a pulse signal converting circuit 1, and a bias current S25 are supplied to an adder 3. Then, an LD driving current S26 drives an LD4 to send out an optical transmission wave. A monitor current S27 from the PD5 which receives the optical transmission wave is converted into the monitor voltage S28 by a current-voltage converting circuit 10. With an amplified monitor voltage S29 form an amplifier 11 where the monitor voltage S28 is supplied, and the input transmission signal S21, the pulse width is detected by the peak value detecting circuits 8 and 9. The peak value detecting signals S22 and S30 are inputted into a comparator 7. A comparison output signal S24 due to the input difference is supplied to the bias current generating circuit 2 to change the bias current S25, thus making the level of the optical transmission wave constant. |
