| 摘要 |
<P>PROBLEM TO BE SOLVED: To keep constant extinction ratio of laser diode output light which is on/off modulated by digital signals. <P>SOLUTION: The output light of laser diode 1 is monitored with a photodiode 2. The level corresponding to the output light "0" level of its monitor current Imon is detected with a DC current detecting circuit 3. The bias current of the laser diode is so controlled that its detection level is constant, resulting in keeping "0" level of the output light constant. The average current of the monitor current Imon is detected with a detection circuit 4, and "1" level of the output light is so controlled that its detection level is constant, resulting in keeping the on/off ratio, or extinction ratio, constant. <P>COPYRIGHT: (C)2006,JPO&NCIPI |
