| 摘要 |
PURPOSE:To prevent disturbance of light output strength waveform resulting from fluctuation of an LD drive operating point and deterioration of modulation band characteristics by stabilizing the potential of one of the electrodes of the LD without using a lead. CONSTITUTION:A reference potential signal of a reference potential circuit 4 is input in a comparative circuit 5 together with the output signal of a drive operating point detecting circuit 3. The circuit 5 detects the potential difference of an input signal and, for example, the current signal corresponding to the potential difference is transmitted in a potential setting circuit 6. The circuit 6 receives the signal of the circuit 5 and, for example, the potential V0 of a negative side electrode is set in order that the signal is at constant level. A capacitor 8 of capacity C0 is provided in parallel with a conductance constituent 7, and so the potential V0 of one electrode of LD 1 is controlled always to be at constant potential difference for average drive potential. Therefore, the disturbance of light output strength waveform resulted from the fluctuation of a drive operating point LD 1 and the deterioration of modulation band charac teristic can be prevented. |
