| 摘要 |
PURPOSE:To automatically adjust the light modulation of a pre-modulating signal. CONSTITUTION:This transmitter is equipped with a modulation adjusting circuit 4 to adjust a pre-modulated electric signal 3 to an suitable modulation, an electric-light converter 6 to convert and output an electric signal 5 to a intensity modulated light signal 7, a light branching device 8 to separate the output light signal to a light transmitting signal 9 and a branching light signal 10 for monitoring, a light-electric converter 11 to convert and output the branching light signal 10 to an electric signal 12, band pass filters 13 and 14 to extract respectively a basic wave component 15 and a higher harmonic distortion component 16 of the pre-modulated electric signal 3 out of an output signal 12, a signal intensity detecting circuit 21 to detect the signal intensity of respective extracted signal components 15 and 16 and a signal ratio detecting circuit 21 to detect a ratio 22 of the signal intensity of the basic wave component 15 of the pre-modulated signal 3 and the signal intensity of the higher harmonic distortion component 16 out of detecting signals 19 and 20. The above-mentioned modulation adjusting circuit 4 is feed-back-controlled so that the ratio 22 of the signal intensity can become the constant value. |
