| 摘要 |
PURPOSE: To generate modulated signal light which has no frequency components more than necessary by providing a generator with an optical filter which eliminates other frequency components than necessary for signal transmission from the modulated output light. CONSTITUTION: Bias current is supplied to a semiconductor laser 11 from a driving circuit 12. When the driving circuit 12 modulates the bias current, the semiconductor laser 11 generates modulated signal light whose output light power has been modulated. The output light from the semiconductor laser 11 passes through an optical filter 13. The transmission central frequency of the optical filter 13 agrees with that of the output light of the semiconductor laser 11 and the transmission frequency width is larger than the one which is required for signal transmission and thereby a frequency expansion of the modulated signal light from the semiconductor laser 11 is narrow. Therefore, the optical filter 13 outputs signal light which has no frequency components more than necessary for signal transmission. |
