| 摘要 |
PURPOSE:To obtain a modulated light output with less distortion from an LED, by detecting and converting part of the output light of a wavelength filter into an electric signal and feeding this electric signal back to the driving circuit for the LED negatively. CONSTITUTION:Signals applied to input terminals 1 and 2 are converted by driving circuits 3 and 4 and LEDs 5 and 6 into light signals varying in intensity and those signals are outputted from an output terminal 18 to an external transmission line through an optical multiplexer 17. In this case, it is necessary to limit the wavelength ranges output spectra of the LEDs 5 and 6 by wavelength filters 7 and 8 without overlapping. For this purpose, the light outputs of the filters 7 and 8 are guided partially to photodetectors 11 and 12 through optical branching fitters 9 and 10 and the remainders are guided to the multiplexer 17. The outputs of detectors 11 and 12 are proportional to the light outputs of the wavelength filters, so they are proportional to the intensity of each spectrum from a terminal 18. Therefore, those electric signals are fed back to voltage addition points 15 and 16 on the input sides of the circuits 3 and 4 through amplifiers 13 and 14 negatively to compress a distortion component due to the insertin of the wavelength filters. |
