| 摘要 |
PROBLEM TO BE SOLVED: To detect a residual AM component which causes distortion and increases long-term reliability by using a balance-type receiver as the photodetector of an AM/FM batch conversion part. SOLUTION: A semiconductor laser element 1 is driven with an AM video signal to obtain a light FM signal. A 3db coupler 3 mixes this light FM signal with the local light from the semiconductor laser element, and beat components are outputted from its two output parts and made incident on two photodetectors 4a and 4b respectively. Then the two photodetectors 4a and 4b which operate differentially outputs only the beat components as electric FM signals. Then a semiconductor laser element 5 is modulated by using the FM signals, and the projected FM-modulated laser light is made incident on an optical fiber 6 and transmitted in the optical fiber 6. |
