| 摘要 |
PROBLEM TO BE SOLVED: To improve transmission quality by compensating for group delay deviation that takes place in the case of modulating an AM signal and a QAM signal into an FM signal and a PM signal to be transmitted. SOLUTION: This signal transmission system is provided with a transmitting part 10, an optical fiber 20 and a receiving part 30. The transmitting part 10 has an FM modulator 11, a 1st amplifier circuit 12 and a semiconductor laser 13 successively from an upstream to a downstream. The receiving part 30 has a photodetector 31, a 2nd amplifier circuit 32 and an FM demodulator 33 successively from an upstream side to a downstream side. Group delay deviation takes places in the 1st amplifier circuit 12, the laser 13, the photodetector 31 and the 2nd amplifier circuit 32. The system is provided with a harmonics generation circuit 51 and a harmonics phase shift circuit 52 on the downstream of the modulator 11. The circuit 51 superimposes the harmonics of an FM signal upon the FM signal, and the circuit 52 shifts the phase of the harmonics and compensates for the group delay deviation. |
