| 摘要 |
PURPOSE:To improve the deterioration in the transmission quality which generates by the periodical noise by the mutual interference between high frequency signals, by a method wherein high frequency signals which are FM modulated, are overlapped to the transmission signals and modulated. CONSTITUTION:An analog signal modulation device is provided with a synthetic circuit 2, a laser diode driving circuit 3, a laser diode 4, a light detection element 5 which is made in a body with the laser diode 4, a feed-back type amplifier 6, a variable high frequency oscillator 7a, a low frequency pattern oscillator 9 which apply FM modulation (frequency modulation) to the variable high frequency oscillator 7a, and a multi-mode fiber 8 which composes a transmission route and has a modulation input signal 1. The maximum value of modulation spectrum which is modulated by the low frequency pattern oscillator 9 can be decreased than carrier wave level when modulation is not performed, and the improvement effect of interference noise by high frequency signals will be increased. |
