Under a certain deliver distance and the light power, the different sub-carries number to exist a best optical modulation index, making the system's carrier-to-noiseratio biggest.
一定的传输距离和发射光功率情况下,不同的子载波数存在一个最佳的光调制指数,使得系统载噪比最大;
2
But to the CW pulse signal with changing carrier wave frequency, common filter cannot achieve narrowband filter, whereas broadband filter cannot reach the request of the signal-noiseratio.
From signal tonoiseratio analysis of the modulation signal, we choose the phase modulation method as the suitable carrier modulation for the twisted-pair.