抄録
In hybrid optical SCM for CATV systems, carriers are modulated by video signals or digital data, so amplitude of a multiplexed signal of these modulation signals is compressed compared with that of the carriers themselves, and frequency of clipping of the multiplexed signal at the laser threshold is decreased. Consequently, BER of the M-QAM signal in the practical hybrid SCM is lower than that of the experimental results. In this paper, we describe BER analysis method that can effectively estimate the BER performance in the practical hybrid SCM by using representative profiles of the modulation signals. The BER of the M-QAM signal, when assuming FDM signal with modulation signals, extremely improved compared with the BER for multiplexed signal of carriers. Furthermore, BER degradations due to clipping can be neglected for the AM signals in setting practical optical modulation indexes. We also study effective OMI ranges of AM and M-QAM signal by using the analysis method. By assuming AM signal with black picture, the OMI range is enlarged and particularly, the OMIs of AM signal agreed with practically setting value in AM-SCM transmission. This OMI range is more practical than that of former studies.
