Abstract

A lot of attention is now being paid to the transmission of digital signals with spectrally efficient M-ary quadrature amplitude modulation (M-QAM) multiplexed with the analog AM-VSB CATV signals through a fiber-optic channel. The advantage of this system is that digital signals are more robust than AM signals with respect to noise, channel interference, and nonlinearity. With AM/QAM hybrid transmission, however, we show here that the AM interference on the QAM channels caused by laser nonlinearity may induce significant performance degradation for the QAM channels. We also show that by using coding we can significantly reduce the interference effect.

© 1993 Optical Society of America