II. Experimental Setup
The experimental setup, shown in Figure 1, consisted of 79 AM-VSB video channels from a cable-TV head end, which were combined with two 256-QAM channels, operating at 40.5 Mb/s at an RF frequency of 571.25 MHz and 643.25 MHz, to directly modulate a 1310-nm DFB laser transmitter. A broadband white Gaussian noise source was used in the QAM link for BER-SNR measurements. After transmission through 10.6 km of a standard single-mode fiber, the combined signal was detected at 0 dBm optical power at the cable TV receiver. The 256-QAM signals were down-converted to IF frequency, demodulated, and then fed to an error detector. The peak modulated video power to the average QAM channel power ratio was 5.6 dB.
Figure 1 The experimental setup for hybrid multichannel AM-VSB/256-QAM video lightwave transmission system.