Overmodulated single-octave subcarrier multiplexed optical networks for multichannel FM video distribution

In subcarrier multiplexed (SCM) multichannel FM video systems, the carrier-to-noise ratio per channel may be increased by overmodulating the laser diode source. The authors predict the overmodulation that may be employed in practice for single-octave SCM transmission in passive optical networks. It is shown that optical modulation indices (OMI) exceeding 500% may be used if the number of subcarriers is large. A 47 dB signal-to-noise ratio (with 4 dB margin) is deemed sufficient for acceptable picture quality in cable distribution systems, while a 56 dB value would be required for long-distance point-to-point optical links