PERFORMANCE OF HYBRID MULTICHANNEL AM 256-QAM VIDEO LIGHTWAVE TRANSMISSION-SYSTEMS/

We report experimental results on the performance of a multichannel hy brid AM/256-QAM video lightwave transmission system. Performance limit ations due to impulse noise using a directly-modulated DFB laser trans mitter and an externally-modulated YAG laser transmitter are presented . We also compared the BER characteristics of 256-QAM versus 64-QAM si gnals with either CW carriers or modulated video signals in such a hyb rid system. Our results indicate that 64-QAM signal performance is mor e robust than that of 256-QAM as expected. Significant 256-QAM BER deg radation is observed with modulated AM-VSB video signals, making it ne cessary to use forward-error-correction code for robust 256-QAM transm ission.