IMPLEMENTATION AND EVALUATION OF A DUAL PARALLEL LINEARIZATION SYSTEMFOR AM SCM VIDEO TRANSMISSION

An externally modulated transmitter has been linearized for AM-SCM vid eo transmission. Linearization was accomplished by combining the outpu ts of two lithium niobate Mach-Zehnder interferometers which were simu ltaneously modulated. By controlling the optical and RF power at each modulator, more than 20 dB of third-order distortion cancellation has been demonstrated for a multitone video spectrum. Results are presente d for both NTSC and PAL B/G frequency plans. The effects of modulator nonideality on system performance are analyzed and confirmed experimen tally. In particular, overall system performance is shown to be very s ensitive to acoustic effects and to optical and electrical multipath i nterference. System modeling is used to provide tolerances on various critical parameters.