Abstract: An optical modulation system having cascade-coupled electro-optic modulator stages in either dual tandem or split tandem configurations. An electrical splitter derives multiple electrical drives for the multiple stages from a single modulating input signal. The multiple drive signals are linearly related in magnitude and preferably induce simultaneous antiphase (180.degree. out-of-phase) optical modulation in the tandem stages. While a double Mach-Zehnder cascade configuration could be used, at least one modulator stage might instead be a balanced-bridge interfometer-type modulator having at least one directional coupler. At least one directional coupler in such a configuration may be a .DELTA..beta. coupler. Application of bias voltages to the interferometer sections and to coupler sections by means of a parametric feedback loop is done in order to simultaneously enhance the linear modulation coefficient, minimize odd order distortions and null the even order distortions that are associated with biased .