1. An optical modulator comprising: a signal distribution network; a plurality of output driver stages coupled to the signal distribution network; a waveguide coupled to the outputs of the output drive stages to receive a voltage across the waveguide; and a plurality of adjustable delay cells between the distribution network and the plurality of output driver stages to apply a differential delay to the output stages, the adjustable delay cells being set to compensate for the optical transmission properties of the waveguide.