An electro-optic modulator such as a Mach-Zehnder interferometer has a segmented optical transmission network with a series of discrete electrodes for successive segments of the network. Respective modulating signals are supplied to the electrodes along transmission lines whose lengths differ from each other, so that modulating signals applied to the inputs of the transmission lines arrive at their respective electrodes in synchronism with the propagation of an optical signal through the optical transmission network. The modulating transmission lines are disposed lateral to and generally coplanar with the optical transmission network, preferably on a separate substrate. The desired differential in transmission line lengths can be achieved by positioning the input ends of the transmission lines along an edge of the input substrate that is at a desired angle to the optical transmission network.