Abstract: Electro-optic modulation of multiple phase modulator waveguides with a single electrode is made possible by determining places of equal electric field strength. Substrate extensions support edges of a wide hot electrode and ground electrodes equally spaced from the wide hot electrodes. Waveguides are positioned in the extensions separated from the electrodes by buffer layers. A wide microstrip hot electrode on a buffer layer, wider substrate and ground has multiple waveguides in the substrate below the buffer layer. A thinned substrate has a microstrip hot electrode and spaced coplanar grounds with multiple waveguides located on both sides. Decreasing substrate thickness flattens the electric field strength between the electrodes and allows multiple waveguides located between the central hot and outer ground electrodes. Adjacent waveguides with different asymmetric waveguide index portion staged along their length eliminate cross talk.