An optical modulator includes: a bottom substrate layer, having a first surface; a traveling-wave electrode, being disposed on the first surface of the bottom substrate layer and including a plurality of ground electrodes and a plurality of signal electrodes between the ground electrode; an optical waveguide disposed inside the bottom substrate layer; and a shield layer, including a substrate and a metal layer, the substrate covering at least a portion of the traveling-wave electrode and the metal layer being disposed on the surface of the substrate facing away from the traveling-wave electrode. Each of the ground electrodes is electrically connected to the metal layer to provide electromagnetic shielding for the signal electrodes between the ground electrodes.