We have demonstrated a Ti∶LiNbO 3 electro-optic electric-field sensor based on 1×2 directional optical waveguide coupler. The symmetric geometry of the 1×2 directional coupler provided the sensor with unique characteristics of intrinsic 3-dB operating point and two complementary outputs. A DC switching voltage of ∼12 V and an extinction ratio of ∼8.1 dB were observed with the coupler at a wavelength of 1.3 μm. The minimum detectable electric fields are ∼0.99 and ∼1.67 V/m corresponding to a dynamic range of ∼29.5 and ∼25 dB at frequencies of 20 and 50 MHz, respectively. The sensors exhibit almost linear response for the applied electric-field intensity from 0.29 to 29.8 V/m .