In this paper, the static optical transfer function of dielectric lithium niobate (LiNbO₃) electro-optic sensors is modeled and experimentally measured. This function represents the transmitted optical power at the output of an optical waveguide in a LiNbO₃ crystal which acts as an electric field sensor. The sensor is electrode-less and operates as a dielectric probe. Under such a condition, the electric field is present in the dielectric media surrounding the waveguide and the measured field intensity is determined by the boundary condition between the media and the LiNbO₃ crystal. The electro-optic transfer function is theoretically modeled and experimentally measured. Such a transfer function shows a sinusoidal shape, from which the half-wave electric field, the optical extinction ratio and the linear and nonlinear regions can be determined. LiNbO₃ electric field sensors are inherently wide band, and a sensing scheme is tested, showing a high-linearity sensing detection of high-intensity and wide-band electric fields.