A distance measuring device includes a light source emitting light, and an integrated electro-optic modulator arranged such that the emitted light passes through an optical waveguide of the electro-optic modulator in a first direction before being emitted from the distance measuring device, and after being reflected from a target passes through the electro-optic modulator in a second direction which is opposite to the first direction. The forward electro-optic response of a modulating region of the electro-optic modulator is the same as the backward electro-optic response, and a center of gravity of the modulation is independent of modulation frequency.