A 4-bit electro-optic A/D converter which utilizes an array of Fabry-perot interferometric modulators composed of proton-exchanged LiNbo3straight channel waveguide with two parallel reflection end faces of the waveguide substrate is reported. The principles of operation of the F-P A/D converter are described. The design parameters, fabrication procedure, the measurement set-up and first-fruits of the experimental model are reported.