Optical devices have the potential for large scale integration and can be successfully used in mission critical environments; in particular optical probes interacting with electric fields can be used in several electromagnetic compatibility (EMC) and industrial, scientifical and medical (ISM) applications. We describe an electro-optical device based on a LiNbO3 Mach-Zehnder integrated interferometer which has, with respect to standard metallic probes, a very reduced coupling effect on the electromagnetic field to be measured. The probe is mainly made by non conductive materials, making such device suitable for experimental measurement of electromagnetic fields in near field region (or Fresnel's one) of transmitting antennas or in their reactive zone. Here no simple theory is available in order to evaluate the fields and mutual coupling between antennas and standard probes strongly affect the measurements: the …