There is a great need for techniques that will permit the evaluation of the micromechanical state of micro-electro-mechanical system (MEMS) devices, at all steps of manufacturing, with respect to material properties, as well as of lifetime and for monitoring mechanical performances of MEMS actuators. We propose a new approach, based on integrated optical read-out using a Mach-Zehnder interferometer (MZI), monolithically integrated on the top of an electrostatically rotatable micromirror loaded with the sensing arm of MZI. The working principle of MZI read-out is based on the local change of the effective refractive index of guided waves of MZI, induced by strains of the deformable structure. A single-mode buried channel waveguide based on the silica/silicon oxinitride/silica structure is used, presenting optical attenuation of . The coupling of the standard optical fiber to the waveguide is based on the V-groove technique, supplemented by micromechanical sawing of the silicon substrate. For TE polarization, the set of obtained parameters is a coupling efficiency of about 55% with a horizontal misalignment of , a vertical misalignment of , and angular precision of on directions of the silicon substrate.