Optical Frequency Domain Reflectometry (OFDR)[1-5] provides valuable complex information (modulus and phase) in the time and optical frequency domains for characterization of new technologies and integrated devices. The standard approach employing fiber based Mach-Zehnder Interferometers (MZI)[1-5] requires dedicated bulky set-ups, subject to demanding stabilization conditions, in order to preserve the light polarization states and the optical phase variations due to temperature changes over long fiber MZIs (> 4-5 meters in some cases due to the required fiber pigtails couple light to/from the photonic chip). Here we propose for the first time to our knowledge a fully Integrated OFDR (IOFDR) approach, where all the required MZI structures are cointegrated with the Device Under Test (DUT). The device was fabricated on a 100mm Si wafer, composed of a SiO2 buffer (2.5 μm thick, n= 1.464) grown by thermal, following a LPCVD Si3N4 layer with thickness 300nm (n= 2.01) and a 2.0 μm thick SiO2 (n= 1.45) deposited by PECVD.