This research proposes improvements to the Mach-Zehnder interference system (MZDIS) that will enable it to assess the noise-to-optical-fiber ratio with a high accuracy of 0.4 dB obtained from an optical signal of 5 to 40 dB. The optical system of the proposed interference system has been modified to improve accuracy at a modulation frequency of 10 GHz, in addition to 3 dB optical couplers (OC), which make up the proposed setup. Two branches receive the signal from the initial connection, one of which contains a phase controller and a light backlight. The free spectral range (distance spectroscopy between two neighboring transmission peaks) is controlled by optical delay. The phase controller synthesizes the optical signal's phase. In the first route, for the technique of Optical signal to noise ratio )OSNR( monitoring, which is based on the cancellation of a certain frequency component of the spectrum of the ovdm signal after optical detection by adding polarization scattering on the signal to allow noise to strike inside this component, has been successfully implemented in the optical Orthogonal Frequency Division collection system with direct detection. This noise's individual and general amplitudes were measured using a narrow beam pass filter. To ascertain the value of Osner. The color dispersion did not affect the measurement accuracy, which was less than 1db and had a satisfactory measurement range of [5-40dB]. In addition, it is not required to send manual tones or decode design modifications, which reduces costs.