A method includes creating Coriolis-based deflection in at least one oscillating flow tube of a flow meter, which is caused by material flowing through the at least one flow tube. The method also includes determining a deflection amplitude and deflection period using interferometric measurements. The method further includes determining a characteristic of the material using the amplitude and period and transmitting the characteristic. A laser interferometer could include a photo-detector. The deflection period could be based on variations in a period of fringes in the photo-detector's output. The deflection amplitude could be based on a number of fringes during the deflection period. A resonant frequency of the at least one flow tube can be determined using the deflection period, and a density of the material can be determined using the resonant frequency. The characteristic of the material could include a mass flow rate or a volumetric flow rate of the material.