The gas turbine operates at different range of speeds. When the natural frequency of the blade becomes equal to the rotor frequency, resonance is said to occur. The gas turbine should not operate at this frequency because it will result in increase in wear and tear of the turbine. The purpose of this paper is to find the resonant frequency using an optical sensor measurement. A pulse generated from reference probe is used to test the vibrations under given conditions. Here, Optical sensor output is synthesized with respect to the reference probe with and without blade vibration. With vibration, sensor output gets modulated with the natural frequency. Thus in this paper we extracted the natural frequency for different rotor speeds and found the resonance. The mean square error is estimated for each of the rotor speed. The same analysis is also concluded for noise corrupted sensor output. © Research India Publications.