Temperature compensation of fiber-optic water flow sensor based on laser-heated silicon Fabry-Perot cavity

Flow measurement by the hot-wire fiber-optic water flow sensor based on laser-heated silicon Fabry-Perot interferometer (FPI) need to compensate the temperature variation of the water. This temperature compensation is required to get the flow speed from a unique calibration irrespective of the initial water temperature. Flow measurement is the wavelength change from the baseline wavelength to the final wavelength due to the laser heating of the silicon FPI and cooling by the flow. Temperature variation of the water will also induce wavelength change in the measurement. This will change the baseline resulting different wavelength shift for different water temperature for a given flow speed. We report a technique to compensate the effect of water temperature change in the flow measurement by using another sensor which will track the temperature of the water. By using the information of the water temperature change, baseline can be defined which will provide unique wavelength change for the flow. Finally, wavelength change corresponding to the flow speed were calibrated using the sensor pair after compensating the water temperature.