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To eliminate the limitations of known optical thermal anemometers, distributed and point fiber optical flowmeters, we determine the prerequisites to design a microwave photonic dual-FBG differential sensor for flow velocity and direction based on like-FBG gauge – phase shifted fiber Bragg gratings or addressed fiber Bragg structures of wavelength or combined wavelength-phase type. In addition, we offer an economical microwave photonics addressed interrogation scheme that does not require complexed optical spectral analysis. The article evaluates the model of proposed sensor and its characteristics in static and dynamic flow conditions using two different schemes for set-up of similar or different gauges. The aim of the work is to search for scientifically based principles for the development of microwave photonic flow and flow direction fiber optic sensors, with the possibility of increasing the resolution and accuracy of measurements in the region of low flow rates, as well as temperature compensation. To achieve the aim, the typical with similar gauges and non-typical with different gauges liquid flow sensors based on the measurement of differential pressure by optoelectronic methods are considered, and the problem setting for determining the flow direction using microwave photonics approaches is given as one of the options for their development. A universal mathematical model for a microwave photonics approaches is considered and the requirements for choosing an element base other than classical FBGs are determined. The possibilities of using flowmeters with a phase π-shift FBG and addressable fiber Bragg structures as sensors, which at first glance could improve their metrological characteristics, but are not widely used for this, are discussed. The obtained results and directions for further research presented in conclusion.
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