The article proposes the concept of constructing a comprehensive fiber-optic sensor (CFOS) for simultaneous measurement of relative humidity and air temperature, as well as the temperature of a solar cell. The sensor is represented by a double structure, consisting of a two-stage Fabry-Perot interferometer for measuring relative humidity and air temperature and a two-component wave addressable fiber Bragg structure for measuring the temperature of a solar cell. The sensor is inserted orthogonally to the plane of the solar photovoltaic panel into the technological hole formed in it so that the distance between the addressable fiber Bragg structure(s) and the Fabry-Perot interferometer module allows simultaneous measurement of relative humidity and air temperature, as well as the temperature of the solar panel. A change in relative humidity affects only the refractive index of the outer interferometer, while a change in air temperature affects the refractive index of both interferometers. Changing the temperature of the solar cell only affects the central wavelength of the addressable fiber Bragg structure. By solving a system of equations using the specified parameters, relative humidity and air temperature, as well as the temperature of the solar battery, can be controlled simultaneously. The structure and design of an integrated fiber-optic sensor and the results of the first experiments are presented, which confirmed the possibility of simultaneous measurement of the parameters under consideration that affect the efficiency of solar panels.
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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