Pressure monitoring has an important significance in fields such as petrochemical, energy, and power engineering. Compared to electronic pressure sensors, fiber optic grating pressure sensors have the advantages of small size, simple structure, and anti-electromagnetic interference. This paper proposes a polymer encapsulated fiber Bragg grating (FBG) dynamic pressure sensor and uses a semiconductor optical amplifier (SOA) - fiber ring laser (FRL) and an array waveguide grating (AWG) demodulator to form a fiber Bragg grating dynamic pressure sensing demodulation system. The experimental results show that the laser output of the SOA-FRL system is stable; in the fiber Bragg grating pressure test, the pressure sensitivity of the dynamic pressure sensor based on SOA-FRL can reach -33.17 pm/MPa at two pressure environments of 1~ 20 MPa and 0.1~0.8 MPa. The temperature dependence test shows that the sensitivity of the dynamic pressure sensor is 8.14 pm/℃ in the temperature range of 23 ~ 60℃. The temperature sensitivity of the dynamic pressure sensor is slightly lower than that of the reference FBG sensor (9.79 pm/℃). In addition, the effects of different sensitizing materials on the sensitivity of the pressure sensor are compared. The results show that the sensitivity of polymer materials is higher than that of metal materials. Because the proposed dynamic pressure sensor system based on fiber ring laser and array waveguide grating demodulator has the characteristics of high sensitivity, simple structure, and the demodulation of dynamic signals, it has a promising application prospect in oil exploitation, transportation, structural monitoring and other fields.
A photonic integrated adaptive two-wave mixing (TWM) interferometer is designed for demodulation of FBG acoustic emission sensor signals, whose various optical elements are integrated in a substrate material with photorefractive properties. A ridge waveguide based on InP:Fe is designed. Each component of the photonic integrated TWM interferometer is analyzed and optimized to minimize the loss of light in the transmission of the TWM interferometer and obtain the best demodulation performance. The feasibility of the optimized structure of the photonic integrated adaptive TWM interferometer is verified in theory, and the optimized structure will contribute to the miniaturization and integration of the TWM demodulation system based on InP:Fe.
Distributed sensing technology provides engineers with powerful tools for position sensing, 3D sensing, shape sensing, and model validation applications. A new method for fiber-optic 3D shape sensing that can be used in minimally invasive biomedical devices is presented. A shape sensor was made using a heat-shrink tube, a Teflon hard tube and three strings of fiber Bragg grating (FBG). The sensor has compact structure, good flexibility. Besides, a shape reconstruction algorithm is established, for the location of each FBG array on the sensor, the calculation method of curvature and torsion is designed, and the continuous functions of curvature and torsion are constructed by cubic spline interpolation. The shape reconstruction under different bending conditions is realized by using the coordinate system rotation method. In the error analysis stage, the curvature error and torsion angle error of the sensor are optimized by introducing the scale factor. The results show that the optimized algorithm has good shape reconstruction effect.
A method using fiber Bragg grating (FBG) array-based shape sensing is proposed for structure health monitoring of cylindrical marine structures in this paper. Because of the characteristics of FBG, any strain applied on the FBG is encoded as a wavelength shift of the light reflected by FBG. FBG sensors, with flexibility and small size, are bonded on the surface of the cylindrical shell structure to measure the strain of each fiber Bragg grating on the same certain points. And then we analyze the relationship of each parameter between FBG sensors and cylindrical structure. Experimental results prove that it is feasible for this method using FBG array-based shape sensing to monitor the deformation of the cylindrical structure. This method can be widely adopted in structure health monitoring of curved structures due to high precision, simple operation and low cost.
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