Optical fiber strain sensor principle and application field
Published time: 2019-09-30
Principle of optical fiber strain sensor
Optical fiber strain sensor is a widely used sensor type in the world. It has many advantages that are incomparable with electric sensors, such as being immune to electromagnetic fields and other external environmental changes, high sensitivity, small size, good insulation, and distribution measurement. It is a key component for long-term and real-time online structural health monitoring, and is of great significance for ensuring the safety of large facilities and preventing the occurrence of malignant and catastrophic accidents.
The fiber strain sensor is characterized in that it is provided with an equal-strength cantilever beam and a temperature compensation block. The cantilever top of the beam has a knife edge of about 10 mm inside the end, which is used for hanging static loading, and has a rectangular beam body with a length of about 80-150 mm inside the blade edge. It is used to transmit the static load; it is followed by the effective length of the equal-strength cantilever beam. The shape of the beam body in the axial direction is T-shaped, that is, the head is large and small, and the axis on the upper surface of the beam is marked with a scale for the distributed optical fiber sensor. Position, that is, installing a single-mode tight-fitting optical fiber or a packaged single-mode tight-fitting optical fiber or a point-packaged optical fiber grating, and fixing the single-mode tight-fitting optical fiber to be fixed with an adhesive material on the equal-strength beam body On the lower surface, one end of the fiber is fixed on the surface of the temperature compensation block with the same adhesive material, and the other end is connected to the demodulation system for demodulating the fiber strain sensor: firstly, the fiber strain sensor is collected by the distributed fiber strain gauge demodulator. The initial strain value; at the same time, the initial strain value of the resistance strain gauge is collected by the dynamic static strain gauge. If the static load rate is determined, it is also necessary to adjust or record the dial gauge or dial gauge on the three-point deflection meter. Start value; then load step by step, successively collect or record the readings of the fiber strain sensor, the resistance strain gauge and the three-point deflection meter, and use the dialometer to determine the curvature under static load on the dial gauge or the minute gauge; if it is dynamic load The dynamic loading system is used to generate the vibration of the beam body. The dynamic strain spectrum of the resistance strain gauge is collected by the dynamic static strain gauge. The dynamic strain spectrum of the fiber strain sensor is collected by the fiber strain sensor demodulator. The sampling frequency of the fiber-optic strain sensor is evaluated and its real-time performance is evaluated, and the strain value of the temperature compensation section is subtracted from the measured total distributed fiber strain value to remove the influence of the temperature change.
Fiber strain sensor advantages
2. Small size
3. Anti-electromagnetic interference
4. Corrosion resistance
5. No side effects on reinforcing fibers
6. High sensitivity
7. Good compatibility with composite materials
8. Does not affect structural performance
9. Can be tested remotely
11. Real time
Fiber strain sensor application field
Optical fiber strain sensors are mainly used in industries, agriculture, national defense, construction, environment, energy, transportation and other fields.
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