Fiber optic sensors are widely used in structure monitoring and smart materials to measure the temperature. In this paper, a novel fiber-mercury temperature sensor (FMTS) is designed and tested. The sensor is made usi...
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ISBN:
(纸本)0819467278
Fiber optic sensors are widely used in structure monitoring and smart materials to measure the temperature. In this paper, a novel fiber-mercury temperature sensor (FMTS) is designed and tested. The sensor is made using the surface of the mercury to act as the reflector. The intensity of the reflective light is the function of the distance between the surface of the mercury and the fiber end, which is determined by the thermal extension of the mercury. And different length of the mercury in the capillary defines different sensitivity of the sensor. The modulation function of the sensor is analyzed. Experiment was carried out to evaluate the performance of the sensor, and the results present a good correlation between the theoretical and experimental result.
In this paper, fiber Bragg grating (FBG) sensors network in the subgrade temperature monitoring system in Qinghai-Tibet railway is presented. The principle of the FBG temperature sensor is introduced and the feasibili...
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ISBN:
(纸本)9780819469472
In this paper, fiber Bragg grating (FBG) sensors network in the subgrade temperature monitoring system in Qinghai-Tibet railway is presented. The principle of the FBG temperature sensor is introduced and the feasibility of the FBG sensors in the permafrost regions of Qinghai-Tibet plateau is analyzed. The FBG sensor network architecture is introduced. This sensor network includes the sensor chains embedded in the roadbed, slave optical cables, work stations including the FBG sensor interrogator and the optical router, master optical cables, and center workstation. We give the primary experimental result of this sensor network in monitoring the roadbed temperature of the railway at DK0985+000 near Chumar River. Fifteen FBG temperature sensors were embedded into the roadbed monitoring hole. The temperature data was collected after a month when the temperature field in the monitoring hole is stable. The result of the experiment shows that the FBG temperature sensors have an accuracy of 0.1 centigrade. Furthermore, the experimental result shows the stability and reliability of the FBG sensor network in the harsh environment of Qinghai-Tibet plateau. In the end, the conclusion is drawn and the prospect of the FBG sensor network in monitoring other parameters in the Qinghai-Tibet plateau is also presented.
In this paper, a novel fiber optic concrete sensor based on extrinsic fiber Fabry-Perot interferometer (EFPI) is designed and analyzed. Two fiber ends are inserted into a glass capillary and encapsulated into a cement...
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ISBN:
(纸本)9780819465368
In this paper, a novel fiber optic concrete sensor based on extrinsic fiber Fabry-Perot interferometer (EFPI) is designed and analyzed. Two fiber ends are inserted into a glass capillary and encapsulated into a cement cylinder to act as the sensor head. In this way, the cement cylinder itself is the sensor head instead of the traditional steel tube, which makes it very convenient to embed the sensor head into the concrete, because the cement consists with the concrete well. Based on the theory of white light interferometry and the theory of elasticity, the wavelength modulation method and the strain transfer are analyzed theoretically. The demodulation system is also introduced in this paper. The experiment being made by our research group is aimed at testing the consistency, stability, reliability and the sensitivity of the fiber optic sensor. The sensor head of the cement cylinder is embedded into a model ferroconcrete beam together with traditional strain gauges. The experiment is carried out using the PEM-500A hydraulic pulsation fatigue test machine after 2 million stress circles. The readout of the fibre optic sensor and the strain gauges is recorded and made a contrast. It can be found from the result that the fibre optic sensors have good stability and reliability, the accuracy for the fibre optic sensor is better than 0.5 micro-strain, which shows that the sensor can meet the demand of the long-term monitoring of large-size concrete structure.
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