Real-time health monitoring of engineering structures is crucial for improving structural safety, extending the lifespan of structures, and reducing maintenance costs. In this paper, based on the strain monitoring data from distributed fiber optic sensors, a deformation reconstruction algorithm is established to obtain structural deformation information from strain measurements. An experimental test is conducted on a reinforced concrete plate subjected to explosive loads. Distributed fiber optic strain sensors are embedded in the upper and lower surfaces of the plate, and the deformation of the concrete plate under different blast conditions is evaluated by varying the explosive yield. The comparison between the reconstructed deformation results and the actual state of the structure (obtained through high-precision laser scanning) shows that the error of the structural deformation monitoring system based on fiber optic sensors is less than 3mm.
This paper aims to realize the structural safety monitoring of protective engineering by conducting experimental research on the application of fiber optic grating sensors in high-speed penetration and damage monitoring. The study designs a miniaturized flexible fiber optic grating strain sensor for dynamic strain measurement during high-speed penetration and damage of the target body by projectiles, and verifies its measurement performance by comparing it with strain gauges. The experimental results demonstrate that the dynamic strain measurement results of the fiber optic grating strain sensor during high-speed penetration and damage are consistent with those of the strain gauges and the actual situation. The fiber optic grating strain sensor can achieve dynamic strain measurement during high-speed penetration and damage processes. Moreover, the variance of strain measurement results from the fiber optic grating strain sensors is much smaller than that of the strain gauges. This study validates that fiber optic grating strain sensors have the advantages of convenient installation, suitability for embedding, no need for electrical power, safety against explosions, immunity to electromagnetic interference, and strong environmental adaptability. They provide comparable results to strain gauges for measuring highspeed dynamic strains while overcoming the challenges associated with strain gauge installation difficulties, susceptibility to damage during embedding, high grounding requirements, poor environmental adaptability, and high surface bonding requirements. Therefore, fiber optic grating strain sensors are an important new technological approach that can replace strain gauges in future safety and health monitoring of protective engineering projects during wartime.
Protective engineering structures are designed to withstand and mitigate the effects of penetration explosions. However, such explosions can generate a variety of toxic gases, including TVOC, CO2, CO, HCHO, C6H6, NH3, Rn, NOx, PM2.5, PM10 and etc. The presence of these toxic gases poses a significant threat to the health and safety of personnel within these structures. Therefore, it is crucial to have timely knowledge of the changing concentrations of toxic gases during penetration explosions in order to effectively minimize harm to occupants. To address this issue, a method is proposed to monitor the concentration of toxic gases in real time during penetration explosions in protective engineering structures. The first step involves eliminating the influence of the explosion itself by using nylon ropes to fill the target projectile. This ensures that the focus is solely on monitoring the toxic gas emissions resulting from the penetration process.
Next, a comprehensive monitoring system is implemented to measure the concentrations of various toxic gases. This system utilizes advanced sensors and detectors capable of detecting TVOC, CO2, CO, HCHO, C6H6, NH3, Rn, NOx, PM2.5, PM10 and etc. The sensors are strategically placed within the protective engineering structure to provide accurate and representative measurements. promptly relays the information to a centralized control center. This enables personnel responsible for the safety of the structure to monitor the changing gas concentrations and take appropriate measures to protect occupants. For example, if the concentration of a particular toxic gas exceeds a predetermined threshold, an alarm can be triggered, prompting immediate evacuation or the activation of ventilation systems to mitigate the risks. By implementing this real-time monitoring system, the potential harm caused by toxic gases during penetration explosions in protective engineering structures can be effectively minimized. The ability to promptly detect and respond to changes in gas concentrations ensures the safety and well-being of personnel within these structures. This research contributes to the advancement of protective engineering practices and provides valuable insights for the design and operation of structures in high-risk environments.
In order to measure the structural strain inside concrete under the impact of explosions and other strong shock loads, a flat-type multi-parameter distributed fiber optic sensor was developed. In this experiment, we employed distributed fiber optic sensing technology by deploying optical fibers at typical positions on the explosive model to monitor the real-time strain distribution of the structure under explosive impacts. Simultaneously, fiber optic grating sensors were embedded in the structure to accurately measure the strain parameters at specific locations. The experimental results demonstrate that the embedded distributed fiber optic sensors can accurately measure the internal strain of the concrete structure. The measured pit diameter on the target surface was 41cm, which is very close to the actual damage range (diameter of 37cm). The measured damage level also aligns with the actual damage level of the target. The fiber optic grating sensors, packaged with glass fiber-reinforced polymer (GFRP), exhibited stable measurements around 298με, which is almost identical to the distributed fiber optic measurement of strain at the center of the target, which was 253με. This technology overcomes the limitations of traditional measurement methods and is suitable for testing dynamic stress and strain under explosive impacts and in harsh environments with moisture and electromagnetic interference. It has excellent prospects for application.
Distributed fiber optic sensing technology is based on Raman scattering and optical time-domain reflection technologies, and consists of two parts: the demodulation host and the fiber optic cable. The system obtains the structural changes of the building through the sensing fiber optic cable, such as sensing the strain, crack, tilt, settlement and other specific changes of the dam and other buildings. By calculating the structural safety condition of the building, the system determines the structural safety level of the dam and other buildings according to the judgment standard of structural safety of the dam and other buildings and the subsequent treatment and remedial measures. Realize the long-term online monitoring of the structural safety of dams and other buildings, and provide long-term sustainable structural safety guarantee for dams and other buildings.
To meet the high-precision positioning requirements of dam health monitoring,this paper designs a high spatial resolution distributed Brillouin dam health monitoring scheme based on DPP-BOTDA (Differential Pulse Pair Brillouin Optical Time Domain Analysis) technology.Due to the large pulse width and strong pulse energy of the two differential pulses used in the Brillouin system, the high-precision measurement of Brillouin frequency shift can be achieved; Moreover, the difference in pulse width between the differential pulse pair is small, which can achieve high spatial resolution and meet the high-precision positioning and measurement requirements for dam health monitoring. The rise and fall time of the pulse signals is a key factor affecting the spatial resolution of DPP-BOTDA systems. To achieve centimeter level spatial resolution, this paper designs a SOA (semiconductor optical amplifiers) narrow pulse driving circuit that can generate pulse signals with rise and fall times less than 1 ns (ps level pulse edge). An experimental setup for the DPP-BOTDA system is built. The SOA narrow pulse driving circuit mentioned above is used to generate pulse signals with pulse widths of 48ns and 50ns, respectively, for differential Brillouin tests. By analyzing the spatial resolution test curve of the system with the differential pulse signals demodulation, it can be concluded that the system can achieve a spatial resolution of 0.2m. It meets the high spatial resolution requirements for dam health monitoring and is of great significance in the field of distributed Brillouin fiber optic sensing applications.
In order to monitor the safety of the whole cable in real time and effectively, this study introduces and adopts distributed optical fiber temperature sensing (DTS) technology as the method of cable safety monitoring. A variety of statistical results are used as the basis for judging the running state. Not only does the whole system have no blind zone of safety monitoring, but also provides accurate alarm information and fast response, which enables managers to deal with faults timely and avoid heavy losses. Therefore, the DTS technology has a high promotion value in the field of cable safety monitoring.
KEYWORDS: Demodulation, Temperature metrology, Spatial resolution, Pulse signals, Frequency response, Data processing, Time-frequency analysis, Signal detection
Traditional Brillouin optical time domain reflectometer (BOTDR) generally uses frequency scanning to obtain the Brillouin gain spectrum. And the measurement speed of the sweeping frequency (SF) method is slow, usually on the order of minutes. In this paper, the mechanism of rapid BOTDR measurement based on sloped-assisted (SA) technology is analyzed, the measurement frequency of SA-BOTDR is theoretically calculated, and the system scheme is proposed and designed. Through experimental research, the temperature measurement range of the system is 25°C~70°C at the end of the 203m sensing fiber. The temperature measurement accuracy is 1.38°C, the spatial resolution is 1.21 m, and the measurement frequency is 11.49 Hz.
The application of distributed optical fiber sensing technology in nuclear island safety monitoring is mainly studied in this paper. The anti-radiation ability of the system is an important index. The distributed optical fiber system in this paper is designed with a special anti-radiation optical fiber. The temperature of power supply cables and other facilities in the nuclear island containment can be distributed monitored in full period in real time. Radiation tests are carried out to validate the anti-radiation performance of the system. 60Co is used as a gamma ray radiation source to generate continuous pulses with an average energy of 1.25 MeV. The rate of radiation dose is 1800 Gy/h and the total radiation dose is 1950 Gy. The anti-radiation ability of anti-radiation optical fiber and common optical fiber is compared. It is proved by tests that common optical fiber sensor has great fiber loss in radiation environment, about 0.5dBm, and the loss is decreasing continuously. Anti-radiation optical fiber has little fiber loss in radiation environment, about 0.12 dBm, and the loss tends to be saturated. During the radiation test, the temperature measurement performance of the distributed optical fiber sensing system using anti-radiation optical fiber and the one using common optical fiber is tested in real time. The results show that the anti-radiation distributed optical fiber sensing system performs well in the whole process, which meets the requirements of temperature monitoring for 1339.2 Gy total radiation dose in the refueling cycle of nuclear island.
An algorithm of Rayleigh noise compensation in dual-end configured distributed temperature sensor (DE-DTS) is proposed in this paper. A 2 km long multi-mode fiber is used to calculate the attenuation of the light within Anti-Stokes and Stokes bandwidth, and figure out the isolation of the wavelength division multiplex through both Anti-Stokes channel and Stokes channel. Experiments are taken out to validate the proposed Rayleigh compensation algorithm. As a result, the Rayleigh noise in both Anti-Stokes component and Stokes component is compensated, and the temperature error of the dual-end configured distributed temperature sensor is revised. With the help of the proposed algorithm, a dual-end DTS can reach to the absolute accuracy of 1.09°C (RMSE) between 180°C to 300°C, which significantly monishes the temperature error compared to the sensor without Rayleigh noise compensation.
KEYWORDS: Raman spectroscopy, Temperature metrology, Signal attenuation, Backscatter, Temperature sensors, Data acquisition, Cesium, Sensing systems, Pulsed laser operation
Numerical assessment of temperature uncertainty of Raman-based distributed temperature sensor is taken out in this paper. The sensing system utilized a modified loop-configuration to avoid stimulated Raman scattering and wavelength dependent loss. The experimental results show that the temperature accuracy reaches 0.74°C (RMSE) between -65°C to 300°C with 2 km fiber under test.
In order to monitor and position the leakage of the heat network in real time effectively, this study introduces and adopts distributed optical fiber temperature sensing (DTS) system as the method of heat network leakage monitoring. The temperature change rate is used as the basis for determining the operating state. Not only does the whole system have no blind zone of leakage monitoring, but also provides accurate alarm information and fast response, which enables managers to deal with faults timely and avoid heavy losses. Therefore, the DTS system has a high promotion value in the field of heat network leakage monitoring.
In this study, distributed optical fiber temperature sensing (DTS) system is used as the method of monitoring the temperature field inside the thermal storage tank. On the basis of a practical engineering application, the temperature field characteristics inside the thermal storage tank is obtained and analyzed when the thermal storage and heating system operates. The results show that the distributed fiber temperature sensing system is convenient to construct and build, and it can provide effective data support for the evaluation and design of the thermal storage and heating system.
Oil storage tank is an important facility for oil production and refining. This paper presents a fire monitoring system for oil storage tank based on distributed optical fiber temperature sensing system(DTS), and demonstrates the laying method for both routing fiber and temperature sensing fiber. This system can realize real-time distributed temperature monitoring on the perimeter of secondary sealing ring of oil storage tank and has various alarm mechanisms. The system has been installed and tested in Shikong oil transportation station of China National Petroleum Corporation(CNPC) in Gansu, China. Through the actual test results, the feasibility and advantages of the distributed optical fiber temperature measurement for oil storage tank are verified and the temperature accuracy of the system is better than 1°C.
Distributed optical fiber temperature sensing system (DTS) is a sensing technology for real-time sensor of spatial temperature field distribution. The technology is based on Raman scattering and optical time domain reflection (OTDR),, and is composed of a demodulation host and a temperature sensing cable. The system obtains the ground temperature field change through the temperature sensing cable, calculates the geothermal energy replenishment amount and the recharge rate, and determines the recovery of the geothermal field after heating. It provides according to setting the allowable amount of geothermal energy to be mined and ensuring the long-term sustainable operation of the geothermal heating system.
This paper analyzes the demand of temperature measurement for high temperature wells of oilfields and demonstrates the unique advantages of the distributed optical fiber temperature sensors in comparison with conventional means for temperature measurement. Through the actual test results of the heavy oil area, the feasibility and advantages of the distributed optical fiber temperature measurement are verified. A summary of development trend of the distributed optical fiber temperature measurement system as the core technology applied in the oilfield logging is also given.
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