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.
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.
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.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.