Research On New Technology Of Bridge Deflection And Displacement Detection Using Optical Fiber And Laser Technology

In order to strengthen the bridge safety management and protect the lives and property of the people,it is important to establish a bridge deflection monitoring system to identify and calibrate the possible structural damage of the bridge in a timely and effective manner.Compared with the traditional electric displacement sensor,the optical fiber is small in size,light in weight,easy to lay in the complex bridge structure,and the optical fiber is not electromagnetic interference in signal transmission,and has strong chemical corrosion resistance,which makes it healthy in the bridge structure.It has broad application prospects in monitoring.This paper has completed the following work in combination with the research of optical fiber and laser technology:(1)A set of bridge deflection and displacement measurement system was developed using optical fiber and laser technology to realize real-time and highprecision measurement of bridge dynamic deflection.The system consists of a selfdesigned fiber laser emission module,a spot image detection module,and a data transmission and display module.In order to evaluate the performance of the system,the article installed and tested the system in the laboratory and outdoor road bridges.The test results show that the measurement accuracy of the system is 0.1 mm,and the measurement frequency is above 15 Hz,which can accurately identify the dynamic deflection changes introduced by the vehicle load.Compared with similar products in the market,the bridge deflection and displacement measurement system proposed in this paper is lower in cost,higher in measurement accuracy,and stronger in antienvironmental interference.(2)Based on the multi-fiber output,the multi-point detection of bridge deflection and the scheme of increasing the displacement measurement range are studied.The article first uses a fiber splitter to evenly distribute the output of one laser to multiple output optical paths,so that multiple transmitters can share one laser,simplifying the structure design and system cost of multi-point measurement.Secondly,the article improves the fiber laser transmitter module through the design of fiber bundle,realizes that one transmitter can generate multiple laser beams at the same time,increase the measurement range of the system,and reduce the difficulty of system installation.(3)Study the characteristics of up-conversion fluorescence in reducing the size of the laser spot and improving the image quality of the spot.The article analyzes the generation mechanism of up-conversion fluorescence and the relationship between upconversion fluorescence and the power of the excitation light source,and designs an up-conversion phosphor plate and uses it as the imaging plane of the spot image detection device.The article compares the spot size and light intensity distribution of the up-conversion fluorescence and the excitation light source under the same light intensity through experiments,and verifies the effect of up-conversion fluorescence in reducing the spot size and improving the imaging quality of the spot.