Distributed optical fiber sensor for tunnel waterlogging based on actively heated method
In response to the current demand for monitoring the waterlogging events and the extent of waterlogging in tunnels,two new types of tunnel waterlogging sensors are developed,and a distributed sensing method for tunnel wa-terlogging based on distributed temperature sensing(DTS)is proposed in this paper.Firstly,the spatial resolution of the sensor is improved by encapsulating the optical sensing cable in a two-dimensional plane spiral pattern and an actively heated method is used to significantly improve the temperature difference of the optical sensing cable at the water-air interface,thereby realizing the identification of the events and range of tunnel waterlogging.Then,through the indoor model tests,the performance and influencing factors of the optical sensing cable are studied.The results show that the two sensors developed have higher spatial resolution.Due to the smaller spacing of the spiral circle,the spatial resolution and positioning accuracy of the spiral type Ⅰ sensor are higher than those of the spiral type Ⅱsensor.Both sensors can accurately identify the water-air interface under various typical working conditions,and their positioning errors are less than 10 cm.The positioning accuracy of the sensors can be improved by appropriate-ly increasing the heating temperature,and the positioning accuracy under the heating conditions of 50 ℃ is signifi-cantly better than 35 ℃ and 20 ℃.
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