An existing communication
optical fiber positioning method based on earthquake
arrival time double difference comprises the steps that firstly, a DAS
system is arranged at one end of an existing communication
optical fiber and communicated, secondly, a plurality of monitoring points are evenly arranged in the length direction of the
optical fiber, at least two earthquake sources are selected on the periphery, and the time when earthquake
waves reach the monitoring points is collected through the DAS
system, and thirdly, the time when the earthquake
waves reach the monitoring points is collected through the DAS
system. The method comprises the following steps: step 1, taking two adjacent monitoring points as a group of monitoring point pairs, calculating
travel time difference from the same seismic source to the group of monitoring point pairs, then calculating to obtain double-difference
travel time of different seismic sources, and covering all the monitoring point pairs, step 4, based on the double-difference
travel time and a
linear relation of relative positions of the adjacent monitoring points, establishing
linear relation expressions of each group, summarizing to form an overdetermined linear equation set, and 5, solving the equation set to obtain the
relative space relation of adjacent monitoring points, combining the absolute coordinates of one end of the optical
fiber, and deriving the absolute coordinates of all the monitoring points through vector superposition to complete positioning. Therefore, the positioning speed is high, and the precision can be guaranteed.