Improvement of Spatial Resolution for BOTDR by Iterative Subdivision Method

An iterative subdivision method is proposed to improve the spatial resolution of Brillouin optical time-domain reflectometry. By considering the affection of the response time of detection system to the detected Brillouin signal together with the probe pulse, an energy density distribution (EDD) is obtained and the fiber which generates the detected Brillouin signal is divided into short segments with equal length. Then the sub Brillouin signal generated from each segment is extracted out of the detected Brillouin signal based on the EDD. By iteratively using the subdivision method along the fiber, a group of Brillouin signals corresponding to short fiber segments can be obtained. So the Brillouin frequency shift of shorter fiber can be obtained and a higher spatial resolution is achieved. To improve the accuracy, a cross correlation algorithm is also used to enhance the signal-to-noise ratio of the Brillouin signal before the subdivision procedure. A spatial resolution of 1.5 m in a 50 km sensing fiber is obtained by using 100 ns probe pulse, and a spatial resolution of 0.1 m in a 1 km sensing fiber is also obtained by using 10 ns probe pulse.