Intrusion Location with Breaking-the-Pulse-Width-Limit Spatial Resolution and High Robustness based on φ-OTDR and Spatial Frequency Analysis Topics: Optical Amplification and Sensing; Optical Modulation and Signal Processing; Optical Sensors In Proceedings of the 14th International Joint Conference on e-Business and Telecommunications - Volume 0ICETE, 17-23, 2017 , Madrid, Spain