Reliable intrusion detection is critical for modern infrastructure security, yet it faces two fundamental challenges: scarcity of labeled samples and lack of model interpretability. Distributed optical fiber vibration sensing (DVS) systems are promising for perimeter security but perform poorly when only a few intrusion samples are available. Most deep models also lack transparency and trustworthiness. To address these issues, we propose an explainable dual-branch feature fusion dynamic class center prototypical n…