In March 2022, the Innovation Academy for Precision Measurement Science and Technology of the Chinese Academy of Sciences laid three optical fibers in the tunnel of Dayun North Station on Shenzhen Metro Line 21. The fibers were installed on both sides and the top of the tunnel using adhesive bonding. By analyzing the collected data, the imaging results can be used to explain the voids in shield tunnel segments and assess the health status of external spatial structures. Additionally, based on vibration energy, frequency, and phase information, external intrusion behaviors such as excavation and pile driving can be effectively identified.