Underground pipeline imaging using broadband fiber optic seismometer array

A fiber optic seismometer with a wide band from 120 s to 4000 Hz has been developed by using the inverted pendulum structure of space light interference and zero pole compensation technology. Combined with Kalman filtering and elliptic fitting demodulation, the phase noise of the system is reduced to 10 ng/√Hz@1 Hz. Based on this fiber optic seismometer, background noise imaging experiments were conducted at the site of known underground pipes. Comparing with ground penetrating radar and electrical seismometer, fiber optic seismometer successfully identified three pipelines with diameters of 2.8 m, 2.2 m, and 0.5 m at varying depth, indicating that its optimal imaging resolution has reached sub-meter levels and the performance better than that of electrical seismometer.