Abstract: Aiming at the problems of low sensitivity, poor signal-to-noise ratio, complex installation, and the need for additional power supply of the traditional power grid dance detector in the face of electromagnetic interference and continuous power supply, we proposed a new double-ended Mach-Zehnder (M-Z) fibre optic seismic detection system. The system adopted double-ended fibre optic M-Z optical path structure, which could achieve long-distance, large-scale, multi-dimensional on-line monitoring and structural safety warning to locate the position of the dance in real time.  The geophone mechanical unit of this system adopted the push-pull structure of silicone elastomer and brass mass block, and after parametric modelling and finite element analysis by ANSYS software, its intrinsic frequency was determined to be 106.77 Hz, with the relative error of only 1.65% compared to the experimental data. The experimental results show that the relative sensitivity of the detector in the range of 0—140 Hz is 41.25—66.78 dB(rad/Pa), which confirms its ability to detect the high sensitivity of the dance signal.

Key words: M-Z interferometer, fiber optic sensing, push-pull structure, finite element analysis