A Novel Three-Component Fiber-Optic Geophone for Distributed Acoustic Sensing System

Distributed acoustic sensing (DAS) is an innovative seismic data acquisition technology in the field of seismic monitoring. It has emerged as a highly attractive and promising fiber-optic sensing technology over the past decade. DAS uses Rayleigh scattering to localize and restore information about fiber vibrations. However, the response of optical fibers to seismic waves is primarily limited to the axial direction due to inherent characteristics of the glass fiber material. As a result, traditional DAS monitoring is restricted to capturing a single component of the seismic signal. To address this limitation and enable optical fibers to have a multicomponent response to seismic waves, this article proposes a DAS-based three-component fiber-optic geophone. Unlike conventional geophone, this proposed scheme does not include any electronic elements, relying solely on the optical fiber for sensing purposes. In this article, the equations of motion for the proposed scheme are derived in detail, and a physical prototype is successfully produced based on the theoretical derivation. We then performed active source excitation experiments in which the proposed three-component fiber-optic geophone captured the acceleration characteristics of the three-component vibration signal and successfully expressed it in phase form, which reflects the strain change in the optical fiber, and compared with the control group (traditional geophone), the signal-to-noise ratio (SNR) of this geophone has a slight improvement of about 1.87 dB, satisfying the requirements of high SNR and low power consumption. At the same time, the scheme maintains the time and spatial consistency with the traditional geophone.