Optical fiber ground earthquake detection method and system

Abstract

The present invention discloses an optical fiber ground earthquake detection method and system. The method comprises: fixing several optical fiber earthquake detectors on a sensing optical cable at intervals to form a row of sensing units, combining several rows of sensing units to form an optical fiber earthquake detector network; laser emitted by a laser device enters an optical branching deviceand is split into several rows of pulsed light signals, the pulsed light signals separately enter several circulators, and each path of pulsed light is uni-directionally transmitted to a port II by aport I in a circulator, and enters each row of sensing units; the pulsed light signals are transmitted on the detector to generate Rayleigh scattering light, the Rayleigh scattering light and Rayleigh backscattering light are transmitted to the port II of the circulator, are output by a port III of the circulator, are converted into an electrical signal after detection of a photoelectric detector, the electrical signal enters a signal processing module, and the signal process module extracts a vector or three-dimensional earthquake signal according to a demodulated vibration signal. The method and the system can implement reusing and network formation of detectors, and can implement large-range quasi-distributed vector or three-dimensional earthquake signal detection.

Description

technical field [0001] The invention relates to the technical field of sensors for detecting seismic wave signals, in particular to an optical fiber ground seismic detection system and method. Background technique [0002] In the field of oil and gas exploration, with the continuous improvement of domestic onshore oil and gas exploration, the exploration targets are becoming more and more complex, and the requirements for resolution and imaging accuracy of seismic exploration are getting higher and higher. "High density, wide frequency band, wide direction, The collection of "super-highway numbers" has become the main development direction of geophysical prospecting technology. There are two main methods of seismic monitoring: borehole monitoring and surface monitoring. Compared with surface monitoring, the advantage of borehole monitoring lies in the high signal-to-noise ratio of data and the ability to avoid ground noise interference. However, in-well monitoring requires...

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Problems solved by technology

However, this technology needs to effectively shield the reference optical fiber. If it is disturbed by the outside world, it will affect the information validity and sensitivity of the sensing optical fiber in the system.

[0006] Although the fiber grating geophone has the advantages of strong anti-interference ability and large-scale networking ability, its sensitivity is not high, the background noise is large, and its ability to detect weak signals is not good.

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