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fiber optic geophone

A technology of geophones and optical fibers, applied in seismic signal receivers, clad optical fibers, optical waveguides, etc., can solve the problems of expensive demodulation equipment, susceptibility to electromagnetic interference, and high noise, and achieve easy multiplexing and networking , Low demodulation cost, simple device demodulation effect

Inactive Publication Date: 2011-11-30
JINAN UNIVERSITY
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

From the working principle, the existing geophones are divided into moving coil type, eddy current type, piezoelectric type, piezoresistive type, etc. Their disadvantages are: they are susceptible to electromagnetic interference and their sensitivity is relatively low, especially electronic devices are prone to electric sparks , there are potential safety hazards when applied in the field of oil and gas exploration
Document "Design and test of a laser-based optical-fiber Bragg-grating accelerometer for seismic applications Gagliardi" (G Gagliardi, M Salza, P Ferraro et al.. Meas. Sci. Technol., 2008, 19(8): 085306) A similar sensor structure is disclosed, which fixes the mass block and FBG on the vertical cylindrical rod. The noise floor of this system is relatively high, and the minimum detectable acceleration can only reach 0.1mg / Hz
These two types of sensors are easy to reuse, but the sensor structure is complex, the volume is large, the response sensitivity is low, and wavelength demodulation is required, and the demodulation equipment is expensive

Method used

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Embodiment 1

[0029] Such as figure 1 As shown, in this embodiment, a fiber optic geophone includes a tilted fiber grating 1, a cladding-core energy recoupling structure 2, a polymer elastic tube 3, a support member 4, a housing 5 and an optical fiber wire 6; One end of the elastic tube 3 is fixed on the supporting member 4, and the other end is suspended in the air to sense the vibration; the tilted fiber grating 1 and the cladding-core energy recoupling structure 2 are all encapsulated in the polymer elastic tube 3; the outer side of the polymer elastic tube 3 is composed of The shell 5 protects; the polymer elastic tube 3 is connected with an external light source and a photodetector through an optical fiber wire 6 . The polymer elastic tube 3 protects the internal tilted fiber grating 1 and at the same time utilizes its own high elasticity to effectively transmit environmental vibrations to the internal optical fiber.

[0030] Such as figure 2 As shown, the cladding-core energy recou...

Embodiment 2

[0036] Present embodiment except following feature other structures are with embodiment 1: as image 3 As shown, the cladding-core energy recoupling structure 2 is processed by the optical fiber tapering method. Among them, when the diameter of the untapered cladding is 125um, the diameter of the fiber taper is controlled between 60 and 90um, which not only ensures sufficient cladding mode-core mode coupling channels, but also prevents the fiber taper from being too thin to reduce its mechanical strength. Similarly, the position of the tapered fiber should be as close as possible to the tilted fiber grating, with a typical spacing of 2 to 5 mm. In this embodiment, 3 mm is selected. The size of the whole sensing probe is less than 15mm.

[0037] The tilted fiber grating 1 adopts a tilted grating, and the tilt angle of the grating is 4 degrees.

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Abstract

The invention discloses an optical fiber geophone, which comprises a tilted optical fiber grating, a cladding-core energy recoupling structure, a polymer elastic tube, a supporting member, a shell and an optical fiber wire. One end of the polymer elastic tube is fixed on the supporting member. The other end is suspended to sense vibration, and the tilted fiber grating and cladding-core energy recoupling structure are all encapsulated in a polymer elastic tube; the outer side of the polymer elastic tube is protected by a shell, and the polymer elastic tube communicates with an external light source and photoelectric detection through an optical fiber wire The cladding-core energy recoupling structure is processed by a dislocation fusion splicing method or a fiber tapering method. The invention adopts a cladding-fiber core energy recoupling structure, which has a compact structure, and the structure is very sensitive to optical fiber micro-bending or optical fiber vibration, has high sensitivity, and the device demodulation is simpler and the demodulation cost is low.

Description

technical field [0001] The invention relates to the field of sensor design for detecting seismic wave signals, in particular to a sensor for detecting weak high / low frequency seismic wave signals based on optical fiber technology. Background technique [0002] Seismometers are widely used in the fields of earthquake disaster prevention, oil and gas exploration, and national defense security monitoring, mainly including: recording the source of the earthquake, studying the internal structure of the earth and the propagation characteristics of seismic waves, and realizing the prediction of impending earthquakes; recording artificial vibrations that occur through the interface of rock formations Elastic waves caused by reflection or refraction, understanding underground geological structures to find oil and gas traps, and realizing oil and gas storage exploration; detecting ground waves caused by intrusion targets, realizing target identification and early warning safety monitor...

Claims

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Application Information

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IPC IPC(8): G01V1/18G02B6/02
Inventor 郭团关柏鸥
Owner JINAN UNIVERSITY
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