CN101231345B - Radiodetector for seismic exploration and transrectification system thereof - Google Patents

Abstract

The invention provides a geophone for seismic exploration and geophone system thereof. The geophone comprises an optical fiber Bragg grating, a mass block, an elastic component and a geophone shell, wherein the optical fiber Bragg grating is connected with the mass block; the mass block is connected with the geophone shell via the elastic component and used for changing the period or refractive index of the optical fiber Bragg grating. The geophone system of the invention has ideal frequency band and a dynamic range as large as possible with respect to the seismic signal response.

Description

Seismic prospecting wave detector and demodulation system thereof

Technical field

The present invention relates to the seismic exploration technique field, relate in particular to the detection technical field in the seismic prospecting, is seismic prospecting wave detector and demodulation system thereof specifically.

Background technology

At present, seismic exploration technique not only is widely used in oil and mineral resources exploration, but also the investigation that is widely used in geologic hazard for example landslide, surface collapse etc. and hydrology prospecting for example seek sources of water etc., and construction quality is surveyed aspects such as for example dam quality testing.

Seismic exploration technique is meant, according to the elasticity reflection of formation rock to seismic event, refraction, phenomenon such as diffraction or frequency dispersion and dynamic characteristic characteristic thereof, pass through PROPAGATION CHARACTERISTICS OF SEISMIC, gather from the buried target body in ground or well with the earthquake pick-up unit and to reflect, refraction, the signal of diffraction or frequency dispersion, be transferred to seismograph and note through acquisition station, by computing machine the signal that is write down is carried out technical finesse and geologic interpretation at last, thereby infer the structure of geology difference body, structure, the technology of predicting oil reservoir or engineering body etc., its exploration process as shown in Figure 1.

And the above-mentioned pick-up unit that is used for above-mentioned seismic prospecting is a kind of vibration signal to be converted to the conversion equipment of detectable signal, and it plays a crucial role in seismic prospecting.

And, the low frequency signal and the higher frequency signal energy that reflex to surface geophone being differed greatly because the earth is different with the high-frequency signal degree of absorption to low frequency signal, this just requires signal detection system that bigger dynamic range is arranged.

And for accurately, detect reliably, above-mentioned pick-up unit should have desirable frequency band and big as far as possible dynamic range to the response of seismic signal.

The dynamic range of current seismic prospecting instrument has reached 130dB, and the dynamic range of wave detector is below 50dB, can not satisfy the needs of high resolving power, great dynamic range seismic prospecting, become the bottleneck of seismic prospecting, as seen the key factor that influences the seismic prospecting precision at present is a seismoreceiver, thereby research and development high precision seismic wave detector has important practical sense.

This with Chinese patent Granted publication CN2558960Y in disclosed fiber-optic bragg grating sensor, with disclosed Fiber Bragg Grating FBG among the Chinese patent notification number CN1466014Y, and the content of disclosed Bragg grating pressure sensor is incorporated in this among the Chinese patent Granted publication CN1153054C, as prior art of the present invention.

Summary of the invention

The object of the present invention is to provide seismic prospecting with wave detector and demodulation system thereof, with the little defective of dynamic range in the middle of the solution prior art.

A purpose of the present invention is, a kind of seismic prospecting wave detector is provided, and this seismic prospecting comprises Fiber Bragg Grating FBG, mass, elastomeric element, wave detector shell, damping ring with wave detector, and wherein said Fiber Bragg Grating FBG links to each other with mass; Described mass is connected with described wave detector shell by described elastomeric element, and changes the cycle or the refractive index of Fiber Bragg Grating FBG by vibration; Wherein, an end of described Fiber Bragg Grating FBG links to each other with described wave detector shell, and the other end links to each other with described mass; One end of described elastomeric element links to each other with described wave detector shell, and the other end links to each other with described mass; Described Fiber Bragg Grating FBG is the grating of plating; Described elastomeric element is a shell fragment, and this shell fragment is the toroidal of fluting or three arm type toroidals of equiarm, and its material is a beryllium-bronze; Being shaped as of described mass is cylindrical or conical, and is made up of two parts up and down.

Another object of the present invention is to, a kind of demodulation system is provided, described demodulation system comprises: wave detector, and this wave detector comprises: Fiber Bragg Grating FBG, mass, elastomeric element, wave detector shell, damping ring, wherein said Fiber Bragg Grating FBG links to each other with mass; Described mass is connected with described wave detector shell by described elastomeric element, and by vibrating cycle or the refractive index that changes Fiber Bragg Grating FBG, generates light signal; Demodulating equipment, it links to each other with described wave detector by optical fiber, and described light signal is converted to optical power signals; Photoelectric conversion device, it receives described optical power signals, and this optical power signals is converted to electric signal; The A/D conversion equipment, it receives described electric signal, and is converted into digital signal; Digital processing unit, it receives described digital signal, and according to described digital signal drawing waveforms figure; Wherein, an end of described Fiber Bragg Grating FBG links to each other with described wave detector shell, and the other end links to each other with described mass; One end of described elastomeric element links to each other with described wave detector shell, and the other end links to each other with described mass; Described Fiber Bragg Grating FBG is the grating of plating; Described elastomeric element is a shell fragment, and this shell fragment is the toroidal of fluting or three arm type toroidals of equiarm, and its material is a beryllium-bronze; Being shaped as of described mass is cylindrical or conical, and is made up of two parts up and down.

Wave detector of the present invention has been broken through the bottleneck of traditional detector, and the performance of wave detector is greatly improved, and will cause the revolution of seismic prospecting equipment.

Demodulation system of the present invention has desirable frequency band and big as far as possible dynamic range to the response of seismic signal.

Description of drawings

Shown in Figure 1 is the synoptic diagram of existing seismic prospecting process.

That shown in Figure 2 is the equivalent model figure of seismic prospecting of the present invention with wave detector.

Shown in Figure 3 is the structured flowchart of seismic prospecting of the present invention with demodulation system.

Shown in Fig. 4 A is the synoptic diagram of the seismic prospecting of embodiments of the invention 1 with wave detector.

Shown in Fig. 4 B is the mass synoptic diagram of the seismic prospecting of embodiments of the invention 1 with wave detector.

Shown in Fig. 4 C is the synoptic diagram of the seismic prospecting of embodiments of the invention 1 with the shell fragment of wave detector.

Shown in Fig. 4 D is the elasticity synoptic diagram of the seismic prospecting of embodiments of the invention 1 with the shell fragment of wave detector.

Shown in Figure 5 is the seismic prospecting photoelectric conversion device of demodulation system and the circuit diagram of amplifying circuit of embodiments of the invention 1.

Shown in Figure 6 is the circuit diagram of the seismic prospecting of embodiments of the invention 1 with the wave filter of demodulation system.

Shown in Figure 7 is the block diagram of the seismic prospecting of embodiments of the invention 1 with the A/D conversion equipment of demodulation system.

Shown in Fig. 8 A is the grating strain of the direct Compression and Expansion method of Fiber Bragg Grating FBG wave detector of embodiments of the invention 1 and the amplitude versus frequency characte figure of external excitation acceleration.

Shown in Fig. 8 B is the grating strain of the direct Compression and Expansion method of Fiber Bragg Grating FBG wave detector of embodiments of the invention 1 and the phase-frequency characteristic figure of external excitation acceleration.

Shown in Figure 9 is a test output voltage and the optical fibre Bragg optical grating strain graph of a relation of embodiment 1.

Shown in Figure 10 A is the synoptic diagram of the seismic prospecting of embodiments of the invention 2 with wave detector.

Shown in Figure 10 B is the synoptic diagram of the seismic prospecting of embodiments of the invention 2 with the mass of wave detector.

Shown in Figure 10 C is the synoptic diagram of the seismic prospecting of embodiments of the invention 2 with the shell fragment of wave detector.

Shown in Figure 11 A is the Fiber Bragg Grating FBG elastic beam method wave detector grating strain of embodiments of the invention 2 and the amplitude versus frequency characte figure of external excitation acceleration.

Shown in Figure 11 B is the Fiber Bragg Grating FBG elastic beam method wave detector grating strain of embodiments of the invention 2 and the phase-frequency characteristic figure of external excitation acceleration.

Embodiment

Below, with reference to description of drawings the specific embodiment of the present invention.

That shown in Figure 2 is the equivalent model figure of seismic prospecting of the present invention with wave detector.As shown in Figure 2, seismic prospecting of the present invention comprises with wave detector: optical fiber Bragg (Bragg) grating, mass, elastomeric element (for example spring), wave detector shell, damping ring, and wherein said Fiber Bragg Grating FBG links to each other with mass; Described mass is connected with described wave detector shell by described elastomeric element, and changes the cycle or the refractive index of Fiber Bragg Grating FBG by vibration.

Shown in Figure 3 is the structured flowchart of seismic prospecting of the present invention with demodulation system.As shown in Figure 3, seismic prospecting of the present invention comprises with demodulation system: wave detector 301, and this wave detector comprises: Fiber Bragg Grating FBG, mass, elastomeric element, wave detector shell, damping ring, wherein said Fiber Bragg Grating FBG links to each other with mass; Described mass is connected with described wave detector shell by described elastomeric element, and by vibrating cycle or the refractive index that changes Fiber Bragg Grating FBG, generates light signal; Demodulating equipment 303, it links to each other with described wave detector 301 by optical fiber 302, and described light signal is converted to optical power signals; Photoelectric conversion device 304, it receives described optical power signals, and this optical power signals is converted to electric signal; A/D conversion equipment 305, it receives described electric signal, and is converted into digital signal; Digital processing unit 306, it receives described digital signal, and according to described digital signal drawing waveforms figure.

Embodiment 1

Shown in Fig. 4 A is the synoptic diagram of the seismic prospecting of embodiments of the invention 1 with wave detector, shown in Fig. 4 B is the mass synoptic diagram of the seismic prospecting of embodiments of the invention 1 with wave detector, and shown in Fig. 4 C is the synoptic diagram of the seismic prospecting of embodiments of the invention 1 with the shell fragment of wave detector.As Fig. 4 A, Fig. 4 B, shown in Fig. 4 C, the seismic prospecting wave detector of present embodiment is the direct Compression and Expansion method of a Fiber Bragg Grating FBG wave detector, (the Bragg grating bandwidth is less than 0.2nm for wherein metallized grating, length is less than 5mm) be engraved on optical fiber 405, and the one end is adhered to oscillating mass piece 404,406, the mass M of mass is 404 and 406 sums among Fig. 1, the other end of above-mentioned grating is adhered to adjusts piece 410, and finally link to each other with wave detector shell 409, the direct Compression and Expansion method of the Fiber Bragg Grating FBG of present embodiment wave detector can be adjusted the primary stress situation of optical fiber by fine-tuning nut 411 in addition.The spacing of mass and wave detector shell 409 is L.One end of shell fragment 401,407 is fixing by supporting ring 402,403, and its other end is connected (elasticity of shell fragment 401 is shown in Fig. 4 D) with mass 404,406.

The assembling of mass and spring leaf for convenience in the present embodiment in addition, mass is formed, promptly is made up of 404 and 406 of Fig. 2 by two parts, and the material of mass is a stainless steel, and density is ρ=7.8g/cm ³, and in order to guarantee the non-directional of wave detector side direction, it is shaped as cylindrical, and the quality of mass is M=28.3g.

And, in order to increase damping ratio, at the annular space of mass 404,406 and wave detector shell 9, be between the damping ring 408 and mass 404,406 of Fig. 1, filling viscosity silicone oil, the annular space spacing is far smaller than relative area, can equivalence be the motion of infinitely great dull and stereotyped gap viscous fluid, height a=2mm when the contact annular, distance h=0.1mm, width b ≈ 2 π R=17 π (mm) inner surface of outer cover of equivalence are equivalent to lower plate and are made as staticly, and the mass outside surface is equivalent to upper plate with speed

Motion, because of viscous fluid is slowly moved, the pressure P that fluid motion produces is zero, law of friction gets in the equation of motion that is flowed by the infinity plane fluid and the newton:

$d=\frac{2\mathrm{\πRa}}{h}\mathrm{\μ}---\left(1\right)$

By damping ratio $\mathrm{\&xi;}=\frac{\mathrm{<figure-callout\; id="0"\; label="d\; d"\; filenames="H071E1556220070815E000061.png,H071E1556220070815E000102.png"\; state="\{\{state\}\}">d</figure-callout>}}{d_{}}$ ξ=0.0075 μ, in order to obtain damping ratio the best, the resisting medium choosing is poor to temperature sensitivity, the methyl-silicone oil of chemistry, stable physical property, air dissolution rate therein is irrelevant with its viscosity, allocates the silicone oil that obtains any viscosity easily.

Methyl-silicone oil can be made into 0.65 * 10 according to concrete purposes ^-6m ²/ s (20 ℃)～2m ²The product of the different viscosities of/s, the silicone oil of viscosity can be allocated according to following experimental formula arbitrarily:

G ₁logμ ₁+G ₂logμ ₂＝(G ₁+G ₂)logμ (2)

In the formula, μ ₁--the viscosity of viscous silicone fluid; μ ₂--the viscosity of silicone oil with low viscosity; μ--the viscosity of preparation viscosity silicone oil; G ₁--the quality of viscous silicone fluid; G ₂--the quality of silicone oil with low viscosity.

The viscosity of silicone oil and the relation of temperature can be expressed as:

logν＝10 ^-Alog(T/298)logν ₂₅ (3)

In the formula, the kinematic viscosity (10 of silicone oil when ν--temperature is T ^-6m ²/ s); T--silicone oil temperature (K); ν ₂₅--the apparent viscosity (10 of silicone oil in the time of 25 ℃ ^-6m ²/ s); The A--constant,

By

Determine, or get empirical value A=2%/℃.

The elasticity coefficient that Bragg grating produces ${\mathrm{<figure-callout\; id="1"\; label="k"\; filenames="H071E1556220070815E000061.png,H071E1556220070815E000102.png"\; state="\{\{state\}\}">k</figure-callout>}}_1=\frac{\mathrm{EA}}{L}=\frac{895.845}{L}N/m,$ For the shell fragment vibration based on vibrational system, the elasticity coefficient of spring is k ₂Must get k more than or equal to the elasticity coefficient of Bragg grating ₂=k ₁Common extension spring will reach k ₁, volume is inevitable very huge, so spring is designed to the shell fragment form.

And because the beryllium-bronze mechanical property is better than steel, plasticity is good under as-quenched, easily produces different shape, and ductility is fabulous, and it is by force the ideal material of shell fragment design that very high intensity and hardness, wear-resisting, endurance, elastic recovery capability are arranged.

Since shell fragment shape difference, the elasticity difference; The shell fragment fluting is different, and the elasticity that shell fragment produces is also different; Shell fragment thickness difference, elasticity are also different.So as required, utilize the finite element analysis method Modeling Calculation, utilize the vertical deviation on limit to be constrained to zero condition, ask for shape, thickness and the fluting number and the size of shell fragment.

The bottom of being inserted in mass when shell fragment is compressed by top, makes mass follow shell fragment to move up and down together, and shell fragment has limited the mass transverse vibration simultaneously, has eliminated the influence of alias, guarantees that optical grating axial is flexible,

When external excitation with acceleration a=a ₀During sin (ω t) excitation, the bragg wavelength displacement of fiber grating is:

Δλ＝0.78λ _Bε＝0.78λ _BDsin(ωt+φ) (4)

In the formula: $D=\frac{1}{L_2}\frac{a_0}{\sqrt{{({\mathrm{\&omega;}}_0^2-{\mathrm{\&omega;}}^2)}^2+{\left(2\mathrm{\&xi;}{\mathrm{\&omega;}}_0\mathrm{\&omega;}\right)}^2}}$

$\mathrm{\&phi;}=-\mathrm{<figure-callout\; id="2"\; label="arctg"\; filenames="H071E1556220070815E000061.png,H071E1556220070815E000102.png"\; state="\{\{state\}\}">arctg</figure-callout>}\frac{2\mathrm{\&xi;}{\mathrm{\&omega;}}_0\mathrm{\&omega;}}{{\mathrm{\&omega;}}_0^2-{\mathrm{\&omega;}}^2}$

${\mathrm{\&omega;}}_0=\sqrt{\frac{k}{M}},$ Natural frequency or resonant frequency are by the structure and material decision of wave detector elastic system, f ₀=400.5Hz.

Sensitivity is the sensitivity of wave detector to excitation (vibration) response, $S=\frac{\mathrm{\&Delta;\&lambda;}}{a}=157.3\mathrm{pm}/g,$ Wherein, g is an acceleration of gravity.

After the direct Compression and Expansion method of Fiber Bragg Grating FBG of the present invention wave detector detects the external excitation mechanical oscillation signal, this external excitation mechanical oscillation signal is converted to light signal, by optical fiber above-mentioned light signal is outputed to demodulating equipment then, the above-mentioned light signal that this demodulating equipment will receive is converted to optical power signals.

Then, above-mentioned demodulating equipment outputs to photoelectric conversion device, amplifying circuit (as shown in Figure 5) with above-mentioned optical power signals, after photoelectric conversion device receives described optical power signals, this optical power signals is converted to electric signal and amplification.

Above-said current signal outputs to above-mentioned A/D conversion equipment (as shown in Figure 7) by after wave filter (as shown in Figure 6) filtering, and this A/D conversion equipment receives described electric signal, and is converted into digital signal.

At last, digital processing unit receives described digital signal, and draws the grating strain of the direct Compression and Expansion method of Fiber Bragg Grating FBG of the present invention wave detector and the amplitude-frequency and the phase-frequency characteristic figure (shown in Fig. 8 A, Fig. 8 B) of external excitation acceleration according to described digital signal.

One test output voltage of present embodiment and optical fibre Bragg optical grating strain relation are as shown in Figure 9.

Embodiment 2

Shown in Figure 10 A is the synoptic diagram of the seismic prospecting of embodiments of the invention 2 with wave detector, shown in Figure 10 B is the synoptic diagram of the seismic prospecting of embodiments of the invention 2 with the mass of wave detector, and shown in Figure 10 C is the synoptic diagram of the seismic prospecting of embodiments of the invention 2 with the shell fragment of wave detector.

As Figure 10 A, Figure 10 B, shown in Figure 10 C, present embodiment seismic prospecting wave detector is a Fiber Bragg Grating FBG elastic beam method wave detector, in this Fiber Bragg Grating FBG elastic beam method wave detector, Fiber Bragg Grating FBG 1004 is pasted on shell fragment 1001,1007, shell fragment 1001,1007 are fixed in shell 1009, and mass is made up of two parts, be 1005 and 1006 of Figure 10 B, the quality of mass is M, the material of mass is a stainless steel, guaranteed the non-directional of wave detector side direction, be shaped as taper shape (as Figure 10 A 1005 and 1006 shown in), the quality of mass is M=19.3g.Spring system is designed to the circular shell fragment shape of 3 arms, material selection beryllium-bronze (shown in Figure 10 C), the outer end of shell fragment 1001,1007 is fixing by supporting ring (as supporting ring 1002 and the supporting ring 1003 of Figure 10 A), the center links to each other with oscillating mass piece 1005,1006, semi-girder length is L, by the crooked strain that gets grating of semi-girder is:

$\mathrm{\&epsiv;}=\frac{F(L-x)\mathrm{<figure-callout\; id="2"\; label="h"\; filenames="H071E1556220070815E000061.png,H071E1556220070815E000102.png"\; state="\{\{state\}\}">h</figure-callout>}}{2{\mathrm{EI}}_z}=\frac{6(L-x)}{E{\mathrm{bh}}^2}F---\left(5\right)$

Wherein, $F=\frac{1}{3}\mathrm{Ma},$ A external excitation acceleration; B shell fragment cantilever deck-siding; H shell fragment thickness.

In order to increase damping ratio, mass and the sticking filling viscous fluid damping of shell annular space (between the mass 1006 and damping ring 1008 as Figure 10 A) are adopted in the design of damping structure, the annular space spacing is far smaller than relative area, can equivalence be the motion of infinitely great dull and stereotyped gap viscous fluid, d=0.94 μ, damping ratio ξ=0.5 μ, wherein, μ is the viscosity of silicone oil.The wavelength shift that is pasted on the grating on the semi-girder is:

$\mathrm{\&Delta;\&lambda;}=-\frac{1.56{\mathrm{\&lambda;}}_B(L-X)}{\mathrm{<figure-callout\; id="2"\; label="E\; bh"\; filenames="H071E1556220070815E000061.png,H071E1556220070815E000102.png"\; state="\{\{state\}\}">E</figure-callout>}{\mathrm{bh}}^{}{}^2}\&CenterDot;{\mathrm{MB\&omega;}}^2\sin (\mathrm{\&omega;t}+\mathrm{\&theta;})---\left(6\right)$

In the formula: $B=\frac{a_0}{\sqrt{{({\mathrm{\&omega;}}_0^2-{\mathrm{\&omega;}}^2)}^2+{\left(2\mathrm{\&xi;}{\mathrm{\&omega;}}_0\mathrm{\&omega;}\right)}^2}}$

$\mathrm{\&phi;}=-\mathrm{<figure-callout\; id="2"\; label="arctg"\; filenames="H071E1556220070815E000061.png,H071E1556220070815E000102.png"\; state="\{\{state\}\}">arctg</figure-callout>}\frac{2\mathrm{\&xi;}{\mathrm{\&omega;}}_0\mathrm{\&omega;}}{{\mathrm{\&omega;}}_0^2-{\mathrm{\&omega;}}^2}$

Semi-girder gets elasticity coefficient $k=\frac{3{\mathrm{<figure-callout\; id="3"\; label="Ebh"\; filenames="H071E1556220070815E000061.png"\; state="\{\{state\}\}">Ebh</figure-callout>}}^3}{4{\mathrm{<figure-callout\; id="3"\; label="L"\; filenames="H071E1556220070815E000061.png"\; state="\{\{state\}\}">L</figure-callout>}}^3}=43.3N/m,$ Natural frequency is f ₀=7.4Hz, wavelength shift sensitivity $S=\frac{\mathrm{\&Delta;\&lambda;}}{a}=1.03\&times;{10}^{-10}{\mathrm{<figure-callout\; id="2"\; label="s"\; filenames="H071E1556220070815E000061.png,H071E1556220070815E000102.png"\; state="\{\{state\}\}">s</figure-callout>}}^2=1\mathrm{nm}/g,$ In the formula, g is an acceleration of gravity.

After Fiber Bragg Grating FBG elastic beam method wave detector of the present invention detects the external excitation mechanical oscillation signal, this external excitation mechanical oscillation signal is converted to light signal, by optical fiber above-mentioned light signal is outputed to demodulating equipment then, the above-mentioned light signal that this demodulating equipment will receive is converted to optical power signals.

Then, above-mentioned demodulating equipment outputs to photoelectric conversion device and amplifying circuit with above-mentioned optical power signals, after photoelectric conversion device receives described optical power signals, this optical power signals is converted to electric signal and amplification.

Above-said current signal outputs to above-mentioned A/D conversion equipment by behind the filter filtering, and this A/D conversion equipment receives described electric signal, and is converted into digital signal.

At last, digital processing unit receives described digital signal, and draws the grating strain of the direct Compression and Expansion method of Fiber Bragg Grating FBG of the present invention wave detector and the amplitude-frequency and the phase-frequency characteristic figure (shown in Figure 11 A, Figure 11 B) of external excitation acceleration according to described digital signal.

Seismic prospecting of the present invention in addition is with in the demodulation system:

1. dynamic range

Seismic event is in the stratum in the communication process, since the diffusion of wavefront, the absorption on stratum, its energy can be subjected to loss, and when ripple reached ground, the superficial reflex ripple was strong because of propagating the little energy of the short loss of distance, the deep reflex ripple is strong because of propagating the long loss macro-energy of distance, and dynamic range is bigger.

In order to guarantee that fiber grating is operated in normal condition, grating is not broken (or bending compression), and the maximum strain of grating should be less than 1%,

1). maximum strain in the present invention gets 0.5%, and the detection technique of grating strain reaches 0.1 μ ε, the dynamic range of grating:

$d=20\log \frac{0.5\%}{0.1\&times;{10}^{-6}}=94\mathrm{dB}---\left(7\right)$

2). maximum strain in the present invention gets 0.3%, and the detection technique of grating strain reaches 0.1 μ ε, the dynamic range of grating:

$d=20\log \frac{0.3\%}{0.1\&times;{10}^{-6}}=90\mathrm{dB}---\left(8\right)$

So grating wave detector dynamic range is bigger, greater than 90dB.

2. natural frequency

The earth is a Hi-pass filter, and the frequency of artificial earthquake generally arrives between the hundreds of hertz at several hertz, and natural frequency is determined by the seismic prospecting purpose.

${\mathrm{<figure-callout\; id="0"\; label="f"\; filenames="H071E1556220070815E000061.png,H071E1556220070815E000102.png"\; state="\{\{state\}\}">f</figure-callout>}}_0=\frac{1}{2\mathrm{\&pi;}}{\mathrm{\&omega;}}_0=\frac{1}{2\mathrm{\&pi;}}\sqrt{\frac{k}{m}}---\left(9\right)$

$A=\mathrm{\&pi;}\&times;{(\frac{125}{2}\&times;{10}^{-6})}^2=1.227\&times;{10}^{-8}\left(m^2\right)$

$k=K+\frac{\mathrm{EA}}{L}=K+\frac{7.3\&times;{10}^{10}\&times;A}{10\&times;{10}^{-3}}=K+89584.5(N/m)$

Make K=89584.5 (N/m), m=11.6g is f then ₀=625.5Hz

3. frequency domain scope

In the present invention can be according to different requirements, change the sensitivity of sensor and the size of natural frequency by the size of quality of regulation piece and the hardness of spring, if wish to measure the frequency domain wide ranges, the elasticity coefficient of spring is strengthened, or reduce the quality of mass.

1) .0.1 * 10 ^-6≤ ε≤0.3% o'clock is by Δ λ=0.7874 λ _Bε gets: 0.12pm≤Δ λ≤3.66nm.

2) .0.1 * 10 ^-6≤ ε≤0.5% o'clock is by Δ λ=0.7874 λ _Bε gets: 0.12pm≤Δ λ≤6nm.

General light source is 40nm, if maximum strain is 0.5%, the multiplexing capacity of wave detector is 40/3.66=10.9, promptly light source can maximum multiplexing 10 grating wave detectors, as maximum strain is 0.3%, the multiplexing capacity of wave detector is 40/6=6.7, and promptly a light source can maximum multiplexing 6 grating wave detectors.If natural frequency is got f ₀=625.5Hz is so the frequency domain scope is 0～442Hz.

4. resolution

The grating demodulation technology of seismic exploration application compatibly is that the grating matching method belongs to the tuning filtering method, and simple in structure, precision is the requirement of seismic exploration high resolving power contentedly, and the resolution of the detection of strain is 1 μ ε, and then wavelength resolution is 1.2pm.

5. sensitivity

The grating wavelength drift is kinetic by the earth, and promptly the grating wavelength deviation sensitivity is the wavelength shift under the mass unit acceleration:

$S=\frac{\mathrm{\&Delta;\&lambda;}}{a}=\frac{{0.78\mathrm{m\&lambda;}}_B}{(\mathrm{EA}+\mathrm{KL})}---\left(10\right)$

The grating wavelength deviation sensitivity is: S=0.077nm/g=77pm/g.

Sensitivity also can be expressed as the Bragg grating pitch rate of change under the mass unit acceleration:

$S=\frac{\mathrm{\&Delta;\&Lambda;}}{a}=\frac{{0.78\mathrm{m\&lambda;}}_B}{{2n}_{\mathrm{eff}}\mathrm{kL}}=\frac{{0.78\mathrm{m\&lambda;}}_B}{{2n}_{\mathrm{eff}}(\mathrm{EA}+\mathrm{KL})}---\left(11\right)$

The sensitivity of Bragg grating pitch is: S=0.026nm/g=26pm/g.

From above-mentioned data as can be known, wave detector of the present invention has been broken through the bottleneck of traditional detector, and the performance of wave detector is greatly improved, and will cause the revolution of seismic prospecting equipment.

Demodulation system of the present invention has desirable frequency band and big as far as possible dynamic range to the response of seismic signal.

In sum; though the present invention discloses as above with preferred embodiment; right its is not in order to restriction the present invention; anyly have the knack of this operator; without departing from the spirit and scope of the present invention; when can doing various changes and retouching, so protection scope of the present invention should be as the criterion with the desired scope of claims.

Claims (4)

1. a seismic prospecting wave detector is characterized in that,

Described seismic prospecting comprises Fiber Bragg Grating FBG, mass, elastomeric element, wave detector shell with wave detector, wherein

Described Fiber Bragg Grating FBG links to each other with mass;

Described mass is connected with described wave detector shell by described elastomeric element, and changes the cycle or the refractive index of Fiber Bragg Grating FBG by vibration;

One end of described Fiber Bragg Grating FBG links to each other with described wave detector shell, and the other end links to each other with described mass; One end of described elastomeric element links to each other with described wave detector shell, and the other end links to each other with described mass;

Described Fiber Bragg Grating FBG is the grating of plating;

Described elastomeric element is a shell fragment, and this shell fragment is the toroidal of fluting or three arm type toroidals of equiarm, and its material is a beryllium-bronze;

Being shaped as of described mass is cylindrical or conical, and is made up of two parts up and down.

2. seismic prospecting wave detector as claimed in claim 1 is characterized in that,

Described Fiber Bragg Grating FBG is pasted on described shell fragment.

3. a demodulation system is characterized in that, described demodulation system comprises:

Wave detector, this wave detector comprises: Fiber Bragg Grating FBG, mass, elastomeric element, wave detector shell, wherein said Fiber Bragg Grating FBG links to each other with mass; Described mass is connected with described wave detector shell by described elastomeric element, and by vibrating cycle or the refractive index that changes Fiber Bragg Grating FBG, generates light signal;

Demodulating equipment, it links to each other with described wave detector by optical fiber, and described light signal is converted to optical power signals;

Photoelectric conversion device, it receives described optical power signals, and this optical power signals is converted to electric signal;

The A/D conversion equipment, it receives described electric signal, and is converted into digital signal;

Digital processing unit, it receives described digital signal, and according to described digital signal drawing waveforms figure;

Wherein, an end of described Fiber Bragg Grating FBG links to each other with described wave detector shell, and the other end links to each other with described mass;

One end of described elastomeric element links to each other with described wave detector shell, and the other end links to each other with described mass;

Described Fiber Bragg Grating FBG is the grating of plating;

Described elastomeric element is a shell fragment, and this shell fragment is the toroidal of fluting or three arm type toroidals of equiarm, and its material is a beryllium-bronze;

Being shaped as of described mass is cylindrical or conical, and is made up of two parts up and down.

4. demodulation system as claimed in claim 3 is characterized in that,

Described Fiber Bragg Grating FBG is pasted on described shell fragment.

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