CN103471701B - A kind of fiber optic acoustic sensors and optical fiber acoustic sounding method - Google Patents
A kind of fiber optic acoustic sensors and optical fiber acoustic sounding method Download PDFInfo
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Abstract
The invention discloses a kind of fiber optic acoustic sensors and optical fiber acoustic sounding method, fiber optic acoustic sensors comprises the first fiber grating, sensing unit, coupling mechanism, the second fiber grating, tunable attenuator, pumping source, wavelength division multiplexer, gain fibre and catoptron; Coupling mechanism comprises four ports, and the first port is connected with the first fiber grating by sensing unit, and the second port is connected with the second fiber grating by tunable attenuator, and the 3rd port is connected with catoptron with gain fibre by wavelength division multiplexer successively; Described pumping source is connected with described wavelength division multiplexer; 4th port is used for being connected with the signal demodulating equipment of outside.Present invention utilizes the method for dual laser gain competition effect and signal transacting employing binary channels work difference, reduce noise, improve sensitivity.The present invention has: highly sensitive, and structure is simple, and firm, cost is low, and product success ratio is high, working stability, to advantages such as environment temperature are insensitive.
Description
Technical field
The invention belongs to fiber optic acoustic sensors field, more specifically, relate to a kind of fiber optic acoustic sensors and optical fiber acoustic sounding method.
Background technology
The basic functional principle of Fibre Optical Sensor is that light is sent into modulator through optical fiber, after parameter to be measured and the light entering modulator zone are interacted, the optical property of light (intensity, wavelength, frequency, phase place, polarization state etc. as light) is caused to change, be called modulated flashlight, photo-detector is being sent into through optical fiber, after demodulation, obtain measured parameter.Fibre Optical Sensor can be used for measuring multiple physical quantity, and such as sound field, electric field, pressure, temperature, angular velocity, acceleration etc., can also complete the measurement task that existing measuring technique has been difficult to.In narrow space, in strong electromagnetic and high-tension environment, Fibre Optical Sensor all shows unique ability.
Sound wave (Sound Wave or Acoustic Wave) is the mode of propagation of sound.Sound wave is a kind of mechanical wave, and vibrated by object (sound source) and produce, the space of Acoustic Wave Propagation is just called sound field.Be a kind of compressional wave when propagating in gas and liquid medium, but may shear wave be mixed with when propagating in solid dielectric.
At present, the method for practical fiber optic acoustic sensors used a transducer and also sensitivity not high.(1) single longitudinal mode polarization beat frequency sound pressure sensor: have thin film at transducing part, acoustic pressure is converted to the pressure of film.(2) single mode-multi-mode-single mode optical fibre sound pressure sensor: be also conduct acoustic pressure with film, cause fibre-optical bending, make energy leakage.(3) fiber grating sound pressure sensor: make the sensitive film of sound wave at the coat of fiber grating.There is energy transducer in these sound wave Fibre Optical Sensors, reduce the utilization of acoustic pressure, sensitivity is low.
The fiber optic acoustic sensors also had makes microstructure, and such as (1) is super bores sound pressure sensor suddenly: transducing part is region optical fiber being pulled into ultra-fine, steep taper.(2) microstructure mass Fibre Optical Sensor: be that optical fiber a bit of coat is wherein retained, put into after hydrofluorite corrodes a period of time and the coat stayed is removed, then corrode.So just leave the microstructured optical fibers of a mass as sensing position.These sound wave Fibre Optical Sensors make complicated, frangible.
The fiber optic acoustic sensors also had is interfere type, and such as (1) Mach-Zahnder interference sonic sensor, bulky, generally all tens meters.(2) graphene film becomes Fabry Perot interference structure: cost is high, and success ratio is extremely low.
In sum, it is low that prior art also exists sensitivity, complex structure, cost hi-tech problem
Summary of the invention
For above defect or the Improvement requirement of prior art, the invention provides a kind of fiber optic acoustic sensors and optical fiber acoustic sounding method, its object is to the sensitivity improving acoustic signals detection, solution sensitivity is low thus, complex structure, the technical matters that cost is high.
The invention provides a kind of fiber optic acoustic sensors, comprise the first fiber grating, sensing unit, coupling mechanism, the second fiber grating, tunable attenuator, pumping source, wavelength division multiplexer, gain fibre and catoptron; Described coupling mechanism comprises four ports, and the first port is connected with the first fiber grating by sensing unit, and the second port is connected with the second fiber grating by tunable attenuator, and the 3rd port is connected with catoptron with gain fibre by wavelength division multiplexer successively; Described pumping source is connected with described wavelength division multiplexer; 4th port is used for being connected with the signal demodulating equipment of outside;
During described fiber optic acoustic sensors work, pumping source exports pump light, pump light is coupled in gain fibre by wavelength division multiplexer, and gain fibre exports spontaneous emission light, and spontaneous emission light inputs in coupling mechanism respectively by gain fibre and wavelength division multiplexer after catoptron reflection, light is divided into two bundles by coupling mechanism, a branch ofly transfer in the first fiber grating by sensing unit, the light consistent with the first fiber bragg grating center wavelength inputs to described coupling mechanism by described sensing unit after being reflected by described first fiber grating, again successively by exporting the radiant light that energy increases after described wavelength division multiplexer and gain fibre, this radiant light is reflected by catoptron, and in the chamber that the first fiber grating and catoptron are formed oscillate, the first laser is exported from the 4th port of described coupling mechanism when the gain of the light consistent with the first fiber bragg grating center wavelength is greater than loss, another light beam transfers in the second fiber grating by tunable attenuator, the light consistent with the second fiber bragg grating center wavelength inputs to coupling mechanism by tunable attenuator after being reflected by the second fiber grating, again successively by exporting the radiant light that energy increases after wavelength division multiplexer and gain fibre, this radiant light is reflected by catoptron, and in the chamber that the second fiber grating and catoptron are formed oscillate, export the second laser when the gain of the light consistent with the second fiber bragg grating center wavelength is greater than loss from the 4th port of described coupling mechanism, described sensing unit comprises the first single-mode fiber, multimode optical fiber and the second single-mode fiber that connect successively.
Further preferably, the coupling mechanism of described coupling mechanism to be power splitting ratio be 1:1.
Further preferably, the core diameter of described multimode optical fiber is 105 microns, and cladding diameter is 125 microns.
Further preferably, described multimode optical fiber is coreless fiber, and the diameter of described coreless fiber is 125 microns.
Present invention also offers a kind of optical fiber acoustic sounding method based on above-mentioned fiber optic acoustic sensors, comprise the steps:
S1: make the luminous power of the first laser and the second laser equal by regulating the pad value of tunable attenuator;
S2: when sensing unit is placed in acoustic wavefield, the net gain of the first laser is subject to the modulation of acoustic signals; The variable quantity of the net gain of described second laser is contrary with the variable quantity of the net gain of described first laser;
The frequency of the optical power change of the S3: the first laser is the frequency of the acoustic signals be detected; The intensity of the acoustic signals be detected is larger, and the amplitude of the optical power change of described first laser is larger.
Further preferably, in step s 2, the net gain of described first laser is subject to the modulated process of acoustic signals and is: the net gain of the first laser reduces along with the increase of acoustic signals; The net gain of the first laser increases along with the reduction of acoustic signals.
Major advantage of the present invention has:
(1) highly sensitive: to be the duty being in small-signal gain in fiber optic acoustic sensors of the present invention, when one of them wavelength obtains gain, the size of light intensity exponentially increases, another wavelength cannot obtain gain simultaneously, gain media now becomes absorbing medium, and energy sharply reduces.So the energy difference of two-beam exponentially changes along with gain.We adopt binary channels to make difference method simultaneously, and sensitivity also can improve twice.
(2) structure is simple, and firm, cost is low, and success ratio is high: introduced in above-mentioned technical background, and existing sonic sensor all have employed complicated transducer, and make its cost high, success ratio is low.We adopt single mode-multi-mode-single mode optical fiber as sensing element, are all basic devices, adopt ripe heat sealing machine just can carry out sensing unit.
(3) working stability, there is the compensating action to environment temperature: first, as select the sensitivity of fiber grating pair temperature of wavelength be 10 micromicrons/degree Celsius, and our filter bandwidht is 80 micromicrons and adjustable, tunable range covers whole C-band, so the change of temperature can be covered, there is retroactive effect.Secondly, our signal receiving adopts binary channels poor, and temperature causes the subtle change of power can eliminate by making difference.
Accompanying drawing explanation
Fig. 1 is the overall theory structure block diagram of the fiber optic acoustic sensors that the embodiment of the present invention provides;
Fig. 2 is the structural representation of sensing element in the fiber optic acoustic sensors that provides of the embodiment of the present invention;
Fig. 3 is the structural representation of the fiber optic acoustic sensors that the embodiment of the present invention provides
Fig. 4 is the realization flow figure of the optical fiber acoustic sounding method that the embodiment of the present invention provides.
Embodiment
In order to make object of the present invention, technical scheme and advantage clearly understand, below in conjunction with drawings and Examples, the present invention is further elaborated.Should be appreciated that specific embodiment described herein only in order to explain the present invention, be not intended to limit the present invention.In addition, if below in described each embodiment of the present invention involved technical characteristic do not form conflict each other and just can mutually combine.
The present invention proposes the optical fiber sound wave method for sensing of a kind of single mode-multi-mode-single mode optical fiber as sensing element, based on dual laser benefit competitive effect, can reduce sensing device volume, improve sensitivity, structure is simple simultaneously, and firm, cost is low, and success ratio is high.Whole system can divide two large divisions, and a part forms dual laser, in the chamber of a sensing unit wavelength wherein; Another part is signal demodulating equipment.
Fig. 1 shows the overall theory structure block diagram of the fiber optic acoustic sensors that the embodiment of the present invention provides, and for convenience of explanation, illustrate only the part relevant to the embodiment of the present invention, details are as follows:
Fiber optic acoustic sensors comprises the first fiber grating 1, sensing unit 2, coupling mechanism 3, second fiber grating 4, tunable attenuator 5, pumping source 6, wavelength division multiplexer 7, gain fibre 8 and catoptron 9; Coupling mechanism 3 comprises four ports, and the first port is connected with the first fiber grating 1 by sensing unit 2, and the second port is connected with the second fiber grating 4 by tunable attenuator 5, and the 3rd port is connected with catoptron 9 with gain fibre 8 by wavelength division multiplexer 7 successively; Pumping source 6 is connected with described wavelength division multiplexer 7; 4th port is used for being connected with the signal demodulating equipment of outside.
During fiber optic acoustic sensors work, pumping source 6 exports pump light, pump light is coupled in gain fibre 8 by wavelength division multiplexer 7, and gain fibre 8 exports spontaneous emission light, and spontaneous emission light inputs in coupling mechanism 3 respectively by gain fibre 8 and wavelength division multiplexer 7 after catoptron 9 reflects, light is divided into two bundles by coupling mechanism 3, a branch ofly transfer in the first fiber grating 1 by sensing unit 2, the light consistent with the first fiber grating 1 centre wavelength inputs to described coupling mechanism 3 by described sensing unit 2 after being reflected by described first fiber grating 1, again successively by exporting the radiant light that energy increases after described wavelength division multiplexer 7 and gain fibre 8, this radiant light is reflected by catoptron 9, and in the chamber that the first fiber grating 1 and catoptron 9 are formed oscillate, the first laser is exported from the 4th port of described coupling mechanism 3 when the gain of the light consistent with the first fiber grating 1 centre wavelength is greater than loss, another light beam transfers in the second fiber grating 4 by tunable attenuator 5, the light consistent with the second fiber grating 4 centre wavelength inputs to coupling mechanism 3 by tunable attenuator 5 after being reflected by the second fiber grating 4, again successively by exporting the radiant light that energy increases after wavelength division multiplexer 7 and gain fibre 8, this radiant light is reflected by catoptron 9, and in the chamber that the second fiber grating 4 and catoptron 9 are formed oscillate, export the second laser when the gain of the light consistent with the second fiber grating 4 centre wavelength is greater than loss from the 4th port of described coupling mechanism 3.
In embodiments of the present invention, coupling mechanism 3 for power splitting ratio be the coupling mechanism of 1:1.
As shown in Figure 2, in embodiments of the present invention, sensing unit 2 comprises the first single-mode fiber 21, multimode optical fiber 22 and the second single-mode fiber 23 that connect successively.Wherein, multimode optical fiber 22 can be 105 microns for core diameter, and cladding diameter is the multimode optical fiber of 125 microns.Multimode optical fiber 22 can also be coreless fiber, and the diameter of coreless fiber is 125 microns.
The Fibre Optical Sensor that the embodiment of the present invention provides; in laser produces; as long as when the gain that the longitudinal mode in chamber obtains exceedes loss, the longitudinal mode first starting of oscillation of maximum net gain (gain deducts loss), the gain according to other longitudinal modes of characteristic of HOMOGENEOUS BROADENING gain media will reduce.But if fruit caving internal memory is at two or more longitudinal mode, when namely their net gain is suitable, strong gain competition will be there is.The gain competition of multiple-wavelength laser, causes the instability that light vibrates in laser chamber.Output spectrum can become very unstable, exports one of them a little while, exports another for a moment.This unfavorable factor should be avoided.The present invention make use of dual laser gain competition effect cleverly, and combines single mode-multi-mode-single mode optical fiber transmission property.Single mode-multi-mode-single mode optical fiber can form modulation different wave length being produced to different transmissivity, when there being tiny signal to act on multimode optical fiber place, can change transmission spectrum to the small modulation of its refractive index or shape deformation, different to different wave length degree of modulation.Namely concerning the light of single wavelength, outer signals changes the transmissivity of light by single mode-multi-mode-single mode optical fiber, namely changes its loss.
It is the duty being in small-signal gain in fiber optic acoustic sensors of the present invention, when one of them wavelength obtains gain, the size of light intensity exponentially increases, and another wavelength cannot obtain gain simultaneously, gain media now becomes absorbing medium, and energy sharply reduces.So the energy difference of two-beam exponentially changes along with gain.Refer to above, the wavelength of the correspondence that net gain is maximum obtains gain at first.Net gain can be regulated by single mode-multi-mode-single mode optical fiber transmission property.When perturbation is at single mode-multi-mode-single mode sensing unit, the light loss on this road is subject to the modulation of perturbation signal, dual wavelength net gain is also corresponding modulated subsequently, this is the competition being regulated dual wavelength gain by loss, finally causes the energy difference of two-beam to change along with the modulation of perturbation signal.Thus effectively raise sensitivity.During above-mentioned sensor output signal, its method is: with tunable optic filter, and by the light of two wavelength separately, dual-port exports, and then receive with photo-detector, finally input oscillograph, energy is poor, abates the noise.
As shown in Figure 3, signal demodulating equipment comprises: fiber optic acoustic sensors comprises adjustable light wave-filter 10, first light probe 11 and the second light probe 12, oscillograph 13.Two port respectively with the first light probes 11 of adjustable light wave-filter 10 are connected with the second light probe 12, and then the first light probe 11 is connected with the second light probe 12 and is connected on oscillograph 13 simultaneously.
When the first and second laser export from the 4th end, enter adjustable light wave-filter 10 separately, and enter the first light probe 11 and the second light probe 12 respectively, last first and second laser input oscillographs 13, binary channels does difference process, just can demodulate acoustic signals.
What the fiber optic acoustic sensors that the present invention proposes utilized dual laser gain competition effect improves sensitivity, and structure is simple simultaneously, and firm, cost is low, and success ratio reaches 100%.
Present invention also offers a kind of optical fiber acoustic sounding method based on above-mentioned fiber optic acoustic sensors, as shown in Figure 4, comprise the steps:
S1: make the luminous power of the first laser and the second laser equal by regulating the pad value of tunable attenuator;
S2: when sensing unit is placed in acoustic wavefield, the net gain of the first laser is subject to the modulation of acoustic signals; The variable quantity of the net gain of described second laser is contrary with the variable quantity of the net gain of described first laser;
The frequency of the optical power change of the S3: the first laser is the frequency of the acoustic signals be detected; The intensity of the acoustic signals be detected is larger, and the amplitude of the optical power change of described first laser is larger.
Wherein, in step s 2, the net gain of described first laser is subject to the modulated process of acoustic signals and is: the net gain of the first laser reduces along with the increase of acoustic signals; The net gain of the first laser increases along with the reduction of acoustic signals.
In sum, the fiber optic acoustic sensors that the embodiment of the present invention provides and the main tool of optical fiber acoustic sounding method have the following advantages: (1) is highly sensitive: be the duty being in small-signal gain in fiber optic acoustic sensors, when one of them wavelength obtains gain, the size of light intensity exponentially increases, another wavelength cannot obtain gain simultaneously, gain media now becomes absorbing medium, and energy sharply reduces.So the energy difference of two-beam exponentially changes along with gain.We adopt binary channels to make difference method simultaneously, and sensitivity also can improve twice.(2) structure is simple, and firm, cost is low, and success ratio is high.Adopting single mode-multi-mode-single mode optical fiber as sensing element, is all basic device, adopts ripe heat sealing machine just can carry out sensing unit.(3) working stability, has the compensating action to environment temperature.First, as select the sensitivity of fiber grating pair temperature of wavelength be 10 micromicrons/degree Celsius, and our filter bandwidht is 80 micromicrons and adjustable, and tunable range covers whole C-band, so can cover the change of temperature, has retroactive effect.Secondly, our signal receiving adopts binary channels poor, and temperature causes the subtle change of power can eliminate by making difference.
The fiber optic acoustic sensors provided in order to the further description embodiment of the present invention and optical fiber acoustic sounding method, below in conjunction with the drawings and specific embodiments, the invention will be further described.
Embodiment 1:
As shown in Figure 3, the fiber optic acoustic sensors of the present embodiment comprises the first fiber grating 1, for wavelength chooses; Sensing unit 2, for catching sound wave feeble signal; Power splitting ratio is the coupling mechanism 3 of 1:1, is the passive device of a kind of transmission and distributing signal, has 4 ports; Reflection wavelength is different from the second fiber grating 4 of the first fiber grating 1, for wavelength chooses; Tunable attenuator 5, can produce certain energy attenuation to signal, the loss of balance two passages; Pumping source 6, for laser instrument provides driving source; Wavelength division multiplexer 7, is coupled to pump energy in gain fibre; Gain fibre 8, for laser instrument provides gain; Catoptron 9, forms the resonator cavity of laser instrument with the first fiber grating 1, second fiber grating 4; Adjustable light wave-filter 10, for filtering optical maser wavelength; First light probe 11 and the second light probe 12, receives light signal and converts electric signal to; Oscillograph 13, receives and demodulates electric signal, is shown by display; Above-mentioned device single-mode fiber connects.
The pump light exported when pumping source 6 is coupled in gain fibre 8 by wavelength division multiplexer 7, produces spontaneous emission light, is transmitted by single-mode fiber, come catoptron 9, spontaneous emission light can reflect back, by gain fibre 8, wavelength division multiplexer 7, be coupled in coupling mechanism 3, energy even is divided into two bundles.Wherein light beam is by sensing unit 2, and information of acoustic wave is just carried in light beam, and be then transferred to the first fiber grating 1, then reflect back in the centre wavelength of fiber grating echo area, other light passes through.The light being positioned at the centre wavelength of the first fiber grating 1 returns sensing unit 2, is coupled to wavelength division multiplexer 7 by coupling mechanism 3, then by gain fibre 8, reflects at catoptron 9, and so forth, stimulated radiation occurs, forms Laser output.Another light beam by tunable attenuator 5, produces fixing decay after coupling mechanism 3.When being transferred to the second fiber grating 4 subsequently, reflect back in the centre wavelength of fiber grating echo area, other light passes through.The light of the bragg reflection wavelength of the second fiber grating 4 returns 5, is coupled to wavelength division multiplexer 7 by coupling mechanism 3, then by gain fibre 8, reflects at catoptron 9, and so forth, stimulated radiation occurs, forms Laser output.Coupling mechanism 3 the 4th port is connected with tunable optic filter 10, object is extracted by the flashlight of generation, the first and second laser are divided into by tunable optic filter 10, be input to power detector 11 respectively, electric signal is converted in 12, process in oscillograph 13 oscillograph, just can obtain the information of signal.
Shown in Fig. 2, it is the structural representation of sensing unit 2 in Fig. 3.Comprise the first single-mode fiber 21 and the second single-mode fiber 23, multimode optical fiber 22, core diameter 105 microns, cladding diameter 125 microns, material is silicon dioxide mainly, but the different .1 to 9 that adulterates defines dual laser, dual wavelength is selected to determine by the first fiber grating 1 and the second fiber grating 4.10 to 13 is signal demodulating systems.
Embodiment 2:
As shown in Figure 3, the fiber optic acoustic sensors of the present embodiment comprises the first fiber grating 1, for wavelength chooses; Sensing unit 2, for catching sound wave feeble signal; Power splitting ratio is the coupling mechanism 3 of 1:1, is the passive device of a kind of transmission and distributing signal, has 4 ports; Reflection wavelength is different from the second fiber grating 4 of the first fiber grating 1, for wavelength chooses; Tunable attenuator 5, can produce certain energy attenuation to signal, the loss of balance two passages; Pumping source 6, for laser instrument provides driving source; Wavelength division multiplexer 7, is coupled to pump energy in gain fibre; Gain fibre 8, for laser instrument provides gain; Catoptron 9, forms the resonator cavity of laser instrument with the first fiber grating 1, second fiber grating 4; Adjustable light wave-filter 10, for filtering optical maser wavelength; First light probe 11 and the second light probe 12, receives light signal and converts electric signal to; Oscillograph 13, receives and demodulates electric signal, is shown by display; Above-mentioned device single-mode fiber connects.
The pump light exported when pumping source 6 is coupled in gain fibre 8 by wavelength division multiplexer 7, produces spontaneous emission light, is transmitted by single-mode fiber, come catoptron 9, spontaneous emission light can reflect back, by gain fibre 8, wavelength division multiplexer 7, be coupled in coupling mechanism 3, energy even is divided into two bundles.Wherein light beam is by sensing unit 2, and information of acoustic wave is just carried in light beam, and be then transferred to the first fiber grating 1, then reflect back in the centre wavelength of fiber grating echo area, other light passes through.The light being positioned at the centre wavelength of the first fiber grating 1 returns sensing unit 2, is coupled to wavelength division multiplexer 7 by coupling mechanism 3, then by gain fibre 8, reflects at catoptron 9, and so forth, stimulated radiation occurs, forms Laser output.Another light beam by tunable attenuator 5, produces fixing decay after coupling mechanism 3.When being transferred to the second fiber grating 4 subsequently, reflect back in the centre wavelength of fiber grating echo area, other light passes through.The light of the bragg reflection wavelength of the second fiber grating 4 returns 5, is coupled to wavelength division multiplexer 7 by coupling mechanism 3, then by gain fibre 8, reflects at catoptron 9, and so forth, stimulated radiation occurs, forms Laser output.Coupling mechanism 3 the 4th port is connected with tunable optic filter 10, object is extracted by the flashlight of generation, the first and second laser are divided into by tunable optic filter 10, be input to power detector 11 respectively, electric signal is converted in 12, process in oscillograph 13 oscillograph, just can obtain the information of signal.
Shown in Fig. 2, it is the structural representation of sensing unit 2 in Fig. 3.Comprise the first single-mode fiber 21 and the second single-mode fiber 23, coreless fiber 22, special multimode optical fiber, diameter 125 microns and be same material.1 to 9 defines dual laser, and dual wavelength is selected to determine by the first fiber grating 1 and the second fiber grating 4.10 to 13 is signal demodulating systems.
The concrete step of experiment is: (1) connects device by Fig. 1, opens pumping source 6, increasing power, exports, slightly larger than threshold power until laser is stable.(2) regulate tunable attenuator 10, make the stable output of dual-wavelength laser, guaranteed output is substantially equal simultaneously.(3) acoustic signals acts on sensing unit 2.(4) by signal demodulating system, the information of acoustic signals is drawn.
In the embodiment of the present invention, dual-wavelength optical-fiber sonic sensor is adopted to measure sound wave.A wavelength is with for referencial use, and another wavelength is used for sensing.Pickup arm adds sensing element.Employing structure is simple, and firm, cost is low, and the single mode that success ratio is high-multi-mode-single mode optical fiber is as sensing element.Meanwhile, signal transacting adopts binary channels to make the method for difference, reduces noise, improves sensitivity.
Those skilled in the art will readily understand; the foregoing is only preferred embodiment of the present invention; not in order to limit the present invention, all any amendments done within the spirit and principles in the present invention, equivalent replacement and improvement etc., all should be included within protection scope of the present invention.
Claims (6)
1. a fiber optic acoustic sensors, it is characterized in that, comprise the first fiber grating (1), sensing unit (2), coupling mechanism (3), the second fiber grating (4), tunable attenuator (5), pumping source (6), wavelength division multiplexer (7), gain fibre (8) and catoptron (9);
Described coupling mechanism (3) comprises four ports, first port is connected with the first fiber grating (1) by sensing unit (2), second port is connected with the second fiber grating (4) by tunable attenuator (5), and the 3rd port is connected with catoptron (9) with gain fibre (8) by wavelength division multiplexer (7) successively; Described pumping source (6) is connected with described wavelength division multiplexer (7); 4th port is used for being connected with the signal demodulating equipment of outside;
During described fiber optic acoustic sensors work, pumping source (6) exports pump light, pump light is coupled in gain fibre (8) by wavelength division multiplexer (7), gain fibre (8) exports spontaneous emission light, and spontaneous emission light inputs in coupling mechanism (3) respectively by gain fibre (8) and wavelength division multiplexer (7) after catoptron (9) reflection, light is divided into two bundles by coupling mechanism (3), a branch of sensing unit (2) that passes through transfers in the first fiber grating (1), described coupling mechanism (3) is inputed to by described sensing unit (2) after the light consistent with the first fiber grating (1) centre wavelength is reflected by described first fiber grating (1), the radiant light of energy increase is exported again successively afterwards by described wavelength division multiplexer (7) and gain fibre (8), this radiant light is reflected by catoptron (9), and in the chamber that the first fiber grating (1) and catoptron (9) are formed oscillate, the first laser is exported from the 4th port of described coupling mechanism (3) when the gain of the light consistent with the first fiber grating (1) centre wavelength is greater than loss,
Another light beam transfers in the second fiber grating (4) by tunable attenuator (5), coupling mechanism (3) is inputed to by tunable attenuator (5) after the light consistent with the second fiber grating (4) centre wavelength is reflected by the second fiber grating (4), the radiant light of energy increase is exported again successively afterwards by wavelength division multiplexer (7) and gain fibre (8), this radiant light is reflected by catoptron (9), and in the chamber that the second fiber grating (4) and catoptron (9) are formed oscillate, the second laser is exported from the 4th port of described coupling mechanism (3) when the gain of the light consistent with the second fiber grating (4) centre wavelength is greater than loss,
Described sensing unit (2) comprises the first single-mode fiber (21), multimode optical fiber (22) and the second single-mode fiber (23) that connect successively.
2. fiber optic acoustic sensors as claimed in claim 1, is characterized in that, described coupling mechanism (3) for power splitting ratio be the coupling mechanism of 1:1.
3. fiber optic acoustic sensors as claimed in claim 1, it is characterized in that, the core diameter of described multimode optical fiber (22) is 105 microns, and cladding diameter is 125 microns.
4. fiber optic acoustic sensors as claimed in claim 1, it is characterized in that, described multimode optical fiber (22) is coreless fiber, and the diameter of described coreless fiber is 125 microns.
5., based on an optical fiber acoustic sounding method for the fiber optic acoustic sensors described in any one of claim 1-4, comprise the steps:
S1: make the luminous power of the first laser and the second laser equal by regulating the pad value of tunable attenuator;
S2: when sensing unit is placed in acoustic wavefield, the net gain of the first laser is subject to the modulation of acoustic signals; The variable quantity of the net gain of described second laser is contrary with the variable quantity of the net gain of described first laser;
The frequency of the optical power change of the S3: the first laser is the frequency of the acoustic signals be detected; The intensity of the acoustic signals be detected is larger, and the amplitude of the optical power change of described first laser is larger.
6. optical fiber acoustic sounding method as claimed in claim 5, in step s 2, the modulated process that the net gain of described first laser is subject to acoustic signals is:
The net gain of the first laser reduces along with the increase of acoustic signals; The net gain of the first laser increases along with the reduction of acoustic signals.
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