CN103471701A - Optical fiber acoustic sensor and optical fiber acoustic detection method - Google Patents
Optical fiber acoustic sensor and optical fiber acoustic detection method Download PDFInfo
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Abstract
The invention discloses an optical fiber acoustic sensor and an optical fiber acoustic detection method. The optical fiber acoustic sensor comprises a first optical fiber grating, a sensing unit, a coupler, a second optical fiber grating, a tunable attenuator, a pumping source, a wavelength division multiplexer, gain optical fibers and a reflector. The coupler comprises four ports, wherein the first port is connected with the first optical fiber grating through the sensing unit, the second port is connected with the second optical fiber grating through the tunable attenuator, the third port is connected with reflector through the wavelength division multiplexer and the gain optical fibers, the pumping source is connected with the wavelength division multiplexer, and the fourth port is connected with an external signal demodulation device. The dual laser gain competitive effect and the two-channel difference signal processing method are utilized to lower noise and improve flexibility. The optical fiber acoustic sensor has the advantages of being high in flexibility, simple in structure, firm, low in cost, high product success rate, stable in work, not flexible to environment temperature, an the like.
Description
Technical field
The invention belongs to the 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 to modulator through optical fiber, after parameter to be measured and the light that enters modulator zone are interacted, cause the optical property (as light intensity, wavelength, frequency, phase place, polarization state etc.) of light to change, be called modulated flashlight, sending into photo-detector through optical fiber, after demodulation, obtain measured parameter.Fibre Optical Sensor can be used for measuring multiple physical quantity, 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 has all demonstrated 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 by object (sound source) generation of vibration, the space of Acoustic Wave Propagation just is called sound field.Be a kind of compressional wave while propagating in gas and liquid medium, but may be mixed with shear wave while 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: at transducing part, thin film is arranged, acoustic pressure is converted to the pressure of film.(2) single mode-multi-mode-single mode optical fibre sound pressure sensor: be also to conduct acoustic pressure with film, cause fibre-optical bending, make energy leakage.(3) fiber grating sound pressure sensor: at the coat of fiber grating, make the film that sound wave is sensitive.There is energy transducer in these sound wave Fibre Optical Sensors, have reduced the utilization of acoustic pressure, and sensitivity is low.
The fiber optic acoustic sensors also had is made microstructure, and such as (1) super steep cone sound pressure sensor: transducing part is the zone that optical fiber is pulled into to ultra-fine, steep taper.(2) microstructure mass Fibre Optical Sensor: be that a bit of coat wherein retains by optical fiber, put into hydrofluorite and after corrosion a period of time, the coat stayed is removed, then corrode.So just stayed the microstructured optical fibers of a mass as the sensing position.These sound wave Fibre Optical Sensors are made complicated, frangible.
The fiber optic acoustic sensors also had is interfere type, and such as (1) Mach, a Zeng Degan relates to 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 exists sensitivity, complex structure, cost hi-tech problem
Summary of the invention
Above defect or Improvement requirement for prior art, the invention provides a kind of fiber optic acoustic sensors and optical fiber acoustic sounding method, its purpose is to improve the sensitivity that acoustic signals is surveyed, and solves thus sensitivity low, 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; The 4th port is for being connected with outside signal demodulating equipment.
Further preferably, during described fiber optic acoustic sensors work, pumping source output pump light, pump light is coupled in gain fibre by wavelength division multiplexer, gain fibre output spontaneous emission light, spontaneous emission light inputs in coupling mechanism by gain fibre and wavelength division multiplexer respectively after mirror reflects, coupling mechanism is divided into two bundles by light, a branch ofly by sensing unit, transfer in the first fiber grating, 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 the first fiber grating, again successively by the radiant light that after described wavelength division multiplexer and gain fibre, the output energy increases, this radiant light is reflected the mirror reflection, and vibration back and forth in the chamber of the first fiber grating and catoptron formation, the 4th port from described coupling mechanism when the gain of the light consistent with the first fiber bragg grating center wavelength is greater than loss is exported the first laser, 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 the radiant light that after wavelength division multiplexer and gain fibre, the output energy increases, this radiant light is reflected the mirror reflection, and vibration back and forth in the chamber of the second fiber grating and catoptron formation, the 4th port from described coupling mechanism when the gain of the light consistent with the second fiber bragg grating center wavelength is greater than loss is exported the second laser.
Further preferably, described coupling mechanism is the coupling mechanism that the power splitting ratio is 1:1.
Further preferably, described sensing unit comprises the first single-mode fiber, multimode optical fiber and the second single-mode fiber connected successively.
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.
The present invention also provides a kind of optical fiber acoustic sounding method of the fiber optic acoustic sensors based on above-mentioned, comprises the steps:
S1: by the pad value of regulating tunable attenuator, make the luminous power of the first laser and the second laser equate;
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 the second laser is contrary with the variable quantity of the net gain of described the first laser;
S3: the frequency of the optical power change of 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 the first laser is just larger.
Further preferably, in step S2, the modulated process that the net gain of described the first laser is subject to acoustic signals is: the net gain of the first laser is along with the increase of acoustic signals reduces; The net gain of the first laser increases along with reducing of acoustic signals.
Major advantage of the present invention has:
(1) highly sensitive: as in fiber optic acoustic sensors of the present invention, to be the duty that is in small-signal gain, when one of them wavelength obtains gain, the size of light intensity is pressed exponent increase, and another wavelength can't obtain gain simultaneously, gain media now becomes absorbing medium, and energy sharply reduces.The energy difference of two-beam is along with gaining by index variation so.We adopt binary channels to make poor method simultaneously, and sensitivity also can improve twice.
(2) simple in structure, firm, cost is low, and success ratio is high: in above-mentioned technical background, introduced, existing sonic sensor has all adopted complicated transducer, makes its cost high, and 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, the compensating action that pair environment temperature is arranged: at first, as the sensitivity of the fiber grating pair temperature of selecting wavelength be 10 micromicrons/degree centigrade, and our filter bandwidht is 80 micromicrons and adjustable, tunable range covers whole C-band, so can cover the variation of temperature, retroactive effect is arranged.Secondly, our signal demodulation adopts binary channels poor, and temperature causes that the subtle change of power can be by doing poor the elimination.
The accompanying drawing explanation
Fig. 1 is the whole theory structure block diagram of the fiber optic acoustic sensors that provides of the embodiment of the present invention;
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 provides of the embodiment of the present invention
Fig. 4 is the realization flow figure of the optical fiber acoustic sounding method that provides of the embodiment of the present invention.
Embodiment
In order to make purpose of the present invention, technical scheme and advantage clearer, 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, is not intended to limit the present invention.In addition, below in each embodiment of described the present invention involved technical characterictic as long as form each other conflict, just can mutually not 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 the sensing device volume, improve sensitivity, simultaneously simple in structure, firm, cost is low, and success ratio is high.Whole system can be divided the two large divisions, and a part is to form dual laser, and sensing unit is therein in the chamber of a wavelength; Another part is signal demodulating equipment.
Fig. 1 shows the whole theory structure block diagram of the fiber optic acoustic sensors that the embodiment of the present invention provides, and for convenience of explanation, only shows the part relevant to the embodiment of the present invention, and details are as follows:
Fiber optic acoustic sensors comprises 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; 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; The 4th port is for being connected with outside signal demodulating equipment.
During fiber optic acoustic sensors work, pumping source 6 output pump lights, pump light is coupled in gain fibre 8 by wavelength division multiplexer 7, gain fibre 8 output spontaneous emission lights, and spontaneous emission light inputs in coupling mechanism 3 by gain fibre 8 and wavelength division multiplexer 7 respectively after catoptron 9 reflections, coupling mechanism 3 is divided into two bundles by light, a branch ofly by sensing unit 2, transfer in the first fiber grating 1, 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 the first fiber grating 1, the radiant light increased by described wavelength division multiplexer 7 and the rear output energy of gain fibre 8 successively again, this radiant light is reflected mirror 9 reflections, and vibration back and forth in the chamber of the first fiber grating 1 and catoptron 9 formation, when being greater than loss, the gain of the light consistent with the first fiber grating 1 centre wavelength exports the first laser from the 4th port of described coupling mechanism 3, another light beam transfers in the second fiber grating 4 by tunable attenuator 5, the light consistent with the second fiber grating 4 centre wavelengths inputs to coupling mechanism 3 by tunable attenuator 5 after being reflected by the second fiber grating 4, the radiant light increased by wavelength division multiplexer 7 and the rear output energy of gain fibre 8 successively again, this radiant light is reflected mirror 9 reflections, and vibration back and forth in the chamber of the second fiber grating 4 and catoptron 9 formation, when being greater than loss, the gain of the light consistent with the second fiber grating 4 centre wavelengths exports the second laser from the 4th port of described coupling mechanism 3.
In embodiments of the present invention, the coupling mechanism that coupling mechanism 3 is 1:1 for the power splitting ratio.
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 connected successively.Wherein, multimode optical fiber 22 can be 105 microns for core diameter, the multimode optical fiber that cladding diameter is 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; when as long as the gain that the longitudinal mode in chamber obtains surpasses loss, the at first starting of oscillation of longitudinal mode of the net gain (gain deducts loss) of maximum, will reduce according to the gain of other longitudinal modes of characteristic of HOMOGENEOUS BROADENING gain media.But at two or more longitudinal modes, when their net gain is suitable, will exist strong gain competition as the fruit caving internal memory.The gain competition of multiple-wavelength laser, what cause light to vibrate in laser chamber is unstable.It is very unstable that output spectrum can become, and exports one of them a little while, exports another for a moment.This unfavorable factor should be avoided.The present invention has utilized 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 the modulation that different wave length is produced to different transmissivities, when there being tiny signal to act on the multimode optical fiber place, to the small modulation of its refractive index or shape deformation, can change transmission spectrum, different to the different wave length degree of modulation.Concerning the light of single wavelength, outer signals changes light by the transmissivity of single mode-multi-mode-single mode optical fiber, namely changes its loss.
It in fiber optic acoustic sensors of the present invention, is the duty that is in small-signal gain, when one of them wavelength obtains gain, the size of light intensity is pressed exponent increase, and another wavelength can't obtain gain simultaneously, gain media now becomes absorbing medium, and energy sharply reduces.The energy difference of two-beam is along with gaining by index variation so.Front has been mentioned, and the wavelength of the correspondence of net gain maximum obtains gain at first.Net gain can be regulated by single mode-multi-mode-single mode optical fiber transmission property.When perturbation during at single mode-multi-mode-single mode sensing unit, the light loss on this road is subject to the modulation of perturbation signal, the dual wavelength net gain is also corresponding modulated subsequently, this is to regulate the competition of dual wavelength gain by loss, and the energy difference that finally causes two-beam is along with the modulation of perturbation signal changes.Thereby effectively raise sensitivity.During above-mentioned sensor output signal, its method is: use tunable optic filter, by the light of two wavelength separately, dual-port output, then receive with photo-detector, finally inputs oscillograph, and 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, the first light probe 11 and the second light probe 12, oscillograph 13.Two ports respectively with the first light probe 11 of adjustable light wave-filter 10 is connected with the second light probe 12, and then the first light probe 11 is connected and is connected on oscillograph 13 simultaneously with the second light probe 12.
Export from the 4th end when the first and second laser, enter adjustable light wave-filter 10 separately, and enter respectively the first light probe 11 and the second light probe 12, last the first and second laser input oscillographs 13, binary channels is done poor the processing, just can demodulate acoustic signals.
The fiber optic acoustic sensors that the present invention proposes utilizes the sensitivity that improves of dual laser gain competition effect, and simultaneously simple in structure, firm, cost is low, and success ratio reaches 100%.
The present invention also provides a kind of optical fiber acoustic sounding method of the fiber optic acoustic sensors based on above-mentioned, as shown in Figure 4, comprises the steps:
S1: by the pad value of regulating tunable attenuator, make the luminous power of the first laser and the second laser equate;
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 the second laser is contrary with the variable quantity of the net gain of described the first laser;
S3: the frequency of the optical power change of 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 the first laser is just larger.
Wherein, in step S2, the modulated process that the net gain of described the first laser is subject to acoustic signals is: the net gain of the first laser is along with the increase of acoustic signals reduces; The net gain of the first laser increases along with reducing of acoustic signals.
In sum, the fiber optic acoustic sensors that the embodiment of the present invention provides and optical fiber acoustic sounding method mainly have following advantage: (1) is highly sensitive: in fiber optic acoustic sensors, be the duty that is in small-signal gain, when one of them wavelength obtains gain, the size of light intensity is pressed exponent increase, another wavelength can't obtain gain simultaneously, gain media now becomes absorbing medium, and energy sharply reduces.The energy difference of two-beam is along with gaining by index variation so.We adopt binary channels to make poor method simultaneously, and sensitivity also can improve twice.(2) simple in structure, 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, have the compensating action of pair environment temperature.At first, as the sensitivity of the fiber grating pair temperature of selecting wavelength be 10 micromicrons/degree centigrade, and our filter bandwidht is 80 micromicrons and adjustable, tunable range covers whole C-band, so can cover the variation of temperature, retroactive effect is arranged.Secondly, our signal demodulation adopts binary channels poor, and temperature causes that the subtle change of power can be by doing poor the elimination.
For fiber optic acoustic sensors and optical fiber acoustic sounding method that the further description embodiment of the present invention provides, 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, selects; Sensing unit 2, for catching the sound wave feeble signal; The coupling mechanism 3 that the power splitting ratio is 1:1, be the passive device of a kind of transmission and distributing signal, and 4 ports are arranged; Reflection wavelength is different from the second fiber grating 4 of the first fiber grating 1, for wavelength, selects; Tunable attenuator 5, can produce certain energy attenuation to signal, the loss of two passages of balance; Pumping source 6, for laser instrument provides driving source; Wavelength division multiplexer 7, be coupled to pump energy in gain fibre; Gain fibre 8, for laser instrument provides gain; Catoptron 9, with the resonator cavity of the first fiber grating 1, the second fiber grating 4 formation laser instruments; Adjustable light wave-filter 10, for filtering optical maser wavelength; The first light probe 11 and the second light probe 12, receive light signal to convert electric signal to; Oscillograph 13, receive and demodulate electric signal, by display, shows; Above-mentioned device connects with single-mode fiber.
The pump light of exporting when pumping source 6 is coupled in gain fibre 8 by wavelength division multiplexer 7, produces spontaneous emission light, by single-mode fiber, transmits, come catoptron 9, spontaneous emission light can reflect back, by gain fibre 8, wavelength division multiplexer 7, be coupled in coupling mechanism 3, and energy even is divided into two bundles.Wherein light beam is by sensing unit 2, and information of acoustic wave just is carried in light beam, then is transferred to the first fiber grating 1, and then the centre wavelength in the fiber grating echo area reflects back, and other light passes through.The light that is positioned at the centre wavelength of the first fiber grating 1 returns to sensing unit 2, by coupling mechanism 3, is coupled to wavelength division multiplexer 7, then by gain fibre 8, in catoptron 9 reflections, and so forth, stimulated radiation occurs, and forms Laser output.Another light beam by tunable attenuator 5, produces fixing decay after coupling mechanism 3.While being transferred to the second fiber grating 4 subsequently, the centre wavelength in the fiber grating echo area reflects back, and other light passes through.The light of the bragg reflection wavelength of the second fiber grating 4 returns to 5, by coupling mechanism 3, is coupled to wavelength division multiplexer 7, then by gain fibre 8, in catoptron 9 reflections, and so forth, stimulated radiation occurs, and forms Laser output.Coupling mechanism 3 the 4th port is connected with tunable optic filter 10, purpose is that the flashlight of generation is extracted, be divided into the first and second laser by tunable optic filter 10, be input to respectively power detector 11, convert electric signal in 12 to, process in oscillograph 13 oscillographs, 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 22,105 microns of core diameters, 125 microns of cladding diameters, material is mainly silicon dioxide, but the different .1 to 9 that adulterate have formed dual laser, dual wavelength is to be 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, selects; Sensing unit 2, for catching the sound wave feeble signal; The coupling mechanism 3 that the power splitting ratio is 1:1, be the passive device of a kind of transmission and distributing signal, and 4 ports are arranged; Reflection wavelength is different from the second fiber grating 4 of the first fiber grating 1, for wavelength, selects; Tunable attenuator 5, can produce certain energy attenuation to signal, the loss of two passages of balance; Pumping source 6, for laser instrument provides driving source; Wavelength division multiplexer 7, be coupled to pump energy in gain fibre; Gain fibre 8, for laser instrument provides gain; Catoptron 9, with the resonator cavity of the first fiber grating 1, the second fiber grating 4 formation laser instruments; Adjustable light wave-filter 10, for filtering optical maser wavelength; The first light probe 11 and the second light probe 12, receive light signal to convert electric signal to; Oscillograph 13, receive and demodulate electric signal, by display, shows; Above-mentioned device connects with single-mode fiber.
The pump light of exporting when pumping source 6 is coupled in gain fibre 8 by wavelength division multiplexer 7, produces spontaneous emission light, by single-mode fiber, transmits, come catoptron 9, spontaneous emission light can reflect back, by gain fibre 8, wavelength division multiplexer 7, be coupled in coupling mechanism 3, and energy even is divided into two bundles.Wherein light beam is by sensing unit 2, and information of acoustic wave just is carried in light beam, then is transferred to the first fiber grating 1, and then the centre wavelength in the fiber grating echo area reflects back, and other light passes through.The light that is positioned at the centre wavelength of the first fiber grating 1 returns to sensing unit 2, by coupling mechanism 3, is coupled to wavelength division multiplexer 7, then by gain fibre 8, in catoptron 9 reflections, and so forth, stimulated radiation occurs, and forms Laser output.Another light beam by tunable attenuator 5, produces fixing decay after coupling mechanism 3.While being transferred to the second fiber grating 4 subsequently, the centre wavelength in the fiber grating echo area reflects back, and other light passes through.The light of the bragg reflection wavelength of the second fiber grating 4 returns to 5, by coupling mechanism 3, is coupled to wavelength division multiplexer 7, then by gain fibre 8, in catoptron 9 reflections, and so forth, stimulated radiation occurs, and forms Laser output.Coupling mechanism 3 the 4th port is connected with tunable optic filter 10, purpose is that the flashlight of generation is extracted, be divided into the first and second laser by tunable optic filter 10, be input to respectively power detector 11, convert electric signal in 12 to, process in oscillograph 13 oscillographs, 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, 125 microns of diameters and be same material.1 to 9 has formed dual laser, and dual wavelength is to be 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, and increasing power, until laser stabilization output is slightly larger than threshold power.(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, draw the information of acoustic signals.
In the embodiment of the present invention, adopt the dual-wavelength optical-fiber sonic sensor to measure sound wave.A wavelength is with for referencial use, and another wavelength is used for sensing.Pickup arm adds sensing element.Adopt simple in structurely, firm, cost is low, and the single mode that success ratio is high-multi-mode-single mode optical fiber is as sensing element.Simultaneously, signal is processed and is adopted binary channels to make poor method, 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 modifications of doing within the spirit and principles in the present invention, be equal to and replace and improvement etc., within all should being included in protection scope of the present invention.
Claims (8)
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, the first port is connected with the first fiber grating (1) by sensing unit (2), 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; Described pumping source (6) is connected with described wavelength division multiplexer (7); The 4th port is for being connected with outside signal demodulating equipment.
2. fiber optic acoustic sensors as claimed in claim 1, it is characterized in that, during described fiber optic acoustic sensors work, pumping source (6) output pump light, pump light is coupled in gain fibre (8) by wavelength division multiplexer (7), gain fibre (8) output spontaneous emission light, spontaneous emission light inputs in coupling mechanism (3) by gain fibre (8) and wavelength division multiplexer (7) respectively after catoptron (9) reflection, coupling mechanism (3) is divided into two bundles by light, a branch ofly by sensing unit (2), transfer in the first fiber grating (1), 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 the first fiber grating (1), again successively by the radiant light that after described wavelength division multiplexer (7) and gain fibre (8), the output energy increases, this radiant light is reflected mirror (9) reflection, and vibration back and forth in the chamber of the first fiber grating (1) and catoptron (9) formation, when being greater than loss, the gain of the light consistent with the first fiber grating (1) centre wavelength exports the first laser from the 4th port of described coupling mechanism (3),
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 the radiant light that after wavelength division multiplexer (7) and gain fibre (8), the output energy increases, this radiant light is reflected mirror (9) reflection, and vibration back and forth in the chamber of the second fiber grating (4) and catoptron (9) formation, when being greater than loss, the gain of the light consistent with the second fiber grating (4) centre wavelength exports the second laser from the 4th port of described coupling mechanism (3).
3. fiber optic acoustic sensors as claimed in claim 1, is characterized in that, the coupling mechanism that described coupling mechanism (3) is 1:1 for the power splitting ratio.
4. fiber optic acoustic sensors as claimed in claim 1 or 2, is characterized in that, described sensing unit (2) comprises the first single-mode fiber (21), multimode optical fiber (22) and the second single-mode fiber (23) connected successively.
5. fiber optic acoustic sensors as claimed in claim 4, is characterized in that, the core diameter of described multimode optical fiber (22) is 105 microns, and cladding diameter is 125 microns.
6. fiber optic acoustic sensors as claimed in claim 4, is characterized in that, described multimode optical fiber (22) is coreless fiber, and the diameter of described coreless fiber is 125 microns.
7. the optical fiber acoustic sounding method based on the described fiber optic acoustic sensors of claim 1-6 any one, comprise the steps:
S1: by the pad value of regulating tunable attenuator, make the luminous power of the first laser and the second laser equate;
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 the second laser is contrary with the variable quantity of the net gain of described the first laser;
S3: the frequency of the optical power change of 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 the first laser is just larger.
8. optical fiber acoustic sounding method as claimed in claim 7, in step S2, the modulated process that the net gain of described the 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 reducing of acoustic signals.
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