CN102680582B - Matching fiber grating acoustic emission sensing system with temperature compensation function - Google Patents
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- CN102680582B CN102680582B CN201210187630.5A CN201210187630A CN102680582B CN 102680582 B CN102680582 B CN 102680582B CN 201210187630 A CN201210187630 A CN 201210187630A CN 102680582 B CN102680582 B CN 102680582B
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Abstract
The invention provides a matching fiber grating acoustic emission sensing system with a temperature compensation function. The system comprises a pump source, an optical wavelength division multiplexer, an erbium-doped fiber, a first optical isolator, a first fiber coupler, a first fiber Bragg grating, a second optical isolator, a second fiber coupler, a second fiber Bragg grating, a photoelectric detection circuit, a pre-amplification circuit, an analog-to-digital conversion circuit, a field programmable gate array (FPGA) and a computer. The system is mainly used for structural health monitoring and the damage detection of important structural parts; and compared with a power fiber Bragg grating emission sensing system, the system with the temperature compensation function has the advantages that the influence of temperature change on a fiber Bragg grating sensor can be effectively reduced, the detection accuracy of the fiber Bragg grating sensor is improved, equipment cost is reduced, and practical engineering application is facilitated.
Description
Technical field
The invention belongs to acoustic emission testing technology field, particularly a kind of matching type fiber grating voice sending sensor system that carries temperature compensation.
Background technology
Metal material or compound substance, because of stressed generation distortion or fracture, discharge the phenomenon of strain energy with the form of elastic wave, be called acoustic emission.Acoustic emission is exactly to adopt highly sensitive calibrate AE sensor Real-time Collection these come from the acoustic emission signal of fault in material, and by the analyzing and processing to these acoustic emission signals, carry out the development of Knowing material defect, to realize the monitoring to material health status.Due to advantages such as the dynamic of acoustic emission, susceptibility, globality, universalities, it is widely used at aspects such as Aeronautics and Astronautics, seismic monitoring and metal processing.
Fiber Bragg Grating FBG is the photosensitivity of utilizing fiber optic materials, produces periodically variable index distribution in fiber core, and its effect is in fact in fibre core, to form a narrow band filter or catoptron.Broadband light enters Fiber Bragg Grating FBG, only has the very narrow light that meets its conditioned reflex to be reflected back by Fiber Bragg Grating FBG.Due to the anti-electromagnetic interference (EMI) of Fiber Bragg Grating FBG, corrosion-resistant, highly sensitive, low and be easy to realize the advantages such as multiplexing to electrical isolation, cost, Fiber Bragg Grating FBG is once appearance, just at sensory field of optic fibre, play a significant role, and be used widely in the monitoring structural health conditions of highway, bridge, mine, geologic prospecting, railway, oil/gas pipeline.
Existing fiber grating sensing system can be measured temperature and strain as Chinese patent CN200920129512.2 " a kind of fiber-optic grating sensor and fiber grating sensing system ", CN200610130121.3 " fiber grating sensing system " simultaneously; Existing optical fiber acoustic emission detection system is suitable for detecting under isoperibol as acoustic emission detection systems such as Chinese patent CN201110207340.8 " a kind of acoustic emission signal sensor-based system based on Fiber Bragg Grating FBG ", if variation of ambient temperature is larger, can affect Fiber Bragg Grating FBG accuracy of detection.
Summary of the invention
The object of the invention is to, overcome existing technology limitation, Fiber Bragg Grating FBG is introduced to acoustic emission field, a kind of matching type fiber grating voice sending sensor system that carries temperature compensation is provided, this system have detection sensitivity high, be not subject to electromagnetic interference (EMI), be suitable for moving/Static Detection, be suitable for the features such as constant temperature/varying temperature environment work.
Technical scheme of the present invention: a kind of matching type fiber grating voice sending sensor system that carries temperature compensation, described sensor-based system comprises: pumping source, light wavelength division multiplexing, Er-doped fiber, the first optoisolator, the first fiber coupler, the first Fiber Bragg Grating FBG, the second optoisolator, the second fiber coupler, the second Fiber Bragg Grating FBG, photodetection circuit, pre-amplification circuit, analog to digital conversion circuit, FPGA, computing machine, wherein, the A port of the first fiber coupler is connected with the first optoisolator, and B port is connected with the first Fiber Bragg Grating FBG, and C port accesses light wavelength division multiplexing by loop, and D port connects the second optoisolator, wherein, the E port of the second fiber coupler connects the second optoisolator, and F port connects photodetector, and G port connects the second Fiber Bragg Grating FBG, and H port is vacant, the pump light that pumping source sends is introduced light path by light wavelength division multiplexing, enter Er-doped fiber, after Er-doped fiber amplifies, by the first optoisolator, enter the A port of the first fiber coupler, light is divided into two-way herein, the port B of leading up to enters the first Fiber Bragg Grating FBG, the narrow band light that only meets the first Fiber Bragg Grating FBG foveal reflex wavelength can be reflected back, and enter light path (light of entry port A is isolated by the first optoisolator) through port C, after repeatedly circulating, light path finally has stable output wavelength and power, another road light arrives the E port of the second fiber coupler through the second optoisolator by port D, be divided into two-way, one tunnel enters vacant end H, the G port of separately leading up to enters the second Fiber Bragg Grating FBG, the second Fiber Bragg Grating FBG receives extraneous acoustic emission signal, there is corresponding drift in centre wavelength, the narrow band light that only meets the second Fiber Bragg Grating FBG foveal reflex wavelength can be reflected back, and arrive photodetection circuit (light by E port is isolated by the second optoisolator) by F port, light signal is converted into electric signal herein, through pre-amplification circuit, amplify again, enter analog to digital conversion circuit and be converted to digital signal output, through FPGA, gather, filtering, after demodulation, obtain on computers analyzing and show.
Further, described pumping source is pump light source, and centre wavelength is 974.54nm, and peak power is 6.77dBm.
Further, described Er-doped fiber line length 20m, core diameter 3 μ m.
Further, described the first fiber coupler, splitting ratio is 40:60, the B end that enters the first Fiber Bragg Grating FBG is 40, for the D end of light path output, is 60; The second fiber coupler, splitting ratio is 50:50, the ratio of light that enters the G port of vacant end H and the second Fiber Bragg Grating FBG is identical.
Further, described the first Fiber Bragg Grating FBG is adjustable grating, match with the second Fiber Bragg Grating FBG for sensing, and reflectivity, side mode suppression ratio, three dB bandwidth, temperature sensitive coefficient parameter are consistent, and centre wavelength differs 0.1nm.
Further, described photodetection circuit is semiconductor InGaAs PIN type photodiode circuit.
Further, described pre-amplification circuit, more than signal to noise ratio (S/N ratio) 50dB, bandwidth 20-1200KHz.
The present invention's advantage is compared with prior art: existing fiber Bragg grating sensor great majority are all operated in constant temperature or temperature variation compared with under circlet border, once variation of ambient temperature is larger, the accuracy of detection of Fiber Bragg Grating FBG just can reduce, affect final detection result, and the present invention adopts the matching type Fiber Bragg Grating FBG acoustic emission signal sensor-based system with temperature compensation, can reduce to greatest extent the impact of temperature on fiber Bragg grating sensor, make fiber Bragg grating sensor under varying temperature environment, there is equally the ability of normal work, reduced the cost of system simultaneously, be beneficial to practical implementation.
Accompanying drawing explanation
Fig. 1 is the schematic diagram that carries the matching type fiber grating voice sending sensor system of temperature compensation;
In figure: 1, pumping source, 2, light wavelength division multiplexing, 3, Er-doped fiber, 4, the first optoisolator, 5, the first fiber coupler, 6, the first Fiber Bragg Grating FBG, 7, the second optoisolator, 8, the second fiber coupler, 9, the second Fiber Bragg Grating FBG, 10, photodetection circuit, 11, pre-amplification circuit, 12, analog to digital conversion circuit, 13, FPGA, 14, computing machine.
Embodiment
Below in conjunction with accompanying drawing, the specific embodiment of the present invention is described, to understand better the present invention.Requiring particular attention is that, in the following description, when adopting the detailed description of known function and design perhaps can desalinate main contents of the present invention, these are described in here and will be left in the basket.
As shown in Figure 1, the matching type fiber grating voice sending sensor system that carries temperature compensation of the present invention comprises: pumping source 1, light wavelength division multiplexing 2, Er-doped fiber 3, the first optoisolator 4, the first fiber couplers 5, the first Fiber Bragg Grating FBG 6, the second optoisolator 7, the second fiber couplers 8, the second Fiber Bragg Grating FBG 9, photodetection circuit 10, pre-amplification circuit 11, analog to digital conversion circuit 12, FPGA13, computing machine 14; Wherein, the A port of the first fiber coupler 5 is connected with the first optoisolator 4, and B port is connected with the first Fiber Bragg Grating FBG 6, and C port accesses light wavelength division multiplexing 2 by loop, and D port connects the second optoisolator 7; Wherein, the E port of the second fiber coupler 8 connects the second optoisolator 7, and F port connects photodetector 10, and G port connects the second Fiber Bragg Grating FBG 9, and H port is vacant; Photodetection circuit 10 accesses pre-amplification circuit 11, analog to digital conversion circuit 12, FPGA13 and computing machine 14 below successively.
The pump light that pumping source 1 sends is introduced light path by light wavelength division multiplexing 2, enter Er-doped fiber 3, after Er-doped fiber 3 amplifies, by the first optoisolator 4, enter the A port of the first fiber coupler 5, light is divided into two-way herein, the port B of leading up to enters the first Fiber Bragg Grating FBG 6, the narrow band light that only meets the first Fiber Bragg Grating FBG 6 foveal reflex wavelength can be reflected back, and enter light path (light of entry port A is isolated by the first optoisolator) through port C, after repeatedly circulating, light path finally has stable output wavelength and power, another road light arrives the E port of the second fiber coupler 8 through the second optoisolator 7 by port D, be divided into two-way, one tunnel enters vacant end H, the G port of separately leading up to enters the second Fiber Bragg Grating FBG 9, the second Fiber Bragg Grating FBG 9 receives extraneous acoustic emission signal, there is corresponding drift in centre wavelength, the narrow band light that only meets the second Fiber Bragg Grating FBG 9 foveal reflex wavelength can be reflected back, and by the second optoisolator 7, isolated by the light of E port by F port arrival photodetection circuit 10(), light signal is converted into electric signal herein, through pre-amplification circuit 11, amplify again, enter analog to digital conversion circuit 12 and be converted to digital signal output, through FPGA13, gather, filtering, after demodulation, on computing machine 14, obtain analyzing and show.
Described pumping source 1 is pump light source.Its effect is for the electronics in Er-doped fiber 3 provides energy, population inversion occurs after it is stimulated, and produces spontaneous radiation, plays the effect of amplification.The pump light source centre wavelength that the present invention uses is 974.54nm, and peak power is 6.77dBm; The Er-doped fiber line length 20m using, core diameter 3 μ m.
Described light wavelength division multiplexing plays the effect that the photosynthetic Wei Yi road of different wave length is transmitted in optical fiber.
Described the first fiber coupler 5, splitting ratio is 40:60, the B end that enters the first Fiber Bragg Grating FBG 6 is 40, for the D end of light path output, is 60; The second fiber coupler 8, splitting ratio is 50:50, enters vacant end H identical with the ratio of the light of the G port of the second Fiber Bragg Grating FBG 9.
Described the first Fiber Bragg Grating FBG 6 is adjustable grating, with the second Fiber Bragg Grating FBG 9(sensing grating) match, centre wavelength differs 0.1nm, reflectivity, side mode suppression ratio, three dB bandwidth parameter should be consistent.When two Fiber Bragg Grating FBGs are during in same temperature field, the centre wavelength drift being caused by temperature is basic identical, this has just reduced the impact of temperature on the second Fiber Bragg Grating FBG 9 to greatest extent, the accuracy of detection that can too not affect the second Fiber Bragg Grating FBG 9, has realized temperature compensation.
Described photodetection circuit 10 is semiconductor InGaAs photodiode.The flashlight inciding on photodetection circuit 10 has passed through a series of optical fiber, interface, coupling mechanism, power attenuation is larger, conventionally in nW magnitude, therefore select semiconductor InGaAs photodiode to carry out photoelectric conversion, it has, and spectral response is wide, photoelectric transformation efficiency is high, good stability, signal to noise ratio (S/N ratio) advantages of higher.
Described pre-amplification circuit 11, plays the effect that the electric signal after opto-electronic conversion is amplified.Because the electric signal of required amplification belongs to wideband feeble signal, thus need select be with wide, the pre-amplification circuit that signal to noise ratio (S/N ratio) is high.The signal to noise ratio (S/N ratio) of the present invention's pre-amplification circuit 11 used more than 50dB, bandwidth 20-1200KHz
Described analog-to-digital conversion circuit 12, plays the effect that the analog electrical signal after amplifying is converted into digital electric signal.
Described FPGA13 play to the digital signal after conversion gather, the effect of filtering, demodulation.
Although above the illustrative embodiment of the present invention is described; so that the technician of this technology neck understands the present invention; but should be clear; the invention is not restricted to the scope of embodiment; to those skilled in the art; as long as various variations appended claim limit and definite the spirit and scope of the present invention in, these variations are apparent, all utilize innovation and creation that the present invention conceives all at the row of protection.
Claims (5)
1. one kind carries the matching type fiber grating voice sending sensor system of temperature compensation, it is characterized in that: described sensor-based system comprises: pumping source (1), light wavelength division multiplexing (2), Er-doped fiber (3), the first optoisolator (4), the first fiber coupler (5), the first Fiber Bragg Grating FBG (6), the second optoisolator (7), the second fiber coupler (8), the second Fiber Bragg Grating FBG (9), photodetection circuit (10), pre-amplification circuit (11), analog to digital conversion circuit (12), FPGA(13), computing machine (14), wherein, the A port of the first fiber coupler (5) is connected with the first optoisolator (4), and B port is connected with the first Fiber Bragg Grating FBG (6), and C port accesses light wavelength division multiplexing (2) by loop, and D port connects the second optoisolator (7), wherein, the E port of the second fiber coupler (8) connects the second optoisolator (7), and F port connects photodetector (10), and G port connects the second Fiber Bragg Grating FBG (9), and H port is vacant, the pump light that pumping source (1) sends is introduced light path by light wavelength division multiplexing (2), enter Er-doped fiber (3), after Er-doped fiber (3) amplifies, by the first optoisolator (4), enter the A port of the first fiber coupler (5), light is divided into two-way herein, the port B of leading up to enters the first Fiber Bragg Grating FBG (6), the narrow band light that only meets the first Fiber Bragg Grating FBG (6) foveal reflex wavelength can be reflected back, and enter light path through port C, after repeatedly circulating, light path finally has stable output wavelength and power, another road light arrives the E port of the second fiber coupler (8) through the second optoisolator (7) by port D, be divided into two-way, one tunnel enters vacant end H, the G port of separately leading up to enters the second Fiber Bragg Grating FBG (9), the second Fiber Bragg Grating FBG (9) receives extraneous acoustic emission signal, there is corresponding drift in centre wavelength, the narrow band light that only meets the second Fiber Bragg Grating FBG (9) foveal reflex wavelength can be reflected back, and arrive photodetection circuit (10) by F port, light signal is converted into electric signal herein, passing through pre-amplification circuit (11) amplifies again, enter analog to digital conversion circuit (12) and be converted to digital signal output, through FPGA(13) gather, filtering, after demodulation, on computing machine (14), obtain analyzing and show,
Described pumping source (1) is pump light source, and centre wavelength is 974.54nm, and peak power is 6.77dBm; Described Er-doped fiber (3) line length 20m, core diameter 3 μ m.
2. a kind of matching type fiber grating voice sending sensor system that carries temperature compensation according to claim 1, it is characterized in that: described the first fiber coupler (5), splitting ratio is 40:60, and the B end that enters the first Fiber Bragg Grating FBG (6) is 40, for the D end of light path output, is 60; The second fiber coupler (8), splitting ratio is 50:50, enters vacant end H identical with the ratio of the light of the G port of the second Fiber Bragg Grating FBG (9).
3. a kind of matching type fiber grating voice sending sensor system that carries temperature compensation according to claim 1, it is characterized in that: described the first Fiber Bragg Grating FBG (6) is adjustable grating, to match with the second Fiber Bragg Grating FBG (9) for sensing, reflectivity, side mode suppression ratio, three dB bandwidth, temperature sensitive coefficient parameter are consistent, and centre wavelength differs 0.1nm.
4. a kind of matching type fiber grating voice sending sensor system that carries temperature compensation according to claim 1, is characterized in that: described photodetection circuit (10) is semiconductor InGaAs PIN type photodiode circuit.
5. a kind of matching type fiber grating voice sending sensor system that carries temperature compensation according to claim 1, is characterized in that: described pre-amplification circuit (11), and more than signal to noise ratio (S/N ratio) 50dB, bandwidth 20-1200KHz.
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