CN102269573B - Quasi-distributed composite structure strain and temperature detection system - Google Patents
Quasi-distributed composite structure strain and temperature detection system Download PDFInfo
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- CN102269573B CN102269573B CN201110112384.2A CN201110112384A CN102269573B CN 102269573 B CN102269573 B CN 102269573B CN 201110112384 A CN201110112384 A CN 201110112384A CN 102269573 B CN102269573 B CN 102269573B
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- optical fiber
- fiber grating
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Abstract
The invention relates to a quasi-distributed composite structure strain and temperature detection system. Light output by a broadband light source passes through an optical fiber isolator and enters the input end of a 2*2 optical fiber coupler; the light output by the 2*2 optical fiber coupler enters the input end of a 1*m optical switch; the light output by the 1*m optical switch enters an m*n network type optical fiber grating sensing head; the light reflected by the m*n network type optical fiber grating sensing head sequentially passes through the 1*m optical switch and the 2*2 optical fiber coupler and further enters the input end of an optical fiber adjustable F-P (Fabry-Perot) filter; and the light output by the optical fiber adjustable F-P filter sequentially passes through a photoelectric conversion module, a signal amplifier, a data acquisition card and a computer, and the computer is used for processing and displaying data. The system utilizes the optical fiber adjustable F-P filter to realize wavelength demodulation of signal light reflected by all sensing optical fiber gratings, and has the advantages of anti-electromagnetic interference effect, all-optical fiber type measurement, a large number of multiplexing measuring points, remote monitoring, non-destructive measurement and the like.
Description
Technical field
The present invention relates to fiber grating sensing technology field, particularly relate to a kind of quasi-distributed composite structure strain and system for detecting temperature with many reference amounts measurement function, multi-point measurement function.
Background technology
Fiber grating is in optical fiber, to set up certain space refractive index cycle to distribute, and makes a kind of optical element that the propagation characteristic of light is changed therein.Fiber grating is in optical fiber, to set up certain space refractive index cycle to distribute, and makes a kind of optical element that the propagation characteristic of light is changed therein.In the time that broadband light incides Fiber Bragg Grating, its catoptrical centre wavelength (Bragg wavelength) λ
b, provided by Bragg equation: λ
b=2n Λ
Wherein, the effective refractive index that n is fibre core, Λ is the grating cycle.When utilizing fiber grating to carry out sensing measurement, measured signal is Wavelength-encoding how simply, quickly and accurately, therefore demodulate wavelength (change amount), is vital problem in fiber grating sensing system.If while adopting in the prior art fiber grating pair multiple spot to measure, use spectrometer etc. to carry out the measurement of wavelength signals more, and make the cost of wavelength signals demodulation higher; And measuring counts is subject to the restriction of light source bandwidth; And when output power one timing of light source, measure and count greatlyr, signal to noise ratio (S/N ratio) is lower, causes measuring error larger.Therefore current fiber grating point multiparameter system, conventionally cost performance low, be difficult to realize remote monitoring and poor repeatability, while measurement, also need to screen a large amount of gibberishes, and the signal to noise ratio (S/N ratio) of measuring is not high simultaneously yet, thereby has influence on the precision of measurement.
Summary of the invention
Technical matters to be solved by this invention be to provide a kind of can be to quasi-distributed composite structure strain and the system for detecting temperature of the Real-Time Monitoring of composite structure health status, have anti-electromagnetic interference (EMI), full fiber type, multiplexing measurement count many, can remote monitoring and realize the advantages such as nondestructive measurement, dirigibility be strong.
The technical solution adopted for the present invention to solve the technical problems is: a kind of quasi-distributed composite structure strain and system for detecting temperature are provided, comprise wideband light source, fibre optic isolater, 2 × 2 fiber couplers, 1 × m photoswitch, m × n network type optical fiber grating sensing head, optical fiber Tunable Fabry-Perot Filter, photoelectric conversion module, signal amplifier, data collecting card and computing machine, described wideband light source output light enters the input end of 2 × 2 fiber couplers through described fibre optic isolater; The output light of 2 × 2 described fiber couplers enters the input end of described 1 × m photoswitch through an output terminal arm of 2 × 2 fiber couplers; Described 1 × m photoswitch output light enters described m × n network type optical fiber grating sensing head; 1 × m photoswitch described in described m × n network type optical fiber grating sensing head reflected light passes through successively and 2 × 2 fiber couplers enter the input end of described optical fiber Tunable Fabry-Perot Filter; The output light of described optical fiber Tunable Fabry-Perot Filter enters described signal amplifier after described photoelectric conversion module; Described signal amplifier is collected in described computing machine by described data collecting card after the signal of receiving is amplified; Described computing machine is connected with described 1 × m photoswitch.
Fiber grating in described m × n network type optical fiber grating sensing head is polarization-maintaining fiber grating.
It is to form path that described 1 × m photoswitch only has the light signal on a road in a time period.
The sequence number of the logical light light path of the 1 × m photoswitch described in described computer control and between the logical light time, or the described computing machine employing time divide equally the 1 × m photoswitch described in mensuration control.
The wavelength of described optical fiber Tunable Fabry-Perot Filter is corresponding with the peak value characteristic wavelength (being transducing signal wavelength) of the fiber grating of described m × n network type optical fiber grating sensing head, now described data collecting card will receive a maximum analog electric signal, and after analog to digital conversion, computing machine can be identified and change peak signal and realize signal demodulation.
The method that paste on fiber grating utilization surface or inside is imbedded of described m × n network type optical fiber grating sensing head is installed to the tested point of measured target.
On another output terminal arm of 2 × 2 described fiber couplers, index-matching fluid is installed.
Beneficial effect
Owing to having adopted above-mentioned technical scheme, the present invention compared with prior art, has following advantage and good effect:
(1) when the present invention only needs a fiber grating just can realize strain and temperature, measure, and the not expensive Wavelength demodulation equipment such as light requirement spectrometer, just can calculate accurately grating wavelength according to the output valve of photoelectric conversion module, again with the comparison of primary wave appearance, just can draw wavelength shift, thereby learn measured size.
(2) the present invention utilized between the logical light time of logical light light path i (i is integer, i=1,2..m) of computer control 1 × m photoswitch, in the time that needs emphasis is monitored, can extend between the logical light time on this road, guaranteed the reliability of monitoring.
(3) the total m of the 1 × m photoswitch in the present invention road, is wherein in series with n optical fiber grating sensing head altogether in i road, and the spatial resolution of measurement can be determined with measuring needs, and the length that I reaches fiber grating is 1cm.
(4) the present invention is in the time that fiber grating is subject to tested parameter to modulate its peak value characteristic wavelength drift, because the wavelength of optical fiber Tunable Fabry-Perot Filter is corresponding with fiber grating peak value characteristic wavelength, make optical fiber Tunable Fabry-Perot Filter output light reach peak response, after opto-electronic conversion and analog to digital conversion, can identify this peak signal by computing machine, realize demodulation, have demodulation speed fast, without advantages such as diadic questions.
(5) in the present invention, the technological level of optical fiber used and components and parts is all very ripe, easy to make feasible, can be widely used in various fields, to practical especially practical significant in the regular detection of composite structure and long term monitoring that promotes fiber grating sensing technology.
Brief description of the drawings
Fig. 1 is structural representation of the present invention.
Embodiment
Below in conjunction with specific embodiment, further set forth the present invention.Should be understood that these embodiment are only not used in and limit the scope of the invention for the present invention is described.In addition should be understood that those skilled in the art can make various changes or modifications the present invention after having read the content of the present invention's instruction, these equivalent form of values fall within the application's appended claims limited range equally.
Embodiments of the present invention relate to a kind of quasi-distributed composite structure strain and system for detecting temperature, as shown in Figure 1, comprise wideband light source 1, fibre optic isolater 2,2 × 2 fiber couplers 3, index-matching fluid 4,1 × m photoswitch 5, m × n network type optical fiber grating sensing head 6, optical fiber Tunable Fabry-Perot Filter 7, photoelectric conversion module 8, signal amplifier 9, data collecting card 10 and computing machine 11, described wideband light source 1 is exported light and is entered the input end of 2 × 2 fiber couplers 3 through described fibre optic isolater 2; An output light part for 2 × 2 described fiber couplers 3 enters described index-matching fluid 4 through an output terminal arm of 2 × 2 fiber couplers 3, to reduce undesired signal light, another part enters the input end of described 1 × m photoswitch 5 through another output terminal arm of 2 × 2 fiber couplers 3; Described 1 × m photoswitch 5 is exported light and is entered described m × n network type optical fiber grating sensing head 6; 1 × m photoswitch, 5 and 2 × 2 fiber couplers 3 described in described m × n network type optical fiber grating sensing head 6 reflected light pass through successively enter the input end of described optical fiber Tunable Fabry-Perot Filter 7; The output light of described optical fiber Tunable Fabry-Perot Filter 7 enters described signal amplifier 9 after described photoelectric conversion module 8; Described signal amplifier 9 is collected in described computing machine 11 by described data collecting card 10 after the signal of receiving is amplified, and carries out data processing and demonstration by computing machine 11; Described computing machine 11 is connected with described 1 × m photoswitch 5.
Fiber grating in the present invention in network type optical fiber grating sensing head 6 is polarization-maintaining fiber grating.For the fiber grating of setting up on polarization maintaining optical fibre, in the time that broadband light incides this polarization-maintaining fiber grating, in its reflectance spectrum, there are two peak value centre wavelengths, the reflection wavelength on corresponding fast axle and slow axis, is expressed as:
λ
Bx＝2Λn
x，
λ
By＝2Λn
y，
Wherein, n
xand n
ybe respectively the effective refractive index of the fast axle of fibre core and slow axis, Λ is the grating cycle.
In disalignment, the difference of the peak value centre wavelength of 2 fiber gratings is:
Δλ＝2ΛΔn
Wherein, Δ n=n
x-n
ytherefore a polarization-maintaining fiber grating has two feature reflection peaks, the variable quantity of the drift value of peak wavelength and its strain, temperature is all good linear relationship, taking the drift value of these two peak value characteristic wavelengths as basis, calculate strain to be measured and temperature, utilize a sensing head to measure the object of two parameters thereby realize simultaneously.Wherein, the parameters such as the peak reflectance wavelength of polarization-maintaining fiber grating, bandwidth, reflectivity should be mated mutually, and in the wavelengthtunable interval of wavelength for fiber F-P adjustable filter, thereby can realize quick and demodulation exactly.
In the present invention, in a time period, to only have the light signal on a road be to form path to 1 × m photoswitch 5, that is to say, the total m of 1 × m photoswitch 5 roads, only have the light signal on a road can form path in section between at a time, next period can other arbitrarily another light path form path.Because some periods only have a light path to form path, therefore the luminous power that enters photoswitch all enters this passage, make the luminous power of the luminous power of this measurement passage and the flashlight of fiber grating reflection all reach maximum, the signal to noise ratio (S/N ratio) of therefore measuring is larger, and measuring accuracy is high.Computing machine 11 can control described 1 × m photoswitch 5 logical light light path sequence number and between the logical light time, also can divide equally the 1 × m photoswitch 5 described in mensuration control the employing time, two kinds of control modes only need be determined according to actual measurement requirement and target, connect computing machine 11 to 1 × m photoswitch 5 by optical fiber remote, realize computing machine 11 1 × m photoswitch 5 is controlled, thereby realized the object of remote monitoring.
The wavelength of described optical fiber Tunable Fabry-Perot Filter 7 is corresponding with the peak value characteristic wavelength of the fiber grating of described m × n network type optical fiber grating sensing head 6.In the time that grating is subject to tested parameter to modulate its peak value characteristic wavelength drift, because the wavelength of optical fiber Tunable Fabry-Perot Filter 7 is corresponding with the fiber grating peak value characteristic wavelength of m × n network type optical fiber grating sensing head 6, can make optical fiber Tunable Fabry-Perot Filter 7 export light and reach peak response, after opto-electronic conversion and analog to digital conversion, can identify this peak signal by computing machine 11, realize demodulation, thus make the present invention have demodulation speed fast, without advantages such as diadic questions.
The fiber grating of described m × n network type optical fiber grating sensing head 6, as the sensitive element of tested parameter, can utilize the method that paste on surface or inside is imbedded to be installed to the tested point of measured target, thereby realize the object of nondestructive measurement.
The specific embodiment of the invention is as follows: (1) is in the time of selection definite wideband light source, should select the light source that power spectrum density is larger, generally should be greater than-20dB/nm, larger to ensure inciding luminous power on sensing grating, make the signal light power of sensor fibre optical grating reflection larger, to improve the precision of measurement; (2) while selecting each fiber grating, its wavelength definite extremely important, the especially selection at the reflection peak characteristic wavelength interval of fiber grating, should take into account and measure the size of counting and the measurement range requirement of each point.Under the requirement that meets measurement range, select the fiber grating of the less a series of fiber gratings in reflection peak characteristic wavelength interval as network consisting formula optical fiber grating sensing head, in the situation that light source bandwidth is certain, realize the quasi-distributed measurement of more measurement points; (3) when selective light switch, the number that m is parallel optical path, m can be infinity in theory; (4) install and when integrated network formula optical fiber grating sensing head, the measurement port number of its parallel connection should mate with the port number of photoswitch, efficiency is measured in waste increase with Avoids or reduces luminous power, n is with maximum number that on the way can series arrangement grating, n is determined jointly by got peak value characteristic wavelength interval and light source bandwidth, taking the light source bandwidth of 80nm as example, if in the optic fiber grating wavelength interval of 2nm, 40 fiber gratings sensings simultaneously of can connecting altogether.Because sensing head contains m × n fiber grating, therefore can realize the real-time measurement of m × n point of composite structure.
Be not difficult to find, when utilizing single fiber grating to realize strain and two parameters of temperature, the present invention measures, and utilize an optical fiber Tunable Fabry-Perot Filter to realize the Wavelength demodulation of all sensor fibre optical grating reflection flashlights, be composite structure strain that a kind of cost performance is high and the quasi-distributed measuring system of temperature.That the present invention also has that anti-electromagnetic interference (EMI), full fiber type are measured, multiplexing measurement is counted is many, can remote monitoring and can realize the advantages such as nondestructive measurement.
It should be noted that, a kind of quasi-distributed composite structure strain that the present invention realizes and system for detecting temperature also can be used for the measurement of other parameters such as structural load amount, magnetic field intensity.
Claims (6)
1. a quasi-distributed composite structure strain and system for detecting temperature, comprise wideband light source (1), fibre optic isolater (2), 2 × 2 fiber couplers (3), 1 × m photoswitch (5), m × n network type optical fiber grating sensing head (6), optical fiber Tunable Fabry-Perot Filter (7), photoelectric conversion module (8), signal amplifier (9), data collecting card (10) and computing machine (11), it is characterized in that, described wideband light source (1) output light enters the input end of 2 × 2 fiber couplers (3) through described fibre optic isolater (2), the output light of described 2 × 2 fiber couplers (3) enters the input end of described 1 × m photoswitch (5) through an output terminal arm of 2 × 2 fiber couplers (3), described 1 × m photoswitch (5) output light enters described m × n network type optical fiber grating sensing head (6), 1 × m photoswitch (5) described in the reflected light of described m × n network type optical fiber grating sensing head (6) passes through successively and 2 × 2 fiber couplers (3) enter the input end of described optical fiber Tunable Fabry-Perot Filter (7), the output light of described optical fiber Tunable Fabry-Perot Filter (7) enters described signal amplifier (9) after described photoelectric conversion module (8), described signal amplifier (9) is collected in described computing machine (11) by described data collecting card (10) after the signal of receiving is amplified, described computing machine (11) is connected with described 1 × m photoswitch (5), fiber grating in described m × n network type optical fiber grating sensing head (6) is polarization-maintaining fiber grating, in the time that broadband light incides described polarization-maintaining fiber grating, in its reflectance spectrum, there are two peak value centre wavelengths, the reflection wavelength on corresponding fast axle and slow axis, is expressed as: λ
bx=2 Λ n
x, λ
by=2 Λ n
y, wherein, n
xand n
ybe respectively the effective refractive index of the fast axle of fibre core and slow axis, Λ is the grating cycle, in disalignment, the difference of two peak value centre wavelengths is: Δ λ=2 Λ Δ n, wherein, Δ n=n
x-n
ytherefore a polarization-maintaining fiber grating has two feature reflection peaks, the variable quantity of the drift value of peak wavelength and its strain, temperature is all good linear relationship, taking the drift value of these two peak value characteristic wavelengths as basis, calculate strain to be measured and temperature, realize and utilize a sensing head to measure the object of two parameters simultaneously, wherein, the peak reflectance wavelength of described polarization-maintaining fiber grating, bandwidth, reflectivity mate mutually, and in the wavelengthtunable interval of wavelength for described optical fiber Tunable Fabry-Perot Filter, realize fast and demodulation exactly.
2. quasi-distributed composite structure strain according to claim 1 and system for detecting temperature, is characterized in that, it is to form path that described 1 × m photoswitch (5) only has the light signal on a road in a time period.
3. quasi-distributed composite structure strain according to claim 1 and system for detecting temperature, it is characterized in that, described computing machine (11) control described 1 × m photoswitch (5) logical light light path sequence number and between the logical light time, or described computing machine (11) the employing time divide equally the 1 × m photoswitch (5) described in mensuration control.
4. quasi-distributed composite structure strain according to claim 1 and system for detecting temperature, it is characterized in that, the wavelength of described optical fiber Tunable Fabry-Perot Filter (7) is corresponding with the peak value characteristic wavelength of the fiber grating of described m × n network type optical fiber grating sensing head (6).
5. quasi-distributed composite structure strain according to claim 1 and system for detecting temperature, it is characterized in that, the method that paste on fiber grating utilization surface or inside is imbedded of described m × n network type optical fiber grating sensing head (6) is installed to the tested point of measured target.
6. quasi-distributed composite structure strain according to claim 1 and system for detecting temperature, is characterized in that, on another output terminal arm of described 2 × 2 fiber couplers (3), index-matching fluid (4) is installed.
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| US20130322490A1 (en) * | 2012-05-31 | 2013-12-05 | Kidde Technologies, Inc. | Optical fiber sensing system |
| CN103148880B (en) * | 2013-03-01 | 2015-04-08 | 黑龙江大学 | Color-filter-based multi-channel fiber bragg grating demodulator |
| CN103398800B (en) * | 2013-07-20 | 2016-05-11 | 北京航空航天大学 | A kind of for large structure quasi-distributed fiber grating temperature strain measuring system |
| CN104215197B (en) * | 2014-03-20 | 2019-07-30 | 哈尔滨工业大学 | Based on three core fibre grating array spatial form measuring device of antiradar reflectivity and method |
| CN105021539B (en) * | 2014-04-29 | 2017-12-01 | 中国矿业大学 | A kind of mining multifunctional sensing and monitoring system based on fiber grating |
| CN106248120A (en) * | 2016-07-28 | 2016-12-21 | 山西省交通科学研究院 | A kind of fiber grating measurement apparatus increasing single measurement range |
| CN106918296A (en) * | 2017-03-23 | 2017-07-04 | 江苏骏龙光电科技股份有限公司 | A kind of fiber grating measurement apparatus strained for bridge cable with temperature monitoring |
| CN108507697B (en) * | 2018-02-28 | 2019-10-29 | 华北电力大学（保定） | A kind of sea water temperature depth profile sampling towed system based on Fibre Optical Sensor |
| CN109827601B (en) * | 2019-03-29 | 2021-09-14 | 重庆文理学院 | Interference type temperature and stress double-parameter measuring system based on special optical fiber |
| CN110530550B (en) * | 2019-08-12 | 2020-10-09 | 温州大学 | Signal demodulation method of quasi-distributed temperature sensing system |
| CN112212898B (en) * | 2020-09-09 | 2022-05-27 | 山东科技大学 | Intelligent skin based on small-size distributed optical fiber sensing array |
| CN112525372B (en) * | 2020-11-10 | 2023-06-27 | 广东工业大学 | Strain temperature simultaneous measurement device and method based on polarization maintaining optical fiber double-arm different-axis interferometer |
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