CN1584725A - Optical fibre grating wavelength demodulating method - Google Patents
Optical fibre grating wavelength demodulating method Download PDFInfo
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- CN1584725A CN1584725A CN 200410020745 CN200410020745A CN1584725A CN 1584725 A CN1584725 A CN 1584725A CN 200410020745 CN200410020745 CN 200410020745 CN 200410020745 A CN200410020745 A CN 200410020745A CN 1584725 A CN1584725 A CN 1584725A
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Abstract
A method for demodulating grating wavelength of optical fibre includes using wideband optical source and a pair of optical fibre connected in series with one as reference and the other as measurement, measuring return power of this pair of optical fibre to obtain reflecting wavelength variation of reference fibre to measurement fibre for achieving wavelength modulation.
Description
Technical field
The invention belongs to Fibre Optical Sensor, field of optical measuring technologies, relate to a kind of optic fiber grating wavelength demodulation method.
Background technology
Fiber grating is a kind of optical filter with narrowband reflection characteristic that is produced on the optical fiber.Because elastic deformation, the thermal expansion character of silica fibre, with and hot light, elasto-optical effect, it has the sensitivity characteristic to temperature and stress.This sensitivity characteristic is linear in certain scope, meets following relation:
Δλ
ε/λ＝ε(1-γ) (1)
Δλ
T/λ＝(α+e)ΔT (2)
In the formula: ε is the strain of optical fiber, and γ is the elasto-optical coefficient of fiber optic materials, and α is the coefficient of thermal expansion of fiber optic materials, and Δ T is a temperature variation,
Be thermo-optical coeffecient.Just need can determine the temperature and the stress of perception according to above-mentioned relation by measuring wavelength change.Make fiber-optic grating sensor practicability, how accurate gordian technique is exactly, and measures the subtle change of its foveal reflex wavelength quickly and easily, i.e. Wavelength demodulation method.
At present, for the Wavelength demodulation technology of fiber grating, traditional means is to use instruments such as spectrometer, monochromator or wavemeter.In addition people have proposed the scheme of some novel wavelength information demodulation, as Mach one Zehnder interferometer method, tunable Fabry one perot filter method, matched fiber grating wave filter method etc.Conclusion is got up, and the demodulation techniques of fiber grating reflected light wavelength can be divided into following several types:
1. certain light signal that has that detected sensing head reflects is directly inputted in spectrometer, monochromator or the wavemeter, directly measures the wavelength location of fiber Bragg grating reflected signal.This demodulation mode measuring accuracy is higher, uses but these instrument only are suitable for the laboratory, and inconvenience is applied in the actual sensor-based system.
2. utilize tunable laser as testing light source, optical maser wavelength continuous sweep in certain scope of output, according to the position of light signal in the scan period, the variation of tested optical fiber optical grating reflection optical wavelength be can draw, measuring optical fiber grating and reference optical fiber grating reflection optical wavelength perhaps drawn.The advantage of this method is the energy of reflection light height, and as long as general light power meter is used as receiving element, signal is easy to detect, the resolution height, and multiplexed realization is simple.But the light source design manufacture difficulty of this method is big, the cost height.
3. utilize wideband light source as testing light source, utilize wave filter or tunable optic filter, come sensed light signal with light power meter as restitution element for sensor fibre optical grating reflection light signal.This method can be divided into reflection-type and transmission-type two classes again.The former principle is as follows: incide on the FBG of receiving end from the reflected light of sensing FBG, if consistent with the reflected light wavelength of receiving end FBG, then be reflected on the detector.Drive reception FBG by PZT and finely tune, obtain the peak wavelength of sensing FBG.The precision of this method is subjected to the restriction of light source stability and external interference, to the stability requirement height of end of probe FBG spectrum.
4. edge filter method, adopt promptly that a kind of to have live width bigger, transmitance is the wave filter of linear change, with the reflecting light appearance convolution of sensing FBG, the signal that obtains is proportional with the position of FBG peak wavelength, thereby can know the FBG wavelength location by inference from signal magnitude, this method requires the edge of demodulator filter very steep, good linearity requires each parameters of operating part of system stable, therefore manufactures and designs and uses comparatively difficult.
Because the defective that said method exists, the demodulation techniques in the fiber grating sensing system become one of major obstacle that this sensing technology applies.In fact, up to the present, can be on market as the fiber grating demodulation device of commodity selling, has only a kind of technology of tunable Fabry one perot filter of use, and because the complicacy of its technology, the price of this product is all very expensive, and response frequency is not high.
Summary of the invention
The object of the present invention is to provide a kind of simple, practical fiber grating demodulation method, overcome the defective of present demodulation techniques, promote the practicability of fiber grating sensing technology.
Ultimate principle of the present invention is, with wideband light source incident pair of series fiber grating together, when their foveal reflex wavelength difference is zero, the luminous power minimum of reflection, only bigger than the back light power of single fiber grating, along with their increase of relative foveal reflex wavelength difference, the luminous power of its reflection also increases, when their relative foveal reflex wavelength difference greater than a half of single fiber grating reflection bandwidth, its reflected optical power will be tending towards a maximal value, and this maximal value is slightly less than two single fiber grating back light power sums.Therefore when the foveal reflex wavelength difference of a pair of fiber grating that is cascaded when changing between half of the single fiber grating reflection bandwidth of zero-sum, can realize measurement by measurement, thereby realize Wavelength demodulation reflected optical power to their relative foveal reflex wavelength difference.When the foveal reflex wavelength difference of selecting two fiber gratings for use during as quiescent point, can obtain the better linearity operating characteristic near 1/4 single fiber grating reflection bandwidth.
Technical solution of the present invention is as follows: use in pairs the fiber grating that is cascaded, and the foveal reflex wavelength difference of a pair of fiber grating is less than half of single fiber grating reflection bandwidth.With wideband light source as testing light source, in a pair of fiber grating, one is used for measuring, another is used to provide reference, when the foveal reflex wavelength of measuring grating changes, the reflected optical power of this a pair of fiber grating will change like this, the luminous power of returning with photoelectric detector (as APD) or other optical power detector measurements, just can calculate and measure the variable quantity of grating, realize Wavelength demodulation with respect to the centre wavelength of reference grating.Be to obtain linear working characteristic, can be with the foveal reflex wavelength difference of a pair of fiber grating single fiber grating reflection bandwidth 1/4 as quiescent point.
Effect of the present invention and benefit are:
(1) the present invention need not special wavelength measurement or filter apparatus, only needs to measure the foveal reflex wavelength relative reference fiber grating foveal reflex wavelength change that back light power just can calculate the measuring optical fiber grating.
(2) the present invention neither needs tuning source when realizing wavelength measurement, does not also need tuned filter, can realize very high frequency response.In fact response speed only depends on the speed of detection to back light power, i.e. the response speed of corresponding photoelectric detector.
(3) measuring system that adopts the present invention to realize can all adopt optical fiber and fiber optic element device, is a kind of full fibre system.Between each device and the element, can fuse, constitute an integral body by optical fiber fusion splicing machine.Therefore, use reliable and stablely, realize instrumentation easily.
(4) the present invention owing to the employing with reference to grating, when surveying stress, can realize Temperature Compensation when realizing Wavelength demodulation; When thermometric is spent, can realize the compensation of counter stress, thereby eliminate influencing each other of temperature, stress.
(5) the present invention compares with methods such as adopting spectrometer, monochromator, wavemeter, boundary filter, simple and practical, be easy to commercialization, with low cost, has good cost performance, and response speed is fast, is convenient to applying of fiber-optic grating sensor, can be widely used in fields such as military affairs, industry, building.
Description of drawings
Accompanying drawing 1 is the system schematic that the present invention is applied to single measurement point.
Wherein: the 1st, wideband light source, 2 is 2 * 2 coupling mechanisms, the 3rd, reference optical fiber grating, the 4th, measuring optical fiber grating, the 5th, photodetector, the 6th, photodetector.
Accompanying drawing 2 is system schematic that the present invention is applied to distributed measurement.
Wherein: the 7th, a fiber grating that is cascaded is right, the 8th, a fiber grating that is cascaded is right, the 9th, wavelength division multiplexer, 10 and 11 are photodetector, wherein fiber grating should be different to 8 back light frequency range with fiber grating to 7, separated by wavelength division multiplexer 9 guaranteeing.
Embodiment
Below in conjunction with technical scheme and accompanying drawing, be described in detail the specific embodiment of the present invention.
Embodiment 1:
The present invention is applied to the situation of single measurement point, as shown in Figure 1, the light that wideband light source 1 sends enters 2 * 2 coupling mechanisms 2, is entered photodetector 6, fiber grating 3 and fiber grating 4 after 2 beam splitting respectively, wherein fiber grating 3 is with reference to grating, and fiber grating 4 is for measuring grating.The foveal reflex wavelength difference of fiber grating 3 and fiber grating 4 is about 1/4 of single fiber grating reflection bandwidth.Measuring optical fiber grating 4 is under measured effect, the reflection kernel wavelength can be moved, the variation that promptly causes reference optical fiber grating 3 and measure the reflection kernel wavelength difference of grating 4, thereby the optical power value that makes photodetector 5 record changes, the measured value of reference light electric explorer 6 again, remove the influence that light source power changes, can obtain the foveal reflex wavelength variable quantity of measuring optical fiber grating 4 relative reference fiber gratings 3, thereby realize Wavelength demodulation.
Embodiment 2:
How the explanation of this example realizes the distributed fiber grating sensing with the present invention.As shown in Figure 2, the light that wideband light source 1 sends enters 2 * 2 coupling mechanisms 2, entered respectively after 2 beam splitting photodetector 6, fiber grating to 7 and fiber grating to 8, fiber grating is 1/4 of single fiber grating reflection bandwidth with fiber grating to 8 relative foveal reflex wavelength difference to 7, and fiber grating should be different to 8 back light frequency range with fiber grating to 7, separated by wavelength division multiplexer 9 guaranteeing.Fiber grating to 7 and fiber grating to 8 back light through 2 * 2 coupling mechanisms 2 after, enter wavelength division multiplexer 9, after wavelength division multiplexer 9 beam split, fiber grating to 7 and fiber grating 8 back light is separated, enter photodetector 10 and photodetector 11 respectively, by the measurement of photodetector 10 and 11 pairs of back light power of photodetector, can realize to fiber grating to 7 and fiber grating to 8 Wavelength demodulation.Photodetector 6 provides the reference that light source power changes, to eliminate the influence of light source power variation to measuring.Wherein wavelength division multiplexer 9 can use dense wave division multiplexer or other light-splitting devices.This scheme can realize the distributed fiber grating sensing that frequency response is very high.
Claims (4)
1. optic fiber grating wavelength demodulation method is characterized in that using in pairs the fiber grating that is cascaded, and the foveal reflex wavelength difference of a pair of fiber grating is less than half of single fiber grating reflection bandwidth.
2. a kind of optic fiber grating wavelength demodulation method according to claim 1, its feature also are a pair of fiber grating that is cascaded, and using its foveal reflex wavelength difference is that 1/4 place of single fiber grating reflection bandwidth is as quiescent point.
3. a kind of optic fiber grating wavelength demodulation method according to claim 1 and 2, its feature also is to adopt wideband light source, the right reflected optical power of fiber grating that is cascaded by the photoelectric detector measurement realizes Wavelength demodulation.
4. according to claim 1,2 or 3 described a kind of optic fiber grating wavelength demodulation methods, its feature also is to use light-splitting device to come the separately back light of each measuring optical fiber grating pair, realizes distributed sensing.
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| Application Number | Priority Date | Filing Date | Title |
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| CNB2004100207450A CN1304900C (en) | 2004-06-12 | 2004-06-12 | Optical fibre grating wavelength demodulating method |
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| CNB2004100207450A CN1304900C (en) | 2004-06-12 | 2004-06-12 | Optical fibre grating wavelength demodulating method |
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Cited By (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101915865A (en) * | 2010-07-05 | 2010-12-15 | 武汉理工大学 | Miniature optical fiber current sensor probe and making method thereof |
| CN102175268A (en) * | 2011-01-29 | 2011-09-07 | 西南交通大学 | Quasi-distributed sensor network based on time division multiplex and matched optical fiber grating technology |
| CN102445216A (en) * | 2010-09-30 | 2012-05-09 | 上海华魏光纤传感技术有限公司 | Dynamic drift demodulation device and method for fiber grating |
| CN102692283A (en) * | 2012-06-11 | 2012-09-26 | 太原科技大学 | Device and method for measuring multi-FBG (fiber bragg grating) colorimetric transient temperature |
| CN105806374A (en) * | 2016-05-06 | 2016-07-27 | 深圳市畅格光电有限公司 | Fiber bragg grating wavelength demodulation method |
| CN104061874B (en) * | 2014-07-09 | 2017-02-15 | 中国科学院半导体研究所 | High-accuracy fiber bragg grating sensing demodulation method for eliminating polarization state influences |
| CN106500822A (en) * | 2016-11-28 | 2017-03-15 | 华北电力大学 | Based on the transformer core system of condition monitoring that M Z interferometers are demodulated |
| CN108196107A (en) * | 2017-12-28 | 2018-06-22 | 重庆大学 | A kind of distributed full photovoltage measuring system and its measuring method |
| CN113080883A (en) * | 2021-04-01 | 2021-07-09 | 四川省人民医院 | Photon sensing system based on radio frequency signal frequency detection and implementation method |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| NO324337B1 (en) * | 1999-09-15 | 2007-09-24 | Optoplan As | Device for painting optical wavelengths |
| CN2605705Y (en) * | 2003-04-03 | 2004-03-03 | 南开大学 | High-speed optical-fiber grating sensing-multiplexing-demodulating apparatus |
-
2004
- 2004-06-12 CN CNB2004100207450A patent/CN1304900C/en not_active Expired - Fee Related
Cited By (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101915865A (en) * | 2010-07-05 | 2010-12-15 | 武汉理工大学 | Miniature optical fiber current sensor probe and making method thereof |
| CN102445216A (en) * | 2010-09-30 | 2012-05-09 | 上海华魏光纤传感技术有限公司 | Dynamic drift demodulation device and method for fiber grating |
| CN102175268A (en) * | 2011-01-29 | 2011-09-07 | 西南交通大学 | Quasi-distributed sensor network based on time division multiplex and matched optical fiber grating technology |
| CN102692283A (en) * | 2012-06-11 | 2012-09-26 | 太原科技大学 | Device and method for measuring multi-FBG (fiber bragg grating) colorimetric transient temperature |
| CN104061874B (en) * | 2014-07-09 | 2017-02-15 | 中国科学院半导体研究所 | High-accuracy fiber bragg grating sensing demodulation method for eliminating polarization state influences |
| CN105806374A (en) * | 2016-05-06 | 2016-07-27 | 深圳市畅格光电有限公司 | Fiber bragg grating wavelength demodulation method |
| CN105806374B (en) * | 2016-05-06 | 2019-02-26 | 深圳市畅格光电有限公司 | A kind of demodulation method of optic fiber grating wavelength |
| CN106500822A (en) * | 2016-11-28 | 2017-03-15 | 华北电力大学 | Based on the transformer core system of condition monitoring that M Z interferometers are demodulated |
| CN108196107A (en) * | 2017-12-28 | 2018-06-22 | 重庆大学 | A kind of distributed full photovoltage measuring system and its measuring method |
| CN113080883A (en) * | 2021-04-01 | 2021-07-09 | 四川省人民医院 | Photon sensing system based on radio frequency signal frequency detection and implementation method |
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|---|---|
| CN1304900C (en) | 2007-03-14 |
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