CN100468008C - Transverse stress sensing system of photonic crystal fiber written with grating and implementing method thereof - Google Patents
Transverse stress sensing system of photonic crystal fiber written with grating and implementing method thereof Download PDFInfo
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- CN100468008C CN100468008C CNB2006100815277A CN200610081527A CN100468008C CN 100468008 C CN100468008 C CN 100468008C CN B2006100815277 A CNB2006100815277 A CN B2006100815277A CN 200610081527 A CN200610081527 A CN 200610081527A CN 100468008 C CN100468008 C CN 100468008C
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Abstract
The invention relates to an optical sensing system for detecting the transverse stress strain. Wherein, the laser outputs light to the polarize controller, to be coupled into the zero double refract or high refract photon crystal optical fiber which is marked with long-period grating and inside the forced unit to sense the external transverse stress; the spectrum detector connected to the output detects the transparent spectrum and outputs the detected information to the signal processing and displaying unit to attain the detect result of transverse stress; the output light of laser via the light circulator is coupled into the photon crystal optical fiber of Prague grating; the photon crystal optical fiber is inside the forced unit; the signal light reflected from the Prague grating via the light circulator is output to the spectrum detector to detect the reflect spectrum and output the detected information to the signal processing and displaying unit to attain the detect result of transverse stress.
Description
Technical field
The present invention relates to a kind of accurately and sensitive optical fiber sensing system to measure transverse stress or strain, particularly based on this transverse-stress sensing system and implementation method with the photonic crystal fiber of grating with the zero birefraction photonic crystal fiber or the high double-refraction photon crystal fiber of grating.
Background technology
The safety of buildings and quality monitoring mainly are stress and the deformation that detects under external force.General detection method is a large amount of distributed strain sheets to be installed in building materials or fiber is experienced in other strain, because the composite structure that fibrous material and building materials constitute can suitably improve the intensity of building materials, therefore, load and the deformation detection of using complex fiber material to carry out buildings is method relatively more commonly used.At building materials or buildings embedded set light transmitting fiber, form Intelligent Composite structure (also being dexterous composite structure), in the time of building materials or buildings generation deformation, the optical fiber that is embedded in wherein can be experienced corresponding stress and strain, its optical characteristics (mainly being transport property) can change immediately, therefore the light signal that transmits in the optical fiber is detected, just can monitor deformation and load change situation in the buildings in real time, thereby realize safety monitoring buildings.This method not only can be used for the detection of buildings, and also has wide application prospects in fields such as machinery, biomedicine, Aero-Space.Utilize optical fiber to carry out stress sensing and detection, not only have the intrinsic superiority of optical fiber, as anti-electromagnetic interference (EMI), physical strength is high, can also realize Distributed Detection, and sensitivity is very high.
Fiber stress sensing and detection technique have experienced the development in 20 years nearly, existing at present multiple strain gauge based on common silica fibre.Optical fiber stress sensor can be divided into meridional stress sensor and transverse-stress sensing device according to the direction of detected stress, can be divided into two big classes, the one, optical-fiber type strain gauge, the 2nd, grating type strain gauge according to basic functional principle.The optical-fiber type strain gauge is exactly that deformation takes place optical fiber under external force, changes the transport property of its pattern, and transmission light is detected the situation of change that can obtain deformation or external force.The grating type strain gauge is to utilize the cycle (vertically) of fiber grating (comprising optical fiber bragg grating FBG and long-period gratings LPG) or symmetry (laterally) to change with external force, thereby changes the transmission spectrum or the reflectance spectrum of grating, realizes the detection that external force is changed.
The optical-fiber type strain gauge to the detection of meridional stress generally all based on the interference effect between a plurality of patterns in dual mode optical fiber or the less fundamental mode optical fibre (few-mode fiber).When optical fiber stretched, the phase relation between the different mode changed, thereby output terminal light field (intensity) generation respective change, according to the periodicity of Strength Changes, can obtain phase change, thereby obtain the deformation or the stress of optical fiber.When common circular fiber is subjected to transverse stress, generally detect the optical path difference and the coherence of two polarized components of back-reflection light, can determine that transverse stress is applied to the lengthwise position on the optical fiber, but be difficult to determine stress intensity.
Because the spectral characteristic of fiber grating is very high to the optical fiber structure and the susceptibility in grating cycle, so, since earlier 1990s, grating came out, extensive studies and application have been obtained based on the Bragg grating of common step-refraction index silica fibre and the sensor of long-period gratings (comprising strain gauge and temperature sensor).When optical fiber is subjected to longitudinal pulling force and when extending, the grating cycle that writes in the core district can corresponding increase, and for Bragg grating, its peak reflectance wavelength moves to the long wavelength; For long-period gratings, its transmission spectrum moves to long wavelength's direction.When optical fiber is subjected to transverse pressure, might as well put on optical fiber side along the x direction by assumed stress, optical fiber x direction size will be dwindled so, and y direction size will enlarge.For circular fiber, will produce intrinsic birefringence; For birefringence fiber, its birefringent characteristic will change.Have the Bragg grating that writes in the birefringent optical fiber or the reflectance spectrum or the transmission spectrum of long-period gratings divides this, two reflection peaks or two groups of transmission spectrums occur, they are corresponding with the pattern of two groups of polarization direction quadratures respectively.When the transverse stress on being added in optical fiber changes, the birefringent characteristic of optical fiber changes immediately, generally speaking, the variation of transverse stress is directly proportional with the wavelength amount of movement of grating spectrum, therefore, moving of two reflection peak wavelength of detection Bragg grating perhaps detected moving of two groups of transmission spectrums of long-period gratings, just can in time detect the variation of transverse stress.
Among " fiber optic grating transverse strain sensor system " Chinese patent CN1155798C, introduced transverse strain sensing system, and can measure the temperature of different location or stressed simultaneously based on the Bragg grating in the ordinary optic fibre.
The longitudinal strain sensitivity of optical fiber is generally 0.8 * 10
-6μ ε
-1, temperature control is 6 * 10
-6℃
-1Utilize Bragg grating to carry out transverse-stress sensing and detection, laboratory sensitivity can reach 0.344nm/ (N.mm
-1); The laboratory sensitivity that utilizes long-period gratings to carry out transverse-stress sensing and detection has then reached 50nm/ (N.mm
-1).
The sensitivity of optical fiber stress sensor is by the main material quartz (SiO of optical fiber
2) decision.SiO
2Young modulus very big, (concrete numerical value is relevant with the doping in the silica fibre, the about 72GPa of non-doping covering generally all to surpass 70GPa, 3% mixes Ge is about 70.8GPa), under external force, its deformation is generally all very little, therefore to the technological requirement of optical fiber stress sensor than higher.For the sensitivity that changes optical fiber transverse-stress sensing device single dependence to the quartz material Young modulus, people attempt to change optical fiber structure, thereby change optical fiber deformation quantity under external force, improve the precision and the sensitivity of optical fiber transverse-stress sensing and detection with this.
Utilize the Bragg grating in the multi-core fiber to carry out the transverse stress detection,, also shown its tempting advantage, utilize the transverse-stress sensing device sensitivity of 4 core fibres to reach 0.24nm/ (N.mm though be the research work of just carrying out recently
-1).
Utilize other hole optical fiber and Bragg grating wherein to carry out transverse stress and detect and then obtained more concern, people are not only from theoretical and experimentally confirmed that this optical fiber can reach 2.0nm/ (N.mm to the sensitivity of transverse stress
-1) more than, and studied its range of dynamic measurement, can realize in 0～38.08MPa scope that the high-precision pressure of 0.03MPa resolution is measured.
The present invention utilizes novel photonic crystal fiber (PCF:Photonic Crystal Fiber), writes Bragg grating or long-period gratings therein, to transverse stress (strain) carry out sensing.
In the photonic crystal fiber cladding regions, longitudinally arranging a large amount of airports.According to leaded light mechanism, it can be divided into two classes, i.e. refractive index leaded light and photon band gap (PBG:Photonic Band Gap) leaded light.The core district of typical refractive index light-guiding photonic crystal fiber is a stuffed quartz, and covering is a porous structure.Airport in the covering has reduced the effective refractive index of covering, thereby satisfies total reflection (TIR:Total InternalReflection) condition, and light is strapped in the transmission of core district.The cladding regions of photon band gap light-conductive optic fibre is a periodic structure, and the photon band gap that it produces can be strapped in light the transmission of fiber cores district.Photon band gap light-conductive optic fibre covering periodic structure is a 2 D photon crystal, and refractive index is only in the variation of xsect intercycle.Vertical along optical fiber, refractive index is uniformly, can not be restricted when light longitudinally transmits.But the Bragg reflection meeting of lateral periodicity structure produces transverse resonance, forms frequency domain (wavelength) band gap.If introduce the periodicity that a line defect is destroyed 2 D photon crystal, will in the photon band gap of cladding structure, produce a defect mode, and can be strapped in the core district along Optical Fiber Transmission.This novel optic mechanism can realize leaded light in the region of low refractive index (as air-core) of optical fiber, and this type optical fiber can not be based on the total reflection leaded light, and its many new features can be widely used in Fibre Optical Sensor and the optical fiber communication.
Up to now, people have utilized various material preparation photonic crystal fibers such as pure quartz, non-quartz glass (as chalcogenide glass, Schott glass) and polymkeric substance.Photonic crystal fiber also has many other new characteristics, as endless single mode, and the big mode field area single-mode fiber, highly nonlinear optical fiber, high birefringence optical fiber, the chromatic dispersion controllable optical fibre, or the like.
In the refractive index leaded light photonic crystal fiber, if along the airport size difference of different directions, perhaps hole shape is oval rather than circular, and perhaps the airport position is asymmetric, can obtain high birefringence.The high magnitude of the comparable traditional panda optic fibre of the birefringence of these high double-refraction photon crystal fibers.Ning Guan has reported a kind of high double-refraction photon crystal fiber, protect partially in the 1620nm scope at 480nm, and polarization interference is better than-25dB, crosstalks in the 1620nm scope at 1300nm and approximately has only-45dB, even polarization interference can not worsen when fiber bending radius has only 10mm yet.The polarization coupled that the high double-refraction photon crystal fiber length that Crystal Fibre A/S (the PCF product more comprehensively behind the purchase Blazephotonics) company provides surpasses 100m is better than 30dB, and birefringent temperature coefficient significantly is lower than common high birefringence optical fiber.These character can be used for the sensor of development of new characteristic.
The research that utilizes photonic crystal fiber to carry out temperature and stress sensing at present begins, but because the application of photonic crystal fiber is at the early-stage, and the detection difficulty of transverse stress is bigger, so still do not see the relevant report based on the transverse-stress sensing of photonic crystal fiber now.We study the deformation situation under external force of photonic crystal fiber and ordinary optic fibre, and the result shows that airport helps strengthening the strain of optical fiber to external force, Kong Yueda, and strain is big more.If increase airport quantity, strain will further increase.The strain size has very strong dependence to the structure of photonic crystal fiber, therefore, can obtain best strain parameter, not only reduce detection difficulty by selecting different photonic crystal fibers, improve detection sensitivity, and can obtain the optimal detection condition of transverse stress.
Accompanying drawing 5,6,7 is three kinds of typical zero birefraction photonic crystal fibers, write Bragg grating (perhaps long-period gratings) therein, when optical fiber is not subjected to any stress, two polarization state degeneracys of basic mode (accompanying drawing 8), there is a loss peak position corresponding with resonance wavelength on the transmission spectrum; When photonic crystal fiber is subjected to transverse pressure, optical fiber produces birefringence, a loss peak originally can be split into two, the wavelength interval of these two loss peak correspondences is directly proportional with the birefringence of optical fiber, therefore, sensing and detection just can be carried out to being applied to the horizontal stress of optical fiber in the peak-to-peak wavelength interval of detecting on the transmission spectrum of loss.
Accompanying drawing 9,10,11,12 is four kinds of typical high double-refraction photon crystal fibers, write Bragg grating (perhaps long-period gratings) therein, on the transmission spectrum of the basic mode of corresponding two polarization direction quadratures two loss peaks (wavelength location corresponding with the resonance wavelength of two polarization states) are arranged respectively.If be applied to the birefringence that the transverse pressure on the photonic crystal fiber increases optical fiber, two peak-to-peak wavelength intervals of loss originally increase under the effect of pressure, and increase is directly proportional with transverse stress; If be applied to the birefringence that transverse pressure on the photonic crystal fiber reduces optical fiber, two peak-to-peak wavelength intervals of loss originally reduce under the effect of pressure, and decrease is directly proportional with transverse pressure.Therefore, sensing and detection just can be carried out to being applied to the horizontal stress of optical fiber in the peak-to-peak wavelength interval of detecting on the transmission spectrum of loss.
Above application is with transverse stress (strain) sensor-based system of the photonic crystal fiber of grating, realize by detecting transmission spectrum, for system with Bragg grating, can detection of reflected the variation of spectrum, same principle can realize that transverse stress (strain) detects.
The present invention---use with the transverse stress strain sensing system of the photonic crystal fiber of grating, utilize the more hypersensitivity of photonic crystal fiber to external force, take zero birefraction photonic crystal fiber or high double-refraction photon crystal fiber, carry out the real-time high-precision detection being applied to the horizontal stress of optical fiber with Bragg grating or long-period gratings.
Further research can realize distributed transverse stress (strain) sensing and detection system or sensor network based on foregoing, heavy construction is carried out the real-time monitoring of the whole strained situation of large tracts of land.
Summary of the invention
An object of the present invention is to provide a kind of zero birefraction photonic crystal fiber transverse stress (strain) sensing and detection system with Bragg grating, further realize distributed sensing system or sensor network, be used to measure transverse stress or strain with stressed orientation independent.
Another object of the present invention provides a kind of high double-refraction photon crystal fiber transverse stress (strain) sensor-based system with Bragg grating, further realizes distributed sensing system or sensor network, is used for direction of measurement relevant transverse stress or strain.
Another object of the present invention provides a kind of zero birefraction photonic crystal fiber transverse stress (strain) sensor-based system with long-period gratings, further realizes distributed sensing system or sensor network, is used for direction of measurement relevant transverse stress or strain.
Another object of the present invention provides a kind of high double-refraction photon crystal fiber transverse stress (strain) sensor-based system with long-period gratings, further realizes distributed sensing system or sensor network, is used for direction of measurement relevant transverse stress or strain.
A kind of optical fiber sensing system that detects the transverse stress strain, mainly comprise laser light source, general single mode fiber, zero birefraction photonic crystal fiber or high double-refraction photon crystal fiber, Bragg grating, optical circulator, stress unit, spectroscopic detector, signal Processing and display unit, laser light source output light is through optical circulator, be coupled into zero birefraction or high double-refraction photon crystal fiber then, with Bragg grating, and be placed in the stress unit on the photonic crystal fiber, be convenient to experience the outside transverse stress that applies, export spectroscopic detector from the flashlight of Bragg grating reflected back to through behind the optical circulator, detection of reflected spectrum, and give signal Processing and display unit with detected information, obtain the testing result of transverse stress.
A kind of optical fiber sensing system that detects the transverse stress strain, mainly comprise laser light source, general single mode fiber, zero birefraction photonic crystal fiber or high double-refraction photon crystal fiber, long-period gratings, Polarization Controller, stress unit, spectroscopic detector, signal Processing and display unit, laser light source output light is coupled into zero birefraction or high double-refraction photon crystal fiber behind Polarization Controller, on the photonic crystal fiber with long-period gratings, and be placed in the stress unit, be convenient to experience the outside transverse stress that applies, the spectroscopic detector that output terminal connects detects transmitted spectrum, and give signal Processing and display unit with detected information, obtain the testing result of transverse stress.
Transverse-stress sensing system and implementation method with the photonic crystal fiber of grating have following steps:
The first, select zero birefraction or high double-refraction photon crystal fiber for use, make Bragg grating or long-period gratings therein, determine the resonance wavelength of grating by the transmission spectrum of measuring grating;
The second, select the laser works wave band, make its resonance wavelength that can cover the grating that sensor-based system uses, and definite corresponding system laser light source and the photodetector that use, and active and passive devices such as Polarization Controller, optical circulator;
The 3rd, be placed in the stress unit with the photonic crystal fiber of grating, be convenient to optical fiber is applied outside transverse stress;
The 4th, laser light source output light is coupled into photonic crystal fiber with it behind Polarization Controller;
The 5th, connect the sensor-based system light path, and accurately adjust, make system responses, sensitivity, precision etc. best;
The 6th, use optical circulator, reflected light is connected to spectroscopic detector, detection of reflected spectrum; Perhaps, directly the optical fiber far-end is connected to spectroscopic detector, detects transmitted spectrum;
The 7th, debug signal is handled and display unit, and detection signal is handled and is presented on the terminal device, realizes the real-time detection of transverse stress.
Principle of the present invention is to utilize the transport property of grating in the photonic crystal fiber and the relation of optical fiber transverse deformation to carry out transverse stress (strain) sensing and detection.Transverse stress makes optical fiber produce transverse strain, not only change the symmetry of optical fiber, also change the shape of airport in the optical fiber, and the quartz material refractive index is changed because of pressure, thereby change the transport property of optical fiber, mainly be transmission and the mode refractive index that changes each pattern, thereby change the birefringence of optical fiber.In the zero birefraction photonic crystal fiber, write Bragg grating or long-period gratings, under the effect of transverse stress (accompanying drawing 14), produce linear birefrigence, no longer has only a resonance wavelength on optical grating reflection spectrum or the transmission spectrum, but be split into and two two resonance wavelengths that polarization state is corresponding, reflection peak (accompanying drawing 19 appears in these two resonance wave strong points, accompanying drawing 20), the wavelength interval is directly proportional with the basic mode mode birefringence of optical fiber, thereby is proportional to the outside transverse stress that is applied on the optical fiber.Therefore, detect the variation at interval of two reflection peak wavelength or transmission loss peak wavelength, just can realize the real-time monitoring of transverse stress.
There is intrinsic birefringence in two basic modes (accompanying drawing 13) of high double-refraction photon crystal fiber, and it is high more a lot of than traditional birefringence fiber, write Bragg grating or long-period gratings therein, even without outside transverse stress, the loss peak of reflectance spectrum peak value or transmission spectrum also is that the wavelength interval is proportional to the birefringence of optical fiber in two resonance wave strong points of separating (accompanying drawing 21).External stress is applied to optical fiber when horizontal (the power F of accompanying drawing 15 vertical directions) along the optical fiber slow axis, birefringence is reduced, thereby the wavelength interval reduces; When external stress applies along the fast axle of optical fiber (the power F of accompanying drawing 15 horizontal directions), its transverse strain and index distribution are shown in accompanying drawing 16 and accompanying drawing 17, and birefringence increases, and the wavelength interval increases.Therefore, detect the variation at interval of two reflection peak wavelength or transmission loss peak wavelength, can realize the real-time monitoring of transverse stress size and Orientation.
Solution of the present invention mainly contains several gordian techniquies.
The first, the selecting for use of zero birefraction photonic crystal fiber and high double-refraction photon crystal fiber.Because manufacture craft is imperfect, can there be birefringent optical fiber fully generally speaking, but the present invention will utilize the birefringent characteristic of optical fiber to carry out transverse-stress sensing just and detect, and therefore, can be avoided by the intrinsic birefringence problem of optical fiber that defective workmanship causes.
The second, the adjustment of high double-refraction photon crystal fiber attitude is beneficial to detect the external stress direction.In high double-refraction photon crystal fiber, the variation of its mode birefringence is relevant with external force direction, therefore, adjusts the attitude of optical fiber, can determine the direction of outside transverse stress.
The 3rd, the writing of Bragg grating.No matter be zero birefraction or high double-refraction photon crystal fiber sensing system, the present invention needs to write therein Bragg grating, and this is current cutting edge technology.The photonic crystals optical fiber structure more complicated, the technology that especially writes Bragg grating in pure quartzy photonic crystal fiber is difficult more, has only a few experiments report at present in the world, mainly is traditional phase mask version uv-exposure and two kinds of methods of two-photon absorption.
The 4th, the introducing of long-period gratings.No matter be zero birefraction or high double-refraction photon crystal fiber sensing system, the present invention needs to introduce therein long-period gratings, and this is current cutting edge technology.But with respect to the difficulty that writes of Bragg grating, it is much relatively easy to introduce long-period gratings in photonic crystal fiber.Can utilize traditional amplitude mask version uv-exposure method in photonic crystal fiber, to write long-period gratings, also can utilize periodically little curved, methods such as ultrasound wave is coupled, light laser periodicity etching, in photonic crystal fiber, introduce the long-period gratings of equivalence.
The 5th, the detection of optical grating reflection spectrum or transmission spectrum, key is the detection that resonance wavelength changes.By detecting resonance wavelength variation at interval, realize the detection of transverse stress size and Orientation.
Technique effect of the present invention can obtain embodying in real sensor is used.Application is with zero birefraction photonic crystal fiber transverse stress (strain) sensor of grating, because of the optical fiber that uses does not have intrinsic birefringence, the transverse stress that applies from which direction no matter, the transverse deformation that produces and variations in refractive index all are the same to the influence of output light signal, thus can not distinguish transverse stress from direction.The transverse stress that this sensing system can only be used for independent of direction detects.Application is with high double-refraction photon crystal fiber transverse stress (strain) sensor of grating, because of the optical fiber that uses has higher intrinsic birefringence, the transverse deformation that the transverse stress that different directions applies produces is different to the influence of output light signal with variations in refractive index, so this sensing system can be used for the transverse stress detection of directional correlation.
Application can also be improved by following means with the zero birefraction of grating or the technique effect of high double-refraction photon crystal fiber transverse stress (strain) sensor.
The first, when selecting the zero birefraction photonic crystal fiber for use, consider its unimodular property, especially optical fiber structure is to the deciding factor of unimodular property.Responsive as fruit structure deformation ratio under external force, can improve transducer sensitivity.
The second, when selecting high double-refraction photon crystal fiber for use, consider its unimodular property, especially optical fiber structure is to the deciding factor of unimodular property.Responsive as fruit structure deformation ratio under external force, can improve transducer sensitivity.
The 3rd, when selecting high double-refraction photon crystal fiber for use, consider its birefringent characteristic, especially optical fiber structure is to the deciding factor of birefringent characteristic.Responsive as fruit structure deformation ratio under external force, birefringence changes also relatively more responsive, can improve transducer sensitivity.
The 4th, when selecting high double-refraction photon crystal fiber for use, consider the attitude that it is subjected to transverse pressure, mainly be stressed direction, by adjusting the attitude of optical fiber, can find the most responsive direction of external power effect, thereby improve transducer sensitivity.
The 5th, when selecting wavelength detector or spectral detector for use, if its wavelength resolution height, perhaps the responsiveness height is perhaps highly sensitive, the sensitivity that can both improve sensing system.
The 6th, the function of other signal processing of sensing system is improved, and also helps improving the technique effect of sensor.
The 7th, the function of sensing system other parts is improved, and device performance improves, and all helps improving the technique effect of sensing system.
So far, provided and introduced transverse stress (strain) sensor-based system of application with the photonic crystal fiber of grating.Consider detailed introduction of the present invention and accompanying drawing, those professional and technical personnel will obviously see these and other objects of the present invention and advantage.Apparently, the professional and technical personnel can make amendment, change, change, use and use the present invention with comparalive ease, all that not away from modification, the change of essence of the present invention, change, use and use all and be included within the present invention.
Description of drawings
Fig. 1 uses with the transverse stress transmission-type system chart of the photonic crystal fiber of grating;
Fig. 2 uses with the transverse stress reflect system block diagram of the photonic crystal fiber of grating;
Fig. 3 lateral periodicity pressure is introduced the mode of long-period gratings;
Fig. 4 pressure unit structure;
The zero birefraction photonic crystals optical fiber structure in Fig. 5 triangle cycle;
The zero birefraction photonic crystals optical fiber structure in Fig. 6 four directions cycle;
The zero birefraction photonic crystals optical fiber structure in Fig. 7 honeycomb cycle;
The mould field distribution of basic mode in the zero birefraction photonic crystal fiber in Fig. 8 triangle cycle;
First kind of high double-refraction photon crystal fiber structure of Fig. 9;
Second kind of high double-refraction photon crystal fiber structure of Figure 10;
The third high double-refraction photon crystal fiber structure of Figure 11;
The 4th kind of high double-refraction photon crystal fiber structure of Figure 12;
The mould field distribution of basic mode in the high double-refraction photon crystal fiber of Figure 13 Figure 10 correspondence;
The stressed synoptic diagram of Figure 14 zero birefraction photonic crystal fiber;
The stressed synoptic diagram of high double-refraction photon crystal fiber of Figure 15 Figure 10 correspondence;
The optical fiber of Figure 16 Figure 10 correspondence is the Strain Distribution after stressed along quick shaft direction;
The optical fiber of Figure 17 Figure 10 correspondence is the index distribution after stressed along quick shaft direction;
The relation of long-period gratings cycle and resonance wavelength in the photonic crystal fiber in Figure 18 triangle cycle;
Figure 19 zero birefraction photonic crystal fiber borough chief periodic optical grating transmission spectrum;
Fiber Bragg Grating FBG reflectance spectrum and transmission spectrum in Figure 20 zero birefraction photonic crystal fiber;
Figure 21 high double-refraction photon crystal fiber lining glug optical grating reflection spectrum and transmission spectrum.
Embodiment
In order to be illustrated more clearly in the present invention, the present invention will be further described below in conjunction with case study on implementation and accompanying drawing, but should not limit protection scope of the present invention with this.
Introduce long-period gratings transverse stress (strain) sensor-based system in the photonic crystal fiber, a kind of optical fiber sensing system that detects the transverse stress strain, mainly comprise laser light source, general single mode fiber, Polarization Controller, zero birefraction photonic crystal fiber or high double-refraction photon crystal fiber, long period fiber grating, stress unit, photodetector, signal Processing and display unit.Laser light source output light-wave section should be able to cover the resonance wavelength of long-period gratings.
Shown in the accompanying drawing 1, optical fiber is zero birefraction or high double-refraction photon crystal fiber among the figure, and is stressed in the pressure unit shown in the accompanying drawing 4, form periodically little bending, 1 is optical fiber, and 2 is the pressure unit base, periodically groove is arranged, and 3 is the pressure unit loam cake, and 4 is the position of optical fiber in pressure unit; Mode according to accompanying drawing 3 is introduced long-period gratings in optical fiber.Light transfers to the transverse stress detection zone through general single mode fiber, and light passes through optical fiber under the transverse stress effect, and exports photo-detector (wavelength or spectrographic detection) to, surveys the variation of its transmission spectrum or resonance wavelength; Through signal sampling, processing, demonstration, figure and data result that the output transverse stress detects.
When photonic crystal fiber was subjected to transverse pressure in the stress unit of making through specialized designs, generating period was little curved, introduced vertically modulation by periodically little bending in photonic crystal fiber, formed equivalent long-period gratings.Parameters such as the depth of modulation of long-period gratings can change with transverse stress, thereby change the transport property of grating, therefore can detect the variation of extraneous stress.
Write transverse stress (strain) sensor-based system of Bragg grating in the photonic crystal fiber, a kind of optical fiber sensing system that detects the transverse stress strain, mainly comprise laser light source, general single mode fiber, zero birefraction photonic crystal fiber or high double-refraction photon crystal fiber, Bragg grating, stress unit, optical circulator, photodetector, signal Processing and display unit.Laser light source output light-wave section should be able to cover the resonance wavelength of Bragg grating.
Shown in the accompanying drawing 2, optical fiber is zero birefraction or high double-refraction photon crystal fiber among the figure, wherein with Bragg grating; Light transfers to the transverse stress detection zone through circulator and general single mode fiber, and light passes through optical fiber under the transverse stress effect; Reflex to circulator through Bragg grating, export photo-detector (wavelength or spectrographic detection) to from a port of circulator, survey the change in location and the wavelength interval of reflectance spectrum peak wavelength, wavelength interval between the resonance wavelength of two polarization state correspondences of photodetector detection changes, and this variation is proportional to transverse stress; Through signal sampling, processing, demonstration, figure and data result that the output transverse stress detects.
Because the intrinsic birefringent change of high double-refraction photon crystal fiber is relevant with external force direction, therefore change the birefringence that the transverse stress direction can change optical fiber, thereby change the Bragg grating reflectance spectrum peak wavelength situation of change at interval that writes wherein, therefore, through signal sampling, processing, demonstration, can obtain the result of the size and Orientation of transverse stress.
Claims (8)
1. optical fiber sensing system that detects the transverse stress strain, mainly comprise laser light source, general single mode fiber, zero birefraction photonic crystal fiber or high double-refraction photon crystal fiber, Bragg grating, optical circulator, stress unit, spectroscopic detector, signal Processing and display unit is characterized in that: laser light source output light is through optical circulator, be coupled into zero birefraction or high double-refraction photon crystal fiber then, with Bragg grating, and be placed in the stress unit on the photonic crystal fiber, be convenient to experience the outside transverse stress that applies, export spectroscopic detector from the flashlight of Bragg grating reflected back to through behind the optical circulator, detection of reflected spectrum, and give signal Processing and display unit with detected information, obtain the testing result of transverse stress.
2. optical fiber sensing system that detects the transverse stress strain, mainly comprise laser light source, general single mode fiber, zero birefraction photonic crystal fiber or high double-refraction photon crystal fiber, long-period gratings, Polarization Controller, stress unit, spectroscopic detector, signal Processing and display unit is characterized in that: laser light source output light is coupled into zero birefraction or high double-refraction photon crystal fiber behind Polarization Controller, on the photonic crystal fiber with long-period gratings, and be placed in the stress unit, be convenient to experience the outside transverse stress that applies, the spectroscopic detector that output terminal connects detects transmitted spectrum, and give signal Processing and display unit with detected information, obtain the testing result of transverse stress.
3. optical fiber sensing system according to claim 2 is characterized in that: introduce vertically modulation by little the bending of lateral periodicity in photonic crystal fiber, form equivalent long-period gratings.
4. optical fiber sensing system according to claim 2 is characterized in that: photonic crystal fiber is subjected in stress unit in the transverse pressure, and generating period is little curved, forms long-period gratings.
5. optical fiber sensing system according to claim 1 is characterized in that: laser light source output light-wave section covers the resonance wavelength of Bragg grating.
6. optical fiber sensing system according to claim 2 is characterized in that: laser light source output light-wave section covers the resonance wavelength of long-period gratings.
7. optical fiber sensing system according to claim 1 is characterized in that: use optical circulator that the light signal of Bragg grating reflection is coupled to spectroscopic detector.
8. optical fiber sensing system according to claim 1 and 2 is characterized in that: the wavelength interval between the resonance wavelength of two polarization state correspondences of spectroscopic detector detection changes, and this variation is proportional to transverse stress.
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| CNB2006100815277A Expired - Fee Related CN100468008C (en) | 2006-05-26 | 2006-05-26 | Transverse stress sensing system of photonic crystal fiber written with grating and implementing method thereof |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN102135459A (en) * | 2010-12-10 | 2011-07-27 | 杭州恒川科技有限公司 | AWG (Array Waveguide Grating) differential demodulation based intensity detection type PCF-LPG (Long-Period Grating Written in a Photonic Crystal Fiber) stress sensor and device |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102135459A (en) * | 2010-12-10 | 2011-07-27 | 杭州恒川科技有限公司 | AWG (Array Waveguide Grating) differential demodulation based intensity detection type PCF-LPG (Long-Period Grating Written in a Photonic Crystal Fiber) stress sensor and device |
| CN102135459B (en) * | 2010-12-10 | 2013-07-24 | 杭州恒川科技有限公司 | AWG (Array Waveguide Grating) differential demodulation based intensity detection type PCF-LPG (Long-Period Grating Written in a Photonic Crystal Fiber) stress sensor |
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| CN1844856A (en) | 2006-10-11 |
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