CN2783292Y

CN2783292Y - High-precision optical fibre Bragg grating miniature pressure sensor

Info

Publication number: CN2783292Y
Application number: CN 200420057731
Authority: CN
Inventors: 姜德生; 何伟; 王昌
Original assignee: Wuhan University of Technology WUT
Current assignee: Wuhan Ligong Guangke Co Ltd
Priority date: 2004-12-14
Filing date: 2004-12-14
Publication date: 2006-05-24
Anticipated expiration: 2014-12-14

Abstract

The utility model relates to a high-precision optical fiber Bragg grating miniature pressure sensor, which comprises an optical fiber Bragg grating and a pressure deformable body, wherein the pressure deformable body is composed of a rigid sheet. A raised spring piece and a flexible hinge, one end of the raised spring piece is connected with the middle of the rigid sheet through the flexible hinge, and the other movable end point is connected with the center point of the optical fiber Bragg grating, and both ends of the optical fiber Bragg grating are fixed on the rigid sheet. When the spring piece is under transverse pressure, the spring piece is deformed, the movable end point of the spring piece gores the center point of the FBG, and accordingly, the FBG generates tension in the longitudinal direction. In this way, the transverse pressure which acts on optical fiber is converted to action force which is perpendicular to the direction of pressure, and the action force is applied to the FBG, which causes the FBG to generate longitudinal strain and causes the reflection wave length of the FBG to be changed. The borne transverse pressure and the reflection wave length of the grating generates relations, and finally, the measurement purpose is reached. The utility model has the characteristics of high resolution, good repetitiveness, large measurement range, miniaturisation of devices, etc. The utility model can be suitable for various application environments where pressure measurement is needed and uncharitable requirements to the size and the structure of the sensor are prescribed.

Description

High-precision optical fiber Bragg grating micro pressure sensor

Technical field:

The utility model belongs to field of sensing technologies, specifically is a kind of placing in the small size space acting on the novel high-precision Fiber Bragg Grating micro pressure sensor that the horizontal pressure of Fiber Bragg Grating is measured.

Background technology:

Pressure is an important physical parameter that characterizes object state, and its measurement relates to industrial and agricultural production, the various aspects of economic construction.Pressure transducer is a kind of being of wide application, and the sensor that the demand non-constant is big has very extensive and important application prospects.Along with science and technology development, people have also proposed requirements such as precision height, response is fast, the life-span is long to the measurement of pressure.

Fiber-optic grating sensor is a kind of novel sensor that grows up nearly more than ten years, owing to its unique advantage is subjected to paying close attention to widely, and is developed apace.Fiber grating can be divided into Fiber Bragg Grating (Fiber Bragg Grating is called for short FBG) and long period fiber grating (Long Period Fiber Grating is called for short LPFG).FBG is that a kind of fiber core refractive index is along fiber axis device in the optical fiber that is subjected to periodic modulation, it optionally in the broadband light with incident a certain narrowband wavelength optocoupler oppositely synthetic, form reflection, it is long that the centre wavelength of narrowband reflection light is referred to as cloth loudspeaker lattice wave.Cloth loudspeaker lattice wave length is determined by grating constant (effective refractive index of grating and grating fringe cycle), and grating constant is to the strain variation and the temperature variation sensitivity of grating place optical fiber, by long strain and the temperature conditions that just can know grating place optical fiber of the cloth loudspeaker lattice wave that detects optical grating reflection, so FBG can be used for strain sensing and temperature sensing.Because the FBG sensor is to utilize wavelength signals to measure, therefore except the essential safety with traditional fiber sensor, anti-electromagnetic interference (EMI), anticorrosive, transmission range is long, volume is little, the advantage such as in light weight, also have the advantage of following uniqueness:

(1) measuring-signal is not subjected to the influence of factors such as light source fluctuating, bending loss of optical fiber, junction loss and detector are aging, and the influence of factor such as light source fluctuating, bending loss of optical fiber, junction loss and detector be aging is that traditional " light intensity type " Fibre Optical Sensor is difficult to overcome;

(2) avoided the unintelligible of phase measurement in the general interferometric sensor and to the needs of intrinsic reference point, and phase measurement unintelligible and be the intrinsic weakness of traditional " interfere type " Fibre Optical Sensor to the needs of intrinsic reference point;

(3) can use wavelength-division multiplex technique to be connected in series a plurality of Bragg gratings easily in an optical fiber and carry out distributed measurement, this is that traditional Fibre Optical Sensor is irrealizable.

So the fiber-optic grating sensor measuring accuracy is higher, long-time stability better, the scope of application is wider.

Making pressure transducer with FBG generally is FBG and pressure deformation body to be rigidly fixed to together (FBG is attached to the pressure deformation surface or the pressure deformation body of nuzzling in), make the deformation energy of pressure deformation body be transformed into the strain of FBG effectively, in the time of on pressure acts on the pressure deformation body, the pressure deformation body deforms, thereby cause the strain variation of FBG, the changing of cloth loudspeaker lattice wave long hair of optical grating reflection light just can be known pressure condition by the cloth loudspeaker lattice wave that detects optical grating reflection is long like this.For example, it is to adopt FBG is packaged in the polymeric substrates that a kind of method is arranged, polymkeric substance is made the cuboid dress of 10*15*50mm, FBG is positioned at polymeric substrates central authorities, utilize polymkeric substance to amplify the acting force of outer bound pair grating, thereby improved the pressure sensitive coefficient of grating, can produce highly sensitive pressure transducer.But because this pressure transducer is to utilize the longitudinal strain characteristic of FBG to come gaging pressure, therefore this sensor can not be done very for a short time on gauge (pressure direction), thereby has limited the application of this sensor at special occasions.

All need to measure in many application scenarios and act on the horizontal pressure of optical fiber,, pressure is measured thereby can be placed on very little space because only in this way could do very for a short time with sensor thickness size (pressure direction) (hundred micron dimensions).But it is very difficult directly to act on the horizontal pressure of optical fiber with the FBG measurement, and this mainly is because FBG is insensitive to transverse strain, and naked FBG is under the pressure of 70MPa, and wavelength moves and only is so just to be difficult to obtain very high Measurement Resolution by 0.22nm.

At this phenomenon, the someone proposes to utilize the birefringence effect of FBG to develop pressure transducer.The principle of this measurement is: when FBG is subjected to transverse pressure, can produce birefringence effect, birefringence effect causes the pattern in the spectrum to be separated, and the suffered transverse pressure of the wavelength interval between the clastotype and optical fiber is relevant.Can measure in this way and be applied directly to the horizontal pressure of optical fiber.But because the birefringent polarizing spaces of FBG is smaller, this has just brought very big difficulty to demodulation.There are some researchers to propose to develop pressure transducer, are used for the measurement of optical fiber transverse pressure with LPFG.Because the birefringent characteristic of LPFG is relatively more responsive to transverse pressure, its birefringent polarizing separate wavelengths spacing is hundreds of times of FBG.But the jitter of LPFG, and LPFG transmission spectral bandwidth at present is than broad, so measuring accuracy is difficult to improve.Adopt birefringence effect to make sensor in addition, the complicacy of whole sensor-based system improves, and device cost also significantly improves.The research of this respect at present also is in the laboratory study stage, does not have corresponding product development and application.

Summary of the invention:

The technical problems to be solved in the utility model is: a kind of transverse pressure that can measure FBG is provided, and in light weight, the high-precision optical fiber Bragg grating micro pressure sensor that size is little.

The technical scheme that the utility model solves the problems of the technologies described above is: a kind of high-precision optical fiber Bragg grating micro pressure sensor, comprise Fiber Bragg Grating (FBG) and pressure deformation body, Fiber Bragg Grating (FBG) and pressure deformation body link together flexibly.

The pressure deformation body is made up of the shell fragment and the flexible hinge of a rigid sheet, projection, shell fragment one end of projection is connected by flexible hinge and rigid sheet are middle, its another active endpoint then is connected with Fiber Bragg Grating (FBG) central point, and the two ends of Fiber Bragg Grating (FBG) are fixed on the rigid sheet.

When transverse pressure that shell fragment is subjected to, shell fragment produces deformation, the active endpoint of shell fragment is pushed up the central point of FBG, because the two ends of FBG are fixed on the rigid sheet, thereby make FBG longitudinally produce tension force, so just will act on the horizontal pressure of optical fiber and be converted into acting force perpendicular to pressure direction, this acting force puts on FBG and causes it to produce strain longitudinally, cause that the FBG reflection wavelength changes, be related between feasible transverse pressure that is subjected to and the grating reflection wavelength, finally reach the purpose of measurement.We introduce the flexible hinge structure in elastic piece structure, flexible hinge is a kind of simple, reliable and dexterous physical construction, have and be similar to common hinge function, not only displacement can be provided but also can or dwindle displacement by the lever amplification, it is poor to solve common shell fragment recovery preferably, the problem that displacement resolution is low.Owing to can measure the transverse pressure of FBG, so the thickness that can be made into of whole sensor has only hundreds of microns, width has only tens millimeters microdevice.

The utlity model has characteristics such as resolution height, good reproducibility, response time are short, measurement range is big, device miniaturization, need pressure survey and size sensor and structure are had the harsh applied environment that requires applicable to various.

Description of drawings

Fig. 1 is applied to pressure sensing measuring system synoptic diagram for the utility model

Fig. 2 is the utility model structural representation

Fig. 3 is the utility model schematic cross-section

Embodiment

Shown in Fig. 2,3, shell fragment 7, flexible hinge 8 and rigid sheet 9 are formed deformable body, and Fiber Bragg Grating (FBG) 6 two ends closely stick on rigid sheet 9 sides, and center section then is fixed together with shell fragment 7; The center section shell fragment 7 of rigid sheet 9 curves an arc, when shell fragment 7 juts are subjected to transverse pressure, shell fragment 7 just can be out of shape and stretches, the movable end side direction of shell fragment 7 is pushed up the FBG6 center, thereby make it longitudinally produce tension force, so just the optical fiber transverse pressure effectively is converted into the acting force perpendicular to pressure direction, this acting force puts on FBG6 and causes it to produce strain longitudinally, make the reflection wavelength of FBG6 move, just can know suffered pressure condition by detecting wavelength variations.Can arrange FBG in the sensing probe 4, light source 1 whole sensor-based system provides light wave.Light source 1 couples light into Bragg grating by Y type shunt 3, and another minute road port of Y type shunt 3 connects demodulating equipment 2,5 for connecting optical fiber.Below sensing among the present invention and structural principle are done simple introduction.

The sensing principle of FBG: by coupled mode theory as can be known, optical fiber FBG can be coupled to another guided mode that transmits in opposite direction with a guided mode that wherein transmits and form narrowband reflection, and peak reflectance wavelength (Bragg wavelength) is:

λ _B＝2n _effΛ (1)

N in the formula (1) _EffBe the effective refractive index of guided mode, Λ is the grating cycle.

By formula (1) as can be known, the Bragg wavelength is with n _EffChange with Λ.When the residing external environment of grating changed, temperature, ess-strain, pressure that may cause fiber grating itself etc. changed, when the only strained ε of fiber grating does the time spent, and being changed to relatively of its foveal reflex wavelength

Δλ _B/λ _B＝(1-P _e)ε (2)

P in the formula _e=n[P ₁₁-v (P ₁₁+ P ₁₂)/2 are effective elasto-optical coefficient, P ₁₁, P ₁₂Be elasto-optical coefficient, v is the Poisson ratio of core material, and ε is the axial strain amount that external force produces.

By (2) formula as can be known, when axial strain takes place FBG, will cause long variation of cloth loudspeaker lattice wave of grating, we utilize this relation to measure to be measured.

Claims

1, a kind of high-precision optical fiber Bragg grating micro pressure sensor comprises Fiber Bragg Grating and pressure deformation body, it is characterized in that Fiber Bragg Grating and pressure deformation body are linked together flexibly.

2, pressure transducer as claimed in claim 1, it is characterized in that described pressure deformation body by a rigid sheet, the projection shell fragment and flexible hinge form, shell fragment one end of projection is connected by flexible hinge and rigid sheet are middle, its another active endpoint then is connected with the Fiber Bragg Grating central point, and the two ends of Fiber Bragg Grating are fixed on the rigid sheet.