CN105277135B - A kind of high sensitivity optical fiber curvature sensing structure with temperature-insensitive characteristic - Google Patents
A kind of high sensitivity optical fiber curvature sensing structure with temperature-insensitive characteristic Download PDFInfo
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Abstract
The present invention proposes a kind of high sensitivity optical fiber curvature sensing structure with temperature-insensitive characteristic, and the sensing element centered on three core fibres, three fibre cores of three core fibres are triangular arranged.Wide spectrum optical enters multimode fibre 9 by single-mode fiber 3, inspires multiple transmission modes, and transmission mould field becomes big, subsequently enters three core fibres 10, three core mode individual transmission distancesLAfter reenter multimode fibre 9, now the light of three patterns is interfered, and optical signal is modulated, then continues to propagate forward in single-mode fiber 3 in the form of single mode, is finally recorded by spectroanalysis instrument 2.Amount of movement by detecting interference spectrum can extrapolate the variable quantity of curvature.Test result indicates that the optical fiber sensing structure can measure bending curvature, and obtain good linear characteristic, it is 2.79 m in curvature range‑1~3.24 m‑1When measurement sensitivity up to 28.29nm/m‑1。
Description
Technical field
The present invention relates to a kind of high sensitivity optical fiber curvature sensing structure with temperature-insensitive characteristic, belongs to optical fiber biography
Sensor technical field.
Background technology
In many fields such as industry, manufacturing industry and construction industry, as mechanical arm, building structure health monitoring, bridge are built
If, machine components processing, MEMS etc., curvature is a very important parameter.But due to being difficult straight in practice
Connect measurement, but the information such as strain for passing through structure extrapolates curvature information indirectly, so that the direct measurement of curvature
As a problem.Traditionally there is the Bending Deformation size that a variety of methods can obtain structure, but mostly by certain condition system
It can not recover, not be suitable for flush type measurement etc..Therefore, Curvature Optical Fiber Sensor has small volume with it,
Light weight, it is flexible and arise at the historic moment the advantages of be applied to flush type distribution measuring.Fibre Optical Sensor currently used for curvature measurement
Device, typically using the wavelength shift detection technique of fiber grating, LPFG, Curvature varying is converted into the change of strain
Change to measure, these method systems are complicated, involve great expense, had a great influence by external environment (such as temperature), it may appear that
The problem of cross sensitivity.
In recent years, intermode interference optical fiber sensing technology as a kind of new optical fiber sensing technology due to highly sensitive
Degree, the advantages of production process is simple, and cost is low and increasingly obtain the extensive concern of domestic and foreign scholars, utilize the original of intermode interference
The method of reason measurement curvature is developed rapidly.2011, Yuan Gong et al. were proposed single-mode fiber-multimode fibre-single mode
The intermode interference optical fibre sensor structure of optical fiber structure is attached in flexible metal beam to measure the curvature (document of crossbeam
1.Y.Gong,T.Zhao,Y.J.Rao,and Y.Wu.“All-fiber curvature sensor based on
multimode interference.”IEEE Photonics Technology Letters,2011,23(11):679-
68.).The same year, Portuguese Susana Silva propose a kind of temperature and strain insensitive intermode interference optical fiber curvature sensing
Device (document 2.S.Silva, O.Frazao, J.Viegas, L.A.Ferreira, F.M.Araujo, F.Xavier Malcata,
and J.L.Santos.“Temperature and strain-independent curvature sensor based on
a singlemode/multimode fiber optic structure.”Measurement Science&Technology,
2011,22(8):85201-85206.), Temperature cross-over sensitivity is eliminated by detecting two obvious troughs in transmission spectrum simultaneously
Influence.In terms of curvature is measured, applying for multi-core fiber occupies a tiny space in Curvature Optical Fiber Sensor.By detecting multicore
The change of interferometric phase in optical fiber between multiple cores can obtain curvature information.The multi-core fiber interferometer in more early period is phase
Position modulation type, such as M.J.Gander of Univ Heriot Watt of Britain et al. build four-core fiber Reflective spatial light path system
System, light are coupled into four-core fiber after object lens focus on, and emergent light hot spot is beaten at far field, form interference hot spot, change optical fiber
The angle of bending and the change that hot spot is recorded with ccd array, can extract out the change (document of interferometric phase after signal transacting
3.M.J.Gander,D.Macrae,E.A.C.Galliot,R.McBride,J.D.C.Jones,P.M.Blanchard,
J.G.Burnett,A.H.Greenaway,and M.N.Inci.“Two-axis bend measurement using
multicore optical fibre.”Optics Communications,2000,182(1-3):115–121.).It is but empty
Between light path it is bulky, it is easily excessively complicated by external interference, demodulating system.With the development of demodulation techniques, Wavelength demodulation is abandoned
Complicated CCD demodulating systems, multi-core fiber Wavelength demodulation interferometer turn into a kind of new sensing arrangement for being more suitable for sensing.
A kind of strain based on five core fibres and curvature sensor are proposed in the article that Chunying Guan delivered in 2015
(document 4.C.Guan, X.Zhong, G.Mao, T.Yuan, J.Yang, and L.Yuan. " In-line Mach-Zehnder
interferometric sensor based on a linear five-core fiber.”IEEE Photonics
Technology Letters,2015,27(6):635-638.), five fibre core yi word pattern arrangement form non-centrosymmetric structures,
Curvature sensitivity is up to 10.37nm/m-1.Although this method has used five core fibres, but each fibre core Energy distribution is uneven, edge
Core mode energy is faint, can not be applied to sensing well, obtain high sensitivity.
The content of the invention
(1) technical problems to be solved
It is an object of the invention to overcome the shortcomings of that existing Curvature Optical Fiber Sensor is easily affected by temperature, a kind of knot is proposed
Structure is simple, intermode interference curvature sensing structure that is easily prepared and can realizing high-sensitivity measurement.
(2) technical scheme
In order to achieve the above object, the present invention proposes that a kind of high sensitivity optical fiber curvature with temperature-insensitive characteristic passes
Feel structure, have studied the curvature and temperature characterisitic of this novel optical fiber curvature sensing structure.The structure is centered on three core fibres
Sensing element, two sections of multimode fibres of welding are as bridge between the single-mode fiber and three core fibres at both ends, to obtain high quality
Interference spectrum, while suppress the interference of cladding mode.In experiment, wide spectrum light source 1 sends wide spectrum optical, and wide spectrum optical is jumped via single mode
Optical signal is modulated after line 3 enters to inject multimode-tri- cores-multimode fibre structure 5, and three core fibre inner core intermodes interfere,
Caused interference spectrum is detected by spectroanalysis instrument 2.Platforms 7 are adjusted as the feed unit of optical fiber curvature by the use of two three-D displacements,
A pair of clampers 4 are by fiber gripper, and the micrometer caliper 6 by adjusting three directions makes optical fiber parallel with experimental bench 8 and and water
Prosposition moves feed direction and is consistent, and when adjustment of displacement platform produces displacement in the horizontal direction, optical fiber is bent therewith, and curvature changes
Become.The structure, which is positioned in insulating box, can change its temperature.Measured by building the experimental provision and confirm the knot
Structure has the interference spectrum of the temperature-responsive of muting sensitivity, highly sensitive curvature response and high quality.
In such scheme, three described core fibre intermode interference curvature sensing structures can be by optical fiber cutting knife and fused fiber splice
Machine completes.Single-mode fiber is completed after being cut flat with multimode fibre end face by automatic welding function, multimode fibre and three core light
Fine end face is completed after cutting flat with by manual weld function, and splicing parameter is：Strength of discharge 100；Discharge time 3000ms；Z-direction
15 μm of advance distance；Retract 0 μm of distance in direction.
In such scheme, three described core fibre intermode interference curvature sensing structures, multimode fibre and three core fibre length
Respectively 2mm and 12cm, multimode fibre use centreless multimode fibre, 125 μm of diameter, and three core fibre outer cladding diameters are phases therewith
125 μm of matching, three fibre cores are fiber core with single-mold, and mode field diameter is 10.34 μm.
In such scheme, in three described core fibre intermode interference curvature sensing structures, three fibre cores of three core fibres are
In triangular arranged centered on the covering center of circle, the distance of center circle between fibre core is more than 20 μm.
In such scheme, in three described core fibre intermode interference curvature sensing structures, three fibre cores tool of three core fibres
There is the thermo-optical coeffecient of certain refringence and they very close.
In such scheme, the experimental provision be by wave-length coverage 1525nm~1565nm amplified spontaneous emission
(Amplified Spontaneous Emission, ASE) light source 1, wavelength discrimination are 0.02nm spectroanalysis instrument 2 and one
What platform 7 formed is adjusted to the three-D displacement that precision is 10 μm.
In such scheme, the experimental provision changes its curvature indirectly by changing the chord length of optical fiber arc, its geometrical relationship
Optional approximate formula describes, and x is the push-in stroke of micrometer caliper, L0For original chord length.
(3) beneficial effect
It can be seen from the above technical proposal that the invention has the advantages that：
1) have using the principle measurement curvature of three core fibre intermode interferences than other optical fiber curvature sensing technologies higher
Sensitivity, less expensive cost, simpler manufacturing process, and compact-sized, parameter is various, is more suitable for practical application.
2) structure of this principle measurement curvature using three core fibre intermode interferences provided by the invention, by three cores
Multimode fibre is introduced between optical fiber and single-mode fiber makes more light enter in the fibre core rather than covering of three core fibres, it is suppressed that covering
Interference of the interference to its curvature characteristic and temperature characterisitic between pattern, the temperature-insensitive characteristic and curvature that ensure that the structure are rung
The linearity answered.
3) structure of this principle measurement curvature using three core fibre intermode interferences provided by the invention, by three cores
Multimode fibre is introduced between optical fiber and single-mode fiber and the intetference-fit strengthening of transmission spectrum is significantly improved, from 3dB or so
14dB is brought up to, the halfwidth of trough substantially narrows, and is more beneficial for the monitoring to trough amount of movement.
4) structure of this principle measurement curvature using three core fibre intermode interferences provided by the invention, because of its more fibre core
Independence and thermo-optical coeffecient it is close and with temperature-insensitive characteristic, the interference for effectively avoiding temperature change from bringing.
Brief description of the drawings
The parameter for the intermode interference optical fiber curvature sensing arrangement that following figure is taken is identical with embodiment.
Fig. 1 is the intermode interference curvature sensing structural representation based on three core fibres；
Fig. 2 is after being not introduced into the core fibre of single-mode fiber-three-single-mode fiber structure of multimode fibre and introducing multimode fibre
The comparison diagram of constructive interference spectrum shown in Fig. 1；
Fig. 3 is the curvature measurement schematic device of three core fibre intermode interference structures；
Fig. 4 is the sensitivity matched curve of three core fibre intermode interference structure measurement curvature；
Fig. 5 is sensitivity matched curve of the three core fibre intermode interference structures to temperature characterisitic.
Embodiment
For the object, technical solutions and advantages of the present invention are more clearly understood, below in conjunction with specific embodiment, and reference
Accompanying drawing, concrete structure, principle and the structure optimization process of the present invention are described in further detail.
The present invention proposes a kind of high sensitivity optical fiber curvature sensing structure with temperature-insensitive characteristic, such as Fig. 1 institutes
Show, the sensing element centered on three core fibres, three fibre cores of three core fibres are triangular arranged, and fiber core radius r is fine
Distance is d between core.Wide spectrum optical enters multimode fibre 9 by single-mode fiber 3, inspires multiple transmission modes, and transmission mould field becomes big,
Three core fibres 10 are subsequently entered, reenter multimode fibre 9 after three core mode individual transmission distance L, now three patterns
Light interfere, optical signal is modulated, then continues to propagate forward in single-mode fiber 3 in the form of single mode, and interference spectrum is final
Recorded by spectrometer, λ is the optical wavelength of free space, InAnd ImThe energy intensity of different core modes is represented,Represent to appoint
Effective refractive index between two patterns of anticipating is poor, and the length of three core fibres is L.When optical fiber experiences stress and curved with certain curvature
Qu Shi, due to the intrinsic photoelastic effect of quartz material, the refractive index of optical fiber changes in cross-sectional direction, the folding of curved interior
Penetrate rate reduce and outside then raises, thereforeChange, cause the movement of spectrum.
Bridge of one section of shorter multimode fibre as connection is added between single-mode fiber and multimode fibre, it is therefore an objective to profit
Multiple patterns onwards transmission simultaneously is inspired with the characteristics of its large mode field, the higher pattern mode field area of exponent number is bigger, and light is full of
Whole 125 μm of multimode fibre fibre cores and be no longer bound in 9 μm of single-mode fiber fibre core, therefore have more light being capable of direct-coupling
Enter the fibre core of three core fibres.Meanwhile length is shorter can ensure that light is nearly free from phase difference in multimode fibre.Made in experiment
Two kinds of structures of multimode fibre are made to be not introduced into and have introduced and to contrast its transmission spectrum as shown in Figure 2.As can be seen that due to introducing
Multimode fibre makes three cores possess more multi-energy, and transmission spectrum fringe contrast is higher, and trough bandwidth substantially narrows, and with compared with
Uniform free space spectrum width, is more convenient for being monitored trough.In addition, into three core fibre fibre cores light increase mean into
The light energy entered in covering is reduced, and interference of the cladding mode to interference spectrum is effectively suppressed.
Fig. 3 is the curvature measurement schematic device of three core fibre intermode interference structures.Wave-length coverage be 1525nm~
1565nm wide spectrum light source 1 sends wide spectrum optical, wide spectrum optical via single mode wire jumper 3 enter to inject multimode-tri- cores-multimode fibre 5 it
Optical signal is modulated afterwards, and three core fibre inner core intermodes are interfered, and caused interference spectrum is detected by spectroanalysis instrument 2.With two
Fiber gripper is passed through three sides of adjustment by feed unit of the individual three-D displacement adjustment platform 7 as optical fiber curvature, a pair of clampers 4
To micrometer caliper 6 make optical fiber parallel with experimental bench 8 and with horizontal displacement feed direction be consistent, when adjustment of displacement platform exists
When horizontal direction produces displacement, optical fiber is bent therewith, curature variation.The horizontal direction micrometer caliper of three-dimensional adjustment platform is with 20 μm
Direction from interval to optical fiber be fed, be often fed once with spectrometer record interference spectrum change, displacement is converted into curvature
The response curve for drawing curature variation time spectral shift momentum afterwards is as shown in Figure 4.Understand to survey by the fitting a straight line slope provided in Fig. 4
Frequency range is measured in 2.79m-1~3.24m-1When curvature sensitivity be -28.29nm/m-1, linear regression value is 0.9956.This spirit
Sensitivity is higher than the curvature sensitivity number provided in document 1,2 and 4.
Test and the temperature characterisitic of the three core fibres intermode interference curvature sensing structure is studied.The structure is placed
In insulating box, regulation temperature is changed to 75 DEG C from 30 DEG C, often changes the change of 3 DEG C of record interference spectrums, draws the song such as Fig. 5
Line.Due to the limitation (0.02nm) of Laboratory Spectra instrument wavelength discrimination, change caused by 3 DEG C can not be resolved out.To reality
Test after data are fitted and understand only 0.0022nm/ DEG C of the temperature control of the three core fibres intermode interference curvature sensing structure,
Cross sensitivity sensitivity of the curvature to temperature is less than 10-4m-1/ DEG C, it can be considered that the structure has temperature-insensitive characteristic,
Curvature measurement is not disturbed by temperature change.
Claims (1)
- A kind of 1. high sensitivity optical fiber curvature sensing structure with temperature-insensitive characteristic, it is characterised in that：The optical fiber curvature Sensing arrangement is all optical fibre structure of the sensing element centered on the core fibre of single mode three, in order to improve between basic mode and three cores Coupling efficiency, each one section of length of welding is more for the centreless of 125 μm of 2mm diameters between general single mode Transmission Fibers and the core fibre of single mode three Mode fiber is as bridge, based on the principle of interference between three core fibres, three basic modes, using the refractive index of three independent fibre cores because curved Caused elasto-optical effect when bent and change this feature and realize highly sensitive curvature measurement.
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| CN114562953A (en) * | 2022-01-11 | 2022-05-31 | 北京邮电大学 | Bending measurement structure, experimental instrument and sensor of asymmetric double-core optical fiber |
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