CN106525770A - Refractive index sensor adopting Michelson structure based on CNT (carbon nanotube) modified thin core fiber - Google Patents
Refractive index sensor adopting Michelson structure based on CNT (carbon nanotube) modified thin core fiber Download PDFInfo
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- CN106525770A CN106525770A CN201710029943.0A CN201710029943A CN106525770A CN 106525770 A CN106525770 A CN 106525770A CN 201710029943 A CN201710029943 A CN 201710029943A CN 106525770 A CN106525770 A CN 106525770A
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- 239000000835 fiber Substances 0.000 title claims abstract description 75
- 239000002041 carbon nanotube Substances 0.000 title claims abstract description 22
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 title claims abstract description 15
- 229910021393 carbon nanotube Inorganic materials 0.000 title claims abstract description 15
- 238000005253 cladding Methods 0.000 claims abstract description 22
- 230000035945 sensitivity Effects 0.000 claims abstract description 8
- 239000013307 optical fiber Substances 0.000 claims description 14
- 230000004048 modification Effects 0.000 abstract description 5
- 238000012986 modification Methods 0.000 abstract description 5
- 230000008021 deposition Effects 0.000 abstract description 4
- 230000000694 effects Effects 0.000 abstract description 2
- 238000012544 monitoring process Methods 0.000 abstract description 2
- 230000008859 change Effects 0.000 description 26
- 238000001228 spectrum Methods 0.000 description 7
- 238000005259 measurement Methods 0.000 description 6
- 238000000151 deposition Methods 0.000 description 5
- 238000000034 method Methods 0.000 description 4
- 238000000985 reflectance spectrum Methods 0.000 description 4
- 239000010409 thin film Substances 0.000 description 4
- 230000002452 interceptive effect Effects 0.000 description 3
- 230000000149 penetrating effect Effects 0.000 description 3
- 230000008033 biological extinction Effects 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 238000002474 experimental method Methods 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- 230000011514 reflex Effects 0.000 description 2
- 238000003466 welding Methods 0.000 description 2
- 241000252506 Characiformes Species 0.000 description 1
- 241000872198 Serjania polyphylla Species 0.000 description 1
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
- 238000002835 absorbance Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000005137 deposition process Methods 0.000 description 1
- 238000011010 flushing procedure Methods 0.000 description 1
- 238000009434 installation Methods 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 239000002210 silicon-based material Substances 0.000 description 1
- 229910052709 silver Inorganic materials 0.000 description 1
- 239000004332 silver Substances 0.000 description 1
- 230000003595 spectral effect Effects 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/41—Refractivity; Phase-affecting properties, e.g. optical path length
- G01N21/45—Refractivity; Phase-affecting properties, e.g. optical path length using interferometric methods; using Schlieren methods
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- Investigating Or Analysing Materials By Optical Means (AREA)
Abstract
The invention provides a refractive index sensor adopting a Michelson structure based on a CNT (carbon nanotube) modified thin core fiber. The sensor is characterized by comprising a single mode fiber (1), the thin core fiber (2), a micro arc top end cladding (3) and a CNT deposition layer (4), wherein the single mode fiber (1) is connected with the thin core fiber (2) connected with the micro arc top end cladding (3), and the CNT deposition layer (4) covers the surfaces of the thin core fiber (2) and the micro arc top end cladding (3). The sensor is high in sensitivity, micro in structure, simple to produce and applicable to various actual engineering, CNTs with the high refractive index can increase the effective refractive index of the cladding, the effective refractive index difference between a cladding mode and a fiber core mode due to increase of the external environment refractive index is reduced, and the wavelength drift distance of the sensor is smaller than that of a sensor which is not modified with CNTs. The strength drift distance of the sensor can be increased by properly controlling the CNT modification thickness, the effect on wavelength can be reduced to the greatest extent, and the sensor is applied to refractive index monitoring in actual life.
Description
Technical field
The invention provides a kind of index sensor of the Michelson structure for being modified CNT based on thin-core fibers, is belonged to
Technical field of optical fiber sensing.
Background technology
A kind of important Fibre Optical Sensor of optic fibre refractive index sensor, some common methods for improving transducer sensitivity
It is to carry out some special dissolvings to optical fiber or chemical treatment makes the refractive index of its environment to external world more sensitive, but these sides
Method reduces the pliability of optical fiber itself while refractive index sensitivity is improved so as to limited by some in actual applications
System.Most of index sensors can be drifted about with the increase wavelength of extraneous refractive index simultaneously, and therefore intensity will not be sent out
Raw regular or obvious fluctuating.Such sensor is easily limited by FSR (Free Spectral Rang), and not
Continuous monitoring in real time can be carried out in relatively wide ranges of indices of refraction.In the last few years, increasing people were in optical fiber table
Face deposits thin film to improve the sensing characteristicses of sensor.This kind of sensor has low cost, easily makes, makes the folding of structure
The advantages of penetrating the measurement range of rate and change with the change of external environment.
All -fiber Michelson's interferometer is a kind of important fibre optic interferometer, and its structure is divided to two kinds, and one kind is at one section
In the middle of single-mode fiber, welding goes out a structure, and the structure can inspire cladding mode, while the end face of optical fiber can plate high reflection
The silver of rate, can reflect back into the cladding mode for inspiring in fibre core and interfere with the light that transmits in fibre core, or can be by optical fiber
End face welding goes out some special constructions, can excite the cladding mode of higher level time.Second structure be by a section single-mould fiber with
Special optical fiber is welded together, and inspires cladding mode using the unmatched principle of core diameter of the single-mode fiber with special optical fiber.
The structured refractive rate sensitivity is very high, can carry out the bilingual tune of wavelength and intensity.
CNT is a kind of material for having high absorbance and the black with high refractive index to light, another aspect CNT pair
There is good compatibility can form thin film in silicon face in silicon materials.It is important that based on its sensing principle, can make
The measurement range increase of the refractive index of script structure, and as extraneous refraction index changing interferes the intensity change of wave spectrum to be carried
It is high.
The content of the invention
It is an object of the invention to provide a kind of refractive index sensing of the Michelson structure for modifying CNT based on thin-core fibers
Device.The installation cost is low, is easy to make, and can make the measurement range increase of the refractive index of script structure, and with extraneous folding
Penetrating rate change interferes the intensity change of wave spectrum to be improved.
The present invention is realized by following technology：
A kind of index sensor of the Michelson structure for modifying CNT based on thin-core fibers, it is characterised in that：By single mode
Optical fiber (1), thin-core fibers (2), differential of the arc top covering (3), CNT sedimentaries (4) composition；Single-mode fiber (1) and thin-core fibers (2)
It is connected, differential of the arc top covering (3) is connected with thin-core fibers (2), CNT sedimentaries (4) parcel thin-core fibers (2), differential of the arc top bag
The surface of layer (3).
A kind of index sensor of described Michelson structure for modifying CNT based on thin-core fibers, it is characterised in that：
Single-mode fiber (1), thin-core fibers (2), differential of the arc top covering (3) can be using G.652 single-mode fiber, the fibres of thin-core fibers (2)
Core and cladding diameter are respectively 4 μm and 124.5 μm, and length L of thin-core fibers (2) is 2mm, length l on differential of the arc top covering (3)
For 45.08 μm.
A kind of index sensor of described Michelson structure for modifying CNT based on thin-core fibers, it is characterised in that：
CNT sedimentaries (5) are uniformly deposited on the surface of optical fiber using CNT.
The present invention operation principle be：According to the interference formula of Michelson's interferometer it is：
Wherein E1And E2It is basic mode and the size of cladding mode for exciting respectively, Δ n=n1-n2It is that the fibre core of cladding mode has
Effect refractivity, l1It is two times of L, λ is operation wavelength,It is initial phase.The change of the refractive index of external environment have impact on bag
The effective refractive index of layer model, so that cause the change of phase place.
This can explain Michelson structure based on thin-core fibers with the change wavelength of external environment refractive index and strong
Degree all there occurs significantly change.Michelson structure after CNTs modifieds, as shown in Figure 2.As CNTs is a kind of
The material of high index of refraction and high absorptivity, then high index of refraction characteristic causes the effective refractive index of cladding mode to change,
This will affect the intensity of the evanescent wave of the cladding mode on thin-core fibers surface, cause wavelength and the extinction ratio of drift value interfering crest and trough
Change.When the refractive index of external environment changes, end face has been modified the thin-core fibers of CNTs and has also been changed, cladding mode
Formula evanescent wave reflex strength can use formula：
Wherein a=4 π k/ λ are the absorptances of CNT layers,ncladAnd namIt is covering and extraneous ring respectively
The refractive index in border.rX, yIt is the reflection coefficient interfered in different layers.Corresponding four layers is fiber core respectively, covering, carbon nanotube thin film
Also external environment.It can be seen that the change of external environment refractive index have impact on the change of R from formula.When external environment is reflected
When rate is less than the refractive index of covering, the increase of external environment refractive index will cause the reduction of R, it means that have little evanescent wave
Energy be reflected back toward fibre core and interfere with the basic mode of fibre core, so as to ultimately result in the reduction of extinction ratio.The change of wherein R will
The change of the R of the sensor than unmodified CNT is bigger, because for the sensing of unmodified CNT, the intensity of cladding mode is only
The Fresnel reflection being to rely between fibre cladding and external environment.Carbon nanotube thin film will improve the reflex strength of cladding mode, because
This will occur bigger change with the intensity of the change of external environment refractive index, drift value interfering crest and trough.
The invention has the beneficial effects as follows：Use a kind of simple and effective deposition process that CNTs is deposited on light in an experiment
Fine end face.Based on its sensing principle, the measurement range increase of the refractive index of script structure can be made, and with extraneous folding
Penetrating rate change interferes the intensity change of wave spectrum to be improved.The thin-core fibers structure that so deposited CNTs overcomes the limit of FSR
System.While basisThe CNT of high index of refraction will increase the effective refractive index of covering, then external environment refractive index
The cladding mode that causes of increase will reduce with the effective refractive index difference of core mode, so as to the sensor wavelength drift value with it is unmodified
The sensor of CNT is compared and will be reduced.The modification thickness of appropriate control CNT will increase the drift value of sensor intensity, can be with
Reduce the impact to wavelength as far as possible.
Description of the drawings
Fig. 1 is that the structure index sensor of the Michelson knot for modifying CNT based on thin-core fibers of the present invention shows
Fig. 2 is the change lab diagram of interference spectrum before and after sensor of the invention modification CNT
Fig. 3 is sensor of the invention with the variation diagram of the change interference spectrum of external environment refractive index
Fig. 4 is the fitted figure of the external environment refractive index with interference peaks wavelength of the present invention
Fig. 5 is the external environment refractive index and the fitted figure for interfering peak intensity of the present invention
Specific embodiment
The experimental provision of optic fibre refractive index sensor：
A kind of system of the index sensor of the Michelson structure for modifying CNT based on thin-core fibers includes a bandwidth
Light source, fiber coupler and spectrogrph.Structure after the process of Piranha solution is connected on spectrogrph and light source during experiment.It is logical
Light deposition method is crossed, during fiber end face is deposited on, output energy is 95dB to wideband light source originally, is adjusted to
The energy of 120dB, about 20mW, extend into the end face of structure in CNT solution in this case and continues 20min, light heat
Temperature can slowly be increased, uniformly structure on the surface of the optical fiber, is then immersed in the water flushing two little by deposition to make CNT
When, the CNT of non-stably depositing is rinsed out.In the thickness that the process of whole deposition is monitored to control CNT using spectrogrph,
To guarantee that the structure after modifying has good interference spectrum.
Below in conjunction with the accompanying drawings and embodiment the invention will be further described：
Referring to accompanying drawing 1, a kind of index sensor of the Michelson structure for modifying CNT based on thin-core fibers, its feature
It is：It is made up of single-mode fiber (1), thin-core fibers (2), differential of the arc top covering (3), CNT sedimentaries (4)；Single-mode fiber (1) with
Thin-core fibers (2) are connected, and differential of the arc top covering (3) is connected with thin-core fibers (2), CNT sedimentaries (4) parcel thin-core fibers (2),
The surface on differential of the arc top covering (3).Single-mode fiber (1), thin-core fibers (2), differential of the arc top covering (3) can be using G.652 single
Mode fiber, the fibre core of thin-core fibers (2) and cladding diameter are respectively 4 μm and 124.5 μm, and length L of thin-core fibers (2) is 2mm,
Length l on differential of the arc top covering (3) is 45.08 μm.CNT sedimentaries (4) are uniformly deposited on the surface of optical fiber using CNT.
Fig. 2 shows the aerial reflectance spectrum of thin-core fibers structure before and after modification.It can be seen that the structure after modification
Reflectance spectrum drifts about to long wave direction.The high index of refraction of CNT causes the change of the effective refractive index of cladding mode, dry so as to cause
Relate to wave spectrum and red shift occurs.The sensor modified is carried out into the measurement of refractive index.
Show the change of the change reflectance spectrum with extraneous refractive index.The unmodified refractive index based on thin-core fibers
Sensor refractive index scope is 1.33RIU (Refractive Index) -1.38RIU, and the sensitivity after Wavelength demodulation is
228.85nm/RIU, the sensitivity after intensity demodulation are -158.75dB/RIU.Reflectance spectrum to depositing the sensor of CNT is carried out
Demodulation finds that wave length shift is not changed significantly with unmodified, but intensity drift increases the refractive index sensitivity after demodulation
For -183.67dB/RIU, and the measurement range of the refractive index of sensor increases to 1.40.
Fig. 4 shows change of the extraneous refractive index with wavelength.
Fig. 5 shows change of the extraneous refractive index with intensity.
Claims (3)
1. it is a kind of to be based on the index sensor that thin-core fibers modify the Michelson structure of CNT (Carbon Nanotube), its
It is characterised by：It is made up of single-mode fiber (1), thin-core fibers (2), differential of the arc top covering (3), CNT sedimentaries (4)；Single-mode fiber
(1) it is connected with thin-core fibers (2), differential of the arc top covering (3) is connected with thin-core fibers (2), CNT sedimentaries (4) wrap up thin core light
Fine (2), the surface on differential of the arc top covering (3)；Sensitivity degree of the present invention is high, and structure is small, makes simple, can apply to all kinds of
In Practical Project.
2. it is according to claim 1 it is a kind of based on thin-core fibers modify CNT Michelson structure index sensor,
It is characterized in that：Single-mode fiber (1), thin-core fibers (2), differential of the arc top covering (3) can be using G.652 single-mode fiber, thin cores
The fibre core of optical fiber (2) and cladding diameter are respectively 2 μm～5 μm and 120 μm～130 μm, length L of thin-core fibers (2) for 2mm～
5mm, length l on differential of the arc top covering (3) is 40 μm～50 μm.
3. it is according to claim 1 it is a kind of based on thin-core fibers modify CNT Michelson structure index sensor,
It is characterized in that：CNT sedimentaries (4) are uniformly deposited on the surface of optical fiber using CNT.
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| Application Number | Priority Date | Filing Date | Title |
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| CN201710029943.0A CN106525770A (en) | 2017-01-12 | 2017-01-12 | Refractive index sensor adopting Michelson structure based on CNT (carbon nanotube) modified thin core fiber |
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| CN201710029943.0A CN106525770A (en) | 2017-01-12 | 2017-01-12 | Refractive index sensor adopting Michelson structure based on CNT (carbon nanotube) modified thin core fiber |
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2006171580A (en) * | 2004-12-17 | 2006-06-29 | Nippon Telegr & Teleph Corp <Ntt> | Light waveform shaper |
| US20120236314A1 (en) * | 2011-03-14 | 2012-09-20 | Imra America, Inc. | Broadband generation of mid ir, coherent continua with optical fibers |
| CN206594060U (en) * | 2017-01-12 | 2017-10-27 | 中国计量大学 | A kind of index sensor for the Michelson structure that CNT is modified based on thin-core fibers |
-
2017
- 2017-01-12 CN CN201710029943.0A patent/CN106525770A/en active Pending
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2006171580A (en) * | 2004-12-17 | 2006-06-29 | Nippon Telegr & Teleph Corp <Ntt> | Light waveform shaper |
| US20120236314A1 (en) * | 2011-03-14 | 2012-09-20 | Imra America, Inc. | Broadband generation of mid ir, coherent continua with optical fibers |
| CN206594060U (en) * | 2017-01-12 | 2017-10-27 | 中国计量大学 | A kind of index sensor for the Michelson structure that CNT is modified based on thin-core fibers |
Non-Patent Citations (2)
| Title |
|---|
| WEI CHANG WONG等: "Highly sensitive miniature photonic crystal fiber refractive index sensor based on mode field excitation" * |
| Y.C. TAN等: "Carbon-nanotube-deposited long period fiber grating for continuous refractive index sensor applications" * |
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Application publication date: 20170322 |