CN113324948A - Temperature and refractive index double-parameter sensor for mixed liquid core optical fiber long period grating - Google Patents
Temperature and refractive index double-parameter sensor for mixed liquid core optical fiber long period grating Download PDFInfo
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- 239000007788 liquid Substances 0.000 title claims abstract description 86
- 239000013307 optical fiber Substances 0.000 title description 34
- 239000000835 fiber Substances 0.000 claims abstract description 77
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims abstract description 44
- 239000010453 quartz Substances 0.000 claims abstract description 42
- 239000006185 dispersion Substances 0.000 claims abstract description 29
- 238000005253 cladding Methods 0.000 claims description 15
- PEDCQBHIVMGVHV-UHFFFAOYSA-N Glycerine Chemical compound OCC(O)CO PEDCQBHIVMGVHV-UHFFFAOYSA-N 0.000 claims description 13
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 5
- 239000003292 glue Substances 0.000 claims description 4
- 230000009977 dual effect Effects 0.000 claims 3
- 238000002360 preparation method Methods 0.000 abstract description 2
- 230000035945 sensitivity Effects 0.000 description 10
- 238000005259 measurement Methods 0.000 description 8
- 230000008859 change Effects 0.000 description 7
- 238000000411 transmission spectrum Methods 0.000 description 4
- 230000008878 coupling Effects 0.000 description 3
- 238000010168 coupling process Methods 0.000 description 3
- 238000005859 coupling reaction Methods 0.000 description 3
- 235000011187 glycerol Nutrition 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 238000005452 bending Methods 0.000 description 2
- 230000005540 biological transmission Effects 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000003825 pressing Methods 0.000 description 2
- 238000011160 research Methods 0.000 description 2
- 238000004088 simulation Methods 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000010891 electric arc Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 230000000737 periodic effect Effects 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 238000007789 sealing Methods 0.000 description 1
- 239000000377 silicon dioxide Substances 0.000 description 1
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- G—PHYSICS
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- 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
- G01N21/4133—Refractometers, e.g. differential
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
- G01K11/00—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00
- G01K11/32—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00 using changes in transmittance, scattering or luminescence in optical fibres
- G01K11/3206—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00 using changes in transmittance, scattering or luminescence in optical fibres at discrete locations in the fibre, e.g. using Bragg scattering
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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
- G01N21/4133—Refractometers, e.g. differential
- G01N2021/414—Correcting temperature effect in refractometers
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Abstract
The invention discloses a mixed liquid core fiber long period grating temperature and refractive index double-parameter sensor, which comprises a first single mode fiber, a first quartz capillary, a mixed liquid core fiber, a second quartz capillary and a second single mode fiber which are connected in sequence, wherein the fiber core of the mixed liquid core fiber is mixed liquid with a specific dispersion curve, a long period fiber grating is manufactured on the mixed liquid core fiber, and different resonance peaks in the long period fiber grating are all positioned near dispersion turning points of different modes. The invention can simultaneously measure the temperature and the refractive index, and has the advantages of small volume, low cost and simple and easy preparation method.
Description
Technical Field
The invention belongs to the technical field of optical fiber sensing and communication, and particularly relates to a temperature and refractive index dual-parameter sensor based on a mixed liquid core long-period optical fiber grating.
Background
Long Period Fiber Grating (LPFG) is one kind of fiber grating, the period is between tens to hundreds of micrometers, the principle is that the coupling of the forward transmission mode between the fibers is the principle, and the band stop characteristic is shown in the observation of the transmission end. The coupling influence of external environment such as temperature, strain, transverse load, bending and the like on optical fiber modes is large, so that the LPFG resonant wavelength shifts, and the sensor is a high-sensitivity sensor and is often used for measuring parameters such as temperature, refractive index, humidity, bending, strain and the like. With the intensive research on the LPFG, people are not limited to the research on the LPFG in a single-mode optical fiber, and a plurality of special optical fibers LPFG emerge.
When LPFG is used for temperature sensing, the main materials of the fiber core and the cladding of the common single-mode fiber are quartz, and the thermal-optical coefficients of the fiber core and the cladding are not very different and are about 7.8-10-6The temperature sensitivity of conventional single mode fiber LPFG is therefore low, typically a few tens of pm/c.
In addition, in actual sensing measurement, the sensor cannot be influenced by only one parameter, changes of temperature, humidity, strain, environmental refractive index and the like generally exist simultaneously, and particularly, the influence factor of the temperature must be considered in the measurement process of the refractive index.
Disclosure of Invention
Aiming at the problems of low sensitivity of the conventional LPFG temperature sensor and temperature crosstalk of an optical fiber refractive index sensor, the invention provides a mixed liquid core optical fiber long-period grating temperature and refractive index dual-parameter sensor which can realize high-sensitivity measurement of temperature and refractive index dual-parameters.
The technical scheme adopted by the invention is as follows:
the temperature and refractive index double-parameter sensor comprises a first single-mode fiber, a first quartz capillary tube, a mixed liquid core fiber, a second quartz capillary tube and a second single-mode fiber which are connected in sequence, wherein the fiber core of the mixed liquid core fiber is mixed liquid with a specific dispersion curve, the long-period fiber grating is prepared on the mixed liquid core fiber, and different resonance peaks in the long-period fiber grating are all located near dispersion turning points of different modes.
According to the technical scheme, the mixed liquid is a mixed liquid of glycerol and water.
According to the technical scheme, the mixed liquid core optical fiber comprises a cladding and a circular air hole, wherein the long-period fiber grating is arranged in the circular air hole, and the mixed liquid is filled in the circular air hole.
According to the technical scheme, the inner diameter of the first quartz capillary is slightly larger than that of the first single-mode fiber, and the inner diameter of the second quartz capillary is slightly larger than that of the second single-mode fiber.
According to the technical scheme, the absolute value of the thermo-optic coefficient of the mixed liquid is more than 10-4/℃。
According to the technical scheme, the refractive index of the mixed liquid is always 3.10 higher than that of the two quartz capillaries-3～7·10-3。
And connecting the tail fibers at two ends of the mixed liquid core optical fiber with the first single-mode optical fiber through the quartz capillary.
According to the technical scheme, one end of each of the first quartz capillary and the second quartz capillary, which is close to the mixed liquid core optical fiber, stores one section of mixed liquid.
And the joint of the mixed liquid core optical fiber and the quartz capillary at the two ends is sealed and fixed by ultraviolet glue.
The invention has the following beneficial effects: the invention can realize a plurality of resonance peaks working near the dispersion turning point by injecting the mixed liquid with a specific dispersion curve into the hollow optical fiber, and can realize high-sensitivity double-parameter measurement of temperature and refractive index. When the difference between the dispersion curve of the fiber core of the mixed liquid and the dispersion curve of the quartz cladding is large, the LPFG can work near the dispersion turning point under different grating periods according to the numerical simulation result. For LPFG with a specific period, the resonance peak changes greatly when the temperature changes, a plurality of modes of dispersion turning points can appear, the sensitivity of different resonance peaks near the dispersion turning points is high and different, and the simultaneous high-sensitivity measurement of double parameters can be realized.
Drawings
The invention will be further described with reference to the accompanying drawings and examples, in which:
FIG. 1 is a schematic structural diagram of a mixed liquid core fiber long period grating temperature and refractive index dual-parameter sensor according to an embodiment of the present invention;
FIG. 2 is a dispersion curve of a mixed liquid and quartz according to an embodiment of the present invention
FIG. 3 is a graph showing the relationship between the grating period and the resonant wavelength for different cladding modes at 25 deg.C, 28 deg.C, and 31 deg.C for a long-period grating in accordance with an embodiment of the present invention.
In the figure: 1. the optical fiber comprises a first single-mode optical fiber, 2, a first quartz capillary, 3, a mixed liquid core optical fiber, 4, a second quartz capillary, 5, a second single-mode optical fiber, 6, mixed liquid, 7, a long-period grating and 8, and an ultraviolet glue sealing joint.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
The mixed liquid core optical fiber long period grating temperature and refractive index double-parameter sensor can realize simultaneous measurement of temperature and refractive index double parameters.
The temperature and refractive index double-parameter sensor based on the mixed liquid core fiber long-period grating comprises a first single-mode fiber 1, a first quartz capillary tube 2, a mixed liquid core fiber 3, a second quartz capillary tube 4 and a second single-mode fiber 5 which are connected in sequence. The tail fibers at two ends of the mixed liquid core optical fiber 3 penetrate through the quartz capillary and are connected with the single mode optical fiber. The mixed liquid core optical fiber 3 is a round hole optical fiber, the mixed liquid 6 of glycerin and water is injected into the fiber core, and a long-period optical fiber grating is manufactured on the mixed liquid, and different resonance peaks in the long-period optical fiber grating are all positioned near dispersion turning points of different modes. That is, the long period grating in the mixed liquid core fiber will have dispersion turning points of multiple modes with temperature change, and different resonance peaks are all located near the dispersion turning points. Therefore, a plurality of resonance peaks working near the dispersion turning point can be realized, and high-sensitivity double-parameter measurement on temperature and refractive index can be realized.
Further, a first quartz capillary 2 connects the first single mode fiber 1 and the mixed liquid core fiber 3, and a second quartz capillary 2The quartz capillary 4 is connected with the second single-mode fiber 5 and the mixed liquid core fiber 3, and the joint of the mixed liquid core fiber 3 and the quartz capillary at the two ends is sealed and fixed by ultraviolet glue. The long period fiber grating can use CO2Laser, arc discharge, metal channel plate pressing and the like. For example, the grating may be fabricated on the cladding of the mixed liquid core fiber 3, or the shape of the mixed liquid core fiber may be modulated by pressing the entire structure with a metal groove.
In the invention, the single-mode optical fiber and the mixed liquid core optical fiber can be connected through the quartz capillary, so that the single-mode optical fiber and the mixed liquid core optical fiber can be well butted, and a section of liquid can be stored in the quartz capillary to reduce the influence caused by the volume change of the liquid when the temperature changes.
The sensor of the invention injects liquid into the hollow optical fiber to serve as a fiber core, the liquid at the fiber core can be made into mixed liquid with refractive index slightly higher than that of quartz by using materials with higher thermo-optic coefficient according to a certain proportion, for example, the thermo-optic coefficient is-2.8.10-4Glycerol and thermo-optic coefficient of-1.45.10/deg.C-4When water was mixed at 94% and 6% by volume, the dispersion curve of the mixed liquid and the quartz capillary at this time is shown in fig. 2. The dispersion curve of the mixed liquid is greatly different from that of the quartz capillary, and the refractive index of the mixed liquid is always higher than that of the quartz capillary by 3-10-3～7·10-3The relationship between the period and the wavelength corresponding to the different modes of the LPFG is shown in fig. 3. When the period of the grating is determined, dispersion turning points corresponding to a plurality of modes can be generated in the transmission spectrum corresponding to the LPFG along with the temperature change, and when light enters a cladding layer with a low thermal light coefficient through the LPFG coupling from a liquid fiber core with a high thermal light coefficient, the transmission spectrum can generate larger wavelength drift along with the temperature change. Near the dispersion inflection point of the LPFG, the corresponding sensor has extremely high sensitivity. Because the sensitivities of different modes are different, the multi-parameter measurement can be carried out on the change of the external environment, and the sensitivity is very high.
In the preferred embodiment of the present invention, the core diameter of the first single mode fiber 1 and the second single mode fiber 5 is 8.2 microns, and the cladding diameter is 125 microns; the inner diameters of the air holes of the first quartz capillary and the second quartz capillary are slightly larger than that of the single-mode fiber, and are about 127 μm in the embodiment of the invention, the outer diameter is 200-300 μm, the outer diameter is 250 μm in the embodiment of the invention, the cladding diameter of the mixed liquid core fiber is 125 μm, and the diameter of the inner circular hole is 10 μm.
The mixed liquid is a light guide material with higher thermo-optic coefficient, and the thermo-optic coefficient is more than 10-4V. C. The mixture of glycerol and water can be selected, the shorter the filling liquid length of the hollow-core optical fiber with small aperture is, the shorter the manufacturing time is because the filling liquid speed is lower, but the grating length is about 2-4cm, and a length is reserved to connect with a capillary, so the filling length of the mixed liquid in the liquid-core optical fiber is about 4-8 cm.
The phase matching curves of different cladding modes at different temperatures obtained by simulation calculation are shown in fig. 3, and the long-period grating can generate a multi-dispersion turning point along with the temperature change when the period is hundreds of microns.
The long-period grating is generally formed by performing refractive index periodic modulation on an optical fiber, a fundamental mode is coupled with a cladding mode when being transmitted forwards, different resonance loss bands generate transmission spectrums at different central wavelengths, and the central wavelength lambda of the mth-order mode transmission spectrumres,mDetermined by the phase matching condition:
where a represents the period of the grating,
the effective refractive index of the fundamental mode is expressed,
representing the effective refractive index of the m-order cladding mode. The temperature sensitivity of the LPFG can be expressed as:
where alpha is the thermal expansion coefficient of the core of the mixed liquid, T is the temperature of the external environment, gamma represents the waveguide dispersion, and gamma istempRepresents the temperature-dependent coefficient, expressed as:
in which ξcoAnd xiclIs the thermo-optic coefficient of the mixed liquid core and the silica cladding. Due to thermo-optic coefficient xi of liquid corecoFar greater than thermo-optic coefficient xi of quartz claddingclAnd in the vicinity of the dispersion turning point,
the value of (c) tends to be infinite, and thus the corresponding sensor has extremely high temperature sensitivity.
In summary, the high thermo-optic coefficient of the liquid fiber core of the sensor of the invention enables the sensor to have high sensitivity to temperature, the dispersion curve of the mixed liquid and the dispersion curve of quartz have larger difference by changing the components of the mixed liquid, after a proper period is selected to manufacture the long-period grating, dispersion turning points of different modes can appear in a smaller wavelength range along with the change of the temperature of the environment, and different resonance peaks in the long-period fiber grating are all positioned near the dispersion turning points of different modes, so that the sensitivity is higher and different, thereby the sensor can simultaneously measure double parameters of temperature and refractive index, and has small volume, low cost and simple and easy preparation method.
It will be understood that modifications and variations can be made by persons skilled in the art in light of the above teachings and all such modifications and variations are intended to be included within the scope of the invention as defined in the appended claims.
Claims (9)
1. The double-parameter sensor is characterized by comprising a first single-mode fiber, a first quartz capillary tube, a mixed liquid core fiber, a second quartz capillary tube and a second single-mode fiber which are sequentially connected, wherein the fiber core of the mixed liquid core fiber is mixed liquid with a specific dispersion curve, a long-period fiber grating is manufactured on the mixed liquid core, and different resonance peaks in the long-period fiber grating are all located near dispersion turning points of different modes.
2. The mixed liquid core fiber long period grating temperature and refractive index dual-parameter sensor of claim 1, wherein the mixed liquid is a mixed liquid of glycerol and water.
3. The mixed liquid core fiber long period grating temperature and refractive index dual parameter sensor of claim 1 wherein the mixed liquid core fiber comprises a cladding and a circular air hole, the circular air hole is filled with the long period fiber grating and the mixed liquid.
4. The mixed liquid core fiber long period grating temperature and refractive index dual parameter sensor of claim 1, wherein the first quartz capillary has an inner diameter slightly larger than the first single mode fiber, and the second quartz capillary has an inner diameter slightly larger than the second single mode fiber.
5. The mixed liquid core fiber long period grating temperature and refractive index dual-parameter sensor of claim 1, wherein the absolute value of the thermo-optic coefficient of the mixed liquid is greater than 10-4/℃。
6. The mixed liquid core fiber long period grating temperature and refractive index dual parameter sensor of claim 1 wherein the mixed liquid refractive index is always higher than the two quartz capillaries.
7. The mixed liquid core fiber long period grating temperature and refractive index dual-parameter sensor of claim 1, wherein the pigtails at both ends of the mixed liquid core fiber are connected with the first single mode fiber through a quartz capillary.
8. The mixed liquid core fiber long period grating temperature and refractive index dual-parameter sensor according to any one of claims 1-7, wherein the first quartz capillary and the second quartz capillary store a section of mixed liquid at the end near the mixed liquid core fiber.
9. The mixed liquid core fiber long period grating temperature and refractive index double-parameter sensor according to claim 8, wherein the joint of the mixed liquid core fiber and the quartz capillary at both ends is sealed and fixed by ultraviolet glue.
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Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101261165A (en) * | 2008-04-24 | 2008-09-10 | 上海交通大学 | Concentration tunable mixing liquid core optical fiber temperature sensor |
| CN203811537U (en) * | 2014-01-15 | 2014-09-03 | 中国计量学院 | Refraction index and temperature measurement sensor based on LPFG (Long Period Fiber Grating) |
| CN107490561A (en) * | 2017-07-24 | 2017-12-19 | 温州大学 | A kind of highly sensitive inclined optical fiber grating low-refraction sensing detection device |
| CN107687907A (en) * | 2017-07-17 | 2018-02-13 | 东北大学 | A kind of temperature sensing method based on liquid filling hollow annular fiber grating |
| CN109211838A (en) * | 2018-07-25 | 2019-01-15 | 东北大学 | A kind of long period photonic crystal fiber grating index sensor of hypersensitivity |
| CN110260920A (en) * | 2019-06-26 | 2019-09-20 | 哈尔滨工程大学 | Temperature and refractive index dual sampling device based on directional coupler and long-period fiber grating |
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- 2021-05-28 CN CN202110590404.0A patent/CN113324948A/en active Pending
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101261165A (en) * | 2008-04-24 | 2008-09-10 | 上海交通大学 | Concentration tunable mixing liquid core optical fiber temperature sensor |
| CN203811537U (en) * | 2014-01-15 | 2014-09-03 | 中国计量学院 | Refraction index and temperature measurement sensor based on LPFG (Long Period Fiber Grating) |
| CN107687907A (en) * | 2017-07-17 | 2018-02-13 | 东北大学 | A kind of temperature sensing method based on liquid filling hollow annular fiber grating |
| CN107490561A (en) * | 2017-07-24 | 2017-12-19 | 温州大学 | A kind of highly sensitive inclined optical fiber grating low-refraction sensing detection device |
| CN109211838A (en) * | 2018-07-25 | 2019-01-15 | 东北大学 | A kind of long period photonic crystal fiber grating index sensor of hypersensitivity |
| CN110260920A (en) * | 2019-06-26 | 2019-09-20 | 哈尔滨工程大学 | Temperature and refractive index dual sampling device based on directional coupler and long-period fiber grating |
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