CN112525297A - Liquid level sensing probe based on fiber bragg grating - Google Patents
Liquid level sensing probe based on fiber bragg grating Download PDFInfo
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- CN112525297A CN112525297A CN202011539309.XA CN202011539309A CN112525297A CN 112525297 A CN112525297 A CN 112525297A CN 202011539309 A CN202011539309 A CN 202011539309A CN 112525297 A CN112525297 A CN 112525297A
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- 239000000835 fiber Substances 0.000 title claims abstract description 67
- 239000007788 liquid Substances 0.000 title claims abstract description 52
- 239000000523 sample Substances 0.000 title claims abstract description 30
- 238000005253 cladding Methods 0.000 claims abstract description 52
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims abstract description 22
- 239000013307 optical fiber Substances 0.000 claims abstract description 22
- 239000000377 silicon dioxide Substances 0.000 claims abstract description 11
- 235000012239 silicon dioxide Nutrition 0.000 claims abstract description 9
- 239000002131 composite material Substances 0.000 claims abstract description 5
- 229910052732 germanium Inorganic materials 0.000 claims abstract description 4
- GNPVGFCGXDBREM-UHFFFAOYSA-N germanium atom Chemical compound [Ge] GNPVGFCGXDBREM-UHFFFAOYSA-N 0.000 claims abstract description 4
- -1 polytetrafluoroethylene Polymers 0.000 claims abstract description 4
- 229920001343 polytetrafluoroethylene Polymers 0.000 claims abstract description 4
- 239000004810 polytetrafluoroethylene Substances 0.000 claims abstract description 4
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 claims abstract description 3
- 229910052796 boron Inorganic materials 0.000 claims abstract description 3
- 230000003287 optical effect Effects 0.000 claims description 25
- 239000004642 Polyimide Substances 0.000 claims description 3
- 229920001721 polyimide Polymers 0.000 claims description 3
- 229920002635 polyurethane Polymers 0.000 claims description 3
- 239000004814 polyurethane Substances 0.000 claims description 3
- 230000001681 protective effect Effects 0.000 claims description 3
- 230000008859 change Effects 0.000 abstract description 5
- 238000000034 method Methods 0.000 abstract description 4
- 230000005540 biological transmission Effects 0.000 abstract description 3
- 238000010892 electric spark Methods 0.000 abstract description 3
- PXGOKWXKJXAPGV-UHFFFAOYSA-N Fluorine Chemical compound FF PXGOKWXKJXAPGV-UHFFFAOYSA-N 0.000 abstract 1
- 229910052731 fluorine Inorganic materials 0.000 abstract 1
- 239000011737 fluorine Substances 0.000 abstract 1
- 238000005259 measurement Methods 0.000 description 6
- 230000035945 sensitivity Effects 0.000 description 4
- 238000005516 engineering process Methods 0.000 description 3
- 230000008569 process Effects 0.000 description 3
- 230000007797 corrosion Effects 0.000 description 2
- 238000005260 corrosion Methods 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 238000012544 monitoring process Methods 0.000 description 2
- 239000012071 phase Substances 0.000 description 2
- NWHAUAZVLJCRBB-UHFFFAOYSA-N [Si](=O)=O.[B] Chemical compound [Si](=O)=O.[B] NWHAUAZVLJCRBB-UHFFFAOYSA-N 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000009835 boiling Methods 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 230000003111 delayed effect Effects 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 230000003993 interaction Effects 0.000 description 1
- 239000007791 liquid phase Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000035484 reaction time Effects 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 238000009834 vaporization Methods 0.000 description 1
- 230000008016 vaporization Effects 0.000 description 1
Images
Classifications
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F23/00—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm
- G01F23/22—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water
- G01F23/28—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water by measuring the variations of parameters of electromagnetic or acoustic waves applied directly to the liquid or fluent solid material
- G01F23/284—Electromagnetic waves
- G01F23/292—Light, e.g. infrared or ultraviolet
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/02—Optical fibres with cladding with or without a coating
- G02B6/02057—Optical fibres with cladding with or without a coating comprising gratings
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/02—Optical fibres with cladding with or without a coating
- G02B6/036—Optical fibres with cladding with or without a coating core or cladding comprising multiple layers
- G02B6/03616—Optical fibres characterised both by the number of different refractive index layers around the central core segment, i.e. around the innermost high index core layer, and their relative refractive index difference
- G02B6/03622—Optical fibres characterised both by the number of different refractive index layers around the central core segment, i.e. around the innermost high index core layer, and their relative refractive index difference having 2 layers only
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/44—Mechanical structures for providing tensile strength and external protection for fibres, e.g. optical transmission cables
- G02B6/4401—Optical cables
- G02B6/4429—Means specially adapted for strengthening or protecting the cables
- G02B6/443—Protective covering
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- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Electromagnetism (AREA)
- Thermal Sciences (AREA)
- Fluid Mechanics (AREA)
- Measurement Of Levels Of Liquids Or Fluent Solid Materials (AREA)
- Measuring Temperature Or Quantity Of Heat (AREA)
Abstract
The invention relates to an optical fiber liquid level sensing probe based on an optical fiber grating. The liquid level sensing probe comprises a long-period fiber grating and a composite material outer sheath. The long-period fiber grating measures the liquid level information by measuring the change of the refractive index of the surrounding environment. The fiber core is made of silicon dioxide doped with germanium or boron, the inner cladding is made of silicon dioxide, the outer cladding is made of silicon dioxide doped with fluorine, and the outer sheath is made of composite materials such as polytetrafluoroethylene. The sensor utilizes optical fibers as a sensitive element and a transmission channel, modulates the propagation behavior mode of light, and obtains accurate liquid level information by measuring the change of light wave parameters. The measuring method is intrinsically safe, the front end of the sensor is passive, no complex cable is required to be connected, no risk of electric spark exists, and the device is suitable for the ultralow-temperature environment.
Description
Technical Field
The invention belongs to the technical field of fiber grating sensing, and particularly relates to a liquid level sensing probe based on fiber gratings.
Background
The existing domestic low-temperature liquid level measurement technology mainly uses mechanical and electronic liquid level sensors, and the sensors have the defects of poor measurement precision, relatively delayed reaction time and poor safety and cannot meet the requirement of real-time continuous liquid level change monitoring. Internationally, the countries such as the United states and the like successively develop novel ultrasonic liquid level sensors and optical fiber liquid level sensors, and the measurement system and the product series have high precision, complete functions and high automation degree. The optical fiber sensor has the advantages of low power consumption, corrosion resistance, ultralow temperature environment resistance, electromagnetic interference resistance, remote monitoring and high sensitivity, so that the optical fiber sensor becomes the future development direction of low-temperature liquid level measurement.
Generally, the low-temperature liquid has the characteristics of small density, low boiling point, easy vaporization and the like, and when the liquid capacity changes, the liquid in the container is frequently converted between a gas phase, a liquid phase or a gas-liquid two-phase state, so that the liquid level measurement precision is greatly influenced. On the other hand, the liquid capacity can generate larger temperature impact in the changing process, the liquid level sensor needs to be normal in function within the temperature impact range, the structure is not damaged, electric sparks are not generated outwards in the working process of the instrument, and the safety of the container is guaranteed.
Disclosure of Invention
The invention aims to overcome the defects and provide an optical fiber liquid level sensing probe capable of resisting ultralow temperature, through the design of a fiber core, an inner cladding, an outer cladding and an outer sheath, optical fibers are used as a sensitive element and a transmission channel to modulate the propagation behavior mode of light, accurate liquid level information is obtained by measuring the change of light wave parameters, the measuring means is intrinsically safe, the front end of the sensor is passive, no complex cable is required to be connected, no risk of electric spark exists, and the optical fiber liquid level sensing probe is suitable for the ultralow temperature environment.
In order to achieve the above purpose, the invention provides the following technical scheme:
the invention provides a liquid level sensing probe based on fiber bragg grating, which sequentially comprises a coaxial fiber core, an inner cladding, an outer cladding and an outer sheath from inside to outside;
the fiber core is used for transmitting optical signals; the fiber core is provided with a fiber grating structure and is used for diffraction of optical signals;
the inner cladding is used for diffracting the optical signal transmitted in the fiber core to the inner surface of the outer cladding;
the outer cladding is used for transmitting the optical signal diffracted by the inner cladding to the outer surface of the outer cladding so that the optical signal interacts with the medium to be detected;
the outer sheath is of a hollow structure, protects the optical fiber liquid level sensing probe and enables a medium to be detected to contact with the outer surface of the outer sheath through the protective sheath;
the refractive index of the core > the refractive index of the inner cladding > the refractive index of the outer cladding.
Furthermore, the fiber core is silicon dioxide doped with germanium or boron, and the refractive index is more than or equal to 1.45.
Furthermore, the length of the fiber grating structure of the fiber core is less than or equal to 60mm, and the period is hundreds of microns.
Furthermore, the light source emitting the optical signal is a swept-frequency laser or a wide-bandwidth light source, and the wavelength is 1300nm to 1700 nm.
Furthermore, the inner cladding is silicon dioxide, and the refractive index is 1.445-1.45.
Further, the outer cladding layer is fluorine-doped silicon dioxide, and the refractive index is 1.44-1.445.
Further, the outer sheath is made of a composite material which can resist 20K ultralow temperature; the material of the outer sheath includes but is not limited to polytetrafluoroethylene, polyimide or polyurethane.
Furthermore, a gap is arranged between the outer sheath and the outer cladding, and the medium to be measured can enter between the outer sheath and the outer cladding and contact with the outer surface of the outer cladding.
Furthermore, the number of the fiber grating structures arranged on the fiber core is more than or equal to 2.
Furthermore, the gap between the outer sheath and the outer sheath is more than or equal to 0.55 mm.
Compared with the prior art, the invention has the following beneficial effects:
(1) the invention relates to a liquid level sensing probe based on a fiber bragg grating, which realizes transmission of optical signals and diffraction of the optical signals from a fiber core to an outer cladding layer simultaneously by designing the structures of the fiber core, the inner cladding, the outer cladding and the outer sheath, particularly by matching the refractive indexes of the fiber core, the inner cladding and the outer cladding, and can improve detection sensitivity.
(2) The fiber core is provided with the fiber grating structure, the fiber grating with consistent center wavelength, bandwidth and sensitivity is established to construct the sensing network in a time division multiplexing mode, and the front end of the sensor is passive and does not need to be connected with a complex cable.
(3) The invention is provided with the ultralow temperature resistant outer sheath, so that the optical fiber liquid level sensing probe is suitable for low temperature environment and has good application prospect in the field of low temperature liquid level measurement.
Drawings
FIG. 1 is a schematic view of the overall structure of a liquid level sensing probe based on fiber bragg grating according to the present invention;
FIG. 2 is a schematic cross-sectional view of a liquid level sensing probe based on fiber bragg grating according to the present invention;
FIG. 3 is a schematic side view of a liquid level sensing probe based on fiber bragg gratings according to the present invention.
Detailed Description
The features and advantages of the present invention will become more apparent and appreciated from the following detailed description of the invention.
The word "exemplary" is used exclusively herein to mean "serving as an example, embodiment, or illustration. Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments. While the various aspects of the embodiments are presented in drawings, the drawings are not necessarily drawn to scale unless specifically indicated.
The low-temperature liquid level sensing of the invention adopts the optical fiber sensing technology to monitor the liquid level in the container in real time. The optical fiber liquid level sensing probe adopts an optical fiber grating array technology, establishes optical fiber gratings with consistent center wavelength, bandwidth and sensitivity characteristics, and constructs a sensing network in a time division multiplexing mode. The structure of the optical fiber liquid level sensing probe is shown in figures 1,2 and 3. The optical signal is diffracted when passing through the fiber grating inscribed on the sensing fiber, and the central wavelength of the diffracted light is affected by the environment to generate drift and is transmitted back to the optical signal modem. By demodulating the central wavelength distribution of the reflected light signal, the environmental information of any grating point on the optical fiber is obtained, and the solution level is accurately positioned.
In the process of measuring the liquid level of the optical fiber, the optical signal modem is arranged outside the storage box and is not influenced by the ultralow-temperature environment of the storage box. The optical fiber liquid level sensing probe is arranged in the storage tank, is stable in nature, resistant to corrosion and high pressure, and is made of low-temperature materials and low-temperature coatings to normally transmit optical signal sensitive surrounding environment information in an ultralow-temperature environment. The specific scheme is as follows:
the invention provides a liquid level sensing probe based on fiber bragg grating, which sequentially comprises a coaxial fiber core 1, an inner cladding 3, an outer cladding 4 and an outer sheath 6 from inside to outside;
the fiber core 1 is used for transmitting optical signals; the fiber core 1 is provided with a fiber grating structure 5 for diffraction of optical signals, the central wavelength of diffraction optical signals is related to the refractive index of the surrounding environment, and the refractive index parameter of the surrounding environment is obtained by measuring the central wavelength of the long-period fiber grating, so that accurate liquid level information in the container is obtained;
the inner cladding 3 is used for diffracting the optical signal transmitted in the fiber core 1 to the inner surface of the outer cladding 4;
the outer cladding layer 4 is used for further transmitting the optical signal diffracted by the inner cladding layer 3 to the outer surface of the outer cladding layer 4, so that the optical signal and a medium to be detected in the surrounding environment generate interaction;
the outer sheath 6 is of a hollow structure, protects the optical fiber liquid level sensing probe and enables a medium to be detected to contact with the outer surface of the outer sheath 4 through the protective sheath 6;
the refractive index of the core 1 > the refractive index of the inner cladding 3 > the refractive index of the outer cladding 4.
Furthermore, the fiber core 1 is doped with germanium or boron silicon dioxide, and the refractive index is more than or equal to 1.45.
Furthermore, the fiber grating structure length of the fiber core 1 is less than or equal to 60mm, and the period is hundreds of microns.
Furthermore, the light source for emitting the optical signal is a swept-frequency laser or a wide-bandwidth light source, and the wavelength is 1300nm to 1700 nm.
Further, the inner cladding 3 is silicon dioxide, and the refractive index is 1.445-1.45, preferably 1.45.
Further, the outer cladding layer 4 is fluorine-doped silicon dioxide, and has a refractive index of 1.44-1.445, preferably 1.445.
Further, the outer sheath 6 is made of composite material which can resist ultra-low temperature; preferably, the outer sheath 6 is made of polytetrafluoroethylene, polyimide or polyurethane, so as to reduce the strain of the optical fiber sensor caused by temperature impact and the change of the central wavelength and the light intensity.
Further, a gap is formed between the outer sheath 6 and the outer cladding 4, and a medium to be measured can enter between the outer sheath 6 and the outer cladding 4 and contact with the outer surface of the outer cladding 4, namely the outer sheath 6 and the outer cladding 4 are loosely wrapped.
Further, the number of the fiber grating structures 5 arranged on the fiber core 1 is more than or equal to 2, that is, the liquid level height of the solution in the container to be measured is determined according to the received light intensity and the central wavelength of the reflected light returned by each fiber grating sensor by at least two fiber grating structures 5 continuously inscribed on the fiber core 1.
Furthermore, the gap between the outer sheath 6 and the outer sheath 4 is more than or equal to 0.55 mm.
The invention has been described in detail with reference to specific embodiments and illustrative examples, but the description is not intended to be construed in a limiting sense. Those skilled in the art will appreciate that various equivalent substitutions, modifications or improvements may be made to the technical solution of the present invention and its embodiments without departing from the spirit and scope of the present invention, which fall within the scope of the present invention. The scope of the invention is defined by the appended claims.
Those skilled in the art will appreciate that those matters not described in detail in the present specification are well known in the art.
Claims (10)
1. A liquid level sensing probe based on fiber bragg grating is characterized by sequentially comprising a coaxial fiber core (1), an inner cladding (3), an outer cladding (4) and an outer sheath (6) from inside to outside;
the fiber core (1) is used for transmitting optical signals; the fiber core (1) is provided with a fiber grating structure (5) for diffraction of optical signals;
the inner cladding (3) is used for diffracting the optical signal transmitted in the fiber core (1) to the inner surface of the outer cladding (4);
the outer cladding layer (4) is used for transmitting the optical signal diffracted by the inner cladding layer (3) to the outer surface of the outer cladding layer (4) so that the optical signal interacts with a medium to be detected;
the outer sheath (6) is of a hollow structure, protects the optical fiber liquid level sensing probe and enables a medium to be detected to contact with the outer surface of the outer sheath (4) through the protective sheath (6);
the refractive index of the fiber core (1) is more than that of the inner cladding (3) and more than that of the outer cladding (4).
2. The liquid level sensing probe based on the fiber bragg grating as claimed in claim 1, wherein the fiber core (1) is silica doped with germanium or boron, and the refractive index is larger than or equal to 1.45.
3. The fiber grating-based liquid level sensing probe as claimed in claim 1, wherein the fiber grating structure (5) of the fiber core (1) has a length of 60mm or less and a period of several hundred microns.
4. The fiber grating-based liquid level sensing probe according to claim 1, wherein the light source emitting the optical signal is a swept-frequency laser or a broad bandwidth light source, and the wavelength is 1300nm to 1700 nm.
5. The liquid level sensing probe based on the fiber bragg grating as claimed in claim 1, wherein the inner cladding (3) is silicon dioxide, and the refractive index is 1.445-1.45.
6. The fiber grating-based liquid level sensing probe as claimed in claim 1, wherein the outer cladding (4) is fluorine-doped silica with a refractive index of 1.44-1.445.
7. The fiber grating-based liquid level sensing probe according to claim 1, wherein the outer sheath (6) is made of a composite material resistant to ultra-low temperature; the outer sheath (6) is made of polytetrafluoroethylene, polyimide or polyurethane.
8. The fiber bragg grating-based liquid level sensing probe as claimed in claim 1, wherein a gap is formed between the outer sheath (6) and the outer cladding (4), and a medium to be measured can enter between the outer sheath (6) and the outer cladding (4) and contact with the outer surface of the outer cladding (4).
9. The liquid level sensing probe based on the fiber bragg grating as claimed in claim 1, wherein the number of the fiber bragg grating structures (5) arranged on the fiber core (1) is more than or equal to 2.
10. The fiber bragg grating based liquid level sensing probe according to any one of claims 1 to 8, wherein the gap between the outer sheath (6) and the outer sheath (4) is more than or equal to 0.55 mm.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202011539309.XA CN112525297A (en) | 2020-12-23 | 2020-12-23 | Liquid level sensing probe based on fiber bragg grating |
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| CN202011539309.XA CN112525297A (en) | 2020-12-23 | 2020-12-23 | Liquid level sensing probe based on fiber bragg grating |
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Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20080085080A1 (en) * | 2006-10-05 | 2008-04-10 | Harris Corporation | Fiber Optic Device for Measuring a Parameter of Interest |
| CN101194160A (en) * | 2005-05-26 | 2008-06-04 | 三菱电机株式会社 | Optical fiber sensor |
| CN102226725A (en) * | 2011-03-29 | 2011-10-26 | 哈尔滨工程大学 | Inner-wall waveguide long-time cycle fiber grating sensor |
| CN103149629A (en) * | 2011-12-07 | 2013-06-12 | 西安金和光学科技有限公司 | Fluorescence fiber grating |
| CN112067843A (en) * | 2020-09-07 | 2020-12-11 | 桂林电子科技大学 | Optical fiber acceleration measuring device based on fiber core mismatch |
-
2020
- 2020-12-23 CN CN202011539309.XA patent/CN112525297A/en active Pending
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101194160A (en) * | 2005-05-26 | 2008-06-04 | 三菱电机株式会社 | Optical fiber sensor |
| US20080085080A1 (en) * | 2006-10-05 | 2008-04-10 | Harris Corporation | Fiber Optic Device for Measuring a Parameter of Interest |
| CN102226725A (en) * | 2011-03-29 | 2011-10-26 | 哈尔滨工程大学 | Inner-wall waveguide long-time cycle fiber grating sensor |
| CN103149629A (en) * | 2011-12-07 | 2013-06-12 | 西安金和光学科技有限公司 | Fluorescence fiber grating |
| CN112067843A (en) * | 2020-09-07 | 2020-12-11 | 桂林电子科技大学 | Optical fiber acceleration measuring device based on fiber core mismatch |
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Application publication date: 20210319 |