CN102928045A - Optical fiber Michelson interference liquid level sensor - Google Patents
Optical fiber Michelson interference liquid level sensor Download PDFInfo
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- CN102928045A CN102928045A CN2012104883692A CN201210488369A CN102928045A CN 102928045 A CN102928045 A CN 102928045A CN 2012104883692 A CN2012104883692 A CN 2012104883692A CN 201210488369 A CN201210488369 A CN 201210488369A CN 102928045 A CN102928045 A CN 102928045A
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Abstract
The invention discloses an optical fiber Michelson interference liquid level sensor. A light guide single-mode optical fiber is arranged on the left end surface of a frame; a multi-mode optical fiber is arranged at the tail end of the light guide single-mode optical fiber; a sensitive single-mode optical fiber of which the tail end is installed on the frame is arranged at the tail end of the multi-mode optical fiber; and a high-reflection film is arranged at the tail end of the sensitive single-mode optical fiber. By utilizing the prepared optical fiber Michelson interference liquid level sensor, the liquid levels of water and glycerol-water solutions of different mass concentrations are tested, and the test result shows that the optical fiber Michelson interference liquid level sensor can be used for testing the liquid level change of water and glycerol-water solutions of different mass concentrations; and along with the increase of the mass concentrations of the glycerol-water solutions, the sensitivity degree of the optical fiber Michelson interference liquid level sensor is also increased. The optical fiber Michelson interference liquid level sensor can also be used for testing the liquid level of other liquids.
Description
Technical field
The invention belongs to sensor technical field, be specifically related to liquid level sensor.
Background technology
Liquid level sensor is the surveying instrument of tracer liquid height, and important application is arranged in many aspects, such as fuel storage system, and water level monitoring and some chemical reaction process monitorings etc.At present, liquid level sensor based on the Fibre Optical Sensor principle is once moral interfere type structure of Mach mostly, Fiber Bragg Grating FBG formula structure, long-period fiber grating formula structure and multiple-mode interfence formula structure, long-period fiber grating and Mach once moral interfere type liquid level sensor are generally the transmission-type structure, degree of being practical is lower, and the complex manufacturing process of long-period fiber grating formula liquid level sensor, cost is high, although Fiber Bragg Grating FBG formula humidity sensor stability better, but need when being used for level gauging Fiber Bragg Grating FBG is corroded (physical strength that has reduced sensor) or utilizes comparatively complicated mechanical strain structure, multimode interferometric structure based on coreless fiber is simple, but light loss is larger.Therefore, all be difficult to satisfy the demand of using.
Summary of the invention
Technical matters to be solved by this invention is to overcome the shortcoming of above-mentioned liquid level sensor, provides a kind of reasonable in design, simple in structure, highly sensitive, practical optical fiber Michelson to interfere liquid level sensor.
Solving the problems of the technologies described above the technical scheme that adopts is: be provided with the leaded light single-mode fiber in the framework left side, the tail end of leaded light single-mode fiber is provided with multimode optical fiber, the tail end of multimode optical fiber is provided with tail end and is installed in sensing single-mode fiber on the framework, and the tail end of sensing single-mode fiber is provided with high-reflecting film.
The core diameter of leaded light single-mode fiber of the present invention is 8～10 μ m.The core diameter of multimode optical fiber is 50 μ m or 62.5 μ m or 105 μ m, and the length of multimode optical fiber is 1～3mm.The core diameter of sensing single-mode fiber is 8～10 μ m, and the length of sensing single-mode fiber 3 is at least 1cm.The thickness of high-reflecting film is 1.5～3 μ m.
Diameter the best of the fibre core of leaded light single-mode fiber 1 of the present invention is 9 μ m.Core diameter the best of multimode optical fiber 2 is 105 μ m, and length the best of multimode optical fiber 2 is 2mm.Core diameter the best of sensing single-mode fiber 3 is 9 μ m, and the length of sensing single-mode fiber 3 is at least 1cm.Thickness the best of high-reflecting film is 2 μ m.
The diameter of the fibre core of sensing single-mode fiber of the present invention is identical with the core diameter of leaded light single-mode fiber.
Because the present invention adopts the tail end welding multimode optical fiber of leaded light single-mode fiber, the tail end welding sensing single-mode fiber of multimode optical fiber, the tail end plating high-reflecting film of sensing single-mode fiber consists of the optical fiber Michelson and interferes liquid level sensor.The optical fiber Michelson of embodiment 1 interferes liquid level sensor that the liquid level of the glycerine water solution of water and different quality concentration is tested, test result shows that the present invention can be used for the liquid level variation of test water, the glycerine water solution of test variable concentrations, along with the mass concentration increase of glycerine water solution, the optical fiber Michelson interferes the sensitivity of liquid level sensor to improve.The present invention also can be used for testing the liquid level of other liquid.
Description of drawings
Fig. 1 is embodiments of the invention 1 structural representations.
Fig. 2 is the liquid level and the linear relationship chart of interfering wavelength of the embodiment of the invention 1 test water.
Fig. 3 is the liquid level and the linear relationship chart of interfering wavelength of the embodiment of the invention 2 test water and variable concentrations glycerine water solution.
Embodiment
The present invention is described in more detail below in conjunction with drawings and Examples, but the invention is not restricted to these embodiment.
Embodiment 1
In Fig. 1, it is to be connected by leaded light leaded light single-mode fiber 1, multimode optical fiber 2, sensing single-mode fiber 3, high-reflecting film 4, framework 5 to consist of that the optical fiber Michelson of the present embodiment is interfered liquid level sensor.
Center pit in framework 5 left sides is the commodity of selling on the market with 502 gluing leaded light single-mode fiber 1,502 glue that are connected to, and company limited produces by Taizhou plain multi-purpose adhesive industry, and the core diameter of the present embodiment leaded light single-mode fiber 1 is 9 μ m.In the 1 tail end welding of leaded light single-mode fiber multimode optical fiber 2 is arranged, the core diameter of multimode optical fiber 2 is 105 μ m, and the length of multimode optical fiber 2 is 2mm, and multimode optical fiber 2 tail end weldings have sensing single-mode fiber 3.The core diameter of sensing single-mode fiber 3 is 9 μ m, the length of sensing single-mode fiber 3 is 3cm, vacuum evaporation has high-reflecting film 4 on sensing single-mode fiber 3 breech faces, also can adopt magnetron sputtering high-reflecting film 4, the thickness of high-reflecting film is 2 μ m, high-reflecting film 4 is used for the light reflection, and sensing single-mode fiber 3 tail ends are installed on the center pit of framework 5 right sides, consists of the optical fiber Michelson and interferes liquid level sensor.During use, the left end of framework 5 is fixed, the right-hand member of framework 5 is dipped vertically in liquid, so that high-reflecting film 4 immerses in the liquid, when liquid level rose, the optical fiber Michelson interfered the interference wave long hair of liquid level sensor to give birth to drift, according to drift value, determined that liquid level changes.
Embodiment 2
In the present embodiment, at the center pit of framework 5 left sides with the 502 gluing leaded light single-mode fibers 1 that are connected to, the 1 tail end welding of leaded light single-mode fiber has multimode optical fiber 2, multimode optical fiber 2 tail end weldings have sensing single-mode fiber 3, the core diameter of sensing single-mode fiber 3 is 9 μ m, the length of sensing single-mode fiber 3 is 4cm, and vacuum evaporation has high-reflecting film 4 on sensing single-mode fiber 3 breech faces.The thickness of the fibre core physical dimension of leaded light single-mode fiber 1, the length of multimode optical fiber 2, high-reflecting film 4 is identical with embodiment 1, consists of the optical fiber Michelson and interferes liquid level sensor.
Adopt the optical fiber Michelson of the present embodiment to interfere liquid level sensor to water, the liquid level that to mass percent is 24.13%, 49.74% glycerine water solution is tested, and test result is seen Fig. 3, in Fig. 3, straight line a is the liquid level and the linear relationship of interfering wavelength of water, and corresponding match is closed and is:
y
1＝-0.0498x+1528.2
Straight line b is that mass percent is the linear relationship of 24.13% glycerine water solution, and corresponding match is closed and is:
y
2＝-0.0687x+1528.2
Straight line c is that mass percent is the linear relationship of 49.74% glycerine water solution, and corresponding match is closed and is:
y
3＝-0.0887x+1528.2
As seen from Figure 3, the mass concentration of glycerine water solution is higher, and the optical fiber Michelson interferes the sensitivity of liquid level sensor higher.
In the present embodiment, at the center pit of framework 5 left sides with the 502 gluing leaded light single-mode fibers 1 that are connected to, the core diameter of leaded light single-mode fiber 1 is 8 μ m, in the 1 tail end welding of leaded light single-mode fiber multimode optical fiber 2 is arranged, the core diameter of multimode optical fiber 2 is 105 μ m, the length of multimode optical fiber 2 is 1mm, multimode optical fiber 2 tail end weldings have sensing single-mode fiber 3, the core diameter of sensing single-mode fiber 3 is 8 μ m, the length of sensing single-mode fiber 3 is 1cm, vacuum evaporation has high-reflecting film 4 on sensing single-mode fiber 3 breech faces, the thickness of high-reflecting film is 1.5 μ m, sensing single-mode fiber 3 tail ends are installed on the center pit of framework 5 right sides, and the optical fiber Michelson that consists of the present embodiment is interfered liquid level sensor.
Embodiment 4
In the present embodiment, at the center pit of framework 5 left sides with the 502 gluing leaded light single-mode fibers 1 that are connected to, the core diameter of leaded light single-mode fiber 1 is 10 μ m, in the 1 tail end welding of leaded light single-mode fiber multimode optical fiber 2 is arranged, the core diameter of multimode optical fiber 2 is 105 μ m, the length of multimode optical fiber 2 is 3mm, multimode optical fiber 2 tail end weldings have sensing single-mode fiber 3, the core diameter of sensing single-mode fiber 3 is 10 μ m, the length of sensing single-mode fiber 3 is 10cm, vacuum evaporation has high-reflecting film 4 on sensing single-mode fiber 3 breech faces, the thickness of high-reflecting film is 3 μ m, sensing single-mode fiber 3 tail ends are installed on the center pit of framework 5 right sides, and the optical fiber Michelson that consists of the present embodiment is interfered liquid level sensor.
In above embodiment 1～4, at the center pit of framework 5 left sides with the 502 gluing leaded light single-mode fibers 1 that are connected to, the 1 tail end welding of leaded light single-mode fiber has multimode optical fiber 2, the core diameter of multimode optical fiber 2 is 50 μ m, multimode optical fiber 2 tail end weldings have sensing single-mode fiber 3, and vacuum evaporation has high-reflecting film 4 on sensing single-mode fiber 3 breech faces.The thickness of the fibre core physical dimension of the fibre core physical dimension of leaded light single-mode fiber 1, the length of multimode optical fiber 2, sensing single-mode fiber 3 and length, high-reflecting film 4 is identical with corresponding embodiment, consists of the optical fiber Michelson and interferes liquid level sensor.
Embodiment 6
In above embodiment 1～4, at the center pit of framework 5 left sides with the 502 gluing leaded light single-mode fibers 1 that are connected to, the 1 tail end welding of leaded light single-mode fiber has multimode optical fiber 2, diameter is 62.5 μ m, multimode optical fiber 2 tail end weldings have sensing single-mode fiber 3, and vacuum evaporation has high-reflecting film 4 on sensing single-mode fiber 3 breech faces.The thickness of the fibre core physical dimension of the fibre core physical dimension of leaded light single-mode fiber 1, the length of multimode optical fiber 2, sensing single-mode fiber 3 and length, high-reflecting film 4 is identical with corresponding embodiment, consists of the optical fiber Michelson and interferes liquid level sensor.
Principle of work of the present invention is as follows:
Generally, optical fiber has limited light and has transmitted at fibre core, can not feel the variation of extraneous refractive index, the mismatch that the present invention adopts multimode optical fiber 2 and single-mode fiber fibre core with the core mode partial coupling to fibre cladding, light in fibre core and covering transmission reflects through high-reflecting film 4, be coupled into leaded light single-mode fiber 1 through multimode optical fiber 2 again, owing to having certain phase differential at the light of fiber core and covering transmission, finally cause the formation of Michelson interference spectrum.When the external environment refraction index changing, can cause the change of phase differential, cause the drift of interference spectum wavelength.Therefore when a section of the sensing monofilm optical fiber 3 of sensor is immersed in the water, the cladding-effective-index of water-immersed sensing monofilm optical fiber 3 changes, and the refractive index of the core mode of sensing monofilm optical fiber 3 remains unchanged, and therefore whole phase differential changes, and causes the interference wave length shift.Adopt spectrometer demodulated interferential wavelength shift to determine the height of the liquid level of surveying.The pass of interfering wavelength and liquid level to rise is:
λ in the formula
mBe the interference wavelength,
The refractive index that is not immersed in the water fibre core for sensing monofilm optical fiber 3 is with not to be immersed in the water cladding index poor,
The refractive index that is immersed in the water fibre core for sensing monofilm optical fiber 3 is with to be immersed in the water cladding index poor, L
nBe sensor monofilm optical fiber 3 water-immersed length, m is the exponent number of claddingmode.Following formula shows, along with L
nIncrease,
Reduce, along with the rising of liquid level, interfere wave length shift.
In order to verify beneficial effect of the present invention, the inventor adopts the embodiment of the invention 1 optical fiber Michelson to interfere liquid level sensor to carry out the laboratory study test, and test situation is as follows:
Experimental apparatus: spectroanalysis instrument, model are AQ6370B, are produced by Japanese Agilent company.
1, the liquid level of test water
Adopt the optical fiber Michelson of example 1 to interfere liquid level sensor that the liquid level variation of water is tested, in measuring process, the every rising 1mm of water level, measure the once wavelength of this liquid level sensor reflectance spectrum, the situation of test water level rising 0～28mm, test result sees Table 1, carries out match with Excel software, Fig. 2 is seen in the match of data in the table 1, and corresponding match Guan ㎝ is:
y＝-0.0269x+1570.8
The variation of adopting spectroanalysis instrument survey sensor reflection wavelength to rise with water level, the liquid level sensitivity of test sensors, the linearity, Repeatability.Experimental result sees Table 1.
Table 1 interference wave personal attendant of the present invention water level rising situation of change
| Liquid level (mm) | Absorbing wavelength (nm) |
| 0 | 1570.78 |
| 1 | 1570.74 |
| 2 | 1570.7 |
| 3 | 1570.68 |
| 4 | 1570.66 |
| 5 | 1570.64 |
| 6 | 1570.62 |
| 7 | 1570.56 |
| 8 | 1570.54 |
| 9 | 1570.52 |
| 10 | 1570.5 |
| 11 | 1570.46 |
| 12 | 1570.44 |
| 13 | 1570.42 |
| 14 | 1570.38 |
| 15 | 1570.36 |
| 16 | 1570.32 |
| 17 | 1570.3 |
| 18 | 1570.28 |
| 19 | 1570.26 |
| 20 | 1570.24 |
| 21 | 1570.2 |
| 22 | 1570.18 |
| 23 | 1570.14 |
| 24 | 1570.12 |
| 25 | 1570.08 |
| 26 | 1570.06 |
| 27 | 1570.04 |
| 28 | 1570.02 |
By as seen from Table 1, along with the rising of water level, the optical fiber Michelson interferes the interference wavelength of liquid level sensor to the drift of shortwave direction, according to formula (1), determines that the liquid level of water changes.
Claims (4)
1. an optical fiber Michelson is interfered liquid level sensor, it is characterized in that: be provided with leaded light single-mode fiber (1) in framework (5) left side, the tail end of leaded light single-mode fiber (1) is provided with multimode optical fiber (2), the tail end of multimode optical fiber (2) is provided with tail end and is installed in sensing single-mode fiber (3) on the framework (5), and the tail end of sensing single-mode fiber (3) is provided with high-reflecting film (4).
2. optical fiber Michelson according to claim 1 is interfered liquid level sensor, and it is characterized in that: the core diameter of described leaded light single-mode fiber (1) is 8～10 μ m; The core diameter of described multimode optical fiber (2) is 50 μ m or 62.5 μ m or 105 μ m, and the length of multimode optical fiber (2) is 1～3mm; The core diameter of described sensing single-mode fiber (3) is 8～10 μ m, and the length of sensing single-mode fiber (3) is at least 1cm; The thickness of described high-reflecting film (4) is 1.5～3 μ m.
3. optical fiber Michelson according to claim 2 is interfered liquid level sensor, and it is characterized in that: the diameter of the fibre core of described leaded light single-mode fiber (1) is 9 μ m; The core diameter of described multimode optical fiber (2) is 105 μ m, and the length of multimode optical fiber (2) is 2mm; The core diameter of described sensing single-mode fiber (3) is 9 μ m, and the length of sensing single-mode fiber (3) is at least 1cm; The thickness of described high-reflecting film (4) is 2 μ m.
According to claim 2 or 3 described optical fiber Michelsons interfere liquid level sensors, it is characterized in that: the diameter of the fibre core of described sensing single-mode fiber (3) is identical with the core diameter of leaded light single-mode fiber (1).
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| CN109974814A (en) * | 2019-04-12 | 2019-07-05 | 重庆理工大学 | Michelson liquid level sensor and measurement method are responded based on multiple-mode interfence low temperature |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
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