CN102928045B - Optical fiber Michelson interference liquid level sensor - Google Patents
Optical fiber Michelson interference liquid level sensor Download PDFInfo
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- CN102928045B CN102928045B CN201210488369.2A CN201210488369A CN102928045B CN 102928045 B CN102928045 B CN 102928045B CN 201210488369 A CN201210488369 A CN 201210488369A CN 102928045 B CN102928045 B CN 102928045B
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Abstract
A kind of optical fiber Michelson interference liquid level sensor, framework left side is provided with guide-lighting single-mode fiber, the tail end of guide-lighting single-mode fiber is provided with multimode optical fiber, the tail end of multimode optical fiber is provided with tail end and is arranged on sensing single-mode fiber on framework, and the tail end of sensing single-mode fiber is provided with high-reflecting film.The liquid level of prepared optical fiber Michelson interference liquid level sensor to 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 change of test water, the glycerine water solution of test variable concentrations, along with the mass concentration of glycerine water solution increases, the sensitivity of optical fiber Michelson interference liquid level sensor improves.The present invention also can be used for the liquid level of testing other liquid.
Description
Technical field
The invention belongs to sensor technical field, be specifically related to liquid level sensor.
Background technology
Liquid level sensor is used to the surveying instrument of tracer liquid height, has important application in many aspects, as fuel storage system, and water level monitoring and some chemical reaction process monitorings etc.At present, liquid level sensor based on Fibre Optical Sensor principle is Mach-Zahnder interference formula structure 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-Zahnder interference formula liquid level sensor are generally 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 is better, but for (physical strength reducing sensor) need be corroded during level gauging to Fiber Bragg Grating FBG or utilize comparatively complicated mechanical strain structure, multimode interferometric structure based on coreless fiber is simple, but light loss is larger.Therefore, the demand meeting application is all difficult to.
Summary of the invention
Technical matters to be solved by this invention is the shortcoming overcoming above-mentioned liquid level sensor, provides a kind of reasonable in design, optical fiber Michelson interference liquid level sensor that structure is simple, highly sensitive, practical.
Solving the problems of the technologies described above adopted technical scheme is: on framework left side, be provided with guide-lighting single-mode fiber, the tail end of guide-lighting single-mode fiber is provided with multimode optical fiber, the tail end of multimode optical fiber is provided with tail end and is arranged on sensing single-mode fiber on framework, and the tail end of sensing single-mode fiber is provided with high-reflecting film.
The core diameter of guide-lighting single-mode fiber of the present invention is 8 ~ 10 μm.The core diameter of multimode optical fiber is 50 μm or 62.5 μm or 105 μm, and the length of multimode optical fiber is 1 ~ 3mm.The core diameter of sensing single-mode fiber is 8 ~ 10 μm, and the length of sensing single-mode fiber 3 is at least 1cm.The thickness of high-reflecting film is 1.5 ~ 3 μm.
Diameter the best of the fibre core of guide-lighting single-mode fiber 1 of the present invention is 9 μm.Core diameter the best of multimode optical fiber 2 is 105 μm, and length the best of multimode optical fiber 2 is 2mm.Core diameter the best of sensing single-mode fiber 3 is 9 μm, and the length of sensing single-mode fiber 3 is at least 1cm.Thickness the best of high-reflecting film is 2 μm.
The diameter of the fibre core of sensing single-mode fiber of the present invention is identical with the core diameter of guide-lighting single-mode fiber.
Because the present invention adopts the tail end welding multimode optical fiber of guide-lighting 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 forms optical fiber Michelson interference liquid level sensor.The optical fiber Michelson interference liquid level sensor of embodiment 1 liquid level to 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 change of test water, the glycerine water solution of test variable concentrations, along with the mass concentration of glycerine water solution increases, the sensitivity of optical fiber Michelson interference liquid level sensor improves.The present invention also can be used for the liquid level of testing other liquid.
Accompanying drawing explanation
Fig. 1 is embodiments of the invention 1 structural representations.
Fig. 2 is the liquid level of the embodiment of the present invention 1 test water and the linear relationship chart of interfering wavelength.
Fig. 3 is the liquid level of the embodiment of the present invention 2 test water and variable concentrations glycerine water solution and the linear relationship chart of interfering wavelength.
Embodiment
Below in conjunction with drawings and Examples, the present invention is described in more detail, but the invention is not restricted to these embodiments.
Embodiment 1
In FIG, the optical fiber Michelson interference liquid level sensor of the present embodiment is made up of the guide-lighting single-mode fiber 1 of leaded light, multimode optical fiber 2, sensing single-mode fiber 3, high-reflecting film 4, framework 5 connection.
On the center pit of framework 5 left side, gluing to be connected to guide-lighting single-mode fiber 1,502 glue be the commodity that market is sold with 502, and produced by Taizhou plain multi-purpose adhesive industry company limited, the core diameter of the guide-lighting single-mode fiber 1 of the present embodiment is 9 μm.Have multimode optical fiber 2 in the welding of guide-lighting single-mode fiber 1 tail end, the core diameter of multimode optical fiber 2 is 105 μm, and the length of multimode optical fiber 2 is 2mm, and the welding of multimode optical fiber 2 tail end has sensing single-mode fiber 3.The core diameter of sensing single-mode fiber 3 is 9 μm, the length of sensing single-mode fiber 3 is 3cm, on sensing single-mode fiber 3 breech face, vacuum evaporation has high-reflecting film 4, also magnetron sputtering high-reflecting film 4 can be adopted, the thickness of high-reflecting film is 2 μm, high-reflecting film 4 is for light reflection, and sensing single-mode fiber 3 tail end is arranged on the center pit of framework 5 right side, forms optical fiber Michelson interference liquid level sensor.During use, fixed by the left end of framework 5, the right-hand member of framework 5 is dipped vertically in a liquid, makes high-reflecting film 4 immerse in liquid, and when liquid level rises, the raw drift of interference wave long hair of optical fiber Michelson interference liquid level sensor, according to drift value, determines that liquid level changes.
Embodiment 2
In the present embodiment, the center pit of framework 5 left side is gluingly connected to guide-lighting single-mode fiber 1 with 502, the welding of guide-lighting single-mode fiber 1 tail end has multimode optical fiber 2, the welding of multimode optical fiber 2 tail end has sensing single-mode fiber 3, the core diameter of sensing single-mode fiber 3 is 9 μm, the length of sensing single-mode fiber 3 is 4cm, and on sensing single-mode fiber 3 breech face, vacuum evaporation has high-reflecting film 4.The thickness of the fibre core physical dimension of guide-lighting single-mode fiber 1, the length of multimode optical fiber 2, high-reflecting film 4 is identical with embodiment 1, forms optical fiber Michelson interference liquid level sensor.
Adopt the optical fiber Michelson interference liquid level sensor of the present embodiment to water, be that the liquid level of the glycerine water solution of 24.13%, 49.74% is tested to mass percent, test result is shown in Fig. 3, in figure 3, straight line a is the liquid level of water and the linear relationship of interfering wavelength, and corresponding fit correlation is:
y
1＝-0.0498x+1528.2
The linear relationship of straight line b to be mass percent the be glycerine water solution of 24.13%, corresponding fit correlation is:
y
2＝-0.0687x+1528.2
The linear relationship of straight line c to be mass percent the be glycerine water solution of 49.74%, corresponding fit correlation is:
y
3＝-0.0887x+1528.2
As seen from Figure 3, the mass concentration of glycerine water solution is higher, and the sensitivity of optical fiber Michelson interference liquid level sensor is higher.
Embodiment 3
In the present embodiment, the center pit of framework 5 left side is gluingly connected to guide-lighting single-mode fiber 1 with 502, the core diameter of guide-lighting single-mode fiber 1 is 8 μm, multimode optical fiber 2 is had in the welding of guide-lighting single-mode fiber 1 tail end, the core diameter of multimode optical fiber 2 is 105 μm, the length of multimode optical fiber 2 is 1mm, the welding of multimode optical fiber 2 tail end has sensing single-mode fiber 3, the core diameter of sensing single-mode fiber 3 is 8 μm, the length of sensing single-mode fiber 3 is 1cm, on sensing single-mode fiber 3 breech face, vacuum evaporation has high-reflecting film 4, the thickness of high-reflecting film is 1.5 μm, sensing single-mode fiber 3 tail end is arranged on the center pit of framework 5 right side, form the optical fiber Michelson interference liquid level sensor of the present embodiment.
Embodiment 4
In the present embodiment, the center pit of framework 5 left side is gluingly connected to guide-lighting single-mode fiber 1 with 502, the core diameter of guide-lighting single-mode fiber 1 is 10 μm, multimode optical fiber 2 is had in the welding of guide-lighting single-mode fiber 1 tail end, the core diameter of multimode optical fiber 2 is 105 μm, the length of multimode optical fiber 2 is 3mm, the welding of multimode optical fiber 2 tail end has sensing single-mode fiber 3, the core diameter of sensing single-mode fiber 3 is 10 μm, the length of sensing single-mode fiber 3 is 10cm, on sensing single-mode fiber 3 breech face, vacuum evaporation has high-reflecting film 4, the thickness of high-reflecting film is 3 μm, sensing single-mode fiber 3 tail end is arranged on the center pit of framework 5 right side, form the optical fiber Michelson interference liquid level sensor of the present embodiment.
Embodiment 5
In above embodiment 1 ~ 4, the center pit of framework 5 left side is gluingly connected to guide-lighting single-mode fiber 1 with 502, the welding of guide-lighting single-mode fiber 1 tail end has multimode optical fiber 2, the core diameter of multimode optical fiber 2 is 50 μm, the welding of multimode optical fiber 2 tail end has sensing single-mode fiber 3, and on sensing single-mode fiber 3 breech face, vacuum evaporation has high-reflecting film 4.The thickness of the fibre core physical dimension of guide-lighting single-mode fiber 1, the length of multimode optical fiber 2, the fibre core physical dimension of sensing single-mode fiber 3 and length, high-reflecting film 4 is identical with corresponding embodiment, formation optical fiber Michelson interference liquid level sensor.
Embodiment 6
In above embodiment 1 ~ 4, the center pit of framework 5 left side is gluingly connected to guide-lighting single-mode fiber 1 with 502, the welding of guide-lighting single-mode fiber 1 tail end has multimode optical fiber 2, diameter is 62.5 μm, the welding of multimode optical fiber 2 tail end has sensing single-mode fiber 3, and on sensing single-mode fiber 3 breech face, vacuum evaporation has high-reflecting film 4.The thickness of the fibre core physical dimension of guide-lighting single-mode fiber 1, the length of multimode optical fiber 2, the fibre core physical dimension of sensing single-mode fiber 3 and length, high-reflecting film 4 is identical with corresponding embodiment, formation optical fiber Michelson interference liquid level sensor.
Principle of work of the present invention is as follows:
Under normal circumstances, optical fiber limits light and transmits at fibre core, the change of extraneous refractive index can not be felt, the present invention adopts the mismatch of multimode optical fiber 2 and single-mode fiber fibre core that core mode is partly coupled to fibre cladding, reflect through high-reflecting film 4 at the light of fibre core and covering transmission, be coupled into guide-lighting 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 external environment refraction index changing, the change of phase differential can be caused, cause the drift of interference spectum wavelength.Therefore when a section of 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, therefore overall phase differential changes, and causes interference wave length shift.Spectrometer demodulated interferential wavelength shift is adopted to determine the height of surveyed liquid level.The pass of interfering wavelength and liquid level to rise is:
λ in formula
mfor interfering wavelength,
be not immersed in the water the refractive index of fibre core for sensing monofilm optical fiber 3 and be not immersed in the water clad refractive rate variance,
be immersed in the water the refractive index of fibre core for sensing monofilm optical fiber 3 and be immersed in the water clad refractive rate variance, L
nfor the water-immersed length of sensor monofilm optical fiber 3, m is the exponent number of claddingmode.Above 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, inventor adopts the embodiment of the present invention 1 optical fiber Michelson interference liquid level sensor to carry out laboratory study test, and test situation is as follows:
Experimental apparatus: spectroanalysis instrument, model is AQ6370B, is produced by Japanese Agilent company.
1, the liquid level of test water
The liquid level change of the optical fiber Michelson interference liquid level sensor of example 1 to water is adopted to test, in measuring process, water level often rises 1mm, measure once the wavelength of this liquid level sensor reflectance spectrum, the situation of test water level rising 0 ~ 28mm, test result, in table 1, carries out matching with Excel software, in table 1, Fig. 2 is shown in the matching of data, and corresponding matching Guan ㎝ is:
y＝-0.0269x+1570.8
Adopt the change that spectroanalysis instrument survey sensor reflection wavelength rises with water level, the liquid level Sensitivity of test sensors, the linearity, Repeatability.Experimental result is in 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 |
From table 1, along with the rising of water level, the interference wavelength of optical fiber Michelson interference liquid level sensor, to the drift of shortwave direction, according to formula (1), determines the liquid level change of water.
Claims (1)
1. an optical fiber Michelson interference liquid level sensor, framework (5) left side is provided with guide-lighting single-mode fiber (1), the tail end of guide-lighting single-mode fiber (1) is provided with multimode optical fiber (2), it is characterized in that: the tail end of multimode optical fiber (2) is provided with tail end and is arranged on sensing single-mode fiber (3) on framework (5), and the tail end of sensing single-mode fiber (3) is provided with high-reflecting film (4);
The length of above-mentioned multimode optical fiber (2) is 2mm, and the length of sensing single-mode fiber (3) is 3cm, and the thickness of high-reflecting film (4) is 2 μm.
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| CN105510277B (en) * | 2015-12-01 | 2018-09-21 | 北京无线电计量测试研究所 | A kind of methane optical fiber sensor |
| CN109974814B (en) * | 2019-04-12 | 2021-05-04 | 重庆理工大学 | Low-temperature response Michelson liquid level sensor based on multimode interference and measuring method |
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| CN101162197A (en) * | 2007-11-26 | 2008-04-16 | 重庆大学 | Optical fiber methane sensing system based on fiber core mismatch |
| CN101957227A (en) * | 2010-10-22 | 2011-01-26 | 南京信息工程大学 | Photonic crystal fiber optic liquid level sensor and sensing system formed by same |
| CN102419313A (en) * | 2011-08-12 | 2012-04-18 | 华南师范大学 | Michelson interferometer based optical-fiber refraction index sensor and measuring method thereof |
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|---|---|---|---|---|
| CN101162197A (en) * | 2007-11-26 | 2008-04-16 | 重庆大学 | Optical fiber methane sensing system based on fiber core mismatch |
| CN101957227A (en) * | 2010-10-22 | 2011-01-26 | 南京信息工程大学 | Photonic crystal fiber optic liquid level sensor and sensing system formed by same |
| CN102419313A (en) * | 2011-08-12 | 2012-04-18 | 华南师范大学 | Michelson interferometer based optical-fiber refraction index sensor and measuring method thereof |
Non-Patent Citations (1)
| Title |
|---|
| High temperature fiber sensor with high sensitivity based on core diameter mismatch;Linh Viet Nguyen等;《OPTICS EXPRESS》;20080714;第16卷(第15期);p11369-11375 * |
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