CN101832808A - Taper chirped fiber grating liquid level sensor based on reflection spectrum bandwidth detection - Google Patents
Taper chirped fiber grating liquid level sensor based on reflection spectrum bandwidth detection Download PDFInfo
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- CN101832808A CN101832808A CN 201010149041 CN201010149041A CN101832808A CN 101832808 A CN101832808 A CN 101832808A CN 201010149041 CN201010149041 CN 201010149041 CN 201010149041 A CN201010149041 A CN 201010149041A CN 101832808 A CN101832808 A CN 101832808A
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Abstract
The invention discloses a taper chirped fiber grating liquid level sensor based on reflection spectrum bandwidth detection, belonging to the fiber grating sensing field. A bandwidth light source (1) and a spectrum analyzer (2) of the sensor are respectively connected with two furcation ports of a 2*1 coupler (3); one end of a taper chirped fiber grating (4) is connected with a single-line port of the 2*1 coupler and is fixed on a fixture (5), and the other end thereof is arranged on a sliding fixture (6); the fixture is fixed on a straight guide rail (12) of a vibration isolation platform (7), and the sliding fixture is provided with balls at the bottom thereof and can move freely along the straight guide of the vibration isolation plate; and one end of an inelastic rope (1) is arranged on the sliding fixture, the other end thereof is fixed on a buoy (8) arranged in a liquid tank (11) to be detected, and the middle part thereof is supported at a fixed pulley (9) fixed on the vibration isolation plate. The sensor has simple structure, low cost and high perceptive sensitivity on liquid level change.
Description
Technical field
The present invention relates to a kind of taper chirped fiber grating liquid level sensor that detects based on reflection spectrum bandwidth, belong to the technical field of optical fiber grating sensing.
Background technology
Liquid level sensor is a kind of sensor the most commonly used in the industrial practice, and it is widely used in various industrial control conditions, relates to numerous industries such as water conservancy and hydropower, oil, chemical industry, boats and ships, pipeline.At present liquid level sensor mainly is divided into three types of machinery, electronics and optical fiber according to the principle of work of probe.
Mechanical type liquid level sensor: mainly comprise float-type, bubble type, differential and diaphragm type.The weak point of float-type liquid level sensor is the motion of the easy obstruction gearing of gathering of liquid pollutant arm, thereby causes bigger level gauging error; For bubble type and differential pressure type liquid level sensor, its common issue with is that detection mode is very complicated; Though diaphragm type liquid level sensor equipment is simple, its measurement range is very limited.
The electron type liquid level sensor: a kind of is to utilize air and liquid as the dielectric between the capacitor two-plate, and by the capacitance level gauge of capacitance detecting acquisition liquid level information, it is simple in structure, but very sensitive to interference in the cable and stray capacitance, precision is relatively poor; Thereby another kind is to utilize liquid level to influence the radioactive ray liquid level gauge that radiation detector output obtains liquid level information, but radioactive ray are harmful, need to add tight safeguard measure, use very inconvenience; Also have the bigger ultrasonic liquid level gauge of temperature influence in addition, be only applicable to the electrode-type liquid-level meter of conductive liquid etc.
Optical-fiber type liquid level sensor: compare with electronic method with above-mentioned traditional machinery, the optical-fiber type liquid level sensor has advantages such as size is little, anticorrosive, anti-electromagnetic interference (EMI), is more suitable for using in dangerous rugged surroundings such as inflammable and explosive, poisonous and harmful, strong electromagnetic.In addition because optical fiber is not only sensitive element,, thereby can realize remote remote sensing to liquid level to be measured simultaneously as low loss line.Optical-fiber type liquid level sensor commonly used at present mainly contains:
● intensity reflection type liquid level sensor: utilize that to be positioned at a pair of end face cutting in liquid top smooth and lenticular optical fiber is installed is transmitted and received signal respectively, show the variation of liquid level by the difference of contrasting fluid surface intensity of reflected light, the easy contaminated influence of this sensing probe, measuring accuracy and measurement range are relatively poor.
● be communicated with the type fibre optic liquid level sensor: its principle of work is to utilize linker liquid level change to be changed into the variation of specialty optical fiber such as mercury cladded-fiber covering length, though can effectively improve measuring accuracy and measurement range, but use the optical fiber of special cladding structure, not only cost improves, and also will strengthen and the be connected difficulty of transmission with ordinary optic fibre.
● the Fabry-Perot type optical fiber liquid level sensor: its principle of work is to utilize different liquid levels that the difference that Fabry-Perot-type cavity produces pressure is changed the length of Fabry-Perot-type cavity, thereby the interference light striped is changed.This sensor construction is simple, and is highly sensitive, but it interferes detection mode to be subject to such environmental effects such as temperature, vibration, and long-time stability worsen.
● the grating type optical fiber liquid level sensor: a kind of is the long-period gratings type, and its resonance is based on the coupling between the cladding mode with expansion disappearance characteristic, and resonance wavelength changes responsive to liquid, needn't special processing just can realize sensing function; Another kind is the Bragg grating type, and its resonance effect results from the coupling between constraint fibre core basic mode, grinds by the side, and the covering burn into plates means such as thermoelectric metal film, the basic mode limiting field is drawn formation expansion evanescent field can produce induction to the liquid variation equally.The characteristic that the grating type optical fiber liquid level sensor utilizes grating resonance wavelength to be moved when liquid level change usually realizes level monitoring, for example Chinese utility model patent patent No. 01265843.X and 200320117647.X utilize fluid pressure to change to cause flexible sheet deformation, move and know liquid level information thereby cause being pasted on fiber grating resonance wavelength on the diaphragm.But long-period gratings and Bragg grating have cross-sensitivity such as temperature, bending, and grating resonance wavelength also will move thereupon when the surrounding environment parameter changes, thereby Level Detection is produced than mistake; And the wave length shift of light source and detecting device also can have a strong impact on the Level Detection precision.In addition, existing grating type optical fiber liquid level sensor all is that fiber grating directly is positioned in the liquid, since the intrusion of liquid pollutant and hydrone, the very fast deterioration of fiber grating performance, need the frequent sensing head of changing, cause the interruption of level monitoring and cost to increase greatly.
Summary of the invention
Technical matters to be solved by this invention is: overcome the Level Detection error that the existing fiber raster liquid level sensor causes during environmental change around, the Level Detection precision that produces when light source, photodetector wave length shift reduces, and directly fiber grating is placed testing liquid, problems such as mis-behave, the sensing head that contaminated thing and hydrone influence produce changed frequently, cost increase provide a kind of fiber grating liquid level sensor simple in structure, with low cost, high to the liquid level change perceptual sensitivity.
Technical scheme of the present invention is: construct a kind of taper chirped fiber grating liquid level sensor that detects based on reflection spectrum bandwidth, its building block comprises: wideband light source, spectroanalysis instrument, 2 * 1 coupling mechanisms and sensing main body.Wideband light source, spectroanalysis instrument are connected with two bifurcated ports of 2 * 1 coupling mechanisms respectively, and a word port of 2 * 1 coupling mechanisms connects the sensing main body.
The formation of sensing main body and being connected to: an end of taper chirped fiber grating is connected with a word port of 2 * 1 coupling mechanisms and is installed on the stationary fixture, the other end of taper chirped fiber grating is installed in the bottom the sliding on the anchor clamps of ball is housed, and two anchor clamps are parallel and be installed on the straight guide on the vibration-isolating platform.
Slide anchor clamps and be connected with an end of non-resilient rope, the other end of non-resilient rope is connected on the buoy that is positioned in the testing liquid case, and the middle part of non-resilient rope is supported on the fixed pulley that is fixed on the vibration-isolating platform.Sliding clamp base installation ball also can move freely along the straight guide on the vibration-isolating platform.
Principle of work of the present invention is: based on the taper chirped fiber grating liquid level sensor of reflection spectrum bandwidth detection, made full use of axial strain to the different characteristic of each resonance wavelength influence of taper grating, the ingenious fixed pulley that utilizes is converted into the variation that acts on the optical grating axial strain with liquid level to the variation of buoy longitudinal pulling force, thereby make liquid level and optical grating reflection bands of a spectrum wide corresponding one by one, realize utilizing the novel sensing of bandwidth detection liquid level change.When liquid level rises or descend, the pulling force that acts on the buoy changes, fixed pulley is converted into axial stress along taper chirped fiber grating with this pulling force, because conical fiber each several part xsect difference, strain reduces with the optical fiber tapering and increases, the short resonance wavelength at the little place of chirp grating tapering moves faster under effects of strain than the long resonance wavelength of tapering general goal, thereby causes the optical grating reflection spectrum widening or narrow down.By measuring the variation of grating reflection spectrum bandwidth, just can realize sensor monitoring to liquid level.
The invention has the beneficial effects as follows: this taper chirped fiber grating liquid level sensor that detects based on reflection spectrum bandwidth, because when environmental changes such as light source, detecting device wave length shift and temperature, the long resonance wavelength of taper chirped fiber grating and short resonance wavelength equate to unidirectional amount of movement, adopt the reflection spectrum bandwidth that characterizes long resonance wavelength and short resonance wavelength difference as monitoring variable, effectively overcome environmental factor to the cross interference that the existing fiber raster liquid level sensor produces, improved stability and measuring accuracy; Directly do not contact owing to the sensor fibre grating in addition with testing liquid, liquid pollutant and hydrone can not make the fiber grating performance produce deterioration, thereby avoided frequent replacing grating sensing head to strengthen the problem of system maintenance cost, be a kind of simple in structure, the fiber grating liquid level sensor that cost performance is higher.
Description of drawings
Fig. 1 is the taper chirped fiber grating liquid level sensor structural representation that detects based on reflection spectrum bandwidth.
When Fig. 2 rises for liquid level, the taper chirped fiber grating reflectance spectrum curve that utilizes sensing device of the present invention to monitor.
When Fig. 3 descends for liquid level, the taper chirped fiber grating reflectance spectrum curve that utilizes sensing device of the present invention to monitor.
Fig. 4 is the graph of a relation of liquid level change and taper chirped fiber grating reflectance spectrum bandwidth.
Embodiment
Below in conjunction with accompanying drawing the present invention is further described.
Embodiment one
As Fig. 1, the connection between each device of a kind of taper chirped fiber grating liquid level sensor that detects based on reflection spectrum bandwidth:
Flame fused biconical taper optical fiber parameter: rate of flame travel: 2.5mm/s, draw awl length=70mm; Optical fiber tapering diameter becomes 52 μ m from 125 μ m,
The parameter of taper chirped fiber grating 4 is: phase mask version center cycle 537nm; Grating writes length=30mm, and the reflectance spectrum scope is 1553.5～1557nm;
Taper chirped fiber grating 4 is fixed on the anchor clamps 5 with the end that 2 * 1 coupling mechanisms, 3 one word ports are connected, and the other end of taper chirped fiber grating 4 is installed in and slides on the anchor clamps 6, and two spacing jig 70mm are installed in parallel on the straight guide 12 on the vibration-isolating platform 7;
Buoy 8 is positioned in the testing liquid case 11, and the liquid initial height is decided to be liquid level " 0 " point.
Fig. 2 is liquid level " a 0 " some solid line, when liquid level rising 10mm dotted line and liquid level rising 20mm dotted line, the taper chirped fiber grating reflectance spectrum curve that utilizes sensing device of the present invention to monitor, as seen when liquid level raise, the reflectance spectrum bandwidth of taper chirped fiber grating increased.
Fig. 3 is liquid level " a 0 " some solid line, when liquid level decline 10mm dotted line and liquid level decline 30mm dotted line, the taper chirped fiber grating reflectance spectrum curve that utilizes sensing device of the present invention to monitor, as seen when liquid level reduced, the reflectance spectrum bandwidth of taper chirped fiber grating reduced.
Fig. 4 is the graph of a relation of liquid level change and taper chirped fiber grating reflectance spectrum bandwidth, as seen utilizes fiber grating liquid level sensor of the present invention, can obtain between liquid level change and the reflectance spectrum bandwidth linear relationship one to one.
This sensing device bandwidth is to liquid level susceptibility=50pm/mm, and measurement range is [30mm ,+20mm].
Embodiment two
As Fig. 1, the connection between each device of a kind of taper chirped fiber grating liquid level sensor that detects based on reflection spectrum bandwidth:
The parameter of hydrofluorite corrosion conical fiber is: hydrofluorite corrosion speed=1 μ m/min; Optical fiber promotes 5mm from hydrofluorite every 5min;
The parameter of taper chirped fiber grating is: phase mask version center cycle 534nm; Optical fiber tapering diameter becomes 45 μ m from 125 μ m, length=800mm, and the reflectance spectrum scope is 1548nm～1552nm;
Taper chirped fiber grating 4 is fixed on the anchor clamps 5 with the end that 2 * 1 coupling mechanisms, 3 one word ports are connected, and the other end is installed in and slides on the anchor clamps 6, and two spacing jig 1000mm are installed in parallel on the straight guide 12 on the vibration-isolating platform 7;
One end of non-resilient rope 10 with slide anchor clamps 6 and be connected, the other end of non-resilient rope 10 is connected on the buoy 8, the middle part of non-resilient rope 10 is supported on the fixed pulley 9 that is fixed in vibration-isolating platform 7, the parameter of buoy is: length=50mm, wide=50mm, height=1000mm;
Buoy 8 is positioned in the testing liquid case 11, and the liquid initial height is decided to be liquid level " O " point.
This sensing device principle of work is with embodiment one, measurement range=[400mm ,+400mm].
Claims (3)
1. a taper chirped fiber grating liquid level sensor that detects based on reflection spectrum bandwidth comprises: wideband light source (1), spectroanalysis instrument (2), 2 * 1 coupling mechanisms (3) and sensing main body; Wideband light source (1), spectroanalysis instrument (2) are connected with two bifurcated ports of 2 * 1 coupling mechanisms (3) respectively, and a word port of 2 * 1 coupling mechanisms connects the sensing main body;
It is characterized in that, the formation of sensing main body and connection thereof: an end of taper chirped fiber grating (4) is connected with a word port of 2 * 1 coupling mechanisms (3) and is installed on the anchor clamps (5), and the other end of taper chirped fiber grating (4) is installed in and slides on the anchor clamps (6);
Anchor clamps (5) are fixed on the straight guide (12) on the vibration-isolating platform (7), slide anchor clamps (6) bottom and ball is installed and is moved freely along the straight guide (12) on the vibration-isolating platform (7);
Non-resilient rope (10) one ends are connected and slide on the anchor clamps (6), and non-resilient rope (10) other end is connected on the buoy (8), and the middle part of non-resilient rope (10) is supported on the fixed pulley (9) that is fixed in vibration-isolating platform (7);
Buoy (8) is positioned in the testing liquid case (11).
2. a kind of taper chirped fiber grating liquid level sensor that detects based on reflection spectrum bandwidth according to claim 1 is characterized in that: described wideband light source (1) is positioned at the wideband light source of optical fiber low loss window for Erbium-Doped Fiber Amplifier (EDFA) or LED or other any emission wavelength.
3. a kind of taper chirped fiber grating liquid level sensor that detects based on reflection spectrum bandwidth according to claim 1 is characterized in that: the employed optical fiber of described taper chirped grating (4) is flame fusion awl, hydrofluorite corrosion awl, side grinding awl and other various optical fiber that axially have pyramidal structure.
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Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102620797A (en) * | 2012-03-26 | 2012-08-01 | 武汉理工大学 | Non-contact optical fiber grating liquid level alarm |
| CN103278214A (en) * | 2013-05-29 | 2013-09-04 | 西北大学 | Polarization maintaining optical fiber Bragg grating liquid level sensor |
| CN103309002A (en) * | 2013-06-17 | 2013-09-18 | 南昌大学 | Capillary sensitivity enhancing packaging device capable of applying prestress to fiber grating |
| CN106595484A (en) * | 2016-12-20 | 2017-04-26 | 太原理工大学 | High-precision measuring equipment based on external coupling grating resonant cavity |
| CN106643972A (en) * | 2016-12-20 | 2017-05-10 | 北京交通发展研究院 | Method, device and equipment for obtaining liquid measuring parameters and measuring liquid |
| DE102016125614A1 (en) * | 2016-12-23 | 2018-06-28 | fos4X GmbH | Optical level measuring device and method for measuring a level |
| CN109916282A (en) * | 2019-04-01 | 2019-06-21 | 南京智慧基础设施技术研究院有限公司 | A kind of malformation device and its detection method based on Fibre Optical Sensor |
| CN116880002A (en) * | 2023-09-05 | 2023-10-13 | 深圳市比洋光通信科技股份有限公司 | High-yield fiber grating capillary tube type sensitization packaging device |
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Cited By (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102620797A (en) * | 2012-03-26 | 2012-08-01 | 武汉理工大学 | Non-contact optical fiber grating liquid level alarm |
| CN103278214A (en) * | 2013-05-29 | 2013-09-04 | 西北大学 | Polarization maintaining optical fiber Bragg grating liquid level sensor |
| CN103278214B (en) * | 2013-05-29 | 2015-11-04 | 西北大学 | Polarization maintaining fiber bragg grating liquid level sensor |
| CN103309002A (en) * | 2013-06-17 | 2013-09-18 | 南昌大学 | Capillary sensitivity enhancing packaging device capable of applying prestress to fiber grating |
| CN106595484A (en) * | 2016-12-20 | 2017-04-26 | 太原理工大学 | High-precision measuring equipment based on external coupling grating resonant cavity |
| CN106643972A (en) * | 2016-12-20 | 2017-05-10 | 北京交通发展研究院 | Method, device and equipment for obtaining liquid measuring parameters and measuring liquid |
| CN106595484B (en) * | 2016-12-20 | 2018-11-23 | 太原理工大学 | A kind of high precision measuring device based on external coupling grating resonant cavity |
| DE102016125614A1 (en) * | 2016-12-23 | 2018-06-28 | fos4X GmbH | Optical level measuring device and method for measuring a level |
| CN109916282A (en) * | 2019-04-01 | 2019-06-21 | 南京智慧基础设施技术研究院有限公司 | A kind of malformation device and its detection method based on Fibre Optical Sensor |
| CN116880002A (en) * | 2023-09-05 | 2023-10-13 | 深圳市比洋光通信科技股份有限公司 | High-yield fiber grating capillary tube type sensitization packaging device |
| CN116880002B (en) * | 2023-09-05 | 2023-12-12 | 深圳市比洋光通信科技股份有限公司 | High-yield fiber grating capillary tube type sensitization packaging device |
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Open date: 20100915 |