CN101424623A - Optical fibre grating sensor - Google Patents
Optical fibre grating sensor Download PDFInfo
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- CN101424623A CN101424623A CNA2008102322324A CN200810232232A CN101424623A CN 101424623 A CN101424623 A CN 101424623A CN A2008102322324 A CNA2008102322324 A CN A2008102322324A CN 200810232232 A CN200810232232 A CN 200810232232A CN 101424623 A CN101424623 A CN 101424623A
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- 239000013307 optical fiber Substances 0.000 title claims abstract description 21
- 239000000835 fiber Substances 0.000 claims abstract description 59
- 239000004642 Polyimide Substances 0.000 claims abstract description 10
- 229920001721 polyimide Polymers 0.000 claims abstract description 10
- 238000005259 measurement Methods 0.000 claims description 22
- 238000001514 detection method Methods 0.000 claims description 13
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Abstract
The invention relates to a fiber grating sensor which comprises a wideband light source, optical fibers, a filter with a fixed wavelength, a probe and a fiber grating and is characterized in that a layer of polyimide is plated on the surface of the fiber grating, and the filter with a fixed wavelength only permits a narrow light wavelength band to pass through, permits the passable light wavelength band not to be in a selective function wavelength band of the fiber grating, and forms a preset wavelength difference value with the selective function wavelength band; and after probe light injected in the wideband light source passes through the filter of a fixed wavelength, only the narrow light wavelength band passes through and reaches the probe. When monitored humidity changes to a quantitative value, the selective function wavelength band of the fiber grating at least drifts away to the preset wavelength difference value. At the time, the fiber grating reflects or disperses a probe light signal which is injected in the wideband light source and can pass through the filter with a fixed wavelength, and the probe probes the change of the light signals so as to probe the change of the humidity.
Description
Affiliated technical field
The present invention relates to a kind of fiber-optic grating sensor, is to survey the sensor that humidity changes by optical fiber and fiber grating, belongs to field of sensing technologies.
Background technology
The measurement of humidity is used very extensive in industrial and agricultural production and daily life, greenhouse as agricultural production, the dry run of tobacco, tealeaves, wood working, artificial environments such as medicament compartment, hospital, operating room, bacteria growth chamber, important places such as museum, library, archive office, laboratory, machine room all need to carry out moisture measurement and control.Especially in Minepit environment, water layer caves in to easy initiation of infiltration of rock, by the monitoring that ambient humidity is changed, can avoid the generation of this type of mine disaster effectively.
The most frequently used moisture instruments is a psychrometer at present, utilizes the wet bulb water evaporates to absorb latent heat greater than dry bulb, makes near the temperature of wet bulb be lower than near the temperature of dry bulb, obtains rh value according to temperature difference.But in order correctly to obtain wet-bulb temperature, air should have enough wind speed near the wet bulb.This method is difficult to realize digitizing long-distance transmissions result simultaneously, can't satisfy the actual needs of a lot of productive lifes.
Summary of the invention
The objective of the invention is to formulate the sensor of a kind of use fiber grating (as Bragg grating), to avoid above-mentioned defective.
For this reason, the present invention proposes a kind of fiber-optic grating sensor, comprise wave filter, the detector of wideband light source, optical fiber, fixed wave length and be placed on the optical fiber be positioned at measurement point be used to monitor the fiber grating that humidity changes, it is characterized in that:
-this fiber grating surface is coated with one deck polyimide,
The wave filter of-fixed wave length only allows a narrow optical wavelength band to pass through, pass through and limit other wavelength, and the wavelength band that its permission is passed through is in the selectively acting wavelength band of fiber grating, and has the preset wavelength difference with described selectively acting wavelength,
-wideband light source injects detection light from the so-called incident end of optical fiber, survey light by behind the wave filter of fixed wave length, have only an above-mentioned narrow optical wavelength band to pass through, arrive detector, when monitored humidity variation reaches certain value, be positioned at the preset wavelength difference that the selectively acting wavelength band of the fiber grating of measurement point has drifted about above-mentioned at least, thereby make this selectively acting wavelength band, at least the wave filter that has covered fixed wave length allows the part of the wavelength band that passes through, at this moment, the fiber grating of this measurement point is to wideband light source incident, detection light signal generating that can be by Fixed Wavelength Filter certain reflection or dissipation, promptly the light signal by Fixed Wavelength Filter reduces, detector detects light signal obvious variation, thereby detects the variation of described humidity.
The present invention surveys to be monitored a kind of fiber-optic grating sensor that humidity changes, be to be coated with one deck polyimide on the fiber grating surface, its thickness is the 20-50 micron, when polyimide absorbs or discharges water vapor and makes when himself deforming, fiber grating also changes thereupon, thereby make fiber grating generation axial strain, cause fiber grating selectively acting wavelength band position excursion.If variation has taken place near the humidity of being monitored a fiber grating that is coated with polyimide, and the variation that takes place has reached the degree that we are concerned about, at this moment the selectively acting wavelength band of the fiber grating preset wavelength difference of having drifted about at least, thereby make this selectively acting wavelength band cover the part that to pass through the wavelength band of Fixed Wavelength Filter at least, at this moment, the fiber grating of this measurement point is just to wideband light source incident, detection light signal generating that can be by Fixed Wavelength Filter certain reflection or dissipation, detector detects the variation of transmitted light, this explanation has stress to exist, thereby may detect the variation of corresponding humidity.
In actual engineering, we usually only need obtain the data that a part of humidity changes, just can reach our target, in the humidity warning system in the scene of a needs monitoring humidity, we press for understanding to the moisture condition between the 65%RH to 75%RH the time, we only need to set a monitoring, alarming humidity, as 60%RH, measure then this fiber grating when 60%RH the selectively acting wavelength band and choose the pass through wavelength of a wavelength as the wave filter of fixed wave length, described fiber grating is when 70%RH, the wavelength that the wave filter of the wavelength band of the light signal of its reflection and the fixed wave length of installation allows to pass through has wavelength difference, at this moment detector can detect light signal, this sensor is installed in the place of monitoring, under normal conditions, ambient humidity is between 65%RH to 75%RH the time, the wavelength that the wave filter of the wavelength band of the light signal of its reflection and the fixed wave length of installation allows to pass through has wavelength difference, at this moment detector can detect light signal, have only when the humidity of measurement point near or when reaching 60%RH, the fiber grating selectively acting wavelength band of this measurement point will drift about and allow the wavelength band juxtaposition that passes through with the wave filter of fixed wave length, thereby the wave filter of fixed wave length allowed suitable reflection or the dissipation of detection light signal generating passed through, at this moment, can monitor obvious variation on the detector through the intensity of light signal, thereby triggered the humidity alert if, reached the purpose of monitoring.
Under actual engineering specifications, a value of only monitoring humidity usually is not enough, so the wave filter of a plurality of fixed wave length can be set, it allows different optical wavelength bands to pass through, and the wavelength band that its permission is passed through is not in the selectively acting wavelength band of fiber grating, and have different preset wavelength differences with described selectively acting wavelength, thereby can detect a plurality of values that measurement point humidity changes, the trend that changes of measurement point humidity as can be seen simultaneously is so that better monitoring.
Can a plurality of fiber gratings be set respectively at a plurality of measurement points on the optical fiber, and fiber grating has essentially identical selectively acting wavelength band, thus the variation of measuring the humidity of a plurality of points.
Description of drawings:
Fig. 1 is that the wave filter of reflectance spectrum, a fixed wave length of a Bragg grating of expression allows the spectrum that passes through and both graphs of a relation;
Fig. 2 is that the wave filter of transmitted spectrum, a fixed wave length of a long period fiber grating of expression allows the spectrum that passes through and both graphs of a relation;
Fig. 3 is the structured flowchart of the fiber-optic grating sensor of relevant first embodiment of the present invention of expression;
Fig. 4 is the structured flowchart of the fiber-optic grating sensor of relevant second embodiment of the present invention of expression;
Fig. 5 is the structured flowchart of the fiber-optic grating sensor of relevant the 3rd embodiment of the present invention of expression;
Among the figure: 3 one wideband light sources,
4 one optical branching devices,
5,5a, 5b, 5n one is coated with the fiber grating of polyimide,
6,6a, 6b, 6n one photo-detector,
7 one optical fiber,
10,10a, 10b, the wave filter of 10n one fixed wave length.
Embodiment
Curve 1 among Fig. 1 has schematically shown the reflectance spectrum of a Bragg grating, λ
1And λ
2Be respectively the lower limit and the upper limit wavelength of this Bragg grating reflection wavelength, all wavelength all are the wavelength that Bragg grating can reflect in these two wavelength, are called the reflection wavelength band here.The wave filter that curve 2 has schematically shown a fixed wave length allows the spectrum that passes through, λ
3And λ
4Be respectively the lower edge and the upper edge wavelength of this wavelength band, λ
2And λ
3Between distance be exactly that described preset wavelength is poor.
Curve 11 among Fig. 2 has schematically shown the transmitted spectrum of a long period fiber grating, λ
1And λ
2Be respectively the lower limit and the upper limit wavelength of this long period fiber grating coupling attenuation wavelength, long period fiber grating all has decay to all wavelength in these two wavelength, is called the dissipation wavelength band here.The wave filter that curve 2 has schematically shown a fixed wave length allows the spectrum that passes through, λ
3And λ
4Be respectively the lower edge and the upper edge wavelength of this detection light signal, λ
2And λ
3Between distance be exactly that described preset wavelength is poor.
First embodiment
Fig. 3 is the structured flowchart of the fiber-optic grating sensor of expression first embodiment.The fiber-optic grating sensor of first embodiment by the wave filter 10 of wideband light source 3, photo-detector 6, fixed wave length, be positioned at measurement point and be used to monitor fiber grating that is coated with polyimide 5 and the optical fiber 7 that humidity changes and constitute.Connect with optical fiber between each parts.
The wavelength band that wave filter 10 permissions of fixed wave length are passed through and the reflection wavelength of fiber grating 5 have a default difference, pass through optical fiber 7 from the detection light signal of wideband light source 3 outputs, and reach fiber grating 5, the detection light signal that 5 pairs of wideband light sources of fiber grating 3 inject has narrow band light reflection, at monitored humidity no change or change when not reaching the degree that we are concerned about, the wavelength of reflected light signal is not in the wavelength band that the wave filter 10 of fixed wave length allows to pass through, promptly at this moment in the wideband light source wave filter 10 of a narrow light signal by fixed wave length must be arranged, arrive detector; When the humidity of monitored point changes to the degree of our care, the reflection wavelength that is positioned at the fiber grating 5 of described measurement point brings to few described preset wavelength difference of having drifted about, promptly the fiber grating reflection wavelength band of this measurement point just has juxtaposition with the wavelength that the wave filter permission of fixed wave length is passed through, at this moment, can have at least the light signal of the wave filter that a part can be by fixed wave length to be reflected, at this moment the light signal that passes through the wave filter of fixed wave length reduces, can monitor tangible change in optical signal on the detector, thereby detect the variation of humidity.
Second embodiment
Fig. 4 is the structured flowchart of the fiber-optic grating sensor of expression second embodiment.The fiber-optic grating sensor of second embodiment by the wave filter 10n of the wave filter 10b of the wave filter 10a of wideband light source 3, photo-detector 6a, photo-detector 6b, photo-detector 6n, optical branching device 4, fixed wave length, fixed wave length, fixed wave length, be positioned at measurement point and be used to monitor fiber grating that is coated with polyimide 5 and the optical fiber 7 that humidity changes and constitute.Connect with optical fiber between each parts.
Detection light signal from wideband light source 3 outputs, the detection light signal that 5 pairs of wideband light sources of fiber grating 3 inject has narrow band light reflection, the light signal of transmission arrives the wave filter 10a of fixed wave length through optical branching device 4 and optical fiber 7, the wave filter 10b of fixed wave length and the wave filter 10n of fixed wave length, the wave filter 10a of fixed wave length, the wave filter 10b of fixed wave length, the wavelength band that the wave filter 10n of fixed wave length has different permissions to pass through, and have different preset difference values with the reflection wavelength of fiber grating 5, the variation of monitored humidity can cause the drift of the reflection wavelength band of fiber grating 5, when preset wavelength difference that the reflection wavelength band has drifted about different, photo-detector 6a, photo-detector 6b, photo-detector 6n can detect tangible light signal, and we just can detect a plurality of values that humidity changes.
The 3rd embodiment
Fig. 5 is the structured flowchart of the fiber-optic grating sensor of expression the 3rd embodiment.The fiber-optic grating sensor of the 3rd embodiment by wave filter 10, the photo-detector 6 of wideband light source 3, fixed wave length, be positioned at measurement point and be used to monitor the fiber grating 5a that is coated with polyimide, fiber grating 5b, fiber grating 5n and the optical fiber 7 that humidity changes and constitute.Connect with optical fiber between each parts.
Detection light signal from wideband light source 3 outputs, by optical fiber 7, and reach fiber grating 5a with basic identical reflection wavelength band, fiber grating 5b, fiber grating 5n, the wave filter 10 of fixed wave length allows the wavelength band and the fiber grating 5a that pass through, fiber grating 5b, the reflection wavelength of fiber grating 5n has a default difference, cause the drift of the reflection wavelength band of fiber grating when the variation of the monitored humidity that is positioned at certain measurement point, and when the reflection wavelength band has drifted about described preset wavelength difference, will be reflected by some light signal by the wave filter 10 of fixed wave length, enter into the light signal minimizing of photo-detector 6 like this by the wave filter 10 of fixed wave length, thereby we just can detect the variation of humidity.
As seen, the method according to detection of the present invention is simpler than the method for prior art.
Certainly, the present invention is not limited to the embodiment that the front is introduced, and we can replace whole device with another kind of equivalent arrangements, and do not exceed scope of the present invention.
Claims (3)
1. fiber-optic grating sensor, comprise wave filter, the detector of wideband light source, optical fiber, fixed wave length and be placed on the optical fiber be positioned at measurement point be used to monitor the fiber grating that humidity changes, it is characterized in that:
-this fiber grating surface is coated with one deck polyimide,
The wave filter of-fixed wave length only allows a narrow optical wavelength band to pass through, pass through and limit other wavelength, and the wavelength band that its permission is passed through is in the selectively acting wavelength band of fiber grating, and has the preset wavelength difference with described selectively acting wavelength,
-wideband light source injects detection light from the so-called incident end of optical fiber, survey light by behind the wave filter of fixed wave length, have only an above-mentioned narrow optical wavelength band to pass through, arrive detector, when monitored humidity variation reaches certain value, be positioned at the preset wavelength difference that the selectively acting wavelength band of the fiber grating of measurement point has drifted about above-mentioned at least, thereby make this selectively acting wavelength band, at least the wave filter that has covered fixed wave length allows the part of the wavelength band that passes through, at this moment, the fiber grating of this measurement point is to wideband light source incident, detection light signal generating that can be by Fixed Wavelength Filter certain reflection or dissipation, promptly the light signal by Fixed Wavelength Filter reduces, detector detects light signal obvious variation, thereby detects the variation of described humidity.
2. a kind of fiber-optic grating sensor according to claim 1, it is characterized in that: the wave filter that a plurality of fixed wave length can be set, it allows different optical wavelength bands to pass through, and the wavelength band that its permission is passed through is not in the reflection wavelength band of fiber grating, and have different preset wavelength differences, thereby can detect a plurality of values that measurement point humidity changes with described reflection wavelength.
3. a kind of fiber-optic grating sensor according to claim 1 and 2 is characterized in that: can a plurality of fiber gratings be set respectively at a plurality of measurement points on the optical fiber, and these fiber gratings have essentially identical reflection wavelength band.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNA2008102322324A CN101424623A (en) | 2008-11-12 | 2008-11-12 | Optical fibre grating sensor |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNA2008102322324A CN101424623A (en) | 2008-11-12 | 2008-11-12 | Optical fibre grating sensor |
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| Publication Number | Publication Date |
|---|---|
| CN101424623A true CN101424623A (en) | 2009-05-06 |
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|---|---|---|---|
| CNA2008102322324A Pending CN101424623A (en) | 2008-11-12 | 2008-11-12 | Optical fibre grating sensor |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105738318A (en) * | 2016-02-18 | 2016-07-06 | 北京航天易联科技发展有限公司 | Environment humidity monitoring method and system for cultural relic preservation |
| CN105953940A (en) * | 2016-04-21 | 2016-09-21 | 北京卫星环境工程研究所 | Temperature, humidity and wind speed integrated sensing system of fiber grating |
| CN108872158A (en) * | 2018-05-31 | 2018-11-23 | 京东方科技集团股份有限公司 | Moisture detector |
| CN113267277A (en) * | 2021-05-18 | 2021-08-17 | 天津安物知科技有限公司 | Location perception structure based on light signal changes |
-
2008
- 2008-11-12 CN CNA2008102322324A patent/CN101424623A/en active Pending
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105738318A (en) * | 2016-02-18 | 2016-07-06 | 北京航天易联科技发展有限公司 | Environment humidity monitoring method and system for cultural relic preservation |
| CN105738318B (en) * | 2016-02-18 | 2018-11-06 | 北京航天易联科技发展有限公司 | One kind being used for historical relic's protection ambient humidity monitoring method and its system |
| CN105953940A (en) * | 2016-04-21 | 2016-09-21 | 北京卫星环境工程研究所 | Temperature, humidity and wind speed integrated sensing system of fiber grating |
| CN105953940B (en) * | 2016-04-21 | 2018-03-30 | 北京卫星环境工程研究所 | Temperature, humidity and the wind speed integration composite sensing system of fiber grating |
| CN108872158A (en) * | 2018-05-31 | 2018-11-23 | 京东方科技集团股份有限公司 | Moisture detector |
| CN108872158B (en) * | 2018-05-31 | 2020-12-29 | 京东方科技集团股份有限公司 | Humidity detector |
| CN113267277A (en) * | 2021-05-18 | 2021-08-17 | 天津安物知科技有限公司 | Location perception structure based on light signal changes |
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Open date: 20090506 |