CN101598577A - A kind of fiber-optic grating sensor - Google Patents
A kind of fiber-optic grating sensor Download PDFInfo
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- CN101598577A CN101598577A CNA2008101000643A CN200810100064A CN101598577A CN 101598577 A CN101598577 A CN 101598577A CN A2008101000643 A CNA2008101000643 A CN A2008101000643A CN 200810100064 A CN200810100064 A CN 200810100064A CN 101598577 A CN101598577 A CN 101598577A
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Abstract
The present invention relates to a kind of fiber-optic grating sensor, comprise light source, optical fiber, detector and the fiber grating that is used to monitor the physical quantity variation that is positioned at measurement point that is placed on the optical fiber, it is characterized in that: the detection light signal of light source output injects from the optical fiber input end, survey light wavelength not in the reflection wavelength band of fiber grating, and have the preset wavelength difference with reflection wavelength, one when monitored physical quantity variation reaches certain value, the reflection wavelength that is positioned at the fiber grating of measurement point brings to few preset wavelength difference of having drifted about above-mentioned, thereby make the reflection wavelength band and survey wavelength of optical signal band juxtaposition, at this moment, the fiber grating of this measurement point is just to certain incident end that reflexes to of having surveyed light signal generating, thereby detects the variation of described physical quantity.
Description
Affiliated technical field
The present invention relates to a kind of fiber-optic grating sensor, is the sensor of surveying by optical fiber and fiber grating, surveys the method that physical quantity changes, and this physical quantity can be temperature or the like, and this method belongs to field of sensing technologies.
Background technology
We know that optical fiber is the passage of light conducting signal, because its design feature, optical fiber is very responsive to residing environment, as variation of temperature, optical fiber are shunk, and the result causes it that the variation that detects easily takes place, as the decay increase of light signal.When optical fiber is subjected to mechanical stress, pressure variation, electric field or changes of magnetic field, also above-mentioned variation can take place, therefore, many known sensors are with the variation of fiber-optic probe physical quantity.In this sensor of a part, use fiber grating, relatively be typically Bragg grating.Below we are called Bragg grating with fiber grating, but be not that application of the present invention is only only limited to Bragg grating.
Bragg grating is selected reverberator as a kind of wavelength, the wavelength of reflectance spectrum (being the reflection wavelength band) can be subjected to the influence of STRESS VARIATION and produce mobile, by the monitoring of reflection wavelength Tape movement promptly being known the situation of change of physical quantity.Existing Bragg grating proving installation is to utilize wideband light source to be injected into Bragg grating, and the measurement of the reflected light signal wavelength change of light source being carried out according to Bragg grating, but this method needs expensive instrument that reflection wavelength is carried out demodulation to be determined, this device comprises wideband light source and complicated Wavelength demodulation device, make this device Yin Gaoang in practical engineering application cost and be restricted.
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 light source, optical fiber, detector and be placed on the optical fiber be positioned at measurement point be used to monitor the fiber grating that physical quantity changes, it is characterized in that:
The detection light signal of one light source output injects from an end that is called the incident end of optical fiber, and the wavelength of surveying light signal and has the preset wavelength difference with described reflection wavelength not in the reflection wavelength band of fiber grating,
One when monitored physical quantity variation reaches certain value, the reflection wavelength that is positioned at the fiber grating of measurement point brings to few preset wavelength difference of having drifted about above-mentioned, thereby make this reflection wavelength bring to a few part that has covered described detection wavelength of optical signal band, at this moment, the fiber grating of this measurement point is just to certain reflection of having surveyed light signal generating, a part of promptly surveying light signal reflexes to the incident end, thereby detects the variation of described physical quantity.
The present invention surveys to be monitored a kind of fiber-optic grating sensor that physical quantity changes, it is the variation that has utilized reflected light signal, determine the variation of the physical quantity of described measurement point: if variation has taken place near the physical quantity of being monitored a fiber grating, and the variation that takes place has reached the degree that we are concerned about, at this moment the reflection wavelength of fiber grating brings to few preset wavelength difference of having drifted about, thereby make this reflection wavelength bring to few part of surveying the wavelength of optical signal band that covered, at this moment, the fiber grating of this measurement point is just to certain reflection of having surveyed light signal generating, a part of promptly surveying light signal reflexes to the incident end, this explanation has stress to exist, thereby may detect the variation of respective physical amount.
In actual engineering, we usually only need obtain the data that a part of physical quantity changes, just can reach our target, in the fire temperature warning system, we press for understanding to the state of temperature below 25 ℃ the time, we only need to set a monitoring, alarming temperature, as 65 ℃, then as the fiber grating on the optical fiber of sensor, measure this fiber grating in the time of 65 ℃ the reflection wavelength band and choose a wavelength as the wavelength of surveying light signal, select light source according to this wavelength then, described fiber grating is when normal temperature (as 20 ℃), its reflection wavelength band has wavelength difference with the wavelength of the detection light signal of selecting, this sensor is installed in the place of monitoring, as warehouse etc., under normal conditions, environment temperature generally can not reach 65 ℃, so the detection light signal of injection sensor fiber mainly causes the Rayleigh scattering light signal, sensitive detector mainly detects very faint Rayleigh reflected light signal, have only when the temperature of measurement point near or when reaching 65 ℃, the fiber grating reflection wavelength band of this measurement point will drift about and with the wavelength band juxtaposition of surveying light signal, and to surveying the suitable reflection of light signal generating, at this moment, can monitor tangible light signal on the detector, thereby triggered the fire temperature alert if, reached the purpose of monitoring.
Above-mentioned example, also can realize with the system that wide light source and Wavelength demodulation device are formed, this system data of all fiber gratings under the continuous substantially temperature between can obtaining from normal temperature to the alarm temperature, then the temperature of measurement point near or report to the police when reaching alarm temperature, this system testing has obtained the data that have little significance in a large number as can be seen, and expensive instrument also is higher to maintenance requirement.So in similarity,, obviously be uneconomic with respect to the monitoring system that adopts the inventive method with the monitoring system that wide light source and complicated Wavelength demodulation device are formed.
Under actual engineering specifications, a value of only monitoring physical quantity usually is not enough, so the different a plurality of detection light signals of wavelength can be set, just can monitor a plurality of values of physical quantity, the trend that changes of measurement point physical quantity as can be seen simultaneously is so that better monitoring.
Description of drawings:
Fig. 1 is the reflectance spectrum of a Bragg grating of expression, the spectrum of a detection light signal and both graphs of a relation;
Fig. 2 is the structured flowchart of the fiber-optic grating sensor of relevant first embodiment of the present invention of expression;
Fig. 3 is the structured flowchart of the fiber-optic grating sensor of relevant second embodiment of the present invention of expression;
Fig. 4 is the structured flowchart of the fiber-optic grating sensor of relevant the 3rd embodiment of the present invention of expression;
Among the figure: 3,3a, 3b, 3n one light source,
4,9a, 9b one optical branching device,
5 one fiber gratings
6,6a, 6b, 6n one photo-detector,
7 one optical fiber,
8 one photoswitches,
10a, 10b, 10n one fixed wave filter.
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.Curve 2 has schematically shown a spectrum of surveying light signal, 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. 2 is the structured flowchart of the fiber-optic grating sensor of expression first embodiment.The fiber-optic grating sensor of first embodiment by light source 3, photo-detector 6, optical branching device 4, be positioned at measurement point and be used to monitor fiber grating 5 and the optical fiber 7 that physical quantity changes and constitute.Connect with optical fiber between each parts.Optical branching device 4 can be 2 shunting couplers, also can be optical circulator.
Detection light signal from light source 3 outputs, the wavelength of surveying light signal is not in the reflection wavelength band of fiber grating 5, and default wavelength difference arranged with it, survey light signal by optical branching device 4 and optical fiber 7, and reach fiber grating 5, at monitored physical quantity no change or change when not reaching the degree that we are concerned about, the wavelength of surveying light signal is not at the reflection wavelength band of the fiber grating 5 that is positioned at measurement point, be that fiber grating 5 is not to surveying the light signal reflection, at this moment photo-detector 6 has not detected light signal, when the physical quantity 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, at this moment described reflection wavelength brings to few part of surveying the wavelength of optical signal band that covered, this fiber grating 5 is just to the suitable reflection of having surveyed light signal generating, reflected light signal enters detector 6 by optical fiber 7 and optical branching device, thereby detects the variation of physical quantity.
Second embodiment
Fig. 3 is the structured flowchart of the fiber-optic grating sensor of expression second embodiment.The fiber-optic grating sensor of second embodiment by light source 3a, light source 3b, light source 3n, photo-detector 6, optical branching device 4, photoswitch 8, be positioned at measurement point and be used to monitor fiber grating 5 and the optical fiber 7 that physical quantity changes and constitute.Connect with optical fiber between each parts.Optical branching device 4 can be 2 shunting couplers, also can be optical circulator.
Detection light signal from the different wave length of light source 3a, light source 3b, light source 3n output, the wavelength of surveying light signal is not all in the reflection wavelength band of fiber grating 5, and different preset wavelength differences arranged with it, photoswitch 8 can select the detection light signal of Different Light by optical branching device 4 and optical fiber 7, and reach fiber grating 5, the variation of monitored physical quantity 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, we just can detect a plurality of values that physical quantity changes.
The 3rd embodiment
Fig. 4 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 light source 3a, light source 3b, light source 3n, wave filter 10a, wave filter 10b, wave filter 10n, photo-detector 6a, photo-detector 6b, photo-detector 6n, optical branching device 4, optical branching device 9a, optical branching device 9b, be positioned at measurement point and be used to monitor fiber grating 5 and the optical fiber 7 that physical quantity changes and constitute.Connect with optical fiber between each parts.Optical branching device 4 can be 2 shunting couplers, also can be optical circulator.
From light source 3a, light source 3b, the detection light signal of the different wave length of light source 3n output, the wavelength of surveying light signal is not all in the reflection wavelength band of fiber grating 5, and different preset wavelength differences arranged with it, survey light signal by optical branching device 9a, again by optical branching device 4 and optical fiber 7, and reach fiber grating 5, the variation of monitored physical quantity can cause the drift of the reflection wavelength band of fiber grating 5, when the reflection wavelength band has drifted about described different preset wavelength difference, just have different reflected light by optical fiber 7, optical branching device 4 and optical branching device 9b, enter into different detectors by different wave filters respectively, each wave filter and light source are one to one, and only allow the detection light signal of corresponding wavelength to pass through, other detection filtered optical signal is fallen, and we just can detect a plurality of values that physical quantity changes like this.
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 (2)
1. fiber-optic grating sensor, comprise light source, optical fiber, detector and be placed on the optical fiber be positioned at measurement point be used to monitor the fiber grating that physical quantity changes, it is characterized in that:
The detection light signal of one light source output injects from an end that is called the incident end of optical fiber, and the wavelength of surveying light signal and has the preset wavelength difference with described reflection wavelength not in the reflection wavelength band of fiber grating,
One when monitored physical quantity variation reaches certain value, the reflection wavelength that is positioned at the fiber grating of measurement point brings to few preset wavelength difference of having drifted about above-mentioned, thereby make this reflection wavelength bring to a few part that has covered described detection wavelength of optical signal band, at this moment, the fiber grating of this measurement point is just to certain reflection of having surveyed light signal generating, a part of promptly surveying light signal reflexes to the incident end, thereby detects the variation of described physical quantity.
2. a kind of fiber-optic grating sensor according to claim 1, it is characterized in that: a plurality of light sources inject a plurality of detection light signals from an end that is called the incident end of optical fiber, its wavelength is not all in described reflection wavelength band, and have different preset wavelength differences, thereby can detect a plurality of values that the measurement point physical quantity changes with reflection wavelength.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNA2008101000643A CN101598577A (en) | 2008-06-03 | 2008-06-03 | A kind of fiber-optic grating sensor |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNA2008101000643A CN101598577A (en) | 2008-06-03 | 2008-06-03 | A kind of fiber-optic grating sensor |
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| CNA2008101000643A Pending CN101598577A (en) | 2008-06-03 | 2008-06-03 | A kind of fiber-optic grating sensor |
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Addressee: Xi'an Jinhe Optical Technology Co., Ltd. Document name: Notification of Patent Invention Entering into Substantive Examination Stage |
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Application publication date: 20091209 |