CN101598576A - Survey the method for physical quantity with linear sensor - Google Patents
Survey the method for physical quantity with linear sensor Download PDFInfo
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- CN101598576A CN101598576A CNA2008101000639A CN200810100063A CN101598576A CN 101598576 A CN101598576 A CN 101598576A CN A2008101000639 A CNA2008101000639 A CN A2008101000639A CN 200810100063 A CN200810100063 A CN 200810100063A CN 101598576 A CN101598576 A CN 101598576A
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Abstract
The present invention relates to a kind of method that changes in a plurality of measurement point of sensor with linear sensor detection physical quantity.Sensor has an optical fiber, numerous fiber gratings that also are positioned at a measurement point along fiber distribution are separately arranged, fiber grating has essentially identical selectively acting wavelength band under unstressed effect, it comprises the steps: that injecting one from the incident end of optical fiber surveys light signal, and its wavelength is not in the selectively acting wavelength band; When the physical quantity variation of certain measurement point reaches certain value, the selectively acting wavelength band of the fiber grating of this measurement point floats to and makes this selectively acting wavelength band and the wavelength band juxtaposition of surveying light signal, at this moment, the fiber grating of this measurement point is just to certain reflection or dissipation of having surveyed light signal generating, detect the light intensity variation at exit end, thereby detect the variation of described physical quantity.
Description
Affiliated technical field
The present invention relates to a kind ofly survey the method for physical quantity with linear sensor, particularly the sensor of surveying by optical fiber and fiber grating is surveyed 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 method of testing is that the Bragg grating that utilizes wavelength-division multiplex technique to make a plurality of different grating constants on an optical fiber carries out the Distributed Multi measurement, but this method needs expensive instrument to carry out demodulation, comprise wideband light source and tunable optic filter, make that this method is difficult to obtain promote in practical engineering application.
Summary of the invention
The objective of the invention is to formulate the method that a kind of use has the sensor of fiber grating (as Bragg grating), to avoid above-mentioned defective.
For this reason, the present invention proposes a kind of with the method for physical quantity of linear sensor detection in the variation of a plurality of measurement point of described sensor, described sensor has an optical fiber, numerous fiber gratings that also are positioned at a measurement point along described fiber distribution are separately arranged, described fiber grating has essentially identical selectively acting wavelength band under the situation of unstressed effect
It is characterized in that it comprises the steps:
One end that is called the incident end from optical fiber injects one and surveys light signal, and the wavelength of described detection light signal and has the preset wavelength difference with the selectively acting wavelength not in described selectively acting wavelength band,
One physical quantity when certain measurement point changes when reaching certain value, the preset wavelength difference that the selectively acting wavelength band of the fiber grating of this measurement point has drifted about above-mentioned at least, thereby make this selectively acting wavelength band cover the part of described detection wavelength of optical signal band at least, at this moment, the fiber grating of this measurement point is just to certain effect of having surveyed light signal generating, the part of detection light signal reflects or dissipates, the other end that is called the incident end at optical fiber, be that exit end then detects the variation of surveying light signal strength, thereby detect the variation of described physical quantity.
The method that physical quantity changes is monitored in detection of the present invention, it is the variation that has utilized optical signal transmissive, 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 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 a part of surveying the wavelength of optical signal band at least, at this moment, the fiber grating of this measurement point is just to certain effect of having surveyed light signal generating, a part of promptly surveying light signal reflexes to the incident end or dissipates, detect the variation of surveying light signal strength from exit end, thereby detect the variation of described physical quantity.
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 ℃, distribute on as the optical fiber of sensor then essentially identical fiber grating is set, measure this fiber grating in the time of 65 ℃ the selectively acting wavelength band and choose a wavelength as the wavelength of surveying light signal, described fiber grating is when normal temperature (as 20 ℃), its selectively acting 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 by optical fiber and fiber grating after, the detector that enters exit end obtains light intensity, and with this light intensity as benchmark.At this moment has only normal optical path loss, have only when the temperature of certain measurement point near or when reaching 65 ℃, the fiber grating selectively acting wavelength band of this measurement point will drift about and with the wavelength band juxtaposition of surveying light signal, and to surveying suitable reflection or the dissipation of light signal generating, at this moment, the detector of exit end just detects intensity variations, thereby has triggered the fire temperature alert if, has reached the purpose of monitoring.
Above-mentioned example, also can realize with the system that wide light source and tunable optic filter 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 certain 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 tunable optic filter 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, each wavelength of surveying light signal all has certain wavelength difference with the selectively acting wavelength of fiber grating, so just can monitor a plurality of values of physical quantity, the trend that changes of certain measurement point physical quantity as can be seen simultaneously is so that better monitoring.
In order to improve monitoring sensitivity, two pulses in succession of the detection optical signals of each injection constitute: the wavelength difference of two light pulses is not less than half of described selectively acting wavelength bandwidth, and be not more than described fiber grating selectively acting wavelength bandwidth, physical quantity changes is that the ratio of the intensity of the reflected light signal by two different wave lengths is determined, all in the reflection wavelength band after drift, the detection sensitivity of Shi Xianing can double these two wavelength like this.
As long as calibration sensor correctly in advance, just the respective change (variation of the physical quantity of monitoring just) of the fiber grating selectively acting wavelength band of the variation of the amplitude of emergent light intensity and fiber grating can be connected.
By following description to a sniffer of the present invention and a kind of method, can understand other features and advantages of the present invention, these method and apparatus schematically, never are restrictive just.
Description of drawings:
Fig. 1 is the reflectance spectrum of a Bragg grating, the spectrum of a detection light signal and both relations;
Fig. 2 is the transmitted spectrum of a long period fiber grating, the spectrum of a detection light signal and both relations;
Fig. 3 is the synoptic diagram of a fiber Bragg grating type sensor, and it comprises the relevant necessaries that is used for carrying out according to the present invention desirable detection;
In all figure, identical part has identical label.
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.
Curve 14 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 the coupling attenuation wavelength of this long period fiber grating, long period fiber grating all has decay to all wavelength in these two wavelength, is called the dissipation 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.
Fig. 3 has shown that schematically is used to survey the sensor 10 that physical quantity changes, it has a single-mode fiber 3 as detector, is provided with Bragg grating 4 on optical fiber 3, and they are identical each other, that is to say to have essentially identical reflection wavelength band.
Each Bragg grating 4 constitutes a measurement point on the optical fiber 3, and promptly the point to the variation sensitivity of the physical quantity of being monitored makes sensor 10 can exercise its function.
As monitor temperature, with sensor 10 during, be subjected near the monitoring object just passablely as long as fiber grating is placed in as hygrosensor, for preventing the exterior mechanical interference, fiber grating can be contained in the protection tube.
In addition, sensor 10 has a LASER Light Source 5, an end 11 couplings of it and optical fiber 3.In order to survey the variation of being monitored physical quantity, light source 5 is to the detectable signal of optical fiber 3 emission light pulses 7.
Also comprise a detector 8 in the sensor 10, the other end 12 couplings of it and optical fiber 3 are so that accept response signal by the incident pulse 7 of optical fiber.Detector 8 is connected with display 9 (as display screen), so that show the light intensity that sees through signal.
We introduce now according to the present invention, survey the changing method of a physical quantity (as temperature) with sensor 10.
For example, sensor 10 abuts against by the power cable that will measure local pyrexia abreast, and the local pyrexia of cable will influence its operate as normal.In sensor 10, optical fiber 3 has afforded variation of temperature, like this, and in the just drift of reflection wavelength band of the Bragg grating that is positioned at the temperature variation place of correspondence.By light source 5, we launch the detection light signal of light pulse 7 regularly, when the temperature of the local pyrexia of cable rises to the temperature that we are concerned about, the reflection wavelength band of the corresponding Bragg grating that is positioned at the temperature variation place has just floated to the part that can cover the wavelength band of detecting optical pulses 7 at least, thereby Bragg grating has just produced reflection to detecting optical pulses 7, at this moment, detector detects the minimizing of transmitted light intensity, and corresponding do not have occurrence temperature to change or Bragg grating that temperature variation does not reach the degree place that we are concerned about to the detection light signal reflection of light pulse 7.
Like this, change, just can detect variation of temperature by light intensity on the simple observation display 9.
Under actual engineering specifications, we usually need to monitor a plurality of values of physical quantity, so the different a plurality of detection light signals of wavelength can be set, the detection light signal of similar light pulse 7, be exactly the wavelength difference, repeat said process, just can monitor a plurality of values of physical quantity, the trend that changes of physical quantity as can be seen simultaneously is so that better monitoring.
In order to improve monitoring sensitivity, two pulses in succession of the detection optical signals of each injection constitute: two light pulse λ
5And λ
6Wavelength difference be not less than half of described reflection wavelength bandwidth, and be not more than described reflection wavelength bandwidth, when physical quantity (as temperature) when changing to certain value, λ
5And λ
6Be located in and be subjected to physical quantity to change (as temperature) influence and in the Bragg grating reflection wavelength band after the drift, at this moment can obtain two intensity of surveying light signal, we calculate the difference of ratio of the transmission signal intensity of two pulse signals, then detected the variation of being monitored physical quantity, if carry out suitable demarcation in advance, can also measure the size of this variation.
If wish near the situation about changing of the temperature of the care that measurement detects, only need in advance sensor 10 to be demarcated, near the maximum amplitude with corresponding transmitted pulse of each variation the concern temperature is connected.
In sensor 10, replace the function that Bragg grating does not influence sensor 10 with long period fiber grating, in actual monitoring, can obtain identical effect.
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 embodiment and the method introduced the front, and we can replace whole device with another kind of equivalent arrangements, and do not exceed scope of the present invention.
Claims (4)
1. survey the method for a physical quantity with linear sensor in the variation of a plurality of measurement point of described sensor, described sensor has an optical fiber, numerous fiber gratings that also are positioned at a measurement point along described fiber distribution are separately arranged, described fiber grating has essentially identical selectively acting wavelength band under the situation of unstressed effect
It is characterized in that it comprises the steps:
One end that is called the incident end from optical fiber injects one and surveys light signal, and the wavelength of described detection light signal and has the preset wavelength difference with the selectively acting wavelength not in described selectively acting wavelength band,
One physical quantity when certain measurement point changes when reaching certain value, the preset wavelength difference that the selectively acting wavelength band of the fiber grating of this measurement point has drifted about above-mentioned at least, thereby make this selectively acting wavelength band cover the part of described detection wavelength of optical signal band at least, at this moment, the fiber grating of this measurement point is just to surveyed light signal generating certain reflection or dissipate, the other end that is called the incident end at optical fiber, be that exit end then detects the variation of surveying light signal strength, thereby detect the variation of described physical quantity.
2. the method for surveying physical quantity with linear sensor according to claim 1, it is characterized in that: 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 selectively acting wavelength band, and with the selectively acting wavelength to have different preset wavelengths poor, thereby can detect a plurality of values that the measurement point physical quantity changes.
3. according to any described method in claim 1 or 2, it is characterized in that: each is surveyed two light pulses in succession of optical signals and forms, the wavelength difference of two light pulses is not less than half of described selectively acting wavelength bandwidth, and be not more than described selectively acting wavelength bandwidth, physical quantity changes is that the ratio of the intensity of the optical signal transmissive by two different wave lengths is determined.
4. according to any described method in the claim 1 to 3, it is characterized in that: in order to measure the variation of described physical quantity, to demarcate in advance, so that all amplitudes of the intensity of described optical signal transmissive and a corresponding amplitude of described physical quantity are connected.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNA2008101000639A CN101598576A (en) | 2008-06-03 | 2008-06-03 | Survey the method for physical quantity with linear sensor |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNA2008101000639A CN101598576A (en) | 2008-06-03 | 2008-06-03 | Survey the method for physical quantity with linear sensor |
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| CN101598576A true CN101598576A (en) | 2009-12-09 |
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| CNA2008101000639A Pending CN101598576A (en) | 2008-06-03 | 2008-06-03 | Survey the method for physical quantity with linear 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 |