CN105352914B - A kind of gas concentration detection system and its method based on dual wavelength light fibre annular-type cavity - Google Patents
A kind of gas concentration detection system and its method based on dual wavelength light fibre annular-type cavity Download PDFInfo
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Abstract
The invention discloses a kind of gas concentration detection system and its method based on dual wavelength light fibre annular-type cavity, the system includes：Microprocessor, microprocessor are connected with current driving circuit, and current driving circuit is connected with Distributed Feedback Laser；The laser signal of Distributed Feedback Laser output is sent to the input that optical fiber two divides two couplers, and divides two couplers to be divided into two ways of optical signals by the optical fiber two；Optical signal is sent to air chamber all the way, and the optical signal exported after air chamber absorbs feeds back to another input that optical fiber two divides two couplers again, forms optic fiber ring-shaped cavity；Another way optical signal is sent to photodetection change-over circuit and carries out being converted to electric signal, the electric signal of photodetection change-over circuit output is successively after signal conditioning circuit and data acquisition circuit processing, it is sent to PC to carry out calculating under test gas absorption loss amount, the concentration of under test gas is finally obtained according to the relation of under test gas concentration and under test gas absorption loss amount.
Description
Technical field
The invention belongs to field of gas detection, more particularly to a kind of gas concentration detection based on dual wavelength light fibre annular-type cavity
System and method.
Background technology
Early in the last century 20's, the mankind have begun to the research to gas detection equipment and method, even to this day, can
CO and CH of the gas of monitoring from early stage；Develop into and cover the explosive gas such as CH, H2The pernicious gases such as S, O2、H2O, the ring such as CO
The comprehensive monitoring device of the alcohol and flue gas of the engineering such as border gas, CO gas and volatilization etc..All kinds of gas sensors also phase
Then give birth to, existing gas sensor master has semiconductor-type gas sensor, electrochemistry type gas sensor, solid-electrolyte gas
Sensor, catalytic combustion type gas sensor, polymer electrolyte gas sensor and optical-fiber type gas sensor etc.
In the last thirty years, it is increasingly becoming research along with optical fiber and the high speed development of optical communication technique, fibre optical sensor
Main flow.To measure low concentration sample, scientific research personnel proposes the scheme of increase absorption length, but also brings absorption cell volume simultaneously
Huge, multiple reflections structure causes stability poor, cavity and each side problem such as eyeglass production and the tired standard of collimation.
1984, the concept of Research on Cavity Ring Down Spectroscopy (CRDs) was formally proposed by Anderson et al. on the basis of forefathers.
Its scheme uses LASER Light Source, and forms optical resonator by two high reflectance eyeglasses, and test substance is filled with resonator
(gas of certain concentration etc.), then pulsed optical signals lotus root is closed and entered in resonator, have a small amount of optical signal every time through high
Reflectance ratio eyeglass is emitted and collected by receiving unit below, the decay for the optical signal being coupled out by measurement in optical resonator
Speed, you can learn the loss value of the optics cavity, and then learn the purpose of the gas concentration in resonator.
Although the Research on Cavity Ring Down Spectroscopy based on space optics has the advantages that high detection sensitivity, such system is still
Several essential defects be present：Such as 1. cavity machining accuracy, high reflectance coating require harsh, and the requirement of end mirror degree of collimation is very
Height, structural stability are poor；2. the difficult efficiency of misfortune conjunction is low between end mirror and optical fiber, easily it is disturbed.
The content of the invention
In order to solve the shortcomings that prior art, the present invention provides a kind of electromagnetism interference, suitable hazardous environment, Stability Analysis of Structures
Property the wide gas concentration detection system and its method based on dual wavelength light fibre annular-type cavity of strong and measurement range.
To achieve the above object, the present invention uses following technical scheme：
A kind of gas concentration detection system based on dual wavelength light fibre annular-type cavity, including：
Microprocessor, the microprocessor are connected with current driving circuit, the current driving circuit and Distributed Feedback Laser phase
Even；
The laser signal of the Distributed Feedback Laser output is sent to the input that optical fiber two divides two couplers, and by described
Optical fiber two divides two couplers to be divided into two ways of optical signals；Wherein, optical signal is sent to air chamber all the way, the light exported after air chamber absorbs
Signal feeds back to another input that optical fiber two divides two couplers again, forms optic fiber ring-shaped cavity；
Another way optical signal is sent to photodetection change-over circuit and carries out being converted to electric signal, the photodetection conversion electricity
The electric signal of road output after signal conditioning circuit and data acquisition circuit processing, is sent to PC and calculates gas to be measured successively
Body absorption loss amount, the dense of under test gas is finally obtained according to the relation of under test gas concentration and under test gas absorption loss amount
Degree.
The signal conditioning circuit includes amplifying circuit, input and the photodetection change-over circuit of the amplifying circuit
Output end is connected, and the output end of amplifying circuit is connected with the input of filter circuit, the output end of filter circuit and data acquisition
The input of circuit is connected.
A kind of gas concentration detection system based on dual wavelength light fibre annular-type cavity, including：
Microprocessor, the microprocessor are connected with current driving circuit, the current driving circuit and Distributed Feedback Laser phase
Even；
The laser signal of the Distributed Feedback Laser output is sent to the input that optical fiber two divides two couplers, and by described
Optical fiber two divides two couplers to be divided into two ways of optical signals；Wherein, optical signal is sent to air chamber all the way, the light exported after air chamber absorbs
Signal feeds back to another input that optical fiber two divides two couplers again, forms optic fiber ring-shaped cavity；
Several optic fiber ring-shaped cavities being connected in series are also set up in the transmission direction of another way optical signal, each optical fiber
The output optical signal of annular chamber is respectively sent to corresponding photodetection change-over circuit and carries out being converted to electric signal, and photodetection turns
The electric signal of circuit output is changed successively after corresponding signal conditioning circuit and the processing of corresponding data acquisition circuit, is sent to
Corresponding PC simultaneously calculates under test gas absorption loss amount, further according to the pass of under test gas concentration and under test gas absorption loss amount
It is to obtain the concentration of under test gas, finally realizes that single channel multipoint gas concentration detects.
A kind of gas concentration detection system based on dual wavelength light fibre annular-type cavity, including：
Microprocessor, the microprocessor are connected with current driving circuit, and the current driving circuit swashs with several DFB
Light device is connected；
The laser signal of each Distributed Feedback Laser output is sent to the input that optical fiber two divides two couplers, and by
The optical fiber two divides two couplers to be divided into two ways of optical signals；Wherein, optical signal is sent to air chamber all the way, is exported after air chamber absorbs
Optical signal feed back to another input that optical fiber two divides two couplers again, form optic fiber ring-shaped cavity；
Another way optical signal is sent to photodetection change-over circuit and carries out being converted to electric signal, and photodetection change-over circuit is defeated
The electric signal gone out after signal conditioning circuit and data acquisition circuit processing, is sent to PC and calculates under test gas suction successively
Waste is received, the concentration of under test gas is obtained further according to the relation of under test gas concentration and under test gas absorption loss amount；
Finally realize that several optic fiber ring-shaped cavities are connected in parallel the multi-channel gas Concentration Testing of form.
A kind of gas concentration detection system based on dual wavelength light fibre annular-type cavity, including：
Microprocessor, the microprocessor are connected with current driving circuit, and the current driving circuit swashs with several DFB
Light device is connected；
The laser signal of each Distributed Feedback Laser output is sent to the input that optical fiber two divides two couplers, and by
The optical fiber two divides two couplers to be divided into two ways of optical signals；Wherein, optical signal is sent to air chamber all the way, is exported after air chamber absorbs
Optical signal feed back to another input that optical fiber two divides two couplers again, form optic fiber ring-shaped cavity；
Several optic fiber ring-shaped cavities being connected in series are also set up in the transmission direction of another way optical signal, each optical fiber
The output optical signal of annular chamber is respectively sent to corresponding photodetection change-over circuit and carries out being converted to electric signal, and photodetection turns
The electric signal of circuit output is changed successively after corresponding signal conditioning circuit and the processing of corresponding data acquisition circuit, is sent to
Corresponding PC simultaneously calculates under test gas absorption loss amount, further according to the pass of under test gas concentration and under test gas absorption loss amount
It is to obtain the concentration of under test gas, finally realizes that multichannel multipoint gas concentration detects.
A kind of detection method of the gas concentration detection system based on dual wavelength light fibre annular-type cavity, including：
Step (1)：The circuit in gas concentration detection system is connected, forms single optic fiber ring-shaped cavity；
Step (2)：The wavelength that Distributed Feedback Laser output laser signal is adjusted by microprocessor is respectively that under test gas absorbs
Wavelength and other wavelength in addition under test gas absorbing wavelength；
Step (3)：By the laser signal of two kinds of wavelength in step (2) respectively by obtaining light after fiber annular cavity-type BPM
Pulse train, and be sent to after processing in PC and carry out solving under test gas absorption loss amount；
Step (4)：According under test gas concentration and the relation of under test gas absorption loss amount, finally it is calculated in air chamber
The concentration of under test gas.
The process of under test gas absorption loss amount is solved in the step (3), including：
Step (3.1)：The data of reception are fitted by PC using exponential function y=a*exp (- b*t), obtain two groups
Solution is respectively (a1, b1) and (a2, b2), wherein y is the value data that PC receives, and t is the time that PC receives data, a and b
It is parameter to be solved；
Step (3.2)：According to formula (1/b1)/T=10*loge/ Γ1(1/b2)/T=10*loge/ Γ2, ask respectively
Solve the intrinsic total losses Γ of system1With system total losses Γ2, wherein T is that light pulse surround the time once in fiber optic loop, is fixed
Value；E refers to natural Exponents；
Step (3.3)：According to gas absorption loss αgasEqual to system total losses Γ2With the intrinsic total losses Γ of system1Difference
Value, finally obtain the absorption loss amount of under test gas.
A kind of detection method of the gas concentration detection system based on dual wavelength light fibre annular-type cavity, including：
Step (1)：The circuit in gas concentration detection system is connected, realizes that multiple optic fiber ring-shaped cavities are connected in series；
Step (2)：The wavelength that Distributed Feedback Laser output laser signal is adjusted by microprocessor is respectively that under test gas absorbs
Wavelength and other wavelength in addition under test gas absorbing wavelength；
Step (3)：The laser signal of two kinds of wavelength in step (2) is passed sequentially through to the fiber annular being connected in series respectively
Light pulse sequence is obtained after cavity-type BPM, and is sent to after processing in PC and carries out solving under test gas absorption loss amount；
Step (4)：According under test gas concentration and the relation of under test gas absorption loss amount, series connection gas is finally calculated
The concentration of under test gas in room in each air chamber.
A kind of detection method of the gas concentration detection system based on dual wavelength light fibre annular-type cavity, including：
Step (1)：The circuit in gas concentration detection system is connected, realizes that multiple optic fiber ring-shaped cavities are connected in parallel；
Step (2)：The wavelength that each Distributed Feedback Laser output laser signal is adjusted by microprocessor is respectively under test gas
Absorbing wavelength and other wavelength in addition under test gas absorbing wavelength；
Step (3)：By the laser signal of two kinds of wavelength in step (2) respectively by being obtained after each fiber annular cavity-type BPM
To light pulse sequence, and it is sent to after processing in PC and carries out solving under test gas absorption loss amount；
Step (4)：According under test gas concentration and the relation of under test gas absorption loss amount, gas in parallel is finally calculated
In room in each air chamber under test gas concentration.
A kind of detection method of the gas concentration detection system based on dual wavelength light fibre annular-type cavity, including：
Step (1)：The circuit in gas concentration detection system is connected, realizes that optic fiber ring-shaped cavity serial-parallel mirror connects；
Step (2)：The wavelength that each Distributed Feedback Laser output laser signal is adjusted by microprocessor is respectively under test gas
Absorbing wavelength and other wavelength in addition under test gas absorbing wavelength；
Step (3)：The fiber annular that the laser signal of two kinds of wavelength in step (2) is connected by serial-parallel mirror respectively
Light pulse sequence is obtained after cavity-type BPM, and is sent to after processing in PC and carries out solving under test gas absorption loss amount；
Step (4)：According under test gas concentration and the relation of under test gas absorption loss amount, finally it is calculated and goes here and there and mix
The concentration of under test gas in each air chamber in connection connection air chamber.
Beneficial effects of the present invention are：
(1) it system inherent loss of the invention, only need to change laser emitting optical wavelength, it is removed object gas feature
Outside absorbing wavelength, the light loss now measured by system is exactly the inherent loss of the system, the detection method of the invention
Under test gas drying in air chamber is surveyed into inherent loss than ever accurately simply, and to improve the real-time of monitoring, and have
The advantages of simple in construction, easy to operate；
(2) present invention is declined using fiber optic loop swings the method that increase air chamber length measures light concentration gas that instead of, and fits
Preferably transmission, electromagnetism interference, suitable hazardous environment, structural stability are strong over long distances, and measurement range is wide；
(3) present invention devises fiber optic loop, and because fiber optic loop declines the presence swung, air chamber can design shorter, then air chamber is accurate
Straight degree will improve, and will reduce light pulse excess loss；
(4) multiple optic fiber ring-shaped cavities are concatenated either and connect or go here and there and hybrid junction mode by the present invention, and multichannel biography can be achieved
Sense, while the gas concentration of multiple spot is detected.
Brief description of the drawings
Fig. 1 is the structural representation of the gas concentration detection system based on dual wavelength light fibre annular-type cavity of the present invention；
Fig. 2 is the photodetection change-over circuit circuit diagram of the present invention；
Fig. 3 is the circuit diagram of the amplifying circuit of the present invention.
Wherein, 1, temperature control circuit；2nd, Distributed Feedback Laser；3rd, current driving circuit；4th, microprocessor；5th, optical fiber two divides two couplings
Clutch；6th, air chamber；7th, photodetection change-over circuit；8th, amplifying circuit；9th, data acquisition circuit；10th, PC.
Embodiment
The present invention will be further described with embodiment below in conjunction with the accompanying drawings：
The embodiment 1 of the gas concentration detection system based on dual wavelength light fibre annular-type cavity of the present invention is as shown in Figure 1：
The detecting system, including temperature control circuit 1, Distributed Feedback Laser 2, current driving circuit 3, microprocessor 4, optical fiber two divide
Two couplers 5, air chamber 6, photodetection change-over circuit 7, amplifying circuit 8, data acquisition circuit 9 and PC 10.
Microprocessor 4 is respectively connected with current driving circuit 3 and temperature control circuit 1, temperature control circuit 1 and the phase of Distributed Feedback Laser 2
Even, current driving circuit 3 is also connected with Distributed Feedback Laser 2, and the drive signal of current driving circuit 3 is sent by microprocessor 4, profit
Electric current driving and temperature-driven are carried out to Distributed Feedback Laser 2 with temperature control circuit 1 and current driving circuit 3, send Distributed Feedback Laser 2
Stable system requirements pulse signal.
Then the connection of Distributed Feedback Laser 2 optical fiber two divides an input of two couplers 5, and inputs light beam is divided into two-way light
Beam, all the way light return another input that optical fiber two divides two couplers 5 after the absorption of 6 gases by air chamber, another way light is straight
Tap into photodetection change-over circuit, then enter data acquisition circuit 9 after signal conditioning circuit is handled and carry out data acquisition
And it is sent into PC 10 and carries out data processing.
Distributed Feedback Laser 2 is also connected with temperature control circuit 1, and temperature control circuit 1 is connected with microprocessor 4.
The signal conditioning circuit includes amplifying circuit 8, input and the photodetection change-over circuit 7 of the amplifying circuit
Output end be connected, the output end of amplifying circuit 8 is connected with the input of filter circuit, and output end and the data of filter circuit are adopted
The input of collector 9 is connected.
Described current driving circuit 3 is formed by connecting by the DA of microprocessor with integrated transporting discharging LM358 chips；
Described Distributed Feedback Laser 2 is WSLS-137010C1424-20 butterfly-type encapsulation (Distributed Feedback
Laser) distributed feedback laser, wavelength are 1370 ± 2nm.
As shown in Fig. 2 the photodetection change-over circuit 7 used in the present embodiment is PIN photodetection change-over circuits.Should
PIN photodetections change-over circuit includes OPA2604 amplifiers, the positive input terminal ground connection of the amplifier, and negative input end passes sequentially through
Photodetector D4 and resistance R38 with from optical fiber two divide two couplers 5 export wherein light path is connected all the way, OPA2604 amplification
RC parallel circuits are also parallel between the negative input end and output end of device.
As shown in figure 3, the amplifying circuit 8 in the present embodiment is made up of operational amplifier OPA2604 and its peripheral circuits；
In figure 3, operational amplifier OPA2604 positive input terminal is grounded by resistance R42, and negative input end passes through resistance R40 light in succession
Electrical resistivity survey surveys the output end of change-over circuit 7；The input of operational amplifier OPA2604 output end connection data acquisition circuit 9；
A branch road is parallel between operational amplifier OPA2604 negative input end and output end, be in series with the branch road resistance R41 and
Rheostat VR2.
Described microprocessor 4 is LPC1758 chips；
Described data acquisition circuit 9 is PCI-1710UL data collecting cards.
Multiple optic fiber ring-shaped cavities can be concatenated either and connect or go here and there and hybrid junction mode by the present invention, and multichannel can be achieved and pass
Sense, while the gas concentration of multiple spot is detected.
First, optic fiber ring-shaped cavity is connected in series：
The gas concentration detection system based on dual wavelength light fibre annular-type cavity, including：
Microprocessor 4, the microprocessor 4 are connected with current driving circuit 3, the current driving circuit 3 and DFB laser
Device 2 is connected；
The laser signal that the Distributed Feedback Laser 2 exports is sent to the input that optical fiber two divides two couplers 5, and by institute
Stating optical fiber two divides two couplers 5 to be divided into two ways of optical signals；Wherein, optical signal is sent to air chamber 6 all the way, defeated after the absorption of air chamber 6
The optical signal gone out feeds back to another input that optical fiber two divides two couplers 5 again, forms optic fiber ring-shaped cavity；
Several optic fiber ring-shaped cavities being connected in series are also set up in the transmission direction of another way optical signal, each optical fiber
The output optical signal of annular chamber is respectively sent to corresponding photodetection change-over circuit 7 and carries out being converted to electric signal, photodetection
The electric signal that change-over circuit 7 exports after corresponding signal conditioning circuit and corresponding data acquisition circuit 9 are handled, passes successively
Deliver to corresponding PC 10 and calculate under test gas absorption loss amount, further according under test gas concentration and under test gas absorption loss
The relation of amount obtains the concentration of under test gas, finally realizes that single channel multipoint gas concentration detects.
2nd, optic fiber ring-shaped cavity is connected in parallel：
The gas concentration detection system based on dual wavelength light fibre annular-type cavity, including：
Microprocessor 4, the microprocessor 4 are connected with current driving circuit 3, the current driving circuit 3 and several
Distributed Feedback Laser 2 is connected；
The laser signal that each Distributed Feedback Laser 2 exports is sent to the input that optical fiber two divides two couplers 5, and
5 devices are coupled by the optical fiber one-to-two and are divided into two ways of optical signals；Wherein, optical signal is sent to air chamber 6 all the way, is absorbed through air chamber 6
The optical signal exported afterwards feeds back to another input that optical fiber two divides two couplers 5 again, forms optic fiber ring-shaped cavity；
Another way optical signal is sent to photodetection change-over circuit 7 and carries out being converted to electric signal, photodetection change-over circuit 7
The electric signal of output after signal conditioning circuit and data acquisition circuit 9 are handled, is sent to PC 10 and calculated to be measured successively
Gas absorption loss amount, the dense of under test gas is obtained further according to the relation of under test gas concentration and under test gas absorption loss amount
Degree；
Finally realize that several optic fiber ring-shaped cavities are connected in parallel the multi-channel gas Concentration Testing of form.
3rd, optic fiber ring-shaped cavity serial-parallel mirror connects：
The gas concentration detection system based on dual wavelength light fibre annular-type cavity, including：
Microprocessor 4, the microprocessor 4 are connected with current driving circuit 3, the current driving circuit 3 and several
Distributed Feedback Laser 2 is connected；
The laser signal that each Distributed Feedback Laser 2 exports is sent to the input that optical fiber two divides two couplers 5, and
Two couplers 5 are divided to be divided into two ways of optical signals by the optical fiber two；Wherein, optical signal is sent to air chamber 6 all the way, is absorbed through air chamber 6
The optical signal exported afterwards feeds back to another input that optical fiber two divides two couplers 5 again, forms optic fiber ring-shaped cavity；
Several optic fiber ring-shaped cavities being connected in series are also set up in the transmission direction of another way optical signal, each optical fiber
The output optical signal of annular chamber is respectively sent to corresponding photodetection change-over circuit 7 and carries out being converted to electric signal, photodetection
The electric signal that change-over circuit 7 exports after corresponding signal conditioning circuit and corresponding data acquisition circuit 9 are handled, passes successively
Deliver to corresponding PC 10 and calculate under test gas absorption loss amount, further according under test gas concentration and under test gas absorption loss
The relation of amount obtains the concentration of under test gas, finally realizes that multichannel multipoint gas concentration detects.
The process of aqueous vapor detection is carried out to air chamber using said detecting system, step is as follows：
1) detecting system is connected；The power supply of each circuit module is connected, debugging light path makes its normal work with circuit；Treat
Survey gas and pour air chamber；
2) bridge resistor in temperature control circuit is set as the constant constant temperature control to realize to Distributed Feedback Laser after a fixed value
System：Because Distributed Feedback Laser drive current variations can cause the change of the output wavelength of Distributed Feedback Laser, so utilizing microprocessor
Produce specific driving current, it is 1368.597nm Distributed Feedback Laser is sent wavelength (water vapor absorption peak is 1368.597nm wavelength)
Pulsed optical signals；
3) adjust and determine the suitable multiplication factor of amplifying circuit of optical signal transmission circuit, to export pulse during adjustment
Signal shows that optimum waveform state is advisable；
4) after multiplication factor is adjusted, regulation microprocessor changes Distributed Feedback Laser driving current so as to change output wave
Long, making output pulse wavelength, light pulse sequence X1 will be obtained by being declined by fiber optic loop after swinging, again outside moisture sorption wavelength
Regulation microprocessor changes Distributed Feedback Laser driving current so as to change output pulse wavelength, output pulse wavelength is inhaled in aqueous vapor
The long 1368.597nm of spike is received, light pulse sequence X2 will be obtained by being declined again by fiber optic loop after swinging, declined to swing twice and distinguished successively
Detected and led to after carrying out opto-electronic conversion, then the amplification of amplified circuit by photoelectric switching circuit by photodetection change-over circuit
Data collecting module collected data are crossed, are sent into PC.
The data of collection are used into exponential fitting function y=a*exp (- b*t) using PC successively；Y connects for PC in formula
The value data of receipts, t are the time that PC receives data, and a and b are parameter to be solved；It is respectively (a to draw two groups of solutions1, b1)
(a2, b2)；
Then by formula te/ T=10*loge/ Γ solve Γ respectively1, Γ2；
T in formulaeFor 1/e ring-down times, e refers to natural Exponents, teIt is able to can be obtained by formula 1/b；
T represents that light pulse surround the time once in fiber optic loop, as long as fiber lengths are certain, T is exactly a definite value, such as
20 meters of optical fiber, then T is just 100ns；
Γ1For the intrinsic total losses of system, Γ1It is represented by Γ1=αf+αcpl+αcol；
Γ2For system total losses, Γ2It is represented by Γ2=αf+αcpl+αcol+αgas；
Wherein, αfRepresent fibre loss, αcplRepresent coupler loss, αcolRepresent collimation loss, αgasRepresent that gas absorbs
Loss.
α is obtained by above-mentionedgas=Γ2-Γ1, then pass through formula αgas=10*log [P (λ)/P0(λ)] and formula C=1/
(βλ*L)*ln[P(λ)/P0(λ)] just try to achieve under test gas concentration；
C is under test gas concentration in formula, and P (λ) is light pulse input power, P0(λ) is light pulse power output, βλBe
The absorption coefficient of gas in specific wavelength, it can be obtained by measuring concentration known gas；L is air chamber physical length；λ is light arteries and veins
The wavelength of punching.
To make test result accurate, said process can be repeated several times.
5) under test gas detection finishes, and closes power supply.
It is a kind of as follows by self-defined wavelength measurement inherent loss step：
1) connection temperature control circuit, temperature control circuit connect Distributed Feedback Laser, electricity to microprocessor connection current driving circuit again simultaneously
Stream drive circuit also connect Distributed Feedback Laser, the drive signal of current driving circuit is sent by microprocessor, using temperature control circuit with
Current driving circuit carries out electric current driving and temperature-driven to Distributed Feedback Laser,
2) wavelength being in outside under test gas characteristic absorption wavelength is selected as measuring system inherent loss light arteries and veins
Rush wavelength (light pulse wavelength be in gas absorb outside, in experiment light pulse loss just all from gas absorption loss it
Outside, both system inherent loss), then change microprocessor output current, also just change Distributed Feedback Laser driving current, DFB swashs
Light device driving current changes, and Distributed Feedback Laser outgoing light pulse wavelength also just changes, by Distributed Feedback Laser emergent light impulse wave
Length is adjusted to above-mentioned selected wavelength.
3) light pulse sequence X2 will be obtained by the light pulse adjusted being declined by fiber optic loop after swinging, light pulse is then by light
Electrical resistivity survey surveys change-over circuit and detects and pass through number after carrying out opto-electronic conversion, then the amplification of amplified circuit by photoelectric switching circuit
According to Acquisition Circuit gathered data, PC is sent into, the data of collection are used into exponential fitting function y=a*exp (- b* using PC
T), then by formula te/ T=10*loge/ Γ solving system inherent losses.
Said process can be repeated several times test inherent loss and improve testing precision.
The present invention is as follows by fiber optic loop the step of swinging detection gas of declining：
1) optical fiber two divides two coupler output two paths of signals, connects air chamber all the way, connects photodetection conversion electricity all the way
Road, air chamber another way are coupled to coupler input；
2) pulse signal, which sends through this cycling circuit decline, swings detection.
Although above-mentioned the embodiment of the present invention is described with reference to accompanying drawing, model not is protected to the present invention
The limitation enclosed, one of ordinary skill in the art should be understood that on the basis of technical scheme those skilled in the art are not
Need to pay various modifications or deformation that creative work can make still within protection scope of the present invention.
Claims (9)
- A kind of 1. gas concentration detection system based on dual wavelength light fibre annular-type cavity, it is characterised in that including：Microprocessor, the microprocessor are connected with current driving circuit, and the current driving circuit is connected with Distributed Feedback Laser；The laser signal of the Distributed Feedback Laser output is sent to the input that optical fiber two divides two couplers, and by the optical fiber Two point of two coupler is divided into two ways of optical signals；Wherein, optical signal is sent to air chamber all the way, the optical signal exported after air chamber absorbs Another input that optical fiber two divides two couplers is fed back to again, forms optic fiber ring-shaped cavity；Another way optical signal is sent to photodetection change-over circuit and carries out being converted to electric signal, and the photodetection change-over circuit is defeated The electric signal gone out after signal conditioning circuit and data acquisition circuit processing, is sent to PC and calculates under test gas suction successively Waste is received, the concentration of under test gas is finally obtained according to the relation of under test gas concentration and under test gas absorption loss amount；Wherein, the data of reception are fitted by PC using exponential function y=a*exp (- b*t), are obtained two groups of solutions and are respectively (a1, b1) and (a2, b2), wherein y is the value data that PC receives, and t is the time that PC receives data, and a and b are to wait to ask Solve parameter；According to formula (1/b1)/T=10*loge/ Γ1(1/b2)/T=10*loge/ Γ2, it is intrinsic that system is solved respectively Total losses Γ1With system total losses Γ2, wherein T is that light pulse surround the time once in fiber optic loop, is definite value；E is referred to certainly Right index；According to gas absorption loss αgasEqual to system total losses Γ2With the intrinsic total losses Γ of system1Difference, finally obtain The absorption loss amount of under test gas.
- A kind of 2. gas concentration detection system based on dual wavelength light fibre annular-type cavity as claimed in claim 1, it is characterised in that The signal conditioning circuit includes amplifying circuit, the input of the amplifying circuit and the output end phase of photodetection change-over circuit Even, the output end of amplifying circuit is connected with the input of filter circuit, the output end of filter circuit and data acquisition circuit it is defeated Enter end to be connected.
- A kind of 3. gas concentration detection system based on dual wavelength light fibre annular-type cavity, it is characterised in that including：Microprocessor, the microprocessor are connected with current driving circuit, and the current driving circuit is connected with Distributed Feedback Laser；The laser signal of the Distributed Feedback Laser output is sent to the input that optical fiber two divides two couplers, and by the optical fiber Two point of two coupler is divided into two ways of optical signals；Wherein, optical signal is sent to air chamber all the way, the optical signal exported after air chamber absorbs Another input that optical fiber two divides two couplers is fed back to again, forms optic fiber ring-shaped cavity；Several optic fiber ring-shaped cavities being connected in series are also set up in the transmission direction of another way optical signal, each fiber annular The output optical signal of chamber is respectively sent to corresponding photodetection change-over circuit and carries out being converted to electric signal, photodetection conversion electricity The electric signal of road output after corresponding signal conditioning circuit and the processing of corresponding data acquisition circuit, is sent to corresponding successively PC and calculate under test gas absorption loss amount, come further according to the relation of under test gas concentration and under test gas absorption loss amount The concentration of under test gas is obtained, finally realizes that single channel multipoint gas concentration detects.
- A kind of 4. gas concentration detection system based on dual wavelength light fibre annular-type cavity, it is characterised in that including：Microprocessor, the microprocessor are connected with current driving circuit, the current driving circuit and several Distributed Feedback Lasers It is connected；The laser signal of each Distributed Feedback Laser output is sent to the input that optical fiber two divides two couplers, and by described Optical fiber two divides two couplers to be divided into two ways of optical signals；Wherein, optical signal is sent to air chamber all the way, the light exported after air chamber absorbs Signal feeds back to another input that optical fiber two divides two couplers again, forms optic fiber ring-shaped cavity；Another way optical signal is sent to photodetection change-over circuit and carries out being converted to electric signal, the output of photodetection change-over circuit Electric signal after signal conditioning circuit and data acquisition circuit processing, is sent to PC and calculates under test gas absorption damage successively Consumption, the concentration of under test gas is obtained further according to the relation of under test gas concentration and under test gas absorption loss amount；Finally realize that several optic fiber ring-shaped cavities are connected in parallel the multi-channel gas Concentration Testing of form.
- A kind of 5. gas concentration detection system based on dual wavelength light fibre annular-type cavity, it is characterised in that including：Microprocessor, the microprocessor are connected with current driving circuit, the current driving circuit and several Distributed Feedback Lasers It is connected；The laser signal of each Distributed Feedback Laser output is sent to the input that optical fiber two divides two couplers, and by described Optical fiber two divides two couplers to be divided into two ways of optical signals；Wherein, optical signal is sent to air chamber all the way, the light exported after air chamber absorbs Signal feeds back to another input that optical fiber two divides two couplers again, forms optic fiber ring-shaped cavity；Several optic fiber ring-shaped cavities being connected in series are also set up in the transmission direction of another way optical signal, each fiber annular The output optical signal of chamber is respectively sent to corresponding photodetection change-over circuit and carries out being converted to electric signal, photodetection conversion electricity The electric signal of road output after corresponding signal conditioning circuit and the processing of corresponding data acquisition circuit, is sent to corresponding successively PC and calculate under test gas absorption loss amount, come further according to the relation of under test gas concentration and under test gas absorption loss amount The concentration of under test gas is obtained, finally realizes that multichannel multipoint gas concentration detects.
- 6. a kind of detection method of gas concentration detection system as claimed in claim 1 based on dual wavelength light fibre annular-type cavity, It is characterised in that it includes：Step (1)：The circuit in gas concentration detection system is connected, forms single optic fiber ring-shaped cavity；Step (2)：The wavelength that Distributed Feedback Laser output laser signal is adjusted by microprocessor is respectively under test gas absorbing wavelength And other wavelength in addition under test gas absorbing wavelength；Step (3)：By the laser signal of two kinds of wavelength in step (2) respectively by obtaining light pulse after fiber annular cavity-type BPM Sequence, and be sent to after processing in PC and carry out solving under test gas absorption loss amount；Step (4)：According under test gas concentration and the relation of under test gas absorption loss amount, finally it is calculated to be measured in air chamber The concentration of gas.
- 7. a kind of detection method of gas concentration detection system as claimed in claim 3 based on dual wavelength light fibre annular-type cavity, It is characterised in that it includes：Step (1)：The circuit in gas concentration detection system is connected, realizes that multiple optic fiber ring-shaped cavities are connected in series；Step (2)：The wavelength that Distributed Feedback Laser output laser signal is adjusted by microprocessor is respectively under test gas absorbing wavelength And other wavelength in addition under test gas absorbing wavelength；Step (3)：The laser signal of two kinds of wavelength in step (2) is passed sequentially through to the optic fiber ring-shaped cavity being connected in series respectively to decline Light pulse sequence is obtained after swinging, and is sent to after processing in PC and carries out solving under test gas absorption loss amount；Step (4)：According under test gas concentration and the relation of under test gas absorption loss amount, finally it is calculated in series connection air chamber The concentration of under test gas in each air chamber.
- 8. a kind of detection method of gas concentration detection system as claimed in claim 4 based on dual wavelength light fibre annular-type cavity, It is characterised in that it includes：Step (1)：The circuit in gas concentration detection system is connected, realizes that multiple optic fiber ring-shaped cavities are connected in parallel；Step (2)：The wavelength that each Distributed Feedback Laser output laser signal is adjusted by microprocessor is respectively that under test gas absorbs Wavelength and other wavelength in addition under test gas absorbing wavelength；Step (3)：By the laser signal of two kinds of wavelength in step (2) respectively by obtaining light after each fiber annular cavity-type BPM Pulse train, and be sent to after processing in PC and carry out solving under test gas absorption loss amount；Step (4)：According under test gas concentration and the relation of under test gas absorption loss amount, finally it is calculated in air chamber in parallel The concentration of under test gas in each air chamber.
- 9. a kind of detection method of gas concentration detection system as claimed in claim 5 based on dual wavelength light fibre annular-type cavity, It is characterised in that it includes：Step (1)：The circuit in gas concentration detection system is connected, realizes that optic fiber ring-shaped cavity serial-parallel mirror connects；Step (2)：The wavelength that each Distributed Feedback Laser output laser signal is adjusted by microprocessor is respectively that under test gas absorbs Wavelength and other wavelength in addition under test gas absorbing wavelength；Step (3)：The optic fiber ring-shaped cavity that the laser signal of two kinds of wavelength in step (2) is connected by serial-parallel mirror respectively is declined Light pulse sequence is obtained after swinging, and is sent to after processing in PC and carries out solving under test gas absorption loss amount；Step (4)：According under test gas concentration and the relation of under test gas absorption loss amount, serial-parallel mirror company is finally calculated Connect the concentration of under test gas in each air chamber in air chamber.
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| CN107192684A (en) * | 2016-03-14 | 2017-09-22 | 热映光电股份有限公司 | Gas concentration arrangement for detecting and its method for detecting |
| CN105699329A (en) * | 2016-04-08 | 2016-06-22 | 济南大学 | Wavelength scanning spectrum gas detection system and method based on double optical fiber annular cavities |
| CN106950194B (en) * | 2017-03-17 | 2018-06-12 | 哈尔滨翰奥科技有限公司 | Gas sensor and the method for detecting concentration of SO 2 gas variation |
| CN107991269B (en) * | 2018-01-23 | 2023-07-14 | 山东省科学院激光研究所 | Multicomponent gas monitoring system, method and device |
| CN108685576B (en) * | 2018-03-23 | 2021-08-31 | 上海师范大学 | Multi-user respiratory frequency detection system based on optical fiber sensing |
| CN109100330B (en) * | 2018-08-24 | 2021-06-01 | 中国科学院上海光学精密机械研究所 | Optical element high reflectivity measuring system and measuring method |
| CN109406450B (en) * | 2018-10-18 | 2021-05-28 | 山东大学 | Multiple absorption type trace gas detection system |
| CN109459393A (en) * | 2018-12-25 | 2019-03-12 | 厦门蓝海之光科技有限公司 | Specific gas multiposition detection system |
| CN109946237B (en) * | 2019-04-09 | 2021-12-03 | 山东大学 | Light intensity enhanced photoacoustic spectroscopy gas detection system |
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