CN110426369A - A kind of distribution type fiber-optic gas-detecting device and method based on sweep frequency technique - Google Patents
A kind of distribution type fiber-optic gas-detecting device and method based on sweep frequency technique Download PDFInfo
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- CN110426369A CN110426369A CN201910696003.6A CN201910696003A CN110426369A CN 110426369 A CN110426369 A CN 110426369A CN 201910696003 A CN201910696003 A CN 201910696003A CN 110426369 A CN110426369 A CN 110426369A
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Abstract
The invention discloses a kind of distribution type fiber-optic gas-detecting device and method based on sweep frequency technique, including first laser device, the first isolator, the first coupler, acousto-optic modulator, sensor fibre, the second erbium-doped fiber amplifier, the second coupler of second laser, scrambler, third coupler, the 4th coupler, the 5th coupler, the first photodetector, the second photodetector, impulse generator, pass through sweep frequency technique, each test point on sensor fibre is taken multiple scan, realizes effective inhibition in dead zone.Direct impulse signal generates back rayleigh scattering signal in sensor fibre, by the Rayleigh scattering signal phase information of detection reflection, obtains the concentration and composition information of upper gas along sensor fibre.The method of the present invention is simple, the detection of high-precision gas concentration information may be implemented, and detect applicability having the same to multiple gases.
Description
Technical field
The present invention relates to a kind of gas-detecting device and methods, and in particular to a kind of continuously distributed formula fiber-optic fiber gas detection
Device and method.
Background technique
The fast-developing bring safety problem very severe of China's economy, all kinds of serious accidents frequently occurred, not only
Personal injury is caused to related practitioner, country is returned and causes huge economic loss, produces severe social shadow
It rings.These accidents are substantially all the relevant issues such as the quick detection for being related to hazardous gas, real-time monitoring.In addition, ring in recent years
Phenomena such as border problem is also outstanding day by day, greenhouse effects, acid rain caused by atmosphere pollution, haze not only to society cause directly or
Indirect economic loss even more causes serious harm to people's health.Optical fiber sensing technology be using optical fiber as carrier,
Perception and the New Sensing Technology for transmitting extraneous measured signal, fibre optical sensor have anti-electricity relative to conventional electrical sensor
Magnetic disturbance and radiation, light, insulation, a variety of advantages such as measurement object is more, reusability is strong, it is more due to optical fiber sensing technology itself
Kind advantage obtains the concern of every field researcher once occurring just having been attached great importance.Therefore, it develops various highly sensitive
Degree, quick response, can be remotely located detection fiber gas sensor it is imperative, it has also become the master of current field of sensing technologies
Want research contents.Currently, the fiber gas sensor of report is concentrated mainly on based on common or photonic crystal fiber point type
On fiber gas sensor, it can not realize therefore remote online gas detection makes full use of photonic crystal fiber in gas
Advantage in physical examination survey, research distribution type fiber-optic gas sensor technology have very important learning value and application value.
2014, the researchers such as Li Gang proposed a kind of distributed gas sensor-based system and its control method, application No. is
201410708072.1, Multichannel photoswitch is controlled by master control borad, a laser control multichannel is realized and carries out gas detection,
Greatly reduce system cost.2015, the researchers such as Zheng Guanghui proposed distributed fiberoptic sensor, application No. is
201510071655.2, using optical fiber by gas-detecting device and including laser source, demodulating equipment, photoelectric detector host
Part is attached, and shoot laser and reflection laser pass through optical fiber and propagate between these, is suitable at a distance
The detection of website gas sensing.2015, the researchers such as Jin Wei proposed the gas detection side based on hollow-core fiber photo-thermal effect
Method and system are detected, method is simple and real application No. is 201510005210.4 using pumping and detecting double excitation scheme
With minimum facula area may be implemented, substantially increase optical power density, so that Photothermal Signals intensity be made to be enhanced.
2018, height is for army building to wait researchers to propose a kind of device and method of continuously distributed formula fiber-optic fiber gas detection, application No. is
201810144950.X makees using femtosecond processing technology production aperture as the storage gas chamber of gas on general single mode fiber
For the interaction zone of gas and light on sensor fibre, gas absorbs pumping laser signal and generates modulation phenomenon, recycles
The back rayleigh scattering detection pump signal of exploring laser light signal in a fiber generates on along the sensor fibre of modulation phenomenon
Phase information realizes the gas concentration information on along sensor fibre.From the point of view of these reports, these inventions are all point type optical fiber
Gas sensor cannot deserve to be called distribution type fiber-optic gas sensor, and cannot realize that upper gas is joined more along optical fiber simultaneously
The measurement of amount is difficult to carry out the implementation of industrialization.
Summary of the invention
Present invention aims at provide a kind of distribution type fiber-optic gas-detecting device and method based on sweep frequency technique, no
The shortcomings that existing gas detection technology can only be overcome and insufficient, the fiber-optic fiber gas detection of realization distributed gas concentration, and
It can be realized the measurement request of quick high accuracy, it is easy to accomplish the advantages that.
Technical solution: to achieve the above object, the technical solution adopted by the present invention are as follows:
A kind of distribution type fiber-optic gas-detecting device based on sweep frequency technique, including first laser device, the first isolator,
One coupler, acousto-optic modulator, the first erbium-doped fiber amplifier, circulator, sensor fibre, the second erbium-doped fiber amplifier,
Two isolators, second laser, laser controller, lock-in amplifier, the second coupler, scrambler, third coupler, the 4th coupling
Clutch, the 5th coupler, the first photodetector, the second photodetector, data acquisition card, signal processing and display unit,
Impulse generator, signal processing and display unit, wherein the first laser device, the first isolator, the first coupler, acousto-optic
Modulator, the first erbium-doped fiber amplifier, circulator, sensor fibre, the second erbium-doped fiber amplifier, the second isolator, second
Laser, laser controller, lock-in amplifier are sequentially connected, second coupler respectively with the first coupler, scrambler,
The connection of three couplers, the 4th coupler are connect with circulator, third coupler, the 5th coupler respectively, the 5th coupling
Clutch is connect with scrambler, the first photodetector respectively, and second photodetector is adopted with third coupler, signal respectively
Truck connection, the signal processing and display unit are connect with first laser device, data acquisition card respectively, the impulse generator
It is connect respectively with acousto-optic modulator, data acquisition card, the data acquisition card amplifies with the first photodetector, locking phase respectively
The laser signal that device, signal processing and display unit connection first laser device 100 issue enters the first coupling through the first isolator 101
Laser signal is divided into two beam signal the first beam laser signal beam laser signals, beam of laser by clutch 102, the first coupler
Signal enters the second coupler as local oscillation signal, and the second beam laser signal enters acousto-optic modulator 103), acousto-optic modulator will
Second beam laser signal is modulated into pulse signal, and the frequency of signal generates frequency displacement, into the first erbium-doped fiber amplifier, warp
The amplified pulse signal of first erbium-doped fiber amplifier enters the port circulator 1051#, exports and enters from the port circulator 2#
Sensor fibre 106, in sensor fibre, pulse signal generates back rayleigh scattering signal, and back rayleigh scattering signal passes through ring
The port shape device 1052# enters circulator 105, and the back rayleigh scattering signal exported from the port circulator 1053# enters the 4th coupling
Back rayleigh scattering signal is divided into two beam signal the first beam back rayleigh scattering signal beams and carried on the back by clutch 115, the 4th coupler
To Rayleigh scattering signal, the first beam back rayleigh scattering signal enters third coupler, the second beam back rayleigh scattering signal into
Enter the 5th the second coupler of coupler and local oscillation signal is divided into two beam signal the first beam local oscillation signal beam local oscillation signals, the first beam
Local oscillation signal enters third coupler, and the signal of third coupler output is converted into telecommunications after entering the first photodetector 118
Number, electric signal, which is input in data acquisition card 119, enters scrambler from the second beam local oscillation signal that the second coupler 112 exports
In 113, by disturbing inclined local oscillation signal into the 5th coupler 116, the signal exported from the 5th coupler enters the second photoelectricity
Electric signal is converted into after detector 117, electric signal is input to the letter all the way that data acquisition card 119 exports in data acquisition card 119
Number enter lock-in amplifier 111, lock-in amplifier output is signally attached to laser controller 110, laser controller it is defeated
Signal drives second laser 109 out, and the laser signal exported from second laser enters second by the second isolator 108 and mixes
Doped fiber amplifier 107, the signal amplified through the second erbium-doped fiber amplifier enters sensor fibre, to be measured in sensor fibre
Gas absorbs the signal exported from the second erbium-doped fiber amplifier 107, phase-modulation phenomenon is generated, from the port circulator 1052#
The pulse electrical signal that the phase information 121 for the pulse signal detection phase-modulation phenomenon being input in sensor fibre generates is connected to
The synchronization signal of electric signal input end driving optical modulator 103 work and 120 outputs of acousto-optic modulator is connected to signal acquisition
The synchronous signal input end of card 119 is to keep data acquisition card, acousto-optic modulator and first laser device to be in synchronous regime, and 120
First laser device is connected, driving first laser device carries out frequency sweep control, and the another way of data acquisition card output is signally attached to letter
Number processing and display unit 120, obtain sensor fibre along on gas concentration information.
Preferred: the first laser device and second laser are wavelength and the humorous laser of power adjustable.
Preferred: the sensor fibre is hollow-core photonic crystal fiber.
Preferred: the sensor fibre has the channel orifices for entering hollow-core fiber as gas along optical fiber surface production.
Preferred: the channel orifices diameter is about 1-10.0 μm.
Preferred: first photodetector, the second photodetector are balanced detector.
A kind of detection method using the distribution type fiber-optic gas-detecting device based on sweep frequency technique, first laser device issue
Laser signal enter the first coupler through the first isolator, laser signal is divided into two beam signals by the first coupler, respectively
First beam laser signal and the second beam laser signal, the first beam laser signal as local oscillation signal enter the second coupler, second
Beam laser signal enters acousto-optic modulator, and the second beam laser signal is modulated into pulse signal, and the frequency of signal by acousto-optic modulator
Rate generates frequency displacement, into the first erbium-doped fiber amplifier, enters through the amplified pulse signal of the first erbium-doped fiber amplifier
The port 1# of circulator, from the port 2# of circulator, output enters sensor fibre, and in sensor fibre, pulse signal is generated backwards
Rayleigh scattering signal, back rayleigh scattering signal enter circulator by the port 2# of circulator, defeated from the port 3# of circulator
Back rayleigh scattering signal out enters the 4th coupler, and back rayleigh scattering signal is divided into two beam signals by the 4th coupler,
Respectively the first beam back rayleigh scattering signal and the second beam back rayleigh scattering signal, the first beam back rayleigh scattering signal into
Enter third coupler, the second beam back rayleigh scattering signal enters the 5th coupler；Local oscillation signal is divided into two by the second coupler
Beam signal, respectively the first beam local oscillation signal and the second beam local oscillation signal, the first beam local oscillation signal enter third coupler, and first
Beam back rayleigh scattering signal and the first beam local oscillation signal are coupled in third coupler, the signal after third coupler output coupling
It is converted into electric signal after into the first photodetector, electric signal is input in data acquisition card；It is exported from the second coupler
Second beam local oscillation signal enters in scrambler, by disturbing inclined local oscillation signal into the 5th coupler, disturb inclined local oscillation signal and
Second beam back rayleigh scattering signal is coupled in the 5th coupler, and the signal exported from the 5th coupler enters the second photodetection
Electric signal is converted into after device, electric signal is input in data acquisition card；The signal all the way of data acquisition card output enters locking phase
Amplifier, lock-in amplifier output are signally attached to laser controller, and the output signal of laser controller drives second laser
Device, the laser signal exported from second laser enters the second erbium-doped fiber amplifier by the second isolator, through the second er-doped
The signal of fiber amplifier amplification enters sensor fibre, and in sensor fibre, under test gas is absorbed from the second Erbium-doped fiber amplifier
The signal of device output, generates phase-modulation phenomenon, is input to the pulse signal detection in sensor fibre from the port 2# of circulator
The phase information of phase-modulation phenomenon；The pulse electrical signal that impulse generator generates is connected to the electric signal input of acousto-optic modulator
End driving optical modulator work, impulse generator and signal processing and the synchronization signal of display unit output are connected to signal acquisition
The synchronous signal input end of card is to keep data acquisition card, acousto-optic modulator and first laser device to be in synchronous regime, at signal
Reason and display unit connect first laser device, and driving first laser device carries out frequency sweep control, the another way of data acquisition card output
It is signally attached to signal processing and display unit, obtains the gas concentration information on along sensor fibre.
It is preferred: to need the relationship of calibration concentration and phase size in advance when the data of display, obtained under different frequency
The curvilinear correlation degree of the distribution type fiber-optic gas sensor obtained indicates are as follows:
The minimum C=0.99 of curvilinear correlation degree, obtains:
Wherein, C is curvilinear correlation degree, and W is detection pulsewidth, and Δ f is the difference on the frequency between two curves.
Preferred: the frequency shift amount of the first laser device and second laser 1ms are less than or equal to 0.017M.
Preferred: the first laser device and the sweep velocity of second laser are less than 17M/S.
The present invention compared with prior art, has the advantages that
The present invention enters hollow light using femtosecond processing technology production aperture as gas on hollow-core photonic crystal fiber
Fine channel, gas absorb pumping laser signal and generate modulation phenomenon, recycle exploring laser light signal in a fiber backwards to auspicious
Benefit scattering detection pump signal generates the phase information on along the sensor fibre of modulation phenomenon, realizes on along sensor fibre
Gas concentration information controls first laser device by computer and carries out slow frequency sweep in measurement process, to eliminate relevant decline
Influence of the noise to distribution type fiber-optic gas detecting system is fallen, the blind area of distribution type fiber-optic gas detection measurement is reduced.Detection dress
Set that system structure is simple, result accuracy is high, stability of instrument is good.
Detailed description of the invention
Fig. 1 is the structural schematic block diagram of apparatus of the present invention；
Fig. 2 is sensor fibre structural schematic diagram of the invention.
Fig. 3 is the frequency domain figure of detection gas position of the invention.
Fig. 4 is the experiment curv figure along sensor fibre of the invention.
Specific embodiment
In the following with reference to the drawings and specific embodiments, the present invention is furture elucidated, it should be understood that these examples are merely to illustrate this
It invents rather than limits the scope of the invention, after the present invention has been read, those skilled in the art are to of the invention various
The modification of equivalent form falls within the application range as defined in the appended claims.
A kind of distribution type fiber-optic gas-detecting device based on sweep frequency technique, as shown in Figure 1, include first laser device 100,
First isolator 101, acousto-optic modulator 103, the first erbium-doped fiber amplifier 104, circulator 105, passes first coupler 102
Photosensitive fine 106, the second erbium-doped fiber amplifier 107, the second isolator 108, second laser 109, laser controller 110, lock
Phase amplifier 111, the second coupler 112, scrambler 113, third coupler 114, the 4th coupler 115, the 5th coupler
116, the first photodetector 117, the second photodetector 118, data acquisition card 119, signal processing and display unit 120,
Impulse generator 121, signal processing and display unit 122, wherein the first laser device 100, the first isolator 101, first
Coupler 102, acousto-optic modulator 103, the first erbium-doped fiber amplifier 104, circulator 105, sensor fibre 106, the second er-doped
Fiber amplifier 107, the second isolator 108, second laser 109, laser controller 110, lock-in amplifier 111 successively connect
It connecing, second coupler 112 is connect with the first coupler 102, scrambler 113, third coupler 114 respectively, and the described 4th
Coupler 115 is connect with circulator 105, third coupler 114, the 5th coupler 116 respectively, and the 5th coupler 116 divides
Do not connect with scrambler 113, the first photodetector 117, second photodetector 118 respectively with third coupler 114,
Data acquisition card 119 connects, the signal processing and display unit 120 respectively with first laser device 100, data acquisition card 119
Connection, the impulse generator 121 are connect with acousto-optic modulator 103, data acquisition card 119 respectively, the data acquisition card 119
First laser device 100 is connect with the first photodetector 117, lock-in amplifier 111, signal processing and display unit 122 respectively
The laser signal of sending enters the first coupler 102 through the first isolator 101, and laser signal is divided into two by the first coupler 102
Beam signal the first beam laser signal beam laser signal, the first beam laser signal enter the second coupler 112 as local oscillation signal,
Second beam laser signal enters acousto-optic modulator 103, and the second beam laser signal is modulated into pulse signal by acousto-optic modulator 103,
And the frequency of signal generates frequency displacement, into the first erbium-doped fiber amplifier 104, amplifies through the first erbium-doped fiber amplifier 104
Pulse signal afterwards enters the port circulator 1051#, and from the port circulator 1052#, output enters sensor fibre 106, in sense light
In fibre 106, pulse signal generates back rayleigh scattering signal, and back rayleigh scattering signal is entered by the port circulator 1052#
Circulator 105, the back rayleigh scattering signal exported from the port circulator 1053# enter the 4th coupler 115, the 4th coupler
Back rayleigh scattering signal is divided into two beam signal the first beam back rayleigh scattering signal beam back rayleigh scattering signals, first
Beam back rayleigh scattering signal enters third coupler, and the second beam back rayleigh scattering signal is coupled into the 5th coupler second
Local oscillation signal is divided into two beam signal the first beam local oscillation signal beam local oscillation signals by device, and the first beam local oscillation signal enters third coupling
Device 114, the signal that third coupler 114 exports are converted into electric signal after entering the first photodetector 118, and electric signal is input to
Enter in scrambler 113 in data acquisition card 119 from the second beam local oscillation signal that the second coupler 112 exports, it is inclined by disturbing
Local oscillation signal enters the 5th coupler 116, and the signal exported from the 5th coupler 116 turns after entering the second photodetector 117
Change electric signal into, the signal all the way that electric signal is input to the output of data acquisition card 119 in data acquisition card 119 enters locking phase and puts
Big device 111, what lock-in amplifier 111 exported is signally attached to laser controller 110, and the output signal of laser controller 110 is driven
Dynamic second laser 109, the laser signal exported from second laser 109 enter the second er-doped light by the second isolator 108
Fiber amplifier 107, the signal amplified through the second erbium-doped fiber amplifier 107 enters sensor fibre 106, in sensor fibre 106,
Under test gas absorbs the signal exported from the second erbium-doped fiber amplifier 107, phase-modulation phenomenon is generated, from circulator 1052#
Port is input to the pulse telecommunications that the phase information 121 of the pulse signal detection phase-modulation phenomenon in sensor fibre 106 generates
The electric signal input end driving optical modulator 103 for number being connected to acousto-optic modulator 103 works, the synchronization signals of 121 and 120 outputs
The synchronous signal input end of data acquisition card 119 is connected to keep data acquisition card 119, acousto-optic modulator 103 and first to swash
Light device 100 is in synchronous regime, 120 connection first laser devices 100, and driving first laser device 100 carries out frequency sweep control, and signal is adopted
The another way of truck output is signally attached to signal processing and display unit 120, obtains the gas concentration on along sensor fibre
Information.
The first laser device 100 and second laser 109 are wavelength and the humorous laser of power adjustable.The sensing
Optical fiber 106 is hollow-core photonic crystal fiber.
Sensor fibre is uniformly distributed along optical fiber surface using the production of femtosecond processing technology or the channel orifices of non-uniform Distribution
Enter the channel of hollow-core fiber as gas, the channel orifices diameter is about 1-10.0 μm.
First photodetector 117, the second photodetector 118 are the photoelectricity spy of balanced detector or other types
Survey device.
A kind of detection method using the distribution type fiber-optic gas-detecting device based on sweep frequency technique, first laser device 100
The laser signal that (narrow line wide cavity tunable laser ECDL) is issued enters 102 (coupling of the first coupler through the first isolator 101
Composition and division in a proportion 80:20), first laser device is narrow line wide cavity tunable laser ECDL, and the detection signal wavelength that output is arranged is
Laser signal is divided into two beam signals by 1550.60nm, output power 14dBm, the first coupler 102, and respectively the first beam swashs
Optical signal and the second beam laser signal, the first beam laser signal (80%) as local oscillation signal enter the second coupler 112, second
Beam laser signal (20%) enters acousto-optic modulator 103, and acousto-optic modulator is Gooch&HouseGo M040, acousto-optic modulator
Fixing frequency displacement is 200MHz, and the period of pulsed light is T=3.3 μ s, pulsewidth w=100ns, and acousto-optic modulator 103 is by the second beam
Laser signal is modulated into pulse signal, and the frequency of signal generates frequency displacement, into the first erbium-doped fiber amplifier 104, first
Erbium-doped fiber amplifier is KPS-BT2-C-30-PB-FA, output power range 10-30dBm, and setting output power is
22dBm enters the port 1# of circulator 105 through the amplified pulse signal of the first erbium-doped fiber amplifier 104, from circulator
105 port 2# output enters sensor fibre 106, and the structure of sensor fibre is as shown in Fig. 2, sensor fibre is the photon of 1000m
Crystal optical fibre is spaced 50m on sensor fibre using femtosecond processing technology and makes a circular hole, as channel orifices, circular hole
Diameter is 6.0 μm, and sensor fibre has been placed on acetylene (C2H2) gas environment in, in sensor fibre 106, pulse signal generate
Back rayleigh scattering signal, back rayleigh scattering signal enters circulator 105 by the port 2# of circulator 105, from circulator
The back rayleigh scattering signal of 105 port 3# output enters the 4th coupler 115, the coupling ratio 50 of the 4th coupler 115:
50, back rayleigh scattering signal is divided into two beam signals by the 4th coupler 115, respectively the first beam back rayleigh scattering signal and
Second beam back rayleigh scattering signal, the first beam back rayleigh scattering signal enter third coupler 114 (coupling ratio 50:50),
Second beam back rayleigh scattering signal enters the 5th coupler 116 (coupling ratio 50:50)；Second coupler 112 (coupling ratio 50:
50) local oscillation signal is divided into two beam signals, respectively the first beam local oscillation signal and the second beam local oscillation signal, the first beam local oscillation signal
Into third coupler 114, the first beam back rayleigh scattering signal and the first beam local oscillation signal are coupled in third coupler 114,
Signal after 114 output coupling of third coupler is converted into electric signal, the first photodetection after entering the first photodetector 118
Device is balanced detector, bandwidth 350MHz, and electric signal is input in data acquisition card 119；It is exported from the second coupler 112
The second beam local oscillation signal enter in scrambler 113, by disturbing inclined local oscillation signal into the 5th coupler 116, disturb inclined sheet
Vibration signal and the second beam back rayleigh scattering signal couple in the 5th coupler 116, from the 5th coupler 116 output signal into
Entering and is converted into electric signal after the second photodetector 117, the second photodetector is balanced detector, bandwidth 350MHz,
Electric signal is input in data acquisition card 119；The signal all the way that data acquisition card 119 exports enters lock-in amplifier 111, locks
Phase amplifier is SR865ALock-In Amplifier, and data acquisition card is DAQPCIE 9081, sample rate 1.25GSa/
S, what lock-in amplifier 111 exported is signally attached to laser controller 110, the output signal driving second of laser controller 110
Laser 109, second laser are Distributed Feedback Laser, wherein a length of 1527-1610nm of cardiac wave, as setting output wavelength
1530.371nm, output power 0dBm, the laser signal exported from second laser 109 are entered by the second isolator 108
Second erbium-doped fiber amplifier 107, the second erbium-doped fiber amplifier are the continuous er-doped of CEFA-C-BO-HP series C-band high power
Fiber amplifier, output power are set as 25dBm, and the signal amplified through the second erbium-doped fiber amplifier 107 enters sensor fibre
106, in sensor fibre 106, under test gas absorbs the signal exported from the second erbium-doped fiber amplifier 107, generates phase tune
Phenomenon processed is input to the phase of the pulse signal detection phase-modulation phenomenon in sensor fibre 106 from the port 2# of circulator 105
Information；The pulse electrical signal that impulse generator 121 generates is connected to the electric signal input end driving light modulation of acousto-optic modulator 103
Device 103 works, and the synchronization signal that impulse generator 121 and signal processing and display unit (computer) 120 export is connected to letter
The synchronous signal input end of number capture card 119 is to keep at data acquisition card 119, acousto-optic modulator 103 and first laser device 100
In synchronous regime, signal processing and display unit 120 connect first laser device 100, and driving first laser device 100 carries out frequency sweep control
System, impulse generator are Agilent 81110A, and the frequency of output signal is 0-330MHz, and data acquisition card 119 exports another
It is signally attached to signal processing and display unit 120 all the way, obtains the gas concentration information on along sensor fibre 106.Finally
The relationship of calibration concentration and phase size in advance is needed when the data of display.The distribution type fiber-optic gas obtained under different frequency
The curvilinear correlation degree of body sensor can be expressed as
Wherein, W is detection pulsewidth, and Δ f is the difference on the frequency between two curves, from formula (1) if can be seen that laser light
The speed of source frequency sweep is slow enough, so that the speed of frequency drift is sufficiently small, then can make distributed light in a short time
The experiment curv of the fiber sensor degree of correlation with higher, and then detect the upper energy absorbed with the presence or absence of gas along sensor fibre
Power is unaffected, due to distributed fiberoptic sensor must frequency of use drift about small, line width light source, this will pass through distribution
Formula fibre optical sensor introduces very strong interference fading noise when detecting sensor fibre.And interference fading noise can be by frequency sweep side
Formula is inhibited, therefore introducing sweep frequency technique can guarantee that distributed fiberoptic sensor measure without dead zone on along optical fiber
When phase change, while the detection of sensor fibre loss event can be carried out.In order to guarantee distributed fiberoptic sensor to sensing
The measurement performance of upper gas detection along optical fiber, the minimum C=0.99 of curvilinear correlation degree, by formula (1) it can be concluded that
From formula (2) as can be seen that when pulse width determines, the maximum speed of laser sweep will be determined, laser
Frequency shift amount f≤0.0017/W=0.017M of 1ms, in an experiment, the pulse width selected are 100ns, the frequency sweep speed of laser
Degree should be less than 0.0017M/0.0001S=17M/S, for the decline noise of effective suppression curve, by the frequency sweep speed of laser
Rate is set as 10M/S.Measure frequency domain figure such as Fig. 3 institute in the case of the phase change that under test gas absorption generates on sensor fibre
Show, as we can see from the figure when distribution type fiber-optic gas sensing system carries out frequency sweep with 10M/S speed, the signal frequency of measurement
For 105.5Hz, signal-to-noise ratio 12dB, distribution type fiber-optic gas detection curve such as figure obtained in different accumulative frequencies
Shown in 4, interference fading noise has obtained good inhibition, and some small loss events can also observe.
In measurement process, first laser device is controlled by computer and carries out slow frequency sweep, is made an uproar with eliminating interference fading
Influence of the sound to distribution type fiber-optic gas detecting system reduces the blind area of distribution type fiber-optic gas detection measurement.
The present invention is the region of detection gas and light interaction using hollow-core photonic crystal fiber as sensor fibre,
In order to reduce dead zone phenomenon caused by interference fading effect in traditional distributed fiber-optic fiber gas detection device, by sweep frequency technique,
Each test point on sensor fibre is taken multiple scan, realizes effective inhibition in dead zone.The signal that second laser issues
It interacting in sensor fibre with gas as pump light, gas generates periodic modulating characteristic after absorbing pump light, the
The gas of detectable signal and periodic modulation that one laser issues interacts, so that the phase of detectable signal generates variation,
Direct impulse signal generates back rayleigh scattering signal in sensor fibre, is believed by the Rayleigh scattering signal phase of detection reflection
Breath obtains the concentration and composition information of upper gas along sensor fibre.The method of the present invention is simple, and high-precision gas may be implemented
The detection of concentration information, and applicability having the same is detected to multiple gases.
The above is only a preferred embodiment of the present invention, it should be pointed out that: for the ordinary skill people of the art
For member, various improvements and modifications may be made without departing from the principle of the present invention, these improvements and modifications are also answered
It is considered as protection scope of the present invention.
Claims (10)
1. a kind of distribution type fiber-optic gas-detecting device based on sweep frequency technique, it is characterised in that: including first laser device
(100), the first isolator (101), the first coupler (102), acousto-optic modulator (103), the first erbium-doped fiber amplifier
(104), circulator (105), sensor fibre (106), the second erbium-doped fiber amplifier (107), the second isolator (108), second
Laser (109), laser controller (110), lock-in amplifier (111), the second coupler (112), scrambler (113), third
Coupler (114), the 4th coupler (115), the 5th coupler (116), the first photodetector (117), the second photodetection
Device (118), data acquisition card (119), signal processing and display unit (120), impulse generator (121), signal processing and aobvious
Show unit (122), wherein the first laser device (100), the first isolator (101), the first coupler (102), acousto-optic modulation
Device (103), the first erbium-doped fiber amplifier (104), circulator (105), sensor fibre (106), the second erbium-doped fiber amplifier
(107), the second isolator (108), second laser (109), laser controller (110), lock-in amplifier (111) successively connect
It connecing, second coupler (112) connect with the first coupler (102), scrambler (113), third coupler (114) respectively,
4th coupler (115) connect with circulator (105), third coupler (114), the 5th coupler (116) respectively, described
5th coupler (116) is connect with scrambler (113), the first photodetector (117) respectively, second photodetector
(118) it is connect respectively with third coupler (114), data acquisition card (119), the signal processing and display unit (120) point
Do not connect with first laser device (100), data acquisition card (119), the impulse generator (121) respectively with acousto-optic modulator
(103), data acquisition card (119) connects, and the data acquisition card (119) is put with the first photodetector (117), locking phase respectively
The laser signal that big device (111), signal processing and display unit (122) connection first laser device 100 issue is through the first isolator
101 enter the first coupler 102, and laser signal is divided into two beam signal the first beam laser signal beams by the first coupler (102)
Laser signal, the first beam laser signal enter the second coupler (112) as local oscillation signal, and the second beam laser signal enters acousto-optic
Modulator 103), the second beam laser signal is modulated into pulse signal by acousto-optic modulator (103), and the frequency of signal generates frequency
Move, into the first erbium-doped fiber amplifier (104), through the first erbium-doped fiber amplifier (104) amplified pulse signal into
Enter the port circulator 1051#, output enters sensor fibre 106, in sensor fibre (106), arteries and veins from circulator (105) port 2#
It rushing signal and generates back rayleigh scattering signal, back rayleigh scattering signal enters circulator 105 by the port circulator 1052#,
The back rayleigh scattering signal exported from the port circulator 1053# enters the 4th coupler 115, and the 4th coupler will be backwards to Rayleigh
Scattered signal is divided into two beam signal the first beam back rayleigh scattering signal beam back rayleigh scattering signals, and the first beam is backwards to Rayleigh
Scattered signal enters third coupler, and the second beam back rayleigh scattering signal, which enters the 5th the second coupler of coupler, believes local oscillator
Number it is divided into two beam signal the first beam local oscillation signal beam local oscillation signals, the first beam local oscillation signal enters third coupler (114), and
The signal of three couplers (114) output is converted into electric signal after entering the first photodetector 118, and electric signal is input to signal and adopts
Enter in scrambler 113 in truck 119 from the second beam local oscillation signal that the second coupler 112 exports, believes by disturbing inclined local oscillator
Number enter the 5th coupler 116, from the 5th coupler (116) export signal enter the second photodetector 117 after be converted into
Electric signal, electric signal are input to the signal all the way that data acquisition card 119 exports in data acquisition card 119 and enter lock-in amplifier
111, lock-in amplifier (111) output is signally attached to laser controller 110, and the output signal of laser controller (110) is driven
Dynamic second laser 109, the laser signal exported from second laser (109) enter the second er-doped by the second isolator 108
Fiber amplifier 107, the signal amplified through the second erbium-doped fiber amplifier (107) enters sensor fibre (106), in sensor fibre
(106) in, under test gas absorbs the signal exported from the second erbium-doped fiber amplifier 107, phase-modulation phenomenon is generated, from annular
What the phase information 121 that the port device 1052# is input to the pulse signal detection phase-modulation phenomenon in sensor fibre (106) generated
The electric signal input end driving optical modulator 103 that pulse electrical signal is connected to acousto-optic modulator (103) works, (121) and 120 defeated
Synchronization signal out is connected to the synchronous signal input end of data acquisition card 119 to keep data acquisition card (119), acousto-optic modulation
Device (103) and first laser device (100) are in synchronous regime, and 120 connections first laser device (100) drive first laser device
(100) frequency sweep control is carried out, the another way of data acquisition card output is signally attached to signal processing and display unit 120, obtains
Gas concentration information on along sensor fibre.
2. the distribution type fiber-optic gas-detecting device based on sweep frequency technique according to claim 1, it is characterised in that: described
One laser (100) and second laser (109) are wavelength and the humorous laser of power adjustable.
3. the distribution type fiber-optic gas-detecting device based on sweep frequency technique according to claim 2, it is characterised in that: the biography
Photosensitive fibre (106) is hollow-core photonic crystal fiber.
4. the distribution type fiber-optic gas-detecting device based on sweep frequency technique according to claim 3, it is characterised in that: the biography
Photosensitive fibre (106) has the channel orifices for entering hollow-core fiber as gas along optical fiber surface production.
5. the distribution type fiber-optic gas-detecting device based on sweep frequency technique according to claim 4, it is characterised in that: described logical
Road hole diameter is about 1-10.0 μm.
6. the distribution type fiber-optic gas-detecting device based on sweep frequency technique according to claim 5, it is characterised in that: described
One photodetector (117), the second photodetector (118) are balanced detector.
7. a kind of detection using any distribution type fiber-optic gas-detecting device based on sweep frequency technique of claim 1 to 6
Method, it is characterised in that: the laser signal that first laser device (100) issues enters the first coupler through the first isolator (101)
(102), laser signal is divided into two beam signals, respectively the first beam laser signal and the second beam laser by the first coupler (102)
Signal, the first beam laser signal enter the second coupler (112) as local oscillation signal, and the second beam laser signal enters acousto-optic modulation
Device (103), the second beam laser signal is modulated into pulse signal by acousto-optic modulator (103), and the frequency of signal generates frequency displacement, into
Enter in the first erbium-doped fiber amplifier (104), enters annular through the first erbium-doped fiber amplifier (104) amplified pulse signal
The port 1# of device (105), from the port 2# of circulator (105), output enters sensor fibre (106), in sensor fibre (106),
Pulse signal generates back rayleigh scattering signal, and back rayleigh scattering signal enters annular by the port 2# of circulator (105)
Device (105), the back rayleigh scattering signal exported from the port 3# of circulator (105) enter the 4th coupler (115), the 4th coupling
Back rayleigh scattering signal is divided into two beam signals, respectively the first beam back rayleigh scattering signal and the second beam by clutch (115)
Back rayleigh scattering signal, the first beam back rayleigh scattering signal enter third coupler (114), the second beam back rayleigh scattering
Signal enters the 5th coupler (116)；Local oscillation signal is divided into two beam signals, respectively the first beam sheet by the second coupler (112)
Vibration signal and the second beam local oscillation signal, the first beam local oscillation signal enter third coupler (114), the first beam back rayleigh scattering letter
Number and the first beam local oscillation signal coupled in third coupler (114), the signal after third coupler (114) output coupling enters the
Electric signal is converted into after one photodetector (118), electric signal is input in data acquisition card (119)；From the second coupler
(112) the second beam local oscillation signal exported enters in scrambler (113), by disturbing inclined local oscillation signal into the 5th coupler
(116), it disturbs inclined local oscillation signal and the second beam back rayleigh scattering signal to couple in the 5th coupler (116), from the 5th coupling
The signal of device (116) output is converted into electric signal after entering the second photodetector (117), and electric signal is input to data acquisition card
(119) in；The signal all the way of data acquisition card (119) output enters lock-in amplifier (111), and lock-in amplifier (111) is defeated
The output signal of being signally attached to laser controller (110) out, laser controller (110) drives second laser (109), from
The laser signal of second laser (109) output enters the second erbium-doped fiber amplifier (107) by the second isolator (108),
The signal amplified through the second erbium-doped fiber amplifier (107) enters sensor fibre (106), in sensor fibre (106), gas to be measured
Body absorbs the signal exported from the second erbium-doped fiber amplifier (107), generates phase-modulation phenomenon, the 2# from circulator (105)
Port is input to the phase information of the pulse signal detection phase-modulation phenomenon in sensor fibre (106)；Impulse generator (121)
The pulse electrical signal of generation is connected to electric signal input end driving optical modulator (103) work of acousto-optic modulator (103), pulse
Generator (121) is connected to the synchronous of data acquisition card (119) with the synchronization signal that signal processing and display unit (120) export
Signal input part to keep data acquisition card (119), acousto-optic modulator (103) and first laser device (100) to be in synchronous regime,
Signal processing and display unit (120) connection first laser device (100), driving first laser device (100) carry out frequency sweep control, letter
The another way of number capture card (119) output is signally attached to signal processing and display unit (120), obtains sensor fibre (106)
Gas concentration information on along the line.
8. the distribution type fiber-optic gas-detecting device based on sweep frequency technique according to claim 7, it is characterised in that: display
The relationship of calibration concentration and phase size in advance, the distribution type fiber-optic gas sensing obtained under different frequency are needed when data
The curvilinear correlation degree of device indicates are as follows:
The minimum C=0.99 of curvilinear correlation degree, obtains:
Wherein, C is curvilinear correlation degree, and W is detection pulsewidth, and Δ f is the difference on the frequency between two curves.
9. the distribution type fiber-optic gas-detecting device based on sweep frequency technique according to claim 8, it is characterised in that: described
The frequency shift amount of one laser (100) and second laser (109) 1ms are less than or equal to 0.017M.
10. the distribution type fiber-optic gas-detecting device based on sweep frequency technique according to claim 9, it is characterised in that: described
First laser device (100) and the sweep velocity of second laser (109) are less than 17M/S.
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