CN107091698B - Brillouin optical time domain analysis system and method - Google Patents
Brillouin optical time domain analysis system and method Download PDFInfo
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- CN107091698B CN107091698B CN201710459472.7A CN201710459472A CN107091698B CN 107091698 B CN107091698 B CN 107091698B CN 201710459472 A CN201710459472 A CN 201710459472A CN 107091698 B CN107091698 B CN 107091698B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
- G01K11/00—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00
- G01K11/32—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00 using changes in transmittance, scattering or luminescence in optical fibres
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/16—Measuring arrangements characterised by the use of optical techniques for measuring the deformation in a solid, e.g. optical strain gauge
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
- G01K11/00—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00
- G01K11/32—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00 using changes in transmittance, scattering or luminescence in optical fibres
- G01K11/3206—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00 using changes in transmittance, scattering or luminescence in optical fibres at discrete locations in the fibre, e.g. using Bragg scattering
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
- G01K11/00—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00
- G01K11/32—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00 using changes in transmittance, scattering or luminescence in optical fibres
- G01K11/322—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00 using changes in transmittance, scattering or luminescence in optical fibres using Brillouin scattering
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Abstract
The present invention relates to a kind of Brillouin optical time domain analysis system and methods, the system is modulated to obtain double frequency light carrier by the continuous light of Electro-optical Modulation link pair, by detection photogenerated link and double-frequency pulse photogenerated link pair double frequency light carrier generate four kinds of different frequencies detection light and double-frequency pulse light, wherein the optical signal power of each frequency all in its non-linear threshold under；Then double-frequency pulse light is controlled by the first Bragg grating module and generates time delay to eliminate the crosstalk of double-frequency pulse light, to form two-way pump light and injection fibre, delay compensation is carried out by the Brillouin signal light that the second Bragg grating module forms detection light and the pump light interaction of injection fibre, finally obtains the Brillouin shift data of optical fiber after signal processing.So as to avoid the nonlinear effect of pure-tone pulse light and the excessively high introducing of signal light power, the power demand of pulsed light is reduced, improves the signal-to-noise ratio of system, and reduces non-local effect caused by pumping exhausts.
Description
Technical field
The present invention relates to monitoring technical fields, more particularly to a kind of Brillouin optical time domain analysis system and method.
Background technique
Distributed fiber optic temperature, strain monitoring system based on Brillouin scattering principle, since it can perceive whole light
Temperature, the spatial distribution of strain and the information changed over time of fine chain road, therefore it is widely used in power cable, tunnel
In the safety monitoring of the major designs such as road piping lane, hydraulic engineering, long distance oil-gas pipeline.However, at present due in sensor fibre
In, the maximum incident optical power of pulsed light and continuous light is rather limited, and the peak power of pulsed light is uncertain due to modulating
For degree not above 100-150mw, continuous light is ultimately limited by the spontaneous brillouin scattering of amplification, and power cannot be greater than 5mw, therefore
The promotion of signal-to-noise ratio and distance can not be realized by infinitely improving the power of pulsed light and continuous light.And the pulsed light of long range and
The interaction of continuous light can cause pumping to exhaust, and then bring serious non-local effect (Non-Local Effect),
The measurement accuracy of system is not only reduced, the time of measuring of system is also extended.
Although the pumping that can reduce the Brillouin light fiber sensor of long range by using double-side band at present exhausts
(Aldo Minardo et al.“A Simple Technique for Reducing Pump Depletion in Long-
Range Distributed Brillouin Fiber Sensors "), still, this method is formed using the double-side band of detection light
Then gain-attenuation type Brillouin optical time domain analysis system filters out stokes light, detection anti-Stokes light, passes in optical fiber
In sensor, the high-order sideband energy of continuous light is shifted to pulsed light, although this method is alleviated to a certain extent due to pumping
The deformation of brillouin gain spectrum caused by exhausting, but in practical applications, since signal light and pulsed light are limited to nonlinear effect,
Therefore, signal-to-noise ratio promotion is not obvious, and there is no the non-local effects for solving the introducing of loop latter half.
And use and inject step pulse light in sensor fibre, the backward Rayleigh that pre- 1 rank sideband of pumping pulse light is generated
It scatters and stimulated Brillouin scattering effect, while sensing impulse and pre- pump occurs with the sensing impulse light transmitted in opposite directions as detection light
Stimulated Brillouin scattering effect, then benefit occur for the spontaneous brillouin scattering signal that pulsed light 0 rank base band preexciting sound wave in Pu generates
With the detection light for returning to incidence end carrying stimulated Brillouin scattering information, the Brillouin shift on optical fiber at each point, the party are obtained
Although method reduces influence of the non-local effect to the measuring precision, but due to the backward Rayleigh scattering luminous intensity of system compared with
It is weak, accordingly, it is difficult to guarantee the stronger signal-to-noise ratio of system.
Summary of the invention
Based on this, it is necessary at present in the brillouin distributed optical fiber sensing system of long range since pumping exhausts
The not high problem with signal-to-noise ratio caused by nonlinear effect provides a kind of Brillouin optical time domain analysis system and method.
A kind of Brillouin optical time domain analysis system, comprising:
Laser, for generating the continuous light of narrow linewidth；
Electro-optical Modulation link obtains double frequency light carrier for being modulated to continuous light；
Photogenerated link is detected, detects light, and injection fibre for generating four tunnels according to double frequency light carrier；
Double-frequency pulse photogenerated link, for generating double-frequency pulse light according to double frequency light carrier；
First Bragg grating module, for generating time delay to double-frequency pulse light to form two-way pump light, and injection light
It is fine；
Second Bragg grating module interacts for the detection light and pump light to injection fibre and in the cloth of formation
Deep signal light carries out delay compensation；
Signal processing module, for carrying out signal processing to the compensated Brillouin signal light of time delay to obtain the cloth of optical fiber
In deep frequency-shift data.
Electro-optical Modulation link includes: in one of the embodiments,
Microwave source, for generating microwave signal；
Frequency demultiplexer, for being divided to microwave signal；
First electrooptic modulator, for being modulated under the inhibition of the microwave signal after frequency dividing to the continuous light of narrow linewidth
To obtain double frequency light carrier；
Wherein, the input terminal of the output end of microwave source and frequency demultiplexer connects, the output end of frequency demultiplexer and the first Electro-optical Modulation
The input terminal of device connects.
Detection photogenerated link includes: in one of the embodiments,
Second electrooptic modulator, for being modulated to double frequency light carrier under the inhibition of microwave signal to obtain four tunnels and visit
Survey light；
First erbium-doped fiber amplifier, for being amplified to four tunnels detection light；
Scrambler, the sensitivity characteristic of the polarization state for eliminating amplified four tunnels detection light, and injection fibre；
Wherein, the input terminal of the second electrooptic modulator be separately connected microwave source output end and the first electrooptic modulator it is defeated
Outlet, the output end of the second electrooptic modulator connect the input terminal of the first erbium-doped fiber amplifier, the first erbium-doped fiber amplifier
Output end connection scrambler input terminal, the output end of scrambler connects optical fiber.
Double-frequency pulse photogenerated link includes: in one of the embodiments,
Pulse-modulator, for being modulated to double frequency light carrier to obtain double-frequency pulse light；
Second erbium-doped fiber amplifier, for being amplified to double-frequency pulse light；
Wherein, the input terminal of pulse-modulator is connect with the output end of the first electrooptic modulator, the output of pulse-modulator
End is connect with the input terminal of the second erbium-doped fiber amplifier.
The first Bragg grating module, the second Bragg grating module respectively include two in one of the embodiments,
Bragg grating, wherein at a distance of l meters between two Bragg gratings, l is greater than the pulse temporal width of pulse-modulator modulation
The product of half and the pulse light velocity.
Pulse-modulator includes in acousto-optic modulator, electrooptic modulator and high-speed optical switch in one of the embodiments,
It is any.
The centre frequency of the light carrier of laser output is ν in one of the embodiments,0, the microwave of microwave source generation
The frequency of signal is 2f0, the frequency of double frequency light carrier is respectively ν0-f0、ν0+f0。
The frequency of four tunnels detection light is respectively ν in one of the embodiments,0-3f0、ν0-f0、ν0+f0、ν0+3f0。
The central wavelength of the first Bragg grating module is ν in one of the embodiments,0-f0、ν0+f0, the second Bradley
The central wavelength of lattice grating module is ν0-3f0、ν0-f0Or ν0+f0、ν0+3f0。
A kind of Brillouin optical time domain analysis method, comprising:
The continuous light for generating narrow linewidth, is modulated continuous light to obtain double frequency light carrier；
Four tunnels, which are generated, according to double frequency light carrier detects light, and injection fibre；
Double-frequency pulse light is generated according to double frequency light carrier, time delay is generated to form two-way pump light to double-frequency pulse light, and
Injection fibre；
To detection light and the pump light interaction of injection fibre, the Brillouin signal light of formation carries out delay compensation, right
Brillouin signal light after delay compensation carries out signal processing to obtain the Brillouin shift data of optical fiber.
Above-mentioned Brillouin optical time domain analysis system and method, by using Electro-optical Modulation link to generate double-frequency pulse light,
The second Bragg grating module is combined to be time-multiplexed by using the first Bragg grating module, so as to avoid single-frequency arteries and veins
It washes the nonlinear effect with the excessively high introducing of signal light power off, reduces the power demand of pulsed light, improve the noise of system
Than, and reduce exhausted due to pumping caused by non-local effect, and then ensured the measurement accuracy to optical fiber.
Detailed description of the invention
Fig. 1 is the structural schematic diagram of Brillouin optical time domain analysis system in one embodiment；
Fig. 2 is the frequency diagram of pulsed light in one embodiment；
Fig. 3 is the frequency diagram of continuous light in one embodiment；,
Fig. 4 is the flow diagram of Brillouin optical time domain analysis method in one embodiment.
In attached drawing, parts list represented by the reference numerals are as follows:
1, laser, the 2, first electrooptic modulator, 3, frequency demultiplexer, the 4, second electrooptic modulator, 5, microwave source, 6, first mixes
Doped fiber amplifier, 7, scrambler, 8, pulse-modulator, the 9, second erbium-doped fiber amplifier, 10, first annular device, 11, first
Bragg grating module, the 12, second circulator, the 13, second Bragg grating module, 14, photoelectric detection module, 15, at signal
Manage module, 16, coupler, 17, optical fiber.
Specific embodiment
In order to make the object, technical scheme and advantages of the embodiment of the invention clearer, below in conjunction with the embodiment of the present invention
In attached drawing, technical scheme in the embodiment of the invention is clearly and completely described, it is clear that described embodiment is
A part of the embodiment of the present invention, instead of all the embodiments.
The embodiment of the invention provides a kind of Brillouin optical time domain analysis systems, including laser, Electro-optical Modulation link, spy
Survey photogenerated link, double-frequency pulse photogenerated link, the first Bragg grating module, the second Bragg grating module and signal
Processing module, wherein laser, for generating the continuous light of narrow linewidth；Electro-optical Modulation link, for being modulated to continuous light
Obtain double frequency light carrier；Photogenerated link is detected, detects light, and injection fibre for generating four tunnels according to double frequency light carrier；It is double
Frequency pulse photogenerated link, for generating double-frequency pulse light according to double frequency light carrier；First Bragg grating module, for double
Frequency pulsed light generates time delay to form two-way pump light, and injection fibre；Second Bragg grating module, for injection fibre
Detection light and pump light interaction and formed Brillouin signal light carry out delay compensation；Signal processing module, for pair
Brillouin signal light after delay compensation carries out signal processing to obtain the Brillouin shift data of optical fiber.
The system of the present embodiment by laser generate narrow linewidth continuous light, by the continuous light of Electro-optical Modulation link pair into
Row modulation obtains double frequency light carrier, generates four by detection photogenerated link and double-frequency pulse photogenerated link pair double frequency light carrier
The detection light and double-frequency pulse light of kind of different frequency, wherein the optical signal power of each frequency all in its non-linear threshold it
Under；Then the crosstalk that double-frequency pulse light is eliminated by the first Bragg grating module control double-frequency pulse light generation time delay, from
And two-way pump light and injection fibre are formed, by the second Bragg grating module to the detection light and pump light phase of injection fibre
Interaction and the Brillouin signal light that is formed carries out delay compensation, draw so as to avoid pure-tone pulse light and signal light power are excessively high
The nonlinear effect entered reduces the power demand of pulsed light, improves the signal-to-noise ratio of system, and reduces since pumping exhausts
Caused non-local effect, and then ensured the measurement accuracy to temperature on optical fiber and strain, finally obtain after signal processing
The Brillouin shift data of optical fiber.
In one embodiment, as shown in Figure 1, Electro-optical Modulation link includes microwave source 5, frequency demultiplexer 3 and the first electric light
The output end of modulator 2, microwave source 5 is connect with the input terminal of frequency demultiplexer 3, the output end of frequency demultiplexer 3 and the first electrooptic modulator 2
Input terminal connection.Wherein, microwave source 5 is for generating microwave signal；Frequency demultiplexer 3, for being divided to microwave signal；First
Electrooptic modulator 2 is modulated to obtain double frequency light the continuous light of narrow linewidth under the inhibition for the microwave signal after frequency dividing
Carrier wave.For example, if the centre frequency for the light carrier that laser 1 exports is ν0, the frequency for the microwave signal that microwave source 5 generates
For 2f0, the frequency that the microwave signal of the first electrooptic modulator 2 is entered after the frequency dividing of frequency demultiplexer 3 is f0, then through the first Electro-optical Modulation
The frequency for the double frequency light carrier that device 2 obtains after modulating is respectively ν0-f0、ν0+f0。
In one embodiment, detection photogenerated link includes the second electrooptic modulator 4, the first erbium-doped fiber amplifier 6
And scrambler 7, the input terminal of the second electrooptic modulator 4 are separately connected the output end and first electrooptic modulator 2 of microwave source 5
Output end, the output end of the second electrooptic modulator 4 connect the input terminal of the first erbium-doped fiber amplifier 6, and the first Er-doped fiber is put
The input terminal of the output end connection scrambler 7 of big device 6, the output end of scrambler 7 connect optical fiber 17.Wherein, the second Electro-optical Modulation
Device 4 is used under the inhibition of microwave signal be modulated double frequency light carrier to obtain four tunnels detection light；First Er-doped fiber is put
Big device 6 is used to amplify four tunnels detection light；Scrambler 7 is used to eliminate the sensitivity of the polarization state of amplified four tunnels detection light
Characteristic, and injection fibre.For example, if the centre frequency for the light carrier that laser 1 exports is ν0, microwave source 5 generate it is micro-
The frequency of wave signal is 2f0, the frequency of the double frequency light carrier obtained after the modulation of the first electrooptic modulator 2 is respectively ν0-f0、ν0+
f0, then through the second electrooptic modulator 4 in microwave signal 2f0Inhibition under to double frequency light carrier ν0-f0、ν0+f0It is modulated acquisition
Four tunnels detection light frequency be respectively ν0-3f0、ν0-f0、ν0+f0、ν0+3f0。
In one embodiment, double-frequency pulse photogenerated link includes pulse-modulator 8 and the second Erbium-doped fiber amplifier
Device 9, the input terminal of pulse-modulator 8 are connect with the output end of the first electrooptic modulator 2, the output end of pulse-modulator 8 and
The input terminal of two erbium-doped fiber amplifiers 9 connects.Wherein, pulse-modulator 8 is used to be modulated double frequency light carrier to obtain
Double-frequency pulse light；Second erbium-doped fiber amplifier 9 is for amplifying double-frequency pulse light.For example, if laser 1 is defeated
The centre frequency of light carrier out is ν0, the frequency for the microwave signal that microwave source 5 generates is 2f0, adjusted through the first electrooptic modulator 2
The frequency of the double frequency light carrier obtained after system is respectively ν0-f0、ν0+f0, then pulse modulated device 8 adjusts double frequency light carrier
The frequency of the double-frequency pulse light obtained after system is ν0-f0、ν0+f0。
In one embodiment, as shown in Figure 1, the system includes laser 1, the first electrooptic modulator 2, frequency demultiplexer 3,
Two electrooptic modulators 4, microwave source 5, the first erbium-doped fiber amplifier 6, scrambler 7, pulse-modulator 8, the second Er-doped fiber are put
Big device 9, first annular device 10, the first Bragg grating module 11, the second circulator 12, the second Bragg grating module 13, light
Electric detecting module 14, signal processing module 15, coupler 16 and optical fiber 17, wherein laser 1 exports the continuous of narrow linewidth
Light, after the microwave signal that frequency demultiplexer 3 generates microwave source 5 divides, the first electrooptic modulator 2 of driving adjusts continuous light
System, to obtain double frequency light carrier, and is divided into two-way for double frequency light carrier by coupler 16, all the way by being produced by microwave source 5
The detection light of four kinds of frequencies is obtained after the second electrooptic modulator 4 modulation that raw microwave signal inhibits, which mixes through first
Doped fiber amplifier 6 is eliminated the sensitivity characteristic of polarization state by scrambler 7 after amplifying, be then injected into optical fiber 17；Another way passes through arteries and veins
Pulse modulator 8 generates double-frequency pulse light after modulating, and is amplified into first annular device 10 through the second erbium-doped fiber amplifier 9, leads to
It crosses the first Bragg grating module 11 control double-frequency pulse light being connected with first annular device 10 and generates time delay to eliminate double frequency arteries and veins
The crosstalk washed off, so that pump light is formed, through 12 injection fibre 17 of the second circulator；Then pass through the second Bragg grating module
The Brillouin signal light for detecting light and pump light interaction and being formed of 13 pairs of injection fibres carries out delay compensation, visits through photoelectricity
It surveys after module 14 and signal processing is carried out to obtain the Brillouin shift data of whole 17 chain road of optical fiber by signal processing module 15.
Its structure of Brillouin optical time domain analysis system provided in this embodiment is simple, by using double electrooptic modulators with life
At double frequency pulsed light, and time-division multiplex technology is combined, so as to avoid the non-of pure-tone pulse light and the excessively high introducing of signal light power
Linear effect reduces pulse light power requirements, improves the signal-to-noise ratio of system.By using Brillouin's loss spectra and continuous light
Polygon band, in optical fiber link, continuous light constantly shifts energy to pulsed light, the non-local effect of system is reduced, to protect
The measurement accuracy on whole section of optical fiber is hindered.
In one embodiment, if the centre frequency for the continuous light that laser 1 exports is ν0, microwave source 5 generate microwave
The frequency of signal is 2f0, then with f after the frequency dividing of frequency demultiplexer 30Frequency drive the first electrooptic modulator 2 to light carrier ν0It is adjusted
It is ν that frequency is obtained after system0-f0、ν0+f0Double frequency light carrier, then divide through coupler 16 for two-way, all the way by being produced by microwave source 5
Raw frequency is 2f0Microwave signal inhibit the second electrooptic modulator 4 modulation after obtain four kinds of frequencies continuous probe light, point
Not Bao Kuo frequency be ν0-3f0、ν0-f0、ν0+f0、ν0+3f0Detection light.Another way generates frequency after the modulation of pulse-modulator 8
Rate is ν0-f0、ν0+f0Double-frequency pulse light.
In one embodiment, the first Bragg grating module 11 may include two Bragg gratings, two Prague
Grating respectively corresponds the frequency ν of two pulses light0-f0、ν0+f0, at a distance of l meters between two Bragg gratings, to make two beam arteries and veins
Wash off in the time domain generate 2*l*n/c second delay (wherein n be optical fibre refractivity, c be vacuum in the light velocity, c/n is pulsed light
The light velocity of speed, i.e. pulsed light in a fiber), and then overlapping is got rid of by the time delay, the crosstalk of two pulses light is eliminated, is mentioned
The high signal-to-noise ratio of system.Wherein, l is greater than the half of pulse temporal width and multiplying for the pulse light velocity that pulse-modulator 8 is modulated
Product.Second Bragg grating module 13 also may include two Bragg gratings, the corresponding frequency of two Bragg gratings
For ν0-3f0、ν0-f0Or ν0+f0、ν0+3f0, two grating spacings length are identical as the first Bragg grating module 11, strictly to mend
The time delay for repaying the introducing of the first Bragg grating module 11, is overlapped signal in the time domain, while incoming photoelectric detection module 14, from
And the signal-to-noise ratio of system is enhanced, improve the measurement accuracy of system.
In one embodiment, as shown in Figure 2 and Figure 3, frequency ν0+3f0Continuous light pass through stimulated Brillouin effect will
Energy transmission is ν to frequency0+f0Pulsed light, frequency ν0+f0Pulsed light by stimulated Brillouin effect by energy transmission
Give frequency ν0-f0Continuous light, frequency ν0+f0Continuous light by stimulated Brillouin effect transfer energy to frequency be ν0-
f0Pulsed light, frequency ν0-f0Pulsed light frequency ν is transferred energy to by stimulated Brillouin effect0-3f0Continuous light,
These four energy transfer processes occur in sensor fibre according to certain time delay, to substantially reduce due to two beam pump lights
Non-local effect caused by loss and mutual crosstalk, reduces the measurement error of system long distance transmission.
In one embodiment, it is contemplated that the effect of dispersion of light in a fiber can take l >=t/2*c/n+1 meters.
In one embodiment, pulse-modulator 8 may include in acousto-optic modulator, electrooptic modulator and high-speed optical switch
It is any, to modulate generation pulse signal.
In one embodiment, laser 1 can use narrow cable and wide optical fiber laser, so that the continuous light tool of output
There is fabulous coherence, the sensor-based system of long range can be suitable for.
In one embodiment, microwave source 5 can use microwave oscillator, to generate the microwave signal of certain frequency.
In one embodiment, first annular device 10 can use three port circulators, and the second circulator 12 can use
Four port circulators.
In one embodiment, laser 1 can specifically be less than 15KHz using line width, and output power is greater than 20mw, center
Wavelength is the narrow line wide cavity laser of 1550.12nm, and the centre frequency of output light carrier is ν0；Microwave source 5 can use
Frequency range is 8GHz-12GHz, and frequency sweep stepping is less than 1MHz, and output power is greater than the microwave oscillator of 27dBm, output frequency
Rate is 2f0Microwave modulated signal.Microwave oscillator is half, that is, f of frequency by the frequency dividing of frequency demultiplexer 30To the first Electro-optical Modulation
Device 2 carries out frequency modulation(PFM), the two microwave modulated signals keep synchronizing, so as to pass through the signal for adjusting microwave oscillator frequency
Rate carries out sweep measurement to brillouin gain spectrum.The input of the output end of narrow line wide cavity laser and the first electrooptic modulator 2
End is connected, and microwave oscillator is connected after the frequency dividing of frequency demultiplexer 3 with the rf inputs of the first electrooptic modulator 2, the first electric light tune
The Dc bias input terminal of device 2 processed inputs suitable voltage value, so that obtaining frequency is ν0-f0、ν0+f0Double frequency light carrier,
The output end of one electrooptic modulator 2 is connected with coupler (50%/50%) 16, and optical path is divided into two, all the way through the second electric light tune
Device 4 processed, the output end of microwave oscillator are connected with the rf inputs of the second electrooptic modulator 4, and suitable Dc bias is arranged
Value, and it is input to the first erbium-doped fiber amplifier 6, the continuous probe light ν of the four kinds of frequencies formed after amplification0-3f0、ν0-f0、ν0+
f0、ν0+3f0Sensor fibre 17 is injected into through scrambler 7.Another way optical signal enters pulse-modulator 8, to generate frequency and be
ν0-f0、ν0+f0Double-frequency pulse light, the output end of pulse-modulator 8 is connected with the second erbium-doped fiber amplifier 9, the light of amplification
Signal enters three port circulators, is transferred to the first Bragg grating module 11 through three port circulators, is formed after reflection
The dipulse pump light of one fixed response time, then sensor fibre 17 is injected through four port circulators, signal light needed for system (injects
The detection light and pump light of optical fiber interact and the Brillouin signal light of formation) enter the second cloth by four port circulators 12
Glug grating module 13 enters photoelectric detection module 14 after filtering, reflecting, finally enters signal processing module 15.
Wherein, the first Bragg grating module 11 is made of two Bragg gratings, and two Bragg gratings are right respectively
The centre frequency answered is ν0-f0、ν0+f0If two Bragg gratings are at a distance of 5m, and two Bragg gratings are that three dB bandwidth is
The fiber grating FBG (Fiber Bragg Grating, abbreviation FBG) of 10GHz, the second Bragg grating module 13 be equally by
Two Bragg grating compositions, at a distance of 5m, corresponding centre frequency is respectively ν0-f0,ν0-3f0, due to stimulated Brillouin effect,
The Brillouin shift amount of sensor fibre is about 2f0, so that frequency is ν0-f0Pulsed light and ν0-3f0Continuous light interaction,
Frequency is ν0+f0Pulsed light and ν0-f0Continuous light interaction.Therefore, if in the first Bragg grating module 11
The corresponding centre frequency of one Bragg grating is ν0-f0, then second Bragg grating in the second Bragg grating module 13
Corresponding centre frequency is ν0-3f0, to realize the compensation being delayed to optical signal.
In one embodiment, the corresponding centre frequency of two Bragg gratings of the second Bragg grating module 13 may be used also
To be respectively ν0+f0、ν0+3f0If the corresponding centre frequency of first Bragg grating in the first Bragg grating module 11
For ν0+f0, then the corresponding centre frequency of second Bragg grating is ν in the second Bragg grating module 130+3f0, thus real
Now to the compensation of optical signal delay.
The embodiment of the invention also provides a kind of Brillouin optical time domain analysis methods, as shown in figure 4, including the following steps:
Step S401 generates the continuous light of narrow linewidth, is modulated to obtain double frequency light carrier to continuous light；
Step S402 generates four tunnels according to double frequency light carrier and detects light, and injection fibre；
Step S403 generates double-frequency pulse light according to double frequency light carrier, generates time delay to double-frequency pulse light to form two-way
Pump light, and injection fibre；
Step S404, when being carried out to the Brillouin signal light that the detection light and pump light of injection fibre interact and formed
Prolong compensation, signal processing is carried out to obtain the Brillouin shift data of optical fiber to the compensated Brillouin signal light of time delay.
The present embodiment generates double-frequency pulse light by using double electrooptic modulators, by using the first Bragg grating mould
Agllutination closes the second Bragg grating module and is time-multiplexed, so as to avoid pure-tone pulse light and the excessively high introducing of signal light power
Nonlinear effect, reduce the power demand of pulsed light, improve the signal-to-noise ratio of system, and reduce since pumping exhausts and draws
The non-local effect risen, and then ensured the measurement accuracy to temperature on optical fiber and strain.
Each technical characteristic of embodiment described above can be combined arbitrarily, for simplicity of description, not to above-mentioned reality
It applies all possible combination of each technical characteristic in example to be all described, as long as however, the combination of these technical characteristics is not deposited
In contradiction, all should be considered as described in this specification.
The embodiments described above only express several embodiments of the present invention, and the description thereof is more specific and detailed, but simultaneously
It cannot therefore be construed as limiting the scope of the patent.It should be pointed out that coming for those of ordinary skill in the art
It says, without departing from the inventive concept of the premise, various modifications and improvements can be made, these belong to protection of the invention
Range.Therefore, the scope of protection of the patent of the invention shall be subject to the appended claims.
Claims (10)
1. a kind of Brillouin optical time domain analysis system characterized by comprising
Laser, for generating the continuous light of narrow linewidth；
Electro-optical Modulation link, for being modulated to obtain double frequency light carrier to the continuous light；
Photogenerated link is detected, detects light, and injection fibre for generating four tunnels according to the double frequency light carrier；
Double-frequency pulse photogenerated link, for generating double-frequency pulse light according to the double frequency light carrier；
First Bragg grating module, for generating time delay to the double-frequency pulse light to form two-way pump light, and injection light
It is fine；
Second Bragg grating module, for the detection light and the pump light interaction to injection fibre in the cloth of formation
Deep signal light carries out delay compensation；
Signal processing module, for carrying out signal processing to the compensated Brillouin signal light of time delay to obtain the Brillouin of optical fiber
Frequency-shift data.
2. Brillouin optical time domain analysis system according to claim 1, which is characterized in that the Electro-optical Modulation link packet
It includes:
Microwave source, for generating microwave signal；
Frequency demultiplexer, for being divided to the microwave signal；
First electrooptic modulator, for being modulated under the inhibition of the microwave signal after frequency dividing to the continuous light of the narrow linewidth
To obtain double frequency light carrier；
The output end of the microwave source and the input terminal of frequency demultiplexer connect, the output end of the frequency demultiplexer and the first electric light tune
The input terminal of device processed connects.
3. Brillouin optical time domain analysis system according to claim 2, which is characterized in that the detection photogenerated link packet
It includes:
Second electrooptic modulator, for being modulated the double frequency light carrier to obtain four under the inhibition of the microwave signal
Road detects light；
First erbium-doped fiber amplifier, for being amplified to four tunnel detection light；
Scrambler, the sensitivity characteristic of the polarization state for eliminating amplified four tunnels detection light, and inject the optical fiber；
The input terminal of second electrooptic modulator is separately connected the output end and first electrooptic modulator of the microwave source
Output end, the output end of second electrooptic modulator connects the input terminal of first erbium-doped fiber amplifier, described
The output end of one erbium-doped fiber amplifier connects the input terminal of the scrambler, and the output end of the scrambler connects the light
It is fine.
4. Brillouin optical time domain analysis system according to claim 2, which is characterized in that the double-frequency pulse photoproduction chaining
Road includes:
Pulse-modulator, for being modulated the double frequency light carrier to obtain double-frequency pulse light；
Second erbium-doped fiber amplifier, for being amplified to the double-frequency pulse light；
The input terminal of the pulse-modulator is connect with the output end of first electrooptic modulator, the pulse-modulator it is defeated
Outlet is connect with the input terminal of second erbium-doped fiber amplifier.
5. Brillouin optical time domain analysis system according to claim 4, which is characterized in that the first Bragg grating mould
Block, the second Bragg grating module respectively include two Bragg gratings, between described two Bragg gratings apartlRice,
In,lGreater than the half of the pulse temporal width of pulse-modulator modulation and the product of the pulse light velocity.
6. Brillouin optical time domain analysis system according to claim 4 or 5, which is characterized in that the pulse-modulator packet
Include any one of acousto-optic modulator, electrooptic modulator and high-speed optical switch.
7. Brillouin optical time domain analysis system according to claim 2, which is characterized in that the light of the laser output carries
The centre frequency of wave is ν0, the frequency for the microwave signal that the microwave source generates is 2f0, the frequency difference of the double frequency light carrier
For ν0-f0、ν0+f0。
8. Brillouin optical time domain analysis system according to claim 7, which is characterized in that the frequency of the four tunnels detection light
Respectively ν0-3f0、ν0-f0、ν0+f0、ν0+3f0。
9. Brillouin optical time domain analysis system according to claim 8, which is characterized in that the first Bragg grating mould
The central wavelength of block is ν0-f0、ν0+f0, the central wavelength of the second Bragg grating module is ν0-3f0、ν0-f0Or ν0+f0、
ν0+3f0。
10. a kind of Brillouin optical time domain analysis method characterized by comprising
The continuous light for generating narrow linewidth, is modulated to obtain double frequency light carrier to the continuous light；
Four tunnels, which are generated, according to the double frequency light carrier detects light, and injection fibre；
Double-frequency pulse light is generated according to the double frequency light carrier, time delay is generated to the double-frequency pulse light to form two-way pumping
Light, and injection fibre；
To the detection light and the pump light interaction of injection fibre, the Brillouin signal light of formation carries out delay compensation, right
Brillouin signal light after delay compensation carries out signal processing to obtain the Brillouin shift data of optical fiber.
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| CN110542447A (en) * | 2019-09-23 | 2019-12-06 | 苏州光格设备有限公司 | Long-distance high-resolution Brillouin optical time domain analyzer |
| CN111307322B (en) * | 2019-12-09 | 2021-12-07 | 北京航天控制仪器研究所 | Distributed optical fiber temperature sensing system based on annular light path |
| CN111220189B (en) * | 2020-01-17 | 2021-04-13 | 西南交通大学 | Brillouin optical time domain analysis sensing device and non-local effect compensation method |
| US11473983B2 (en) * | 2020-07-23 | 2022-10-18 | The Government of the United States of America, as represented by the Secretarv of the Navy | Suppression of noise and cross-talk in brillouin fiber sensors |
| CN112611410B (en) * | 2020-12-08 | 2022-08-05 | 苏州光格科技股份有限公司 | BOTDA system and automatic fiber breaking positioning method thereof |
| CN113049014B (en) * | 2021-03-10 | 2022-04-15 | 太原理工大学 | Time-frequency multiplexing BOTDA system based on pumping light frequency sweep and sensing method |
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