CN103954378B - BOTDR system and its long range detection method based on Bark sequences - Google Patents
BOTDR system and its long range detection method based on Bark sequences Download PDFInfo
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Abstract
The invention discloses a kind of BOTDR system based on Bark sequences and its long range detection method, method includes for continuous light being divided into two-way；It is divided into two groups of unipolarity Bark sequences after generating one group of bipolarity Bark sequence；Detection light is modulated using two groups of unipolarity Bark sequence controls electric fields, obtains two groups of light pulse signals of unipolarity Bark sequences；Injection fibre obtains two groups of backward Brillouin scattering optical signals after two groups of signals are amplified；Local oscillator optical signal is coupled with two groups of backward Brillouin scattering optical signals respectively and is concerned with, two groups of Brillouin scattering electric signals are gathered through opto-electronic conversion, frequency sweep, filter and amplification；Two groups of Brillouin scattering electric signals are carried out into correlation, is obtained along Brillouin shift at fiber distribution every bit, obtain the change of optical fiber environment temperature or strain.Electro-optical Modulation module includes that electro-optic intensity modulation module and Bark sequences occur module in system.The present invention improves signal to noise ratio using the autocorrelation performance of Bark sequences under conditions of System spatial resolution is not reduced, and improves detection range.
Description
Technical field
The present invention relates to a kind of BOTDR system based on Bark sequences and its long range detection method, belong to distributed light
Fine field of sensing technologies.
Background technology
Brillouin light domain reflectometer (Brillouin Optical Time-Domain based on Brillouin scattering
Reflectometry, BOTDR) as one kind of distributed fiberoptic sensor, with high resolution, error be small, sensor fibre cloth
If simple, low cost, easily realization.Using Brillouin shift in optical fiber and optical fiber position strained or temperature relation,
Can be used on power industry, water conservancy industry and civil construction industry, build a bridge and other concrete structures fission monitoring, it is large-scale
The monitoring structural health conditions of civil engineering, traffic highway, subway tunnel industry, the detection of oil and gas industry trouble point.Work as biography
When there is axial strain or temperature change in photosensitive fibre, the arteries and veins of the frequency relative to injection of the dorsad Brillouin scattering in optical fiber
Washing frequency off will occur frequency displacement, and the frequency shift amount of Brillouin scattering light frequency is with the axial strain suffered by optical fiber and temperature change in good
Good linear relationship.The sensing measurement of temperature and strain can be realized using this relation.
Barker sequence (Barker Sequences), is a kind of time-limited non-periodic sequence signal element, also referred to as
Bark sequences.The value of Barker sequence element is "+1 " or " -1 ".Barker sequence have good autocorrelation performance and with
The good cross correlation of other general sequences.It is one of preferred signals unit in Design of Signal, and it applies quite varied.
Traditional BOTDR system is typically using the method for pulse direct detection, the spatial resolution of system and dynamic model
It is trapped among and is determined by the width of pulse to a certain extent.When pulse width is wider, the gross energy of pulse is larger, can obtain preferably
Dynamic range, but spatial resolution can decline, it is difficult to detect compared with mishap point.And pulse width it is narrower when, spatial discrimination
Rate gets a promotion, because pulse self-energy declines, dynamic range reduction.So traditional BOTDR system is in spatial resolution
Be with conflict in dynamic range the two key technologies.The existing BOTDR system based on coding techniques, such as Gloay
And Simplex technologies can solve the contradiction between spatial resolution and dynamic range to a certain extent, but Gloay and
Simplex technologies do not have preferable peak-to-average ratio, and the presence of threshold value is excited due to spontaneous Brillouin, system is more prone to reach and is received
Swash threshold value, dynamic range is not lifted preferably.Gloay and Simplex technologies are obtaining one in practical application in industry
There is larger defect in the time of group data and memory space expense.
The content of the invention
The technical problems to be solved by the invention are to overcome the deficiencies in the prior art, there is provided a kind of based on Bark sequences
BOTDR system and its long range detection method, it is therefore an objective to using the autocorrelation performance of Bark sequences, and by the frequency sweep that is concerned with
Mode is detected, and obtains the distribution in a fiber of Brillouin's frequency spectrum, is realized using temperature, stress and Brillouin shift relation
The sensing of temperature and stress, improves the noise of Brillouin light fiber sensor under conditions of the spatial resolution for not reducing system
Than so as to improve detection range.
It is of the invention specific using following technical scheme solution above-mentioned technical problem：
A kind of BOTDR system long range detection method based on Bark sequences, comprises the following steps：
Step A, continuous light is divided into all the way as the continuous light of detection light and another road as the continuous of relevant local oscillator light
Light；
Step B, one group of bipolarity Brak sequence is firstly generated, the bipolarity Bark sequences are divided into two groups of unipolarities
Bark sequences；Luminous intensity tune is carried out using one group of unipolarity Bark sequence controls electric field to the continuous light as detection light again
System, obtains one group of light pulse signal of unipolarity Bark sequences after modulation；
Step C, the light pulse signal of the unipolarity Bark sequences is amplified after injection fibre, to obtain along fiber distribution
Backward Brillouin scattering optical signal；Will be backward with described according to the local oscillator optical signal obtained as the continuous light of relevant local oscillator light
The coupling of Brillouin scattering optical signal is relevant to obtain Brillouin scattering optical signal, and Brillouin scattering electric signal is obtained through opto-electronic conversion
Afterwards, frequency sweep, filter and amplification are carried out and obtains backward Brillouin scattering electric signal AHk；
Step D, by another group of unipolarity Bark sequence repeat step B and step C in step B, to obtain backward Brillouin
Scattering electric signal NAHk；
Step E, the backward Brillouin scattering electric signal AH by gainedkAnd NAHkCorrelation is carried out, is obtained along the cloth of fiber distribution
In deep scattered power curve；Obtained along the brillouin frequency at fiber distribution every bit according to the Brillouin scattering power curve
Move, the change of optical fiber environment temperature or strain is obtained further according to Brillouin shift.
Further, as a preferred technical solution of the present invention：To the Brillouin scattering power curve in step E
The Brillouin shift at peak-seeking acquisition every bit is carried out, specially：
Step E-1, the Power of Brillouin spectrum addition that will take one section of continuity point in the Brillouin scattering power curve are asked
Averagely, as normal data；
Step E-2, by the deep power spectrum of cloth reason and gained criterion numeral at every bit in the Brillouin scattering power curve
According to carrying out related calculation, the degree of correlation with normal data along the deep power spectrum of cloth reason at optical fiber every bit is obtained；
Degree of correlation highest point, the as brillouin frequency of every bit in step E-3, the selection correlation result
Move.
Further, as a preferred technical solution of the present invention：Using as the company of relevant local oscillator light in the step C
Continuous light carries out polarization state randomization, obtains the local oscillator optical signal that polarization state is evenly distributed.
Further, as a preferred technical solution of the present invention：The sequence of bipolarity Bark sequences in the step B
Length is 7 or 11 or 13.
Further, as a preferred technical solution of the present invention：In the step C in local oscillator optical signal and backward cloth
Deep scattered light signal coupling is relevant to obtain the Brillouin scattering optical signal being made up of difference frequency part.
Further, as a preferred technical solution of the present invention：Frequency sweep process is with Brillouin scattering in the step C
On the basis of the centre frequency of electric signal, swept frequency range is set to positive and negative 100MHz, and sweep interval is 5MHz.
It is according to the above-mentioned BOTDR system long range detection method based on Bark sequences the invention allows for a kind of
System, including light source module, the first coupler, light polarization disturbance module, Electro-optical Modulation module, Optical pulse amplification module, circulator,
Second coupler, optical detection module, scan module, filtration module, amplification module, signal processing module, wherein the light source die
Block is connected with the first coupler；First coupler is connected with Electro-optical Modulation module, light polarization disturbance module respectively；The electricity
Optical modulator module is sequentially connected with Optical pulse amplification module, circulator；One end of the circulator is connected into after optical fiber and the second coupling
Clutch is connected；The light polarization disturbance module is connected with the second coupler；Second coupler and optical detection module, frequency sweep mould
Block, filtration module, amplification module, signal processing module are sequentially connected；The Electro-optical Modulation module includes that electro-optic intensity modulates mould
There is module in block and the Bark sequences being connected with electro-optic intensity modulation module, two groups of lists that module is generated occur by Bark sequences
Polarity Bark sequences control the electric field of electro-optic intensity modulation module respectively, are believed with obtaining two groups of light pulses of unipolarity Bark sequences
Number；Brillouin's coherent detection is carried out by the light pulse signal of two groups of unipolarities Bark sequences respectively and obtains two groups of backward cloth
In deep pool scattering electric signal；The signal processing module is carried out at related post analysis to two groups of backward Brillouin scattering electric signals
Reason obtains Brillouin shift, and the change of optical fiber environment temperature or strain is obtained according to the Brillouin shift.
The present invention uses above-mentioned technical proposal, can produce following technique effect：
(1), present invention incorporates auto-correlation coding techniques and coherent detection method, using Bark in auto-correlation coding techniques
The autocorrelation performance of sequence, can be in the signal to noise ratio of the system of raising, so as to compare pulse under conditions of spatial discrimination is not changed
Obtain longer dynamic range.
(2), using the autocorrelation performance of Bark sequences, using the preferable peak-to-average ratio of Bark sequences itself, average detection light
Power avoids nonlinear effect, reduces signaling number of times.And detected by way of relevant frequency sweep, obtained Brillouin's frequency spectrum
Distribution in a fiber, the sensing of temperature and stress is realized using temperature, stress and Brillouin shift relation, is not reducing
The signal to noise ratio of Brillouin light fiber sensor is improved under conditions of the spatial resolution of system, so as to improve detection range, system is improved
Feasibility.
(3), using the preferable peak-to-average ratio of Bark sequences itself, improve BOTDR system and be excited the relatively low defect of threshold value, profit
With identical code length N, when one group of identical data is obtained, Smplex carries out N-1 detections, and Gloay will carry out 4 detections,
And Bark sequences only need 2 detections, reduce detection time and memory space expense, greatly improve the practicality of coding techniques.
Brief description of the drawings
Fig. 1 is the schematic diagram of BOTDR system of the present invention based on Bark sequences.
Specific embodiment
Embodiments of the present invention are described with reference to Figure of description.
As shown in figure 1, the present invention devises a kind of BOTDR system based on Bark sequences includes light source module, the first coupling
Clutch, light polarization disturbance module, Electro-optical Modulation module, Optical pulse amplification module, circulator, the second coupler, optical detection module,
Scan module, filtration module, amplification module, signal processing module, wherein light source module are connected with the first coupler, light source module
In narrow linewidth laser send continuous light, be divided into the continuous light of two-way by the first coupler：The continuous light of the first via and the second tunnel
The continuous light feeding Electro-optical Modulation module of continuous light, the wherein first via, the continuous light in the second road is used as relevant local oscillator light；Electro-optical Modulation mould
Block is used for the continuous light modulation of the first via into train pulse light, including electro-optic intensity modulation module and with electro-optic intensity modulation module
There is module in connected Bark sequences, two groups of unipolarity Bark sequences that module generation occurs by Bark sequences control electricity respectively
The electric field of light intensity modulation module, to obtain two groups of light pulse signals of unipolarity Bark sequences；Then, in Electro-optical Modulation module
Electro-optic intensity modulation module be sequentially connected with Optical pulse amplification module, circulator, by electro-optic intensity modulation module export two
The light pulse signal of group unipolarity Bark sequences amplifies through Optical pulse amplification module respectively, circulator injection fibre, to obtain edge
The backward Brillouin scattering optical signal of fiber distribution；Light polarization disturbance module is connected with the second coupler, for using as
The continuous light of relevant local oscillator light carries out polarization state randomization and obtains the local oscillator optical signal that polarization state is evenly distributed；Described second
Two groups of backward Brillouin scattering optical signals that circulator is exported are carried out coupling and are concerned with by coupler respectively with local oscillator optical signal again, are obtained
Obtain two groups of Brillouin scattering optical signals；The optical detection module that is separately input to be sequentially connected again, scan module, filtration module, put
Big module, signal processing module are processed, and after every group of signal obtains Brillouin scattering electric signal through opto-electronic conversion, are swept
Frequently, filter and amplification, collection obtains correspondence backward Brillouin scattering electric signal；The backward Brillouin scattering electric signal of gained is carried out
After correlation, analyzing and processing is obtained along the Brillouin shift at the every bit of fiber distribution, and light is obtained according to the Brillouin shift
Fine environment temperature or the change of strain.
BOTDR system long range detection method based on Bark sequences of the invention, it is specific as follows：
Narrow linewidth laser in step A, light source module sends continuous light, by the first coupler after light source module point
Into the continuous light of two-way：The continuous light of the continuous light of the first via and the second road.The first via sends into Electro-optical Modulation as the continuous light of detection light
Module, the continuous light in the second road is used as relevant local oscillator light.
Step B, using Electro-optical Modulation module by the continuous light modulation of the first via into train pulse light, it is specific as follows：
Step B-1, firstly generate bipolarity Brak sequences.
Binary code Bark sequences are a kind of code characters for having a particular law.The Bark sequences A of one nn∈ (- 1 ,+
1), n=0,1,2 ... ..., (L-1).
From the point of view of the definition of Bark sequence auto-correlation functions, the longer the better for Bark sequences.Sequence is more long, and auto-correlation main peak is got over
Height, more sharp, autocorrelation performance is better.Bark sequences are as shown in the table.
| Code (L) | Barker sequence |
| 1 | 1 |
| 2 | 1,1or-1,1 |
| 3 | 1,1, -1 |
| 4 | 1,1,1, -1or1,1, -1,1 |
| 5 | 1,1,1, -1,1 |
| 7 | 1,1,1, -1, -1,1, -1 |
| 11 | 1,1,1, -1, -1, -1,1, -1, -1,1, -1 |
| 13 | 1,1,1,1,1, -1, -1,1,1, -1,1, -1,1 |
According to threshold value is excited in Bark sequences autocorrelation performance and BOTDR system, bipolarity Bark sequences can be selected
Sequence length is 7,11,13 Bark sequences, by selecting sequence more long to obtain stronger detection of optical power, is received
Rear orientation light Signal-to-Noise is higher.
Step B-2, pattern conversion is carried out, bipolar code is converted into being adapted to the unipolar code of Optical Fiber Transmission.
Due to positive light pulse can only be transmitted in optical fiber, so bipolar code to be converted into being adapted to the unipolarity of Optical Fiber Transmission
Code, two groups of unipolar Bark sequences can be divided into by the method for biasing by bipolarity Bark sequences, specifically changed according to such as
Lower formula：
Wherein A is bipolarity Bark sequences, and a is first group of unipolarity Bark sequence, and na is second group of Bark sequence.Can obtain
A=a-na.
Step B-3, using one group of unipolar Bark sequence controls electric field, realize electro-optic intensity modulate.
The one group of unipolarity Bark sequence that will be produced accesses the radio frequency control end of electro-optic intensity modulation module, first via conduct
Detect the light input end mouthful of the continuous soft exchange electro-optic intensity modulation module of light.
Electro-optic intensity modulation is, using the birefringent phenomenon of crystal, incident linearly polarized light to be resolved into o light and e light, profit
Change the refractive index of crystal by electric signal with the electrooptic effect of crystal, so that the phase difference that two oscillating components are formed is controlled, then
Two-beam is superimposed using the relevant principle of light, so as to realize the modulation of luminous intensity.Accessed by one group of unipolarity Bark sequence
The radio frequency control end of electro-optic intensity modulation module controls the change of electric field, realizes the modulation to luminous intensity.Such that it is able in electric light
The light output end of intensity modulated module obtains one group of light pulse signal of unipolarity Bark sequences.By unipolarity Bark sequences
Light pulse signal feeding Optical pulse amplification module is amplified.
Step C, will the unipolarity Bark sequences light pulse signal amplify after through optical circulator injection fibre, couple phase
Frequency sweep, filter and amplification are carried out behind pass and obtains backward Brillouin scattering electric signal.It is specific as follows：
Step C-1, the light pulse signal of one group of unipolarity Bark sequences feeding Optical pulse amplification module is amplified after
Through circulator injection fibre, to obtain backward Brillouin scattering optical signal；
Step C-2, according to the continuous light in the second road as relevant local oscillator light, the local oscillator optical signal of acquisition；In local oscillator light letter
Number obtain when, can by the continuous optical signal in the second road by light polarization disturbance module obtain the local oscillator light that polarization state is evenly distributed
Signal, local oscillator light is eliminated with polarization decay purpose in the relevant detection of back scattering optical coupling to reach.Then it is backward by what is obtained
Brillouin scattering optical signal and local oscillator optical signal couple relevant acquisition Brillouin scattering optical signal by the second coupler, are visited through light
Survey module carries out opto-electronic conversion and obtains Brillouin scattering electric signal；
Coherent detection process is as follows：
Local oscillator optical signal ELOWith backward Brillouin scattering optical signal EBThe separately available equation below of electric field represent：
Wherein, n is the refractive index of testing fiber, and c is the light velocity, rLOIt is the light field vector of local oscillator optical signal, rBDissipated for backward
Penetrate the light field vector of signal, and rLO=rB, ωLOIt is the frequency of local oscillator optical signal, ωBIt is backscatter signal frequency, E* LOFor
The conjugate of local oscillation signal electric field, E* BIt is the conjugate of backward Brillouin scattering optical signal electric field, i is imaginary part, and t is the time.
Enter in photodetector after local oscillator optical signal and the mixing of backward Brillouin scattering optical signal, the field intensity after being concerned with
For：
In above formula for frequency composition ωB+ωLOBeyond photodetector frequency response range, photodetector can only be visited
Error of measurement frequency part ωB-ωLO.Optical signal is obtained after coupling is relevant to be included and frequency part and difference frequency part.According to photoelectric detection module
Investigative range judge whether that the optical signal with frequency part can be obtained, but used in this method optical detection module detection model
It is the optical signal of difference frequency part to enclose.
Step C-3, the Brillouin scattering electric signal to step C-2 acquisitions carry out frequency sweep, filtering, amplify, after collection is obtained
To Brillouin scattering electric signal AHk；
Frequency sweep process is estimated the general frequency displacement position that Power of Brillouin is composed, to believe with backward Brillouin scattering according to sensor fibre
On the basis of the centre frequency of number frequency spectrum, the positive and negative 100MHz in left and right sets the swept frequency range of scan module, and sweep interval is set to
5MHz carries out frequency sweep.
The signal of frequency sweep is filtered further across filtration module, amplification module is amplified, then signal transacting mould
A/D module of the block inside carries out data acquisition, and treatment obtains one group of backward Brillouin scattering electric signal AHk, then preserve.
Step D, by another group of unipolarity Bark sequence repeat step B and step C in step B, to obtain another group of monopole
The backward Brillouin scattering electric signal NAH of property Bark sequencesk。
Step E, to two groups of Brillouin's back scattering electric signal AH of unipolarity Bark sequenceskAnd NAHkSolved after carrying out correlation
Code, is obtained along the Brillouin shift at fiber distribution every bit by peak-seeking.It is specific as follows：
First, gathered two groups of back scattering electric signal AH in signal processing modulekAnd NAHkWith reference to Bark yards
Decoding principle data are decoded.
Decoding process is described below：
First, according to Bark sequence autocorrelation performances：
Ak*Ak=L δk (4)
Wherein AkIt is Bark sequences, L is Bark sequence lengths, and * is accorded with for related operation, δkIt is unit impulse function.
Then the back scattering electric signal AH that will detect then,kAnd NAHkThe letter related to Bark sequences is obtained after subtracting each other
Number, this signal and AkCarry out related calculation, can obtain system response hk, i.e., along the Brillouin scattering power curve of fiber distribution, specifically
It is as follows：
WhereinIt is convolution operator.
Then, cross-correlation peak-seeking is carried out to decoded data, obtains the brillouin frequency at the every bit along fiber distribution
Move.Detailed process is described below：
Step E-1, will decode obtain the Brillouin scattering power curve along fiber distribution take one section of Bu Li of continuity point
Deep power spectrum is added and is averaging, and this data is used for into normal data；
Step E-2, by the cloth deep power spectrum of reason at every bit in the Brillouin scattering power curve along fiber distribution
Carried out related calculation with step E-1 gained normal datas, obtain the deep power spectrum of cloth reason and the standard at the every bit along fiber distribution
The degree of correlation of data.
Degree of correlation highest point in correlation result obtained by step E-3, the selection step E-2, as often
The Brillouin shift of a bit.
Finally, according to Brillouin shift and temperature or the relational implementation of strain to temperature or the sensing of strain.
Therefore, the present invention employs auto-correlation coding techniques and coherent detection method simultaneously, using auto-correlation coding techniques
The signal to noise ratio of system can be improved, so as to obtain longer dynamic range than pulse under conditions of spatial discrimination is not changed,
Improve BOTDR system and be excited the relatively low defect of threshold value, reduce detection time and memory space expense, greatly improve coding techniques
Practicality.
In order to verify BOTDR system of the invention and its long range detection method, spy is verified with specific embodiment.
Wavelength is divided into two-way for the continuous light of the laser emitting wide of 1550nm by the first coupler, wherein all the way as spy
Light-metering, symbol width is modulated to for 20ns by electrooptic modulator, the Bark train pulse light of 13 bit lengths, then is noted after image intensifer
Enter detection electrical distance that sensor fibre coherent detection obtains it is longer for the relatively existing BOTDR systems of 50Km can be detected away from
From Bark sequences only need 2 detections, can compare simple venation under conditions of spatial discrimination is not changed in the signal to noise ratio of the system of raising
Punching obtains bigger dynamic range, reduces detection time and memory space expense, greatly improves the practicality of coding techniques so that
The present invention is verified.
Embodiments of the present invention are explained in detail above in conjunction with accompanying drawing, but the present invention is not limited to above-mentioned implementation
Mode, in the ken that those of ordinary skill in the art possess, can also be on the premise of present inventive concept not be departed from
Make a variety of changes.
Claims (6)
1. the BOTDR system long range detection method of Bark sequences is based on, it is characterised in that comprised the following steps：
Step A, continuous light is divided into all the way as detection light continuous light and another road as relevant local oscillator light continuous light；
Step B, one group of bipolarity Bark sequence is firstly generated, the bipolarity Bark sequences are divided into two groups of unipolarity Bark sequences
Row；Light intensity modulation is carried out using one group of unipolarity Bark sequence controls electric field to the continuous light as detection light again, is adjusted
One group of light pulse signal of unipolarity Bark sequences is obtained after system；
Step C, the light pulse signal of one group of unipolarity Bark sequences is amplified after injection fibre, to obtain along fiber distribution
Backward Brillouin scattering optical signal；Will be backward with described according to the local oscillator optical signal obtained as the continuous light of relevant local oscillator light
The coupling of Brillouin scattering optical signal is relevant to obtain Brillouin scattering optical signal, the Brillouin scattering electric signal obtained through opto-electronic conversion
Afterwards, frequency sweep, filter and amplification are carried out and obtains backward Brillouin scattering electric signal AHk；
Step D, by another group of unipolarity Bark sequence repeat step B and step C in step B, to obtain backward Brillouin scattering
Electric signal NAHk；
Step E, the backward Brillouin scattering electric signal AH by gainedkAnd NAHkCorrelation is carried out, is obtained along the Brillouin of fiber distribution
Scattered power curve；Obtained along the Brillouin shift at fiber distribution every bit according to the Brillouin scattering power curve, then
The change of optical fiber environment temperature or strain is obtained according to Brillouin shift；
Wherein, peak-seeking is carried out to the Brillouin scattering power curve in the step E and obtains Brillouin shift at every bit,
Specially：
Step E-1, the Power of Brillouin spectrum addition that will take one section of continuity point in the Brillouin scattering power curve are averaging,
As normal data；
Step E-2, the deep power spectrum of cloth reason and gained normal data at every bit in the Brillouin scattering power curve are done
Related operation, obtains the degree of correlation with normal data along the deep power spectrum of cloth reason at optical fiber every bit；
Degree of correlation highest point, the as Brillouin shift of every bit in step E-3, the selection correlation result.
2. the BOTDR system long range detection method of Bark sequences is based on according to claim 1, it is characterised in that：It is described
Polarization state randomization will be carried out as the continuous light of relevant local oscillator light in step C, obtain the local oscillator light that polarization state is evenly distributed
Signal.
3. the BOTDR system long range detection method of Bark sequences is based on according to claim 2, it is characterised in that：It is described
The sequence length of bipolarity Bark sequences is 7 or 11 or 13 in step B.
4. the BOTDR system long range detection method of Bark sequences is based on according to claim 3, it is characterised in that：It is described
Local oscillator optical signal couples the relevant Brillouin scattering for obtaining and being made up of difference frequency part with backward Brillouin scattering optical signal in step C
Optical signal.
5. the BOTDR system long range detection method of Bark sequences is based on according to claim 4, it is characterised in that：It is described
On the basis of the centre frequency of Brillouin scattering electric signal, swept frequency range is set to positive and negative 100MHz to frequency sweep process, sweeps in step C
Frequency is at intervals of 5MHz.
6. the system of the BOTDR system long range detection method based on Bark sequences described in 1 to 5 any one claim is based on,
Including light source module, the first coupler, light polarization disturbance module, Electro-optical Modulation module, Optical pulse amplification module, circulator, the
Two couplers, optical detection module, scan module, filtration module, amplification module, signal processing module, wherein the light source module
It is connected with the first coupler；First coupler is connected with Electro-optical Modulation module, light polarization disturbance module respectively；The electric light
Modulation module is sequentially connected with Optical pulse amplification module, circulator；One end of the circulator couples after being connected into optical fiber with second
Device is connected；The light polarization disturbance module is connected with the second coupler；Second coupler and optical detection module, frequency sweep mould
Block, filtration module, amplification module, signal processing module are sequentially connected；It is characterized in that：The Electro-optical Modulation module includes electric light
There is module in intensity modulated module and the Bark sequences being connected with electro-optic intensity modulation module, module occurs by Bark sequences gives birth to
Into two groups of unipolarity Bark sequences control the electric field of electro-optic intensity modulation module respectively, to obtain two groups of unipolarity Bark sequences
Light pulse signal；Brillouin's coherent detection acquisition is carried out by the light pulse signal of two groups of unipolarities Bark sequences respectively
Two groups of backward Brillouin scattering electric signals；The signal processing module carries out phase to two groups of backward Brillouin scattering electric signals
Close post analysis treatment and obtain Brillouin shift, the change of optical fiber environment temperature or strain is obtained according to the Brillouin shift.
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| CN108507981B (en) * | 2018-04-11 | 2020-09-22 | 南京大学 | Silicon-based waveguide back reflection sensing device based on OFDR (optical frequency domain reflectometry) and measuring method thereof |
| CN110361164B (en) * | 2019-08-15 | 2021-08-10 | 广东电网有限责任公司 | Method and system for analyzing breakpoint position and disturbance position of submarine optical cable |
| CN112781634B (en) * | 2021-04-12 | 2021-07-06 | 南京信息工程大学 | BOTDR distributed optical fiber sensing system based on YOLOv4 convolutional neural network |
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