CN103954378A - BOTDR system based on Bark sequences and long-distance detection method thereof - Google Patents
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Abstract
The invention discloses a BOTDR system based on Bark sequences and a long-distance detection method thereof. The method comprises the steps that continuous light is divided into two paths; a set of bipolar Bark sequences is generated, and the bipolar Bark sequences is divided into two sets of unipolar Bark sequences; the two sets of unipolar Bark sequences are utilized for controlling the electric field to modulate probe light, and light pulse signals of the two sets of unipolar Bark sequences are obtained; the two sets of signals are amplified, optical fibers are injected, and two sets of backward Brillouin scattering light signals are obtained; vibration light signals are in coupling coherence with the two sets of backward Brillouin scattering light signals respectively, and two sets of Brillouin scattering electric signals are collected through photovoltaic conversion, frequency sweeping and filter and amplification; the two sets of Brillouin scattering electric signals are in coherence, Brillouin frequency shift of each point distributed along the optical fiber is obtained, and changes of the temperature or strain around the optical fiber are obtained. An electro-optic modulation module in the system comprises an electro-optic intensity modulation module and a Bark sequence generating module. The self-correlation characteristics of the Bark sequences are utilized for improving the signal to noise ratio and improving the distance detecting distance under the condition that the system space resolution ratio is not reduced.
Description
Technical field
The present invention relates to a kind of BOTDR system and long distance measurement method thereof based on Bark sequence, belong to Distributed Optical Fiber Sensing Techniques field.
Background technology
Brillouin light domain reflectometer (Brillouin Optical Time-Domain Reflectometry based on Brillouin scattering, BOTDR) as the one of distributed fiberoptic sensor, have that resolution is high, error is little, sensor fibre lay simple, cost is low, easily realize.Utilize Brillouin shift and optical fiber position in optical fiber the relation of strained or temperature, can be used on power industry, water conservancy industry and civil construction industry, build a bridge and the monitoring of other xoncrete structures fission, the monitoring structural health conditions of large-scale civil engineering, traffic highway, subway tunnel industry, the detection of oil and gas industry trouble spot.In the time there is axial strain or temperature variation in sensor fibre, to there is frequency displacement with respect to the pulsed light frequency of injecting in the frequency of the Brillouin scattering dorsad in optical fiber, the axial strain that the frequency shift amount of Brillouin scattering light frequency and optical fiber are suffered and temperature variation are good linear relationship.Utilize this relation can realize the sensing measurement of temperature and strain.
Barker sequence (Barker Sequences), is a kind of time-limited non-periodic sequence signal element, is also called Bark sequence.The value of Barker sequence element is "+1 " or " 1 ".Barker sequence has good autocorrelation performance and the cross correlation good with other common sequences.It is one of preferred signals unit in Design of Signal, and its application is very extensive.
Traditional BOTDR system generally adopts the method for monopulse direct detection, and the spatial resolution of system and dynamic range are determined by the width of pulse to a certain extent.When pulse width is wider, the gross energy of pulse is larger, can obtain good dynamic range, but spatial resolution can decline, and is difficult to detect compared with mishap point.And pulse width is when narrower, spatial resolution gets a promotion, and because pulse self-energy declines, dynamic range reduces.So traditional BOTDR system is with conflict in spatial resolution and these two gordian techniquies of dynamic range.The existing BOTDR system based on coding techniques, as Gloay and Simplex technology can solve the contradiction between spatial resolution and dynamic range to a certain extent, but Gloay and Simplex technology do not have good peak-to-average ratio, because spontaneous Brillouin is excited the existence of threshold value, make system be more prone to reach to be excited threshold value, dynamic range is not better promoted.There is larger defect in the time and the storage space expense that obtain one group of data in Gloay and Simplex technology in practical application in industry.
Summary of the invention
Technical matters to be solved by this invention is to overcome the deficiencies in the prior art, a kind of BOTDR system and long distance measurement method thereof based on Bark sequence is provided, object is to utilize the autocorrelation performance of Bark sequence, and the mode by relevant frequency sweep is surveyed, obtain the distribution of Brillouin's frequency spectrum in optical fiber, utilize temperature, stress and Brillouin shift relation to realize the sensing of temperature and stress, under the condition of spatial resolution that does not reduce system, improve the signal to noise ratio (S/N ratio) of Brillouin light fiber sensor, thereby improve detection range.
The present invention specifically solves the problems of the technologies described above by the following technical solutions:
The long distance measurement method of BOTDR system based on Bark sequence, comprises the following steps:
Steps A, continuous light is divided into a road as surveying the continuous light of light and another road continuous light as relevant local oscillator light;
Step B, first generate one group of bipolarity Brak sequence, described bipolarity Bark sequence is divided into two groups of unipolarity Bark sequences; Utilize one group of unipolarity Bark sequence control electric field to carry out light intensity modulation to described as the continuous light of surveying light again, after modulation, obtain the light pulse signal of one group of unipolarity Bark sequence;
Step C, the light pulse signal of described unipolarity Bark sequence is amplified after injection fibre, to obtain the backward Brillouin scattering light signal along fiber distribution; Using according to the local oscillator light signal obtaining as the continuous light of relevant local oscillator light and the relevant acquisition of described backward Brillouin scattering light signal coupling Brillouin scattering light signal, after opto-electronic conversion obtains Brillouin scattering electric signal, carry out frequency sweep, filter and amplification acquisition backward Brillouin scattering electric signal AH
k;
Step D, by another group unipolarity Bark sequence repeating step B and step C in step B, to obtain backward Brillouin scattering electric signal NAH
k;
Step e, by the backward Brillouin scattering electric signal AH of gained
kand NAH
kbe correlated with, obtain the Brillouin scattering powertrace along fiber distribution; Obtain along the Brillouin shift at fiber distribution every bit place according to described Brillouin scattering powertrace, then obtain the variation of optical fiber environment temperature or strain according to Brillouin shift.
Further, as a preferred technical solution of the present invention: in step e, described Brillouin scattering powertrace is carried out peak-seeking and obtained the Brillouin shift at every bit place, be specially:
Step e-1, the Power of Brillouin spectrum of getting one section of continuity point in described Brillouin scattering powertrace is added and is averaging, as normal data;
Step e-2, the cloth at every bit place in described Brillouin scattering powertrace is managed to deep power spectrum and gained normal data carries out related calculation, obtain the degree of correlation of managing deep power spectrum and normal data along the cloth at optical fiber every bit place;
Step e-3, choose the highest point of degree of correlation in described related operation result, be the Brillouin shift of every bit.
Further, as a preferred technical solution of the present invention: using carrying out polarization state randomization as the continuous light of relevant local oscillator light, obtain the local oscillator light signal that polarization state is evenly distributed in described step C.
Further, as a preferred technical solution of the present invention: in described step B, the sequence length of bipolarity Bark sequence is 7 or 11 or 13.
Further, as a preferred technical solution of the present invention: the relevant Brillouin scattering light signal being formed by difference frequency part that obtains of local oscillator light signal and the coupling of backward Brillouin scattering light signal in described step C.
Further, as a preferred technical solution of the present invention: in described step C, frequency sweep process is taking the centre frequency of Brillouin scattering electric signal as benchmark, and swept frequency range is set to positive and negative 100MHz, and frequency sweep is spaced apart 5MHz.
The invention allows for a kind of according to the system of the above-mentioned long distance measurement method of BOTDR system based on Bark sequence, comprise light source module, the first coupling mechanism, light polarization disturbance module, electrooptical modulation module, Optical pulse amplification module, circulator, the second coupling mechanism, photodetection module, frequency sweep module, filtration module, amplification module, signal processing module, wherein said light source module is connected with the first coupling mechanism; Described the first coupling mechanism is connected with electrooptical modulation module, light polarization disturbance module respectively; Described electrooptical modulation module is connected successively with Optical pulse amplification module, circulator; One end of described circulator is connected with the second coupling mechanism after being connected into optical fiber; Described light polarization disturbance module is connected with the second coupling mechanism; Described the second coupling mechanism is connected successively with photodetection module, frequency sweep module, filtration module, amplification module, signal processing module; Described electrooptical modulation module comprises electric light intensity modulated module and the Bark sequence generation module being connected with electric light intensity modulated module, two groups of unipolarity Bark sequences that generate by Bark sequence generation module are controlled respectively the electric field of electric light intensity modulated module, to obtain the light pulse signal of two groups of unipolarity Bark sequences; Carry out respectively Brillouin's coherent detection by the light pulse signal of described two groups of unipolarity Bark sequences and obtain two groups of backward Brillouin scattering electric signal; Described signal processing module to described two groups of backward Brillouin scattering electric signal be correlated with post analysis process obtain Brillouin shift, obtain the variation of optical fiber environment temperature or strain according to described Brillouin shift.
The present invention adopts technique scheme, can produce following technique effect:
(1), the present invention combines auto-correlation coding techniques and coherent detection method, utilize the autocorrelation performance of Bark sequence in auto-correlation coding techniques, can improve the signal to noise ratio (S/N ratio) of system, thereby obtaining longer dynamic range than monopulse under the condition that does not change spatial discrimination.
(2), utilize the autocorrelation performance of Bark sequence, adopt the good peak-to-average ratio of Bark sequence self, average detection of optical power is avoided nonlinear effect, reduces signaling number of times.And the mode by relevant frequency sweep is surveyed, obtain the distribution of Brillouin's frequency spectrum in optical fiber, utilize temperature, stress and Brillouin shift relation to realize the sensing of temperature and stress, under the condition of spatial resolution that does not reduce system, improve the signal to noise ratio (S/N ratio) of Brillouin light fiber sensor, thereby raising detection range, the feasibility of raising system.
(3), utilize the good peak-to-average ratio of Bark sequence self, improve BOTDR system and be excited the lower defect of threshold value, utilize identical code length N, in the time obtaining one group of identical data, Smplex carries out N-1 detection, and Gloay will carry out 4 times and survey, and Bark sequence only needs to survey for 2 times, reduce detection time and storage space expense, greatly improve the practicality of coding techniques.
Brief description of the drawings
Fig. 1 is the schematic diagram that the present invention is based on the BOTDR system of Bark sequence.
Embodiment
Below in conjunction with Figure of description, embodiments of the present invention are described.
As shown in Figure 1, the present invention has designed a kind of BOTDR system based on Bark sequence and has comprised light source module, the first coupling mechanism, light polarization disturbance module, electrooptical modulation module, Optical pulse amplification module, circulator, the second coupling mechanism, photodetection module, frequency sweep module, filtration module, amplification module, signal processing module, wherein light source module is connected with the first coupling mechanism, narrow linewidth laser in light source module sends continuous light, be divided into two-way continuous light through the first coupling mechanism: first via continuous light and the second road continuous light, wherein first via continuous light is sent into electrooptical modulation module, the second road continuous light is as relevant local oscillator light, electrooptical modulation module is for being modulated into train pulse light by first via continuous light, comprise electric light intensity modulated module and the Bark sequence generation module being connected with electric light intensity modulated module, two groups of unipolarity Bark sequences that generate by Bark sequence generation module are controlled respectively the electric field of electric light intensity modulated module, to obtain the light pulse signal of two groups of unipolarity Bark sequences, then, electric light intensity modulated module in electrooptical modulation module is connected successively with Optical pulse amplification module, circulator, the light pulse signal of two groups of unipolarity Bark sequences that electric light intensity modulated module is exported is respectively through the amplification of Optical pulse amplification module, circulator injection fibre, to obtain the backward Brillouin scattering light signal along fiber distribution, described light polarization disturbance module is connected with the second coupling mechanism, for obtaining using carrying out polarization state randomization as the continuous light of relevant local oscillator light the local oscillator light signal that polarization state is evenly distributed, described the second coupling mechanism is coupled two groups of backward Brillouin scattering light signals of circulator output respectively and is concerned with local oscillator light signal again, obtains two groups of Brillouin scattering light signals, being input to respectively the photodetection module, frequency sweep module, filtration module, amplification module, the signal processing module that connect successively processes again, every group of signal, after opto-electronic conversion obtains Brillouin scattering electric signal, carries out frequency sweep, filter and amplification, collection and obtains corresponding backward Brillouin scattering electric signal, after the backward Brillouin scattering electric signal of gained is correlated with, analyzing and processing obtains along the Brillouin shift at the every bit place of fiber distribution, obtains the variation of optical fiber environment temperature or strain according to described Brillouin shift.
The long distance measurement method of BOTDR system based on Bark sequence of the present invention, specific as follows:
Narrow linewidth laser in steps A, light source module sends continuous light, and the first coupling mechanism after light source module is divided into two-way continuous light: first via continuous light and the second road continuous light.The first via is sent into electrooptical modulation module as the continuous light of surveying light, and the second road continuous light is as relevant local oscillator light.
Step B, utilize electrooptical modulation module that first via continuous light is modulated into train pulse light, specific as follows:
Step B-1, first generate bipolarity Brak sequence.
Binary code Bark sequence is a kind of code character that has particular law.The Bark sequence A of a n position
n∈ (1 ,+1), n=0,1,2 ..., (L-1).
From the definition of Bark serial autocorrelation function, the longer the better for Bark sequence.Sequence is longer, and auto-correlation main peak is higher, more sharp-pointed, and autocorrelation performance is better.Bark sequence is 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 being excited threshold value in Bark serial autocorrelation characteristic and BOTDR system, bipolarity Bark sequence can Selective sequence length be 7,11,13 Bark sequence, can obtain stronger detection of optical power by the sequence of selecting to grow, the rear orientation light Signal-to-Noise receiving is higher.
Step B-2, carry out pattern conversion, bipolar code is converted to the unipolar code that is applicable to Optical Fiber Transmission.
Owing to can only transmitting positive light pulse in optical fiber, so bipolar code is converted to the unipolar code that is applicable to Optical Fiber Transmission, bipolarity Bark sequence can be divided into two groups of unipolar Bark sequences by the method for biasing, concrete conversion according to following formula:
Wherein A is bipolarity Bark sequence, 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, utilize one group of unipolar Bark sequence control electric field, realize electric light intensity modulated.
By the radio frequency control end of the one group of unipolarity Bark sequence access electric light intensity modulated module producing, the first via accesses the light input end mouth of electric light intensity modulated module as the continuous light of surveying light.
Electric light intensity modulated is to utilize the birefringent phenomenon of crystal, the linearly polarized light of incident is resolved into o light and e light, utilize the electrooptical effect of crystal to be changed the refractive index of crystal by electric signal, thereby control the phase differential that two oscillating components form, the relevant principle of recycling light superposes two-beam, thereby realizes the modulation of light intensity.Access the variation of the radio frequency control end control electric field of electric light intensity modulated module by one group of unipolarity Bark sequence, realize the modulation to light intensity.Thereby can obtain at the light output end of electric light intensity modulated module the light pulse signal of one group of unipolarity Bark sequence.The light pulse signal of this unipolarity Bark sequence is sent into Optical pulse amplification module to be amplified.
Step C, the light pulse signal of described unipolarity Bark sequence is amplified after through optical circulator injection fibre, after coupling is relevant, carry out frequency sweep, filter and amplification obtains backward Brillouin scattering electric signal.Specific as follows:
Step C-1, by the light pulse signal of described one group of unipolarity Bark sequence send into Optical pulse amplification module amplify after through circulator injection fibre, to obtain backward Brillouin scattering light signal;
Step C-2, according to the second road continuous light as relevant local oscillator light, the local oscillator light signal of acquisition; In the time that local oscillator light signal obtains, the second road continuous light signal can be obtained to the local oscillator light signal that polarization state is evenly distributed through light polarization disturbance module, eliminate polarization decay object in local oscillator light and the relevant detection of back scattering optically-coupled to reach.Then the backward Brillouin scattering light signal obtaining and local oscillator light signal are concerned with and are obtained Brillouin scattering light signal by the second coupling mechanism coupling, carry out opto-electronic conversion through photodetection module and obtain Brillouin scattering electric signal;
Coherent detection process is as follows:
Local oscillator light signal E
lOwith backward Brillouin scattering light signal E
belectric field respectively available following formula represent:
Wherein, the refractive index that n is testing fiber, c is the light velocity, r
lOfor the light field vector of local oscillator light signal, r
bfor the light field vector of backscatter signal, and r
lO=r
b, ω
lOfor the frequency of local oscillator light signal, ω
bfor backscatter signal frequency, E
* lOfor the conjugate of local oscillation signal electric field, E
* bfor the conjugate of backward Brillouin scattering light signal electric field, i is imaginary part, and t is the time.
Local oscillator light signal and backward Brillouin scattering light signal mix laggard enter in photodetector, the field intensity after relevant is:
In above formula for frequency composition ω
b+ ω
lOexceed photodetector frequency response range, photodetector only can be surveyed difference frequency part ω
b-ω
lO.After coupling is relevant, obtaining light signal comprises and frequency part and difference frequency part.Judge whether to obtain and frequency light signal partly according to the investigative range of photodetection module, but the photodetection module investigative range adopting in this method is the light signal of difference frequency part.
Step C-3, the Brillouin scattering electric signal that step C-2 is obtained carry out frequency sweep, filtering, amplification, gather and obtain backward Brillouin scattering electric signal AH
k;
Frequency sweep process is estimated the general frequency displacement position of Power of Brillouin spectrum according to sensor fibre, taking the centre frequency of backward brillouin scattering signal frequency spectrum as benchmark, the positive and negative 100MHz in left and right arranges the swept frequency range of frequency sweep module, and frequency sweep is set to 5MHz and carries out frequency sweep.
Further module is carried out filtering to the signal of frequency sweep after filtering, amplification module amplifies, and then signal processing module adopts inner A/D module to carry out data acquisition, processes and obtains one group of backward Brillouin scattering electric signal AH
k, then preserve.
Step D, by another group unipolarity Bark sequence repeating step B and step C in step B, to obtain the backward Brillouin scattering electric signal NAH of another group unipolarity Bark sequence
k.
Step e, Brillouin's back scattering electric signal AH to two groups of unipolarity Bark sequences
kand NAH
kafter being correlated with, decoding, obtains along the Brillouin shift at fiber distribution every bit place by peak-seeking.Specific as follows:
First, according to the two groups of back scattering electric signal AH that gather in signal processing module
kand NAH
kin conjunction with the decoding principle of Bark code to decoding data.
Decode procedure is described below:
First, according to Bark serial autocorrelation characteristic:
A
k*A
k＝Lδ
k (4)
Wherein A
kfor Bark sequence, L is Bark sequence length, and * is related operation symbol, δ
kfor uni-impulse function.
Then, then by the back scattering electric signal AH detecting
kand NAH
kafter subtracting each other, obtain and the signal of Bark Serial relation this signal and A
kcarry out related calculation, can obtain system responses h
k, along the Brillouin scattering powertrace of fiber distribution, specific as follows:
Wherein
for convolution algorithm symbol.
Then, decoded data are carried out to simple crosscorrelation peak-seeking, obtain along the Brillouin shift at the every bit place of fiber distribution.Detailed process is described below:
The cloth that step e-1, the Brillouin scattering powertrace along fiber distribution that decoding is obtained are got one section of continuity point is managed deep power spectrum and is added and is averaging, by these data for normal data;
Step e-2, the described cloth along every bit place in the Brillouin scattering powertrace of fiber distribution is managed to deep power spectrum and step e-1 gained normal data carries out related calculation, obtain the degree of correlation of managing deep power spectrum and normal data along the cloth at the every bit place of fiber distribution.
Step e-3, choose the highest point of degree of correlation in the related operation result that described step e-2 obtain, be the Brillouin shift of every bit.
Finally, the sensing to temperature or strain according to the relational implementation of Brillouin shift and temperature or strain.
Therefore, the present invention has adopted auto-correlation coding techniques and coherent detection method simultaneously, utilize auto-correlation coding techniques can improve the signal to noise ratio (S/N ratio) of system, thereby obtain longer dynamic range than monopulse under the condition that does not change spatial discrimination, improve BOTDR system and be excited the lower defect of threshold value, reduce detection time and storage space expense, greatly improve the practicality of coding techniques.
In order to verify BOTDR system of the present invention and long distance measurement method thereof, spy verifies with specific embodiment.
Wavelength is that the continuous light of the wide laser emitting of 1550nm is divided into two-way by the first coupling mechanism, wherein a road is as surveying light, being modulated to symbol width by electrooptic modulator is 20ns, 13 long Bark train pulse light, after image intensifer, injecting the detection electrical distance that sensor fibre coherent detection obtains is that the relatively existing BOTDR system of 50Km can be surveyed longer distance again, Bark sequence only needs to survey for 2 times, can be in the signal to noise ratio (S/N ratio) that improves system, under the condition that does not change spatial discrimination, obtain larger dynamic range than monopulse, reduce detection time and storage space expense, greatly improve the practicality of coding techniques, the present invention is verified.
By reference to the accompanying drawings embodiments of the present invention are explained in detail above, but the present invention is not limited to above-mentioned embodiment, in the ken possessing those of ordinary skill in the art, can also under the prerequisite that does not depart from aim of the present invention, makes a variety of changes.
Claims (7)
1. the long distance measurement method of the BOTDR system based on Bark sequence, is characterized in that, comprises the following steps:
Steps A, continuous light is divided into a road as surveying the continuous light of light and another road continuous light as relevant local oscillator light;
Step B, first generate one group of bipolarity Bark sequence, described bipolarity Bark sequence is divided into two groups of unipolarity Bark sequences; Utilize one group of unipolarity Bark sequence control electric field to carry out light intensity modulation to described as the continuous light of surveying light again, after modulation, obtain the light pulse signal of one group of unipolarity Bark sequence;
Step C, the light pulse signal of described one group of unipolarity Bark sequence is amplified after injection fibre, to obtain the backward Brillouin scattering light signal along fiber distribution; Using according to the local oscillator light signal obtaining as the continuous light of relevant local oscillator light and the relevant acquisition of described backward Brillouin scattering light signal coupling Brillouin scattering light signal, after the Brillouin scattering electric signal obtaining through opto-electronic conversion, carry out frequency sweep, filter and amplification acquisition backward Brillouin scattering electric signal AH
k;
Step D, by another group unipolarity Bark sequence repeating step B and step C in step B, to obtain backward Brillouin scattering electric signal NAH
k;
Step e, by the backward Brillouin scattering electric signal AH of gained
kand NAH
kbe correlated with, obtain the Brillouin scattering powertrace along fiber distribution; Obtain along the Brillouin shift at fiber distribution every bit place according to described Brillouin scattering powertrace, then obtain the variation of optical fiber environment temperature or strain according to Brillouin shift.
2. the long distance measurement method of the BOTDR system based on Bark sequence according to claim 1, is characterized in that: in described step e, described Brillouin scattering powertrace is carried out peak-seeking and obtained the Brillouin shift at every bit place, be specially:
Step e-1, the Power of Brillouin spectrum of getting one section of continuity point in described Brillouin scattering powertrace is added and is averaging, as normal data;
Step e-2, the cloth at every bit place in described Brillouin scattering powertrace is managed to deep power spectrum and gained normal data carries out related calculation, obtain the degree of correlation of managing deep power spectrum and normal data along the cloth at optical fiber every bit place;
Step e-3, choose the highest point of degree of correlation in described related operation result, be the Brillouin shift of every bit.
3. the long distance measurement method of the BOTDR system based on Bark sequence according to claim 2, is characterized in that: in described step C, using carrying out polarization state randomization as the continuous light of relevant local oscillator light, obtain the local oscillator light signal that polarization state is evenly distributed.
4. the long distance measurement method of the BOTDR system based on Bark sequence according to claim 3, is characterized in that: in described step B, the sequence length of bipolarity Bark sequence is 7 or 11 or 13.
5. the long distance measurement method of the BOTDR system based on Bark sequence according to claim 4, is characterized in that: the relevant Brillouin scattering light signal being made up of difference frequency part that obtains of local oscillator light signal and the coupling of backward Brillouin scattering light signal in described step C.
6. the long distance measurement method of the BOTDR system based on Bark sequence according to claim 5, it is characterized in that: in described step C, frequency sweep process is taking the centre frequency of Brillouin scattering electric signal as benchmark, swept frequency range is set to positive and negative 100MHz, and frequency sweep is spaced apart 5MHz.
7. the system based on the long distance measurement method of BOTDR system based on Bark sequence described in 1 to 6 any one claim, comprise light source module, the first coupling mechanism, light polarization disturbance module, electrooptical modulation module, Optical pulse amplification module, circulator, the second coupling mechanism, photodetection module, frequency sweep module, filtration module, amplification module, signal processing module, wherein said light source module is connected with the first coupling mechanism; Described the first coupling mechanism is connected with electrooptical modulation module, light polarization disturbance module respectively; Described electrooptical modulation module is connected successively with Optical pulse amplification module, circulator; One end of described circulator is connected with the second coupling mechanism after being connected into optical fiber; Described light polarization disturbance module is connected with the second coupling mechanism; Described the second coupling mechanism is connected successively with photodetection module, frequency sweep module, filtration module, amplification module, signal processing module; It is characterized in that: described electrooptical modulation module comprises electric light intensity modulated module and the Bark sequence generation module being connected with electric light intensity modulated module, two groups of unipolarity Bark sequences that generate by Bark sequence generation module are controlled respectively the electric field of electric light intensity modulated module, to obtain the light pulse signal of two groups of unipolarity Bark sequences; Carry out respectively Brillouin's coherent detection by the light pulse signal of described two groups of unipolarity Bark sequences and obtain two groups of backward Brillouin scattering electric signal; Described signal processing module to described two groups of backward Brillouin scattering electric signal be correlated with post analysis process obtain Brillouin shift, obtain the variation of optical fiber environment temperature or strain according to described Brillouin shift.
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106052842A (en) * | 2016-08-05 | 2016-10-26 | 上海交通大学 | Distributed fiber vibration sensing system capable of eliminating declining noises and demodulation method of system |
| CN108507981A (en) * | 2018-04-11 | 2018-09-07 | 南京大学 | Silica-based waveguides back reflection sensing device based on OFDR and its measurement method |
| CN110361164A (en) * | 2019-08-15 | 2019-10-22 | 广东电网有限责任公司 | A kind of submarine optical fiber cable breakpoint location and disturbance location analysis method and system |
| CN112781634A (en) * | 2021-04-12 | 2021-05-11 | 南京信息工程大学 | BOTDR distributed optical fiber sensing system based on YOLOv4 convolutional neural network |
| CN114485747A (en) * | 2021-12-30 | 2022-05-13 | 广州劲联智能科技有限公司 | Brillouin frequency shift extraction method and system |
Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2009047455A (en) * | 2007-08-14 | 2009-03-05 | Yokogawa Electric Corp | Device for measuring optical fiber characteristics |
| CN101476948A (en) * | 2008-12-19 | 2009-07-08 | 南京大学 | Long-distance optical fiber sensing method based on Hadamard matrix self-correlated characteristic |
| CN101825499A (en) * | 2010-05-18 | 2010-09-08 | 华北电力大学（保定） | Method for measuring sea water temperature profile based on optical fiber Brillouin scattering principle |
| CN101839698A (en) * | 2010-04-30 | 2010-09-22 | 南京大学 | BOTDR (Brillouin Optical Time Domain Reflectometer) for calibrating optical power of reference light and calibrating method thereof |
| CN102607451A (en) * | 2012-03-12 | 2012-07-25 | 南京大学（苏州）高新技术研究院 | Wavelength-scanning type Brillouin optical time-domain reflectometer |
-
2014
- 2014-04-30 CN CN201410182920.XA patent/CN103954378B/en active Active
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2009047455A (en) * | 2007-08-14 | 2009-03-05 | Yokogawa Electric Corp | Device for measuring optical fiber characteristics |
| CN101476948A (en) * | 2008-12-19 | 2009-07-08 | 南京大学 | Long-distance optical fiber sensing method based on Hadamard matrix self-correlated characteristic |
| CN101839698A (en) * | 2010-04-30 | 2010-09-22 | 南京大学 | BOTDR (Brillouin Optical Time Domain Reflectometer) for calibrating optical power of reference light and calibrating method thereof |
| CN101825499A (en) * | 2010-05-18 | 2010-09-08 | 华北电力大学（保定） | Method for measuring sea water temperature profile based on optical fiber Brillouin scattering principle |
| CN102607451A (en) * | 2012-03-12 | 2012-07-25 | 南京大学（苏州）高新技术研究院 | Wavelength-scanning type Brillouin optical time-domain reflectometer |
Non-Patent Citations (2)
| Title |
|---|
| YAHEI KOYAMADA: "Fiber-Optic Distributed Strain and Temperature Sensing With Very High Measurand Resolution Over Long Range Using Coherent OTDR", 《JOURNAL OF LIGHTWAVE TECHNOLOGY》 * |
| 加藤悠介等: "Double-pulse brillouin optical time-domain reflectometer using Barker code", 《PROCEEDINGS OF THE 2009 IEICE COMMUNICATIONS SOCIETY CONFERENCE》 * |
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106052842A (en) * | 2016-08-05 | 2016-10-26 | 上海交通大学 | Distributed fiber vibration sensing system capable of eliminating declining noises and demodulation method of system |
| CN108507981A (en) * | 2018-04-11 | 2018-09-07 | 南京大学 | Silica-based waveguides back reflection sensing device based on OFDR and its measurement method |
| 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 |
| CN110361164A (en) * | 2019-08-15 | 2019-10-22 | 广东电网有限责任公司 | A kind of submarine optical fiber cable breakpoint location and disturbance location analysis method and system |
| 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 |
| CN112781634A (en) * | 2021-04-12 | 2021-05-11 | 南京信息工程大学 | BOTDR distributed optical fiber sensing system based on YOLOv4 convolutional neural network |
| CN114485747A (en) * | 2021-12-30 | 2022-05-13 | 广州劲联智能科技有限公司 | Brillouin frequency shift extraction method and system |
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