CN107741243B - A kind of BOTDR system and the method for promoting the lifetime of system - Google Patents
A kind of BOTDR system and the method for promoting the lifetime of system Download PDFInfo
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- G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
- G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
- G01D5/26—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light
- G01D5/32—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light
- G01D5/34—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells
- G01D5/353—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre
- G01D5/35338—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre using other arrangements than interferometer arrangements
- G01D5/35354—Sensor working in reflection
- G01D5/35358—Sensor working in reflection using backscattering to detect the measured quantity
- G01D5/35364—Sensor working in reflection using backscattering to detect the measured quantity using inelastic backscattering to detect the measured quantity, e.g. using Brillouin or Raman backscattering
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Abstract
The invention discloses a kind of BOTDR system and the method for promoting the lifetime of system, BOTDR system includes light source module, the first coupler, Electro-optical Modulation module, pulse generating module, Optical pulse amplification module, circulator, light polarization disturbance module, the second coupler, third coupler, the first optical detection module, scan module, signal processing module, the second optical detection module, feedback module and current control module.The present invention is by increasing feedback module, measure the different piece of whole sensor fibre by several times using different launched powers, and the fiber segment close to light source incidence end is deliberately enabled to generate stimulated Brillouin scattering phenomenon in the measurement process far from luminous source optical fiber section, by the fitting respectively and whole splicing to gradation measurement result, effective Brillouin's crest frequency spectral line of whole sensor fibre is obtained.The present invention solves the problems, such as that measurement distance is reduced caused by increasing because of radiation-induced loss, increases service life of the BOTDR system under space radiation environment.
Description
Technical field
The invention belongs to distributed fiberoptic sensor technical fields, in particular to a kind of BOTDR system and promote this and be
The method in system service life.
Background technique
Brillouin light time domain reflection technology (BOTDR) is a kind of Distributed Optical Fiber Sensing Techniques, and principle is based on from publication
In deep pool scattering.System source injects pulsed light from one end of optical fiber, and from the same end direct impulse light backwards to spontaneous Brillouin
Scattering spectra.By analyzing the heat transfer agent on the available optical fiber of the spectral line.Brillouin scattering is to be lured by the light field in optical fiber with it
Caused by the interaction for the sound field led, Brillouin scattering has the offset in a frequency relative to incident light, is referred to as cloth
In deep frequency displacement.And BOTDR then utilizes the Brillouin shift to analyze heat transfer agent: Brillouin shift and fiber optic temperature and suffered answering
Become related, and the temperature change and suffered axial strain of frequency displacement size and optical fiber are proportional.
With the gradually development of space industry science and technology, the monitoring and protecting of space flight device is also got under severe space environment
More to be paid attention to.However, traditional sensing technology means are but difficult to meet the field to the light-weighted requirement of space flight equipment.
The advantages that BOTDR technology has electromagnetism interference, and light-weight, error is small, high resolution, lays simply, low in cost.It is earliest
Applied to space industry, it is applied to the monitoring in the directions such as electric power, communication, engineering successively in developed country.From the nineties, I
State begins to carry out the application study of optical fiber sensing technology.And in all Distributed Optical Fiber Sensing Techniques, BOTDR relies on its energy
Temperature, strain and other a variety of physical quantitys are measured, while also there are the advantages such as spatial resolution is high, distance sensing is remote, it can be in time
It was found that the problems in large-scale structure and hidden danger, thus be widely used in safety monitoring.
Under the severe radiation environment in universe, ionising radiation, which generates radiation effect, influences BOTDR system, can be by light
The reinforcing of electrical part improves, but optical fiber must be exposed under radiation environment for a long time as the sensing element of BOTDR system.?
Under the influence of radiation, inside of optical fibre can generate colour center, this can generate certain influence, obvious shadow to the sensing capability of optical fiber
Sound is exactly the increase being lost.Although can be improved by the pulse width or the method for power for increasing detection light into fine optical signal
Energy, to increase the sensing scope of system, but the width for increasing light pulse will lead to the spatial resolution decline of system；
And for improving incident optical power, it is limited to the presence that Brillouin is excited threshold value, when detection of optical power is less than Brillouin's stimulated threshold
When value, the energy of the energy and detection light of Brillouin's rear orientation light is in a linear relationship.When detection of optical power is more than to be excited in cloth
When threshold value is excited in deep pool, detection light energy is transferred to Brillouin's stokes light, increases the energy of Brillouin's stokes light, and
Detection light energy can decay rapidly, eventually lead to the dynamic range decline of system.Therefore there is an urgent need to research and propose a kind of raising
The method of BOTDR service life under radiation environment.
Summary of the invention
In order to solve the technical issues of above-mentioned background technique proposes, the present invention is intended to provide a kind of BOTDR system and promotion
The method of the lifetime of system solves that optical fiber is caused to generate colour center effect because of space radiation environment, and damages the transmission of sensor fibre
Consumption increases, and BOTDR system distance sensing reduces.
In order to achieve the above technical purposes, the technical solution of the present invention is as follows:
A kind of BOTDR system worked under space radiation environment, including light source module, the first coupler, Electro-optical Modulation
Module, pulse generating module, Optical pulse amplification module, circulator, light polarization disturbance module, the second coupler, third coupler,
First optical detection module, scan module, signal processing module, the second optical detection module, feedback module and current control module；Light
Source module issues continuous light, which is divided into the continuous light of two-way that energy does not wait by the first coupler, and wherein energy is higher
Continuous light inputs Electro-optical Modulation module all the way, and the lower light continuous all the way of energy is as relevant local oscillator light input light polarization scrambling mould
Block, the pulse electrical signal that Electro-optical Modulation module is generated according to pulse generating module believe the continuous light modulation of input at pulsed light
Number, pulsed optical signals injection fibre after the amplification of Optical pulse amplification module is obtained by circulator along the backward of fiber distribution
Brillouin scattering optical signal, the backward Brillouin scattering optical signal and light polarization disturbing signal that the second coupler exports circulator
The local oscillator optical signal of the random distribution of module output carries out coupling and is concerned with, and exports Brillouin scattering optical signal, and third coupler will
The Brillouin scattering optical signal is divided into energy not equal two ways of optical signals, and wherein the higher optical signal of energy is through the first optical detection mould
Brillouin scattering electric signal is obtained after the photoelectric conversion of block, then through scan module frequency sweep, signal processing module filter and amplification, is obtained
Corresponding backward Brillouin scattering electric signal, the lower optical signal of another way energy is through the second optical detection module input feedback mould
Block, feedback module realize the control of the light signal power issued to light source module by control current control module.
Further, the course of work of the feedback module is as follows:
(a) when light source power is not promoted, obtain cut-point A: the power of Brillouin spectrum increases with distance and is reduced,
The power of Brillouin spectrum is close to background noise power at certain position, i.e., when can not be normal through Lorentz fit, by this
Position mark is A；
(b) source current is controlled to promote light source power, and in this process, judges whether A point is excited: if A point
Phenomenon is excited in generation, then the power near A point generates violent shake not instead of by fixed attenuation coefficient attenuation, when A point is sent out
After phenomenon is excited in life, needs to adjust back light source power and be excited until A point does not generate；
(c) after promoting light source power, judge the farthest point B of testing distance with the presence or absence of effective brillouin scattering signal:
If the signal power at B is not flooded by noise, Lorentz fit can be correctly carried out, then it represents that exist at B at this time effective
Transducing signal.
Further, the continuous light that the first coupler issues light source module is divided into the continuous light of two-way that energy ratio is 9:1.
Further, the Brillouin scattering optical signal of input is divided into the two-way light that energy ratio is 95:5 and believed by third coupler
Number.
Further, the first optical detection module uses APD avalanche diode.
A method of promoting the above-mentioned BOTDR system service life, comprising the following steps:
(1) spectrum of cut-point A and first segment optical fiber is obtained using BOTDR system:
If O point is the signal incidence end of optical fiber, the power of detecting optical pulses is P0, B point is the distalmost end for requiring detection, just
Beginning light source power P0 will be promoted as far as possible under the premise of guarantee does not generate and is excited phenomenon, to promote sensing effect；Before irradiation
The maximum range of system is OC, and after system is radiated, the loss of sensor fibre be will increase, and system is caused not receive
The effective brillouin scattering signal of B point first keeps incident optical power P at this time0Constant, record can obtain effective Brillouin at this time
The farthest point A of scattered signal, while obtaining the Brillouin spectral lines backwards of OA sections of optical fiber；
(2) processing is fitted to the Brillouin spectral lines of OA sections of optical fiber obtained in step (1), to obtain the section
Brillouin's crest frequency of optical fiber；
(3) incident optical signal power is promoted, the spectrum of second segment optical fiber after A point is obtained:
Gradually promote light source power, until that can guarantee: stimulated Brillouin scattering is not generated at point A, and at B point there are
The brillouin scattering signal of effect；Stop promoting light source power at this time, and measured using the power using BOTDR system, obtains A point
Effective sensing data of fine section between B point；
(4) processing is fitted backwards to Brillouin spectral lines to AB fiber segment obtained in step (3), to obtain
The crest frequency of the Brillouin spectral line of this section of optical fiber；
(5) splicing is carried out to the crest frequency of Brillouin spectral line obtained in step (2) and step (4), thus
To Brillouin's peak frequency information of whole section of sensor fibre OB；
(6) light source power is adjusted back to former power P 0, return step (1).
Further, in step (3), if OA sections of optical fiber are not also excited phenomenon, then may be used after promoting light source power
The measurement of crest frequency is carried out with the Brillouin spectral lines of the full section optical fiber OB after hoisting power.
By adopting the above technical scheme bring the utility model has the advantages that
The present invention is measured by several times by adding feedback module in traditional BOTDR system, using different launched powers
The different piece of whole sensor fibre, and deliberately light of the order close to light source incidence end in the measurement process far from luminous source optical fiber section
Fine section generates stimulated Brillouin scattering phenomenon.By the fitting respectively and whole splicing to gradation measurement result, to obtain whole
Effective Brillouin's crest frequency spectral line of sensor fibre, according to Brillouin shift and temperature or the relational implementation of strain to temperature
Degree or the sensing of strain.
Detailed description of the invention
Fig. 1 is the system composition block diagram of the invention；
Fig. 2 is the schematic diagram that optical fiber attenuation is converted with dose of radiation；
Fig. 3 is the relation schematic diagram of Brillouin spectrum power and distance sensing；
Fig. 4 is the schematic diagram for promoting incident optical signal power.
Specific embodiment
Below with reference to attached drawing, technical solution of the present invention is described in detail.
Fig. 1 is BOTDR system structural schematic diagram of the invention, including light source module, the first coupler, light polarization disturb mould
Block, Electro-optical Modulation module, pulse generating module, Optical pulse amplification module, circulator, the second coupler, the first optical detection module,
Scan module, signal processing module, third coupler, the second optical detection module, feedback module and current control module, wherein light
Source module is connected with the first coupler, and the narrow linewidth laser in light source module issues continuous light, is divided by the first coupler
The continuous light of two-way: the continuous light (energy ratio 9:1) of the continuous light of the first via and the second road, wherein the continuous light of the first via is sent into electric light tune
Molding block, the continuous light in the second road is as relevant local oscillator light；The pulse telecommunications that Electro-optical Modulation module is generated according to pulse generating module
Number by the continuous light modulation of the first via at pulsed optical signals, injection light after which is amplified by Optical pulse amplification module
Fibre obtains the backward Brillouin scattering optical signal along fiber distribution by circulator；Second coupler is defeated by circulator again
Backward Brillouin scattering optical signal out carries out coupling respectively relevant, acquisition Brillouin scattering with the local oscillator optical signal of random distribution
Optical signal.
Brillouin scattering optical signal is divided into two-way via third coupler, wherein the optical signal of 95% energy is through all the way
After the photoelectric conversion of one optical detection module obtains Brillouin scattering electric signal, progress frequency sweep, filter and amplification, acquisition acquisition are corresponding
Backward Brillouin scattering electric signal, analysis processing obtains the Brillouin shift along the every bit of fiber distribution, according to the cloth
In deep frequency displacement obtain the variation of optical fiber ambient temperature or strain；The optical signal of 5% energy of another way is by entering the second optical detection
In module, the information then composed containing Power of Brillouin along optical fiber can be passed to feedback module, and feedback module passes through control electric current
Control module realizes the control to light source power.
Feedback control module needs the function realized to include:
A. when light source power is not promoted, obtain cut-point A: the power of Brillouin spectrum increases with distance and is reduced,
It is point A by this position mark when the power of Brillouin spectrum is close to background noise power (can not be normal through Lorentz fit)；
B. source current is controlled to promote light source power, and in this process, judges whether A point is excited: if A point
Phenomenon is excited in generation, then the power near A point generates violent shake not instead of by fixed attenuation coefficient attenuation.When A point is sent out
After phenomenon is excited in life, needs to adjust back light source power and be excited until A is not generated；
C. after promoting light source power, judge the farthest point B of testing distance with the presence or absence of effective brillouin scattering signal: if
Signal power at this is not flooded by noise and (can correctly be carried out Lorentz fit), then it represents that exists at B effectively pass at this time
Feel signal.
Fig. 2 is the schematic diagram for radiating induced attenuation, and the loss of sensor fibre can increase with the increase of dose of radiation, that is, pass
The maximum detectable range of sensing system can be reduced with the increase of radiation length；If under the premise of distance sensing is constant, when
After dose of radiation increase to a certain extent, the brillouin scattering signal of optical fiber connector is eventually flooded by noise, cause BOTDR without
Method works normally.
It is as follows that the present invention promotes the step of BOTDR system service life.
Step 1, the spectrum of cut-point A and first segment optical fiber is obtained using BOTDR system:
Fig. 3 is the relation schematic diagram of Brillouin spectrum power and distance sensing, and O point is the signal incidence end of optical fiber, detects light
The power of pulse is P0, B point is the distalmost end for requiring detection.Primary light source power P 0 will be before guaranteeing not generating and be excited phenomenon
It puts and is promoted as far as possible, to promote sensing effect.The maximum range of system is OC before irradiation, however when system is by one
After the radiation for determining dosage, the loss of sensor fibre be will increase, and system is caused not receive the effective brillouin scattering signal of B point
(being flooded by noise).Incident optical power P is first kept at this time0Constant, the farthest sensing location A point recorded at this time (can get effective
The farthest point of brillouin scattering signal)；The Brillouin spectral lines backwards of OA sections of optical fiber are obtained simultaneously.
It is noted that the determination of A point is the dose of radiation dynamic change being subject to according to system with the increase of dose of radiation
's.Specific manifestation are as follows: it is P that A point, which is in light source power,0Farthest effective distance sensing when (not having hoisting power).
A point is obtained by the feedback control module of system；Specific manifestation are as follows: before promoting light source power, Brillouin spectrum
Power increase with distance and reduce, when the power of Brillouin spectrum (can not be quasi- normal through Lorentz close to background noise power
Close) when, it is point A by this position mark.
Step 2, processing is fitted to the Brillouin spectral line of OA obtained in step 1 sections of optical fiber, to obtain the Duan Guang
Fine Brillouin's crest frequency.
Step 3, incident optical signal power is promoted, the spectrum of second segment optical fiber after A point is obtained:
Fig. 4 is the schematic diagram for promoting incident optical signal power.Light source power is gradually promoted, until that can guarantee: (1) point A
Place does not generate at stimulated Brillouin scattering (2) B point that there are effective brillouin scattering signals.Stop promoting light source power at this time,
And measured using the power using BOTDR system, obtain effective sensing data of fine section between A point and B point.In view of radiating ring
Border may have an impact the threshold value of optical fiber, if after promoting light source power in step 3, OA sections of optical fiber are not also excited existing
As, then it can be used the Brillouin spectral lines of the full section optical fiber OB after hoisting power to carry out the measurement of crest frequency, it is more preferable to obtain
Brillouin spectral lines.
It is noted that the promotion amplitude of incident optical power is according to the reflection specific function of spectral line with the increase of dose of radiation
Rate and dynamic change.Specific manifestation are as follows: the power ascension of light source will guarantee that A point does not generate simultaneously and be excited phenomenon, and B point exists
Effective transducing signal.
The promotion of light source power is regulated and controled by the current control module that feedback module controls.
Whether A point is excited to be judged by feedback control module；Specific manifestation are as follows: during promoting light source power,
If phenomenon is excited in the generation of A point, the power near A point by fixed attenuation coefficient attenuation, does not generate violent shake.When
After A point is excited phenomenon, needs to adjust back light source power and be excited until A is not generated.
B point is judged with the presence or absence of effective brillouin scattering signal by feedback control module；Specific manifestation are as follows: when promotion light
After source power, if the signal power of B point is not flooded by noise and (can correctly be carried out Lorentz fit), then it represents that B point at this time
There are effective transducing signals.
In addition, it is contemplated that the power of stimulated scattering is bigger, to guarantee system normal operation, will be divided by third coupler
The optical signal of two-way is separately detected using different optical detection modules, it is proposed that the first optical detection module uses APD avalanche diode.
Step 4, processing is fitted backwards to Brillouin spectral lines to AB fiber segment obtained in step 3, thus
To the crest frequency of the Brillouin spectral line of this section of optical fiber.
Step 5, splicing is carried out to the crest frequency of Brillouin spectral line obtained in step 2 and step 4, to obtain
Brillouin's peak frequency information of whole section of sensor fibre OB.
Step 6, readjustment light source power repeats step 1 and measures to former power P 0.
Embodiment is merely illustrative of the invention's technical idea, and this does not limit the scope of protection of the present invention, it is all according to
Technical idea proposed by the present invention, any changes made on the basis of the technical scheme are fallen within the scope of the present invention.
Claims (7)
1. a kind of BOTDR system worked under space radiation environment, it is characterised in that: including light source module, the first coupler,
Electro-optical Modulation module, pulse generating module, Optical pulse amplification module, circulator, light polarization disturbance module, the second coupler, the
Three couplers, the first optical detection module, scan module, signal processing module, the second optical detection module, feedback module and electric current control
Molding block；Light source module issues continuous light, which is divided into the continuous light of two-way that energy does not wait by the first coupler, wherein can
Higher light input Electro-optical Modulation module continuous all the way is measured, the lower light continuous all the way of energy is inclined as relevant local oscillator light input light
Vibration disturbance module, the pulse electrical signal that Electro-optical Modulation module is generated according to pulse generating module is by the continuous light modulation of input at arteries and veins
Pulsed light signal, the pulsed optical signals, through circulator injection fibre, obtain edge by circulator after the amplification of Optical pulse amplification module
The backward Brillouin scattering optical signal of fiber distribution, backward Brillouin scattering optical signal that the second coupler exports circulator with
The local oscillator optical signal of the random distribution of light polarization disturbing signal module output carries out coupling and is concerned with, output Brillouin scattering letter
Number, the Brillouin scattering optical signal of the relevant output of coupling is divided into the two ways of optical signals that energy does not wait by third coupler, wherein can
It measures higher optical signal and obtains Brillouin scattering electric signal after the photoelectric conversion of the first optical detection module, then swept through scan module
Frequently, signal processing module filter and amplification obtains corresponding backward Brillouin scattering electric signal, the lower optical signal of another way energy
Through the second optical detection module input feedback module, feedback module issues light source module by control current control module realization
The control of light signal power.
2. working in the BOTDR system under space radiation environment according to claim 1, it is characterised in that: the feedback mould
The course of work of block is as follows:
(a) when light source power is not promoted, obtain cut-point A: the power of Brillouin spectrum increases with distance and is reduced, when certain
The power of Brillouin spectrum is close to background noise power at position, i.e., when can not be normal through Lorentz fit, by this position
Labeled as A；
(b) source current is controlled to promote light source power, and in this process, judges whether A point is excited: if A point generates
Be excited phenomenon, then the power near A point generates violent shake not instead of by fixed attenuation coefficient attenuation, when A point occur by
After swashing phenomenon, needs to adjust back light source power and be excited until A point does not generate；
(c) after promoting light source power, judge the farthest point B of testing distance with the presence or absence of effective brillouin scattering signal: if at B
Signal power do not flooded by noise, can correctly carry out Lorentz fit, then it represents that at this time at B exist effectively sensing letter
Number.
3. the BOTDR system according to claim 1 or claim 2 worked under space radiation environment, it is characterised in that: the first coupling
The continuous light that device issues light source module is divided into the continuous light of two-way that energy ratio is 9:1.
4. the BOTDR system according to claim 1 or claim 2 worked under space radiation environment, it is characterised in that: third coupling
The Brillouin scattering optical signal of input is divided into the two ways of optical signals that energy ratio is 95:5 by device.
5. the BOTDR system according to claim 1 or claim 2 worked under space radiation environment, it is characterised in that: described first
Optical detection module uses APD avalanche diode.
6. a kind of method for promoting the BOTDR system service life described in claim 2, which comprises the following steps:
(1) spectrum of cut-point A and first segment optical fiber is obtained using BOTDR system:
If O point is the signal incidence end of optical fiber, the power of detecting optical pulses is P0, B point is the distalmost end for requiring detection, initial light
Source power P0 will be promoted as far as possible under the premise of guarantee does not generate and is excited phenomenon, to promote sensing effect；System before irradiation
Maximum range be OC, after system is radiated, the loss of sensor fibre be will increase, and system is caused not receive B point
Effective brillouin scattering signal first keeps incident optical power P at this time0Constant, record can obtain effective Brillouin at this time and dissipate
The farthest point A of signal is penetrated, while obtaining the Brillouin spectral lines backwards of OA sections of optical fiber；
(2) processing is fitted to the Brillouin spectral lines of OA sections of optical fiber obtained in step (1), to obtain this section of optical fiber
Brillouin's crest frequency；
(3) incident optical signal power is promoted, the spectrum of second segment optical fiber after A point is obtained:
Light source power is gradually promoted, until that can guarantee: not generating stimulated Brillouin scattering at point A, and exist at B point effective
Brillouin scattering signal；Stop promoting light source power at this time, and measured using the power using BOTDR system, obtains A point and B
Effective sensing data of fine section between point；
(4) processing is fitted backwards to Brillouin spectral lines to AB fiber segment obtained in step (3), to obtain the section
The crest frequency of the Brillouin spectral line of optical fiber；
(5) splicing is carried out to the crest frequency of Brillouin spectral line obtained in step (2) and step (4), to obtain whole
Brillouin's peak frequency information of section sensor fibre OB；
(6) light source power is adjusted back to former power P 0, return step (1).
7. method according to claim 6, it is characterised in that: in step (3), if after promoting light source power, OA sections of light
Fibre is not also excited phenomenon, then the Brillouin spectral lines of the full section optical fiber OB after hoisting power can be used to carry out crest frequency
Measurement.
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