CN104316217A - On-line monitoring system based on brillouin scattering self-temperature-measurement optical fiber composite guide wire - Google Patents
On-line monitoring system based on brillouin scattering self-temperature-measurement optical fiber composite guide wire Download PDFInfo
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Abstract
The invention relates to an on-line monitoring system based on a brillouin scattering self-temperature-measurement optical fiber composite guide wire. The on-line monitoring system comprises a self-temperature-measurement optical fiber composite guide wire, a laser, an optical fiber wavelength division multiplexer, a photoelectricity receiving and amplifying component and a signal acquisition pre-processing system unit, one aluminum wire or steel wire of a center layer or an inner layer of a traditional guide wire is replaced by an optical unit where an optical fiber is implanted in terms of the self-temperature-measurement optical fiber composite guide wire, the system effectively gathers monitoring and managing methods to obtain line guide wire own operation features and surrounding environmental temperature changes, accurate dynamic information can be provided for electric transmission line safety production, operating maintenance management, condition based maintenance, emergency disaster prevention and the like, functions of electric transmission line safety precaution and aid decision making can be achieved, fine management level of operating maintenance and safety production can be improved, and construction and operation of intelligent power grid electric transmission links can be positively facilitated.
Description
Technical field
The present invention relates to one based on Brillouin scattering from thermometric optical fiber composite wire on-line monitoring system.
Background technology
Temperature is the important information that the mankind are engaged in Activities institute GPRS always, and the techniques and methods obtaining temperature information also more and more science, and mankind's temperature that more and more exigence grasps living environment constantly changes.For today of modernization industry, the acquisition of temperature information has wider realistic meaning.People are seeking the various measuring methods of temperature always, and along with the fast development of science and technology, require also more and more higher to the measuring accuracy of temperature.
Take electric signal as the conventional temperature sensor of working foundation, as thermopair, thermistor, pyroelectric detector equitemperature sensor development oneself through very ripe, features such as they are simple with its structure, measuring accuracy is high, cost is low and be widely used in the fields such as national economy, scientific research, national defence.But having under strong electromagnetic or inflammable and explosive occasion, the conventional temperature sensor based on electric signal measurement is just very restricted.
Along with the research and development of optical fiber technology and Fibre Optical Sensor theory, scientific research personnel starts the distributed measurement proposing temperature.Optical fiber has that volume is little, lightweight, flexible, electrical insulating property is good, flexible bending, corrosion-resistant, measurement range large, sensitivity high, to traditional sensor particularly temperature sensor can play expansion improve effect, complete the task that the former has been difficult to even can not complete.Optical fiber sensing technology is used for temperature survey, except having above feature, compared with traditional thermometric instruments, also has that response is fast, a feature such as bandwidth, explosion-proof, anti-flaming, electromagnetism interference.Therefore, optical fiber temperature sensor technology is subject to the great attention of all trades and professions scientific and technical personnel and carries out deep exploration.Point type fibre optic temperature sensor, because the upper easy realization that possesses skills, an anti-interference performance are strong, sensitivity high, obtains very large development.As absorption-type fibre optic temperature sensor, fluorescence decay type fibre optic temperature sensor, thermochromatic effect fibre optic temperature sensor etc.But point temperature sensor only can test certain point or the state of temperature in certain fraction region, cannot the measurement of implementation space Temperature Distribution.The distribution measuring adopting a large amount of point temperature sensors to realize some occasion temperature is uneconomic, or even impossible.Distributed optical fiber temperature sensor can realize the distributed measurement in the temperature field along optical fiber continuous distribution, and the span of test optical fiber can reach tens kms, and spatial resolution is high, error is little, has the higher ratio of performance to price compared with single-point or the accurate distribution measuring of multiple spot.Distributed optical fiber temperature sensor its have many good qualities: 1) optical fiber essence be insulation, be applicable to inflammable, explosive environments; 2) what transmit in optical fiber is that light believes No. one, anti-strong electromagnetic; 3) optical fiber delicate, is easy to install; 4) distributed measurement of temperature is realized.
In scientific research and engineering, many occasions are had to need to determine the distribution of temperature, the thermo parameters method along the line of the pipelines such as such as long distance oil pipeline, telecommunication cable or power cable, the thermo parameters method of large-scale power transformer inside, the Temperature Distribution in bridge, dam, warehouse, heavy construction, tunnel, high pressure vessel, spacecraft body etc.In the production of many industries such as electronics, metallurgy, chemical industry, also all need to monitor multiple temperature spot simultaneously, inflammable, explosive or other material bulk storage tanks Temperature Distribution is stored, the Temperature Distribution etc. of baroque main equipment and apparatus for rotating as measured.
Summary of the invention
Devise that a kind of Centralizing inspection and ladder of management obtain the change of line wire self-operating feature and ambient temperature effectively from thermometric optical fiber composite wire on-line monitoring system based on Brillouin scattering herein, for transmission line of electricity safety in production, operation maintenance management, repair based on condition of component, emergency and disaster prevention etc. provide multidate information accurately, realize the effect of transmission line of electricity safe early warning and aid decision making, improve the fine-grained management level of operation maintenance, safety in production, actively promote intelligent grid transmission of electricity link Construction and operation.
A kind of based on Brillouin scattering from thermometric optical fiber composite wire on-line monitoring system, comprise from thermometric optical fiber composite wire, laser instrument, optical fibre wavelength division multiplexer, opto-electronic receiver and amplifier module, signals collecting pretreatment system components, it is characterized in that: described is that an aluminum steel of conventional wires central core or internal layer or steel wire are replaced with the light unit implanted and have optical fiber from thermometric optical fiber composite wire, its internal layer comprises 6 aluminum steels or steel wire, skin comprises 12 aluminum steels or steel wire, every layer of aluminum steel or steel wire are stranded in lower floor's center core or interior twisted layer with answering uniform close, described smooth unit have employed stainless-steel tube seamless welding technology and is positioned over by data optical fiber in special stainless-steel tube blank pipe, stainless-steel tube external diameter is consistent with adjacent aluminium single cord external diameter, anti-tampering material filling material is adopted to be fixed optical fiber between optical fiber and hollow steel bushing, computing machine controls clock-pulse generator and produces the pulse with certain repetition frequency, and described pulse is modulating pulse laser instrument on the one hand, makes it to produce a series of high-power light pulse, provides synchronizing pulse simultaneously, enter data acquisition state to high-speed data acquisition card, described a series of high-power light pulse enters into sensor fibre through a port of wavelength division multiplexer, and each point place produces rear orientation light in a fiber, turns back to wavelength division multiplexer, rear orientation light leaches stokes light and anti-Stokes light respectively by thin-film interference filters, two other port through wavelength division multiplexer exports, and entering into photoelectric detector (APD) respectively and main amplifier carries out opto-electronic conversion and amplification, signal being amplified to data collecting card can effectively in acquisition range, now the photosignal that the scattering of sensor fibre each point is returned carries out gathering and storing by described data collecting card, produce a fiber optic temperature curve, and wait for that the scattered light electric signal of subsequent optical pulses generation carries out the cumulative sum data processing such as on average, finally carry out temperature demodulation and display by computing machine by compiled software.
Described based on Brillouin scattering from thermometric optical fiber composite wire on-line monitoring system, describedly achieve while electric energy transmitting from thermometric optical fiber composite wire, can effective transmit communications signals.
By to the development from thermometric optical fiber composite wire, realize transmission line wire running temperature change real time monitoring function, realize the Real-Time Monitoring of current carrying capacity of conductor, running temperature, STRESS VARIATION, improve the security of transmission line wire transmission capacity and operation of power networks, reduce grid line loss.
Accompanying drawing explanation
Fig. 1 shows from thermometric optical fiber composite wire structural drawing.
Fig. 2 shows the distributed optical fiber sensing system basic subrack based on BOTDA.
Fig. 3 shows the strained frequency displacement design sketch of optical fiber.
Fig. 4 show optical fiber the movement of strained Brillouin frequency when increasing.
Fig. 5 shows based on Brillouin scattering from thermometric optical fiber composite wire on-line monitoring system.
Fig. 6 shows the scattered light powertrace of different wave length.
Embodiment
Fig. 5 is based on Brillouin scattering from thermometric optical fiber composite wire on-line monitoring system entire block diagram, chief component: the unit such as laser instrument, optical fibre wavelength division multiplexer, opto-electronic receiver and amplifier module, signals collecting pretreatment system;
(1) laser instrument
The wavelength selectable of laser instrument selects 905nm or 1550nm.The signal intensity of anti Stokes scattering photon number and 4 powers of excitation wavelength are inversely proportional to, namely the wavelength of exciting light is longer, but scattered photon signal is more weak. the wavelength of exciting light is shorter, anti-Stokes i} (loss of penetrating light is larger. therefore, short distance side is measured, wavelength can be selected to be the laser instrument of 905nm, then long wavelength laser should be selected for long range measurements, if the response time of avalanche photodide APD is very short, when input optical pulse is approximately rectangle, then No. one, the letter that APD receives is length is v
gon the optical fiber of Δ T/2 all scattered lights and.Not mate if asked during the rising of APD with input pulse width, then spatial resolution depends primarily on the rise time of APD.As being 50ns when pulse width, when the response time of detector meets the demands, then its spatial resolution is 5m.For obtaining higher spatial resolution, the spectral width of laser instrument should be as far as possible narrow.According to actual conditions, the spectral width of laser instrument can be selected between 10 ~ 50nm.Laser instrument is generally with tail optical fiber, and fiber power should be greater than 500mW.
(2) optical fibre wavelength division multiplexer
Optical fibre wavelength division multiplexer is the important component part of the temperature sensitivity of influential system continent and precision.As mentioned above, when the burst pulse light that laser diode sends is propagated in a fiber, the different forward direction of wavelength and back rayleigh scattering, stokes scattering, anti Stokes scattering and brillouin scattering signal can be produced, wherein anti Stokes scattering has higher temperature control, and its photon is used as the carrier of temperature information.The optical fiber backscatter signals with different wave length through optical fibre wavelength division multiplexer, will effectively isolate anti Stokes scattering light signal, or isolates other for side amount or the signal of reference, as Rayleigh scattering, Brillouin scattering.Optical fibre wavelength division multiplexer is a kind of optical dispersion system, and it can utilize the angular dispersion of prism, diffraction light walks slowly like a woman (or fiber grating) and interference of light narrowband light filter realizes.Especially narrowband light filter, according to the different wave length requirement of separation signal, can form the light filter of respective center wavelength and spectral width.
(3) opto-electronic receiver and amplifier module
Opto-electronic receiver and amplifier module are made up of the avalanche photodide with prime amplifier and high-gain, broadband, low noise amplifier.
(4) signal acquiring and processing system
Signal acquiring and processing system is made up of dual channel high speed transient state (1 DAM) signal acquisition process card.Concrete implementation procedure: under the triggering of synchronous control unit, optical sender produces a heavy current pulse, this pulsed drive semiconductor laser produces powerful light pulse, and in injection laser tail optical fiber, the light pulse exported from laser instrument tail optical fiber will enter one section of optical fiber be placed on calibration cell after light path coupler, this section of optical fiber is used for system calibrating temperature, then enters sensor fibre.After laser in a fiber scattering occurs, the Brillouin's rear orientation light carrying temperature information will turn back in light path coupler.Light pulse not only can be coupled directly to sensor fibre by light path coupler. but also the Brillouin scattering being different from emission wavelength scattering can returned is optically coupled to optical splitter.Optical splitter is made up of the optical filter of two different centre wavelengths, they leach stokes light and anti-Stokes light respectively, two ways of optical signals carries out opto-electronic conversion and amplification through receiver, then carry out high speed output by data acquisition unit and be converted to digital quantity, eventually pass and signal is processed further, for the calculating of temperature.
Computing machine controls clock-pulse generator and produces the pulse with certain repetition frequency, this pulse is modulating pulse laser instrument on the one hand, make it to produce a series of high-power light pulse, there is provided synchronizing pulse to high-speed data acquisition card simultaneously, entering data acquisition state. light pulse enters into sensor fibre through a port of wavelength division multiplexer, and each point place produces rear orientation light in a fiber, turns back to wavelength division multiplexer.Rear orientation light leaches stokes light and anti-Stokes light respectively by thin-film interference filters, outer two ports of order through wavelength division multiplexer export, and entering into photoelectric detector (APD) respectively and main amplifier carries out opto-electronic conversion and amplification, signal being amplified to data collecting card can effectively in acquisition range.Now the photosignal that the scattering of sensor fibre each point is returned carries out gathering and storing by data collecting card, produces a fiber optic temperature curve, and waits for that the scattered light electric signal of subsequent optical pulses generation carries out the cumulative sum data processing such as on average.Finally carry out temperature demodulation and display by computing machine by compiled software.
Utilizing Brillouin scattering to carry out Fibre Optical Sensor is the new and high technology grown up in recent years, because the frequency displacement of brillouin scattering signal and intensity are by the impact of the temperature suffered by optical fiber and strain, so the temperature of optical fiber and the distributed intelligence of strain just can be obtained by the intensity or frequency displacement measuring Brillouin signal.Have direct-detection type and Heterodyne detect type, its thermometric distance, resolution is high, complex structure.Its ultimate principle adopts tunable continuous wave laser to inject continuous light; adopt pulsed laser to inject light pulse at the other end: by making continuous light optical frequency than height (or low) Brillouin shift of pulsed light, and make continuous light experience gain (or loss); Optoisolator is respectively equipped with, with stable output optical frequency between optical fiber two ends and two laser instruments; The light intensity of back light is detected at injected pulse the end APB or quick Pjrl that mix germanium.When thermometric, tuning continuous laser optical frequency, makes from being detected brillouin gain (or loss) signal a little returned maximum; Detect the optical frequency of now two-laser with radio frequency spectroanalysis instrument poorer, namely this be detected Brillouin shift a little.
Based on this technology sensor typical structure as shown in Figure 2.One pulsed light (pump light Pulse) and a continuous light (detecting light CW) are injected sensor fibre by tunable laser respectively that be in optical fiber two ends, when pump light with detection light frequency difference with when in optical fiber, the Brillouin shift in certain region is equal, will produce Brillouin amplification effect (excited Brillouin) in this region, there is energy trasfer in two light beams each other.Due to Brillouin shift and temperature, strain and there is linear relationship, therefore, while carrying out regulating continuously to the frequency of two-laser, by detecting the luminous power from optical fiber coupled one end continuous light out, difference on the frequency corresponding when just can determine that on optical fiber each segment region, energy trasfer reaches maximum, thus obtain temperature, strain information, realize distributed measurement.
the size of Brillouin scattering optical frequency shift is decided by acoustic velocity.The temperature experienced due to sensor fibre and strain can affect the acoustic velocity of inside of optical fibre, and the temperature that Brillouin shift is experienced by sensor fibre and strain determine formula 1:
In formula
,
be respectively the variable quantity of temperature and strain;
,
be respectively temperature and the coefficient of strain of Brillouin shift, these coefficients can be determined by experiment.Fig. 3 and Fig. 4 provides the schematic diagram of frequency displacement and strain stress relation, and temperature and frequency displacement also have corresponding relation.
The present invention is based on distributed fiber temperature sensing principle, founding mathematical models, by a large amount of simulation calculation, simulation test, in-site measurement diagnosis research, propose to twist in conventional wires and carbon-fibre wire and take root in light unit into there being optical fiber into one, the distributed measurement in the temperature field along optical fiber continuous distribution can be realized, the span of test optical fiber can reach tens kms, spatial resolution is high, error is little, compared with single-point or the accurate distribution measuring of multiple spot, there is higher cost performance, and then develop and a set ofly can realize transformer station's conductor temperature DATA REASONING, gather, transmission integration, man-machine interface close friend is convenient to vast work about electric power personnel temperature measuring equipment easy to use.By research of the present invention; transmission line of electricity operation maintenance personnel can be made to grasp the running status of line wire in time; wire running status is made prediction, early warning, safety assessment etc.; Timeliness coverage exception or fault; timely process, scientificlly and effectively prevents area power grid to run fluctuation, avoids accident to magnify further; cause electric grid large area power cut, and the economic loss caused.
The operation wavelength of system i.e. the operation wavelength of pulsed laser are the important performance indexes of pulsed laser.The operation wavelength of system directly has influence on the selection of the device parameters such as respective wavelength scope of Interleave muiltiplexing component element, filter plate group, sensor fibre, APD.Therefore be necessary to analyze the rational selection of system wavelength.
1), the relation of system works wavelength and luminous power to be checked
From optical fiber itself, there is loss in light transmission in a fiber, Transmission loss reduces with the increase of optical wavelength, and optical fiber Brillouin scattered signal dies down with the increase of wavelength.In addition, the spectrum of electrooptical device and avalanche photodide APD is also far from linearly.Everything all proposes a problem, how to select the operation wavelength of sensor-based system, and the scattered light of system luminous power to be checked (namely entering into the scattered light power of APD) just can be made maximum, and namely signal to noise ratio (S/N ratio) is maximum.And the cardinal principle that the thermometric mechanism of system determines centre wavelength optimization is: make the intensity of the back scattering Anti-Stokes signal of the optical fiber connector getting back to optical fiber top maximum, there is formula 2
In formula, L is fiber lengths; P
0for light source enters the luminous power at optical fiber top; P
as(L) for optical fiber connector returns the anti-Stokes luminous power at optical fiber top; K
asbe one and close the relevant coefficient such as efficiency and the optical fiber back scattering factor with the misfortune of Brillouin scattering cross section, Brillouin shift place fiber optic component; R
as(T) be the i on population of lower energy level; λ
asfor anti Stokes scattering optical wavelength; α
0, α
asbe respectively the loss of optical fiber in light source center wavelength and anti Stokes scattering light wave strong point.
The decay of optical fiber roughly can be divided three classes: absorption loss, added losses and scattering loss.Absorption loss is mainly from three aspects: in the Intrinsic Gettering of fiber optic materials, material, Impurity Absorption and structure Atom defect absorb.Added losses are the losses produced after optical fiber cabling.Scattering loss mainly refers to Rayleigh scattering, and it belongs to intrinsic scattering, causes because refractive index in fiber optic materials is uneven.Loss and the wavelength biquadratic of Rayleigh scattering are inversely proportional to.I.e. formula 3:
In formula, A is scale-up factor, is determined by concrete sensor fibre.Have a large amount of known about the document of fibre loss, for silicon materials optical fiber within the scope of 0.6-1.6 μm, Rayleigh scattering is the main intrinsic source of loss, namely has formula 4:
Make dPas (L)/d λ 0=0, have formula 5:
In formula, Δ v is Brillouin shift.By specific loss profile fiber, the wavelength in different thermometric distance situation can be obtained.For given sensor fibre and thermometric distance, from the angle improving Anti-Stokes signal luminous power to be checked, system has a best centre wavelength.Be greater than or less than this centre wavelength, all can weaken the luminous power of Anti-Stokes signal.And this optimal wavelength increases with the increase of thermometric distance.
2), the relation of system works wavelength and temperature control
Based on the temperature-measuring system of distributed fibers of backward Brillouin scattering, be realize temperature survey, as formula 6 according to the strength ratio of Stokes and anti-Stokes two paths of signals:
In formula, h is Planck constant, and c is the light velocity, and k is Boltzmann constant, and T is absolute temperature, and Δ v is Brillouin shift.When the temperature control of system has been defined as slight temperature change, causes the change of intensity level R (T), namely had formula 7:
According to Brillouin spectrum, it is formula 8 that semiconductor pulse laser operation wavelength and brillouin scattering signal centre wavelength are closed:
Bring formula 8 into formula 7, the temperature control obtaining system after abbreviation is mathematic(al) representation, namely has formula 9
Formula 9 shows, the temperature control of system, when other condition is certain, is chosen the increase of semiconductor laser centre wavelength with system and improves.In real system, temperature control is lower than what calculate with formula 9, reason is just that hangover that backward Rayleigh scattering composes is mixed and bleeds in the Brillouin signal section of diving, and Rayleigh scattering is to temperature-insensitive, even if the Brillouin's optical filter making isolation higher can not address this problem at all.Formula 9 can be obtained from formula 8
Definition Δ s, Δ as are respectively Stokes, distance between Anti-Stokes signal centre wavelength and semiconductor laser centre wavelength.Then for the semiconductor laser under specified criteria, separation delta s, Δ as are larger, and mean that the mixed Rayleigh signal bled in Brillouin signal is more weak, corresponding system temperature sensitivity is also higher.For same sensor fibre, the centre wavelength of system is longer, and the distance between corresponding brillouin scattering signal and excitation signal is also larger, more favourable to the actual temperature sensitivity improving system.
3), the relation of system works wavelength and job stability
The job stability of system refers to: along with the continuous firing of semiconductor laser; its centre wavelength often can be drifted about to long wavelength direction because of tube core heating; the centre wavelength of corresponding brillouin scattering signal also can change thereupon, thus affects the duty of whole system.
Although the centre wavelength drift value of high-quality semiconductor laser is less, bring obvious adverse effect also can to the system of high-performance parameter.Formula 10 can be obtained from formula 9:
In formula, the coefficient of deviation of Cs, Cas difference Stokes and Anti-Stokes signal, it shows the ratio that Brillouin signal centre wavelength changes with the drift of excitation signal centre wavelength.Cs > 1, Cas < 1 can be found out from formula formula 9.Namely the drift value of Stokes signal centre wavelength is greater than the drift value of excitation signal centre wavelength, and one and with the proportional increase of increase of excitation signal centre wavelength.Similarly, the drift value of Anti-Stokes signal centre wavelength is less than the drift value of excitation signal centre wavelength; And the proportional reduction of the increase with excitation signal centre wavelength.Therefore, from system works stability angle, system centre wavelength chooses short wavelength is favourable.
As can be seen from above Several Analysis: the optimum centre wavelength of system is actual is select the thermometric of optical fiber, system apart from closely-related with system.When both are certain, from system temperature sensitivity angle, system ripple one is long, and the longer the better; From job stability angle, system wavelength should select short wavelength: and from the angle of luminous power to be detected, system only has an optimal wavelength.The deficiency maximum based on backward Brillouin scattering temp measuring system one is: the intensity of brillouin scattering signal is too weak.Therefore, choosing of system optimal centre wavelength considered emphatically, on the basis of signal intensity, to take into account temperature control and the stability of system.Simultaneously. also should from the angle of reality, the factors such as the universality of consideration semiconductor laser centre wavelength and photoelectric detector, the mainly spectral response range of APD, select suitable system centre wavelength, Stokes optical wavelength and anti-Stokes optical wavelength are in the flat site of APD spectral response range.Can show that a relational expression that more can embody luminous power to be checked and system works wavelength is formula 11 by formula analysis above:
In formula, A is a series of constants irrelevant with wavelength.Be combined in the loss factor of different incident wavelength and anti-Stokes wave strong point, the scattered light powertrace of different wave length as shown in Figure 6 can be obtained.
As can be seen from Figure 6, when distance sensing is comparatively near, during as being less than 40 meters, the anti-Stokes light that when laser is near wavelength a1 (840nm), sensor fibre tail end returns is the strongest; When distance sensing is within the scope of 400m-2200m, the best effort wavelength of laser instrument is near a2 (1320nm), and single-mode fiber is better than a4 multimode optical fiber; And for the longer sensor-based system of distance sensing, the operation wavelength of a3 (l550nm) demonstrates superiority, and single-mode fiber is equally than a5 multimode optical fiber better effects if.Can find out again from Fig. 3, along with the increase of distance sensing, the best effort wavelength of corresponding laser instrument moves to longer wavelength direction.This provides theoretical foundation just to this items selection operation wavelength, have selected 1.550nm as operation wavelength.In a word, the selection of system works wavelength will be as the criterion with the overall performance of system, reasonably to select best effort wavelength.
The temperature signal of brillouin distributed fibre optic temperature sensor is that scattering coefficient is very little entrained by the backward anti-Stokes astigmatism in optical fiber.And the size of this signal power decides the detection accuracy of APD, the gain coefficient of prime amplifier and main amplifier, to such an extent as to the acquisition range of data collecting card.Therefore be necessary to carry out a quantitative analytical calculation to the backward anti-Stokes Brillouin scattering luminous power in optical fiber.In real application systems, because pump light pulse out also just will arrive photo-detector through parts such as optical fiber splitter, sensor fibre, optical filters afterwards from fiber amplifier.Like this, the backward anti-Si Kesi Brillouin scattering luminous power public affairs 12 that light pulse is complete after the loss of light wavelength division multiplexing, light filter plate insertion loss and sensor fibre are drawn:
In formula, v is light transmission speed in a fiber; E0 is the energy of pump light pulse: h, k are respectively Planck's constant and Boltzmann constant; Δ v is the Brillouin shift amount of optical fiber; Γ as is the scattering coefficient of the backward anti-Si Kesi Brillouin scattering in optical fiber unit length; α 0, α as are respectively incident pump light and the anti-Stokes Brillouin scattering loss factor in a fiber in unit length; L be on corresponding optical fiber a certain measurement point to measuring the distance of starting point; T is the absolute temperature of this measurement point; η 0, η 1, η 2 is respectively that incident pump light enters the light percent of pass of sensor fibre by optical fiber splitter, backward anti-Stokes Brillouin scattering enters by optical fiber splitter the light percent of pass of optical filter, backward anti-Stokes Brillouin scattering to enter photo-detector light percent of pass by optical filter.
Next a quantitative analytical calculation is carried out to backward anti-Stokes Brillouin scattering power P as (T), only need calculate the minimum value of Pas (T) herein and just can.Carry out analysis to formula 12 known, after system is determined, parameter v, h, k, Δ v, Γ as, α 0, α as, η 0, η 1, η 2 is by constant, and therefore all Pas (T) only change with the change of E0, T and L.Further analysis finds, Pas (T) and E0 are proportional, increases and increases, reduce with the increase of L with T.The experimentally system system index that will reach, system operating temperatures scope is-20 DEG C ~ 120 DEG C, distance sensing 4km, spatial resolution 1m.Therefore when calculating, measurement point is taken at the distalmost end 4km place of sensor fibre, temperature is assumed to-20 DEG C, and pulsed laser peak power is 10W, and light impulse length is 1Ons
The constant known by oneself is calculated:
These constants are brought in formula 12 and can be obtained
From result of calculation above, the backward anti-Stokes Brillouin scattering luminous power that photo-detector receives is greatly close to nW magnitude.That is, the backward anti-Stokes Brillouin scattering that photo-detector detects is submerged in the middle of noise completely, therefore flashlight to be extracted from noise, except improving the detection sensitivity of photo-detector as far as possible, effective signal transacting measure must be taked.
The foregoing is only preferred embodiment of the present invention, not in order to limit the present invention, all any amendments done within the spirit and principles in the present invention, equivalent replacement and improvement etc., all should be included within protection scope of the present invention.
Claims (3)
1. one kind based on Brillouin scattering from thermometric optical fiber composite wire on-line monitoring system, comprise from thermometric optical fiber composite wire, laser instrument, optical fibre wavelength division multiplexer, opto-electronic receiver and amplifier module, signals collecting pretreatment system components, it is characterized in that: described is that an aluminum steel of conventional wires central core or internal layer or steel wire are replaced with the light unit implanted and have optical fiber from thermometric optical fiber composite wire, its internal layer comprises 6 aluminum steels or steel wire, skin comprises 12 aluminum steels or steel wire, every layer of aluminum steel or steel wire are stranded in lower floor's center core or interior twisted layer with answering uniform close, described smooth unit have employed stainless-steel tube seamless welding technology and is positioned over by data optical fiber in special stainless-steel tube blank pipe, stainless-steel tube external diameter is consistent with adjacent aluminium single cord external diameter, anti-tampering material filling material is adopted to be fixed optical fiber between optical fiber and hollow steel bushing, computing machine controls clock-pulse generator and produces the pulse with certain repetition frequency, and described pulse is modulating pulse laser instrument on the one hand, makes it to produce a series of high-power light pulse, provides synchronizing pulse simultaneously, enter data acquisition state to high-speed data acquisition card, described a series of high-power light pulse enters into sensor fibre through a port of wavelength division multiplexer, and each point place produces rear orientation light in a fiber, turns back to wavelength division multiplexer, rear orientation light leaches stokes light and anti-Stokes light respectively by thin-film interference filters, two other port through wavelength division multiplexer exports, and entering into photoelectric detector (APD) respectively and main amplifier carries out opto-electronic conversion and amplification, signal being amplified to data collecting card can effectively in acquisition range, now the photosignal that the scattering of sensor fibre each point is returned carries out gathering and storing by described data collecting card, produce a fiber optic temperature curve, and wait for that the scattered light electric signal of subsequent optical pulses generation carries out the cumulative sum data processing such as on average, finally carry out temperature demodulation and display by computing machine by compiled software, realize the continuous function form sensing with distance on whole fiber lengths to go out the change of measured parameter with fiber lengths.
2. according to claim 1 based on Brillouin scattering from thermometric optical fiber composite wire on-line monitoring system, it is characterized in that, describedly achieve while electric energy transmitting from thermometric optical fiber composite wire, can effective transmit communications signals.
3. according to claim 1 based on Brillouin scattering from thermometric optical fiber composite wire on-line monitoring system, it is characterized in that, there is following relation in operation wavelength and the luminous power to be checked of described pulsed laser:
In formula, A is scale-up factor, and L is fiber lengths; Pas is the anti-Stokes luminous power that optical fiber connector returns to optical fiber top; α 0, α as are respectively the loss of optical fiber in light source center wavelength and anti Stokes scattering light wave strong point, and λ as is anti Stokes scattering optical wavelength; Δ v is Brillouin shift.
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| CN106257249A (en) * | 2015-11-13 | 2016-12-28 | 云南航天工程物探检测股份有限公司 | It is applicable to temperature-measuring system of distributed fibers and the temp measuring method of tunnel thermometric |
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| CN106257249A (en) * | 2015-11-13 | 2016-12-28 | 云南航天工程物探检测股份有限公司 | It is applicable to temperature-measuring system of distributed fibers and the temp measuring method of tunnel thermometric |
| CN105758328A (en) * | 2016-05-17 | 2016-07-13 | 安徽师范大学 | Nano-strain-order dynamic optical fiber strain sensing device and sensing method thereof |
| CN105758328B (en) * | 2016-05-17 | 2018-04-06 | 安徽师范大学 | A kind of Dynamic Optical Fiber strain sensing device for straining magnitude of receiving |
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| CN108011664B (en) * | 2017-10-11 | 2020-05-26 | 中国船舶重工集团公司第七一五研究所 | Noise separation method for optical fiber sensing remote demodulation system |
| CN108731839A (en) * | 2018-05-07 | 2018-11-02 | 珠海西默电气股份有限公司 | The method of distributed optical fiber temperature sensing system and the automatic parameter for obtaining calibration |
| CN109000822A (en) * | 2018-09-07 | 2018-12-14 | 中国南方电网有限责任公司超高压输电公司贵阳局 | Distributed fiber temperature measuring device |
| CN113405538A (en) * | 2021-06-07 | 2021-09-17 | 核工业西南物理研究院 | Device and method for calibrating spatial measurement position of laser scattering diagnosis system |
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