CN101298992A - Distributed type fiber optic sensor based on optical fiber cavity attenuation and vibration technique - Google Patents
Distributed type fiber optic sensor based on optical fiber cavity attenuation and vibration technique Download PDFInfo
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- CN101298992A CN101298992A CNA2008100183897A CN200810018389A CN101298992A CN 101298992 A CN101298992 A CN 101298992A CN A2008100183897 A CNA2008100183897 A CN A2008100183897A CN 200810018389 A CN200810018389 A CN 200810018389A CN 101298992 A CN101298992 A CN 101298992A
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Abstract
The invention relates to a distributing optical fiber sensor based on the fiber cavity ring-down technology, characterized in that, a laser outical source is connected with an optical fiber spliter connected with a plurality of adjustable optical attenuators; a first optical fiber ring is connected with an adjustable optical attenuator, and the other optical fiber rings are connected with the corresponding adjustable optical attenuators through the revelent optical fiber delay line; a plurality of output ends of the optical fiber ring are connected with the optical fiber combiner which is connected with a high speed photodetector, a high speed A/D conversion and signal process module in turn; the optical fiber ring is respectively connected with an optical fiber coupler at the upper and lower two ends of the ring optical fiber, while the left side and he right side are respectively connected with a single-mode fiber optical fiber and an optical fiber sensing elements. The invention has the beneficial effect that, the measurement of the intensity or the wavelength is converted to that of the optical fiber ring ring-down time, which realizes the one time of measurement is just the millisecond magnitude with simple demodulation method, and easily realizes the distributing optical fiber sensor to measure a plurality of physical quantity at the same time.
Description
Technical field
The present invention relates to a kind of distributed fiberoptic sensor based on the optical fiber cavity attenuation and vibration technique, belong to the Fibre Optical Sensor field, is a kind of design and demodulation method thereof of distributed fiberoptic sensor.
Background technology
Optical fiber sensing technology is that a kind of that last century, the seventies developed rapidly along with the development of optical fiber and Fibre Optical Communication Technology is carrier with light, and optical fiber is medium, the novel sensing technology of perception and transmission outer signals.Compare with traditional mechanical and electrical type sensor, Fibre Optical Sensor has the advantage of following several respects: (1) is highly sensitive, and dynamic range is big; (2) anti-electromagnetic interference (EMI), electrical insulating property is good, and is anticorrosive, can work under High Temperature High Pressure and rugged surroundings such as inflammable and explosive; (3) sensing head is simple in structure, and size is little, and is in light weight, is fit to imbed in the large scale structure; (4) loss is little, can realize remote detection; (5) optical fiber is lightly soft, and easily multiplexing and formation sensing network is easy to realize distributed sensing or the like.Therefore Fibre Optical Sensor has been subjected to the generally attention of countries in the world and has carried out extensive studies once coming out, and it has obtained widespread use at aspects such as military affairs, national defence, space flight and aviation, industrial and mining enterprises, energy environment protection, Industry Control, medical and health, metrology and measurement, building, household electrical appliance at present.
Since people's reported first such as Morey in 1989 are used as sensing with fiber grating, optical fiber grating sensing is as one of Fibre Optical Sensor important branch, become the big focus of one in the Fibre Optical Sensor research field, fiber-optic grating sensor is except the advantage with ordinary optic fibre sensor, also has own unique advantage, as: metrical information is a Wavelength-encoding, has avoided factors such as intensity of light source fluctuating, optical fiber micro-bending and coupling loss that measurement result is impacted; Have very high reliability and stability; Be convenient to constitute various forms of optical fiber sensing networks, carry out large-area multimetering; Can realize absolute measurement etc.Fiber-optic grating sensor is mainly used in parameters such as inside configuration strain, pressure, temperature, vibration, load fatigue and structural damage is monitored at present, and the distributed fiber grating sensor is mainly used in the strain sensing aspect.
The method of traditional measuring optical fiber grating wavelength drift is directly to observe by spectrometer, but the resolution of normal optical spectrometer has only 0.01nm, and volume is big, price is high, is usually used in the laboratory demodulation, does not reach the requirement of engineering applicationization and industrialization.Personnel make great efforts for many years after deliberation, and people have proposed the multiple demodulation techniques that optic fiber grating wavelength changes that are used for.Demodulation method commonly used at present is divided into interferometric method and filter method two big classes, mainly contain: non-equilibrium Mach-Zehnder (Mach-Zehnder, M-Z) fibre optic interferometer demodulation method, non-equilibrium Michelson (Michelson) interferometer demodulation method and Sai Nake (Sagnac) fibre optic interferometer demodulation method and Turnning optical fibre method Fabry-perot (Fabry-P é rot, F-P) filters demodulate method, the edge filter method, the matched filtering method, the Wavelength matched demodulation method of tunable laser, grating dispersion method and chirp grating detection method etc., these technology respectively have relative merits, are applicable to the sensor-based system of different condition.
People have proposed a kind of novel fiber grating demodulation method based on the optical fiber cavity attenuation and vibration technique in recent years, and this method is converted to measurement to the optical fiber cavity ring-down time with the demodulation of wavelength, has improved the precision and the speed of demodulation.People such as Gupta M were at paper " Cavity-enhanced spectroscopy in optical fibers " (Optics Letters in 2002,2002,27 (21): utilize the single-mode fiber optical cavity of the long end face plating high-reflecting film of 10m to carry out the medium refraction index sensing Study of An 1878-1880); People such as Tarsa P B were at paper " Cavity ringdown strain gauge " (OpticsLetters in 2004,2004,29 (12): utilize the single-mode fiber optical cavity of end face plating highly reflecting films 1339-1341) and carried out pull sensing research as the double-tapered fiber of sensing element, but above two kinds of methods will be plated highly reflecting films at fiber end face, processing technology is difficulty relatively, the high-reflection region of reflectance coating generally has only tens nm in addition, has limited the scope of used optical maser wavelength greatly.Chuji Wang in 2004 etc. are at paper " Fiber ringdown pressure sensors " (Optics Letters, 2004,29 (4): 352-254) with " Fiber loop ringdown for physical sensor development:pressuresensor " (Applied Optics, 2004,43 (35): propose 6458-6464) to utilize the fiber optic loop structure in 0-9.8 * 10
6In the Pa scope pressure sensing of single-mode fiber is studied, and obtained the United States Patent (USP) mandate on July 10th, 2007, the patent No. is 7,241,986, B2.Chuji Wang in 2006 etc. are again at paper " An alternative method to developfibre grating temperature sensors using the fibre loop ringdown scheme " (MeasurementScience and Technology, 2006, utilize the fiber optic loop structure to Fiber Bragg Grating FBG (Fiber Bragg Grating 17:1741-1751), FBG) and long period fiber grating (Long-period fiber grating, LPFG) carried out the temperature sensing experiment, and in the mandate of acquisition on January 29th, 2008 United States Patent (USP), the patent No. is 7,323,677, B1; People such as NiN were at paper " Cavity ring-down long-period fibre grating strainsensor " (Measurement Science and Technology in 2007,2007, utilize fiber optic loop and LPFG to carry out the stress sensing experiment in 18:3135-3138).But used method once all can only fiber-optic grating sensor of demodulation in the above several pieces of documents, can not satisfy the requirement of distributed sensing.
Summary of the invention
The technical matters that solves
For fear of the deficiencies in the prior art part, the present invention proposes a kind of distributed fiberoptic sensor based on the optical fiber cavity attenuation and vibration technique, can satisfy based on the decline fiber-optic grating sensor that swings demodulation method of optical fiber cavity to be difficult to satisfy the demand of distributed sensing.
Technical scheme
A kind of distributed fiberoptic sensor based on the optical fiber cavity attenuation and vibration technique is characterized in that: comprise pulsed laser light source 1, optical fiber splitter 2, some adjustable optical attenuators 3
1～n, some fibre delay lines 4
1～n-1, some fiber optic loop 5
1～n, optical fiber combiner 6, high-speed photodetector 7, high speed analog-digital conversion (A/D) conversion and signal processing module 8; LASER Light Source 1 links to each other with optical fiber splitter 2, and optical fiber splitter 2 connects some adjustable optical attenuators 3
1～nFirst fiber optic loop 5
1Directly and adjustable optical attenuator 3
1Connect other fiber optic loop 5
2～nAll pass through corresponding fibre delay line 4
1～n-1Back and corresponding adjustable optical attenuator 3
2～nConnect; Some fiber optic loop 5
1～nOutput terminal connect optical fiber combiner 6, optical fiber combiner 6 interconnects successively with high-speed photodetector 7, high-speed a/d conversion and signal processing module again; Described fiber optic loop 5
1～nBe up and down two ends fiber coupler 9 and 11 and the single-mode fiber 10 and the fiber sensing element 12 of the left and right sides be linked in sequence, wherein the port of the low splitting ratio of fiber coupler 9 is as input end, the port of the low splitting ratio of fiber coupler 11 is as output terminal.
Described optical fiber splitter 2 and optical fiber combiner 6 are 1 * n wavelength division multiplexer.
Described optical fiber splitter 2 is and some adjustable optical attenuators 3
1～nSeveral 1 * 2 fiber couplers 2 that quantity equates
1～nAnd index-matching fluid 2
N+1Be in series; The optical fiber combiner 6 that adapts with it is n * 1 optical-fiber bundling devices.
The length L of described fibre delay line
i=5 (τ
1+ τ
2+ ... + τ
i) c/n
Eff, wherein: i is 0～n-1, τ
iBe fiber optic loop 5
iThe ring-down time of interior pulse laser, c is the light velocity, n
EffEffective refractive index for optical fiber.
Described wavelength division multiplexer is: grating type wavelength division multiplexer, dielectric film filtering type wavelength division multiplexer or integrated type optical waveguide wavelength division multiplexer.
Described fiber sensing element 12 is: Fiber Bragg Grating FBG, long period fiber grating, Fabry-Perot optical fiber cavity, optical fiber micro-bending device or single-mode fiber.
Described fiber coupler 9 and 11 is 1 * 2 fiber coupler, and its splitting ratio was greater than 90%: 10%.
The length span of described single-mode fiber 10 exists
With
Between, t wherein
pPulse width for pulsed laser.
Beneficial effect
The invention has the beneficial effects as follows: will be converted into measurement to the measurement of intensity or wavelength the fiber optic loop ring-down time based on the Fibre Optical Sensor of optical fiber cavity attenuation and vibration technique.When the effect of external physical quantity changes the insertion loss of fiber optic loop inner fiber sensing element,, whenever detour and once will the variable quantity that insert loss be amplified once, so its measuring accuracy is than higher because pulse laser constantly detours in ring; The ring-down time of each pulse laser in fiber optic loop be generally in the microsecond magnitude, swings signal and carry out multiple averaging even will decline to each in follow-up processing procedure, and as long as the time of realizing one-shot measurement is also a millisecond magnitude, thereby measuring speed is very fast; The laser pulse sequence of surveying is the relative value of intensity, thus light source the fluctuating of intrinsic laser pulse intensity to not influence of measurement result; Demodulation method is simple, is easy to realize miniaturization, through engineering approaches and practicability; Realize distributed sensing easily, the fiber sensing element in each fiber optic loop can be different, can measure simultaneously a plurality of physical quantitys, and be easy to expand the number of sensing head.
Description of drawings
Fig. 1: be the structural representation of distributed fiberoptic sensor first embodiment that the present invention is based on the optical fiber cavity attenuation and vibration technique;
Fig. 2: be the structural representation of distributed fiberoptic sensor second embodiment that the present invention is based on the optical fiber cavity attenuation and vibration technique;
Fig. 3: for experiment measuring of the present invention from fiber optic loop 5
1 Signal 1 is swung in declining of output;
Fig. 4: for the present invention from fiber optic loop 5
1, 5
2..., 5
nOutput decline swing signal 1,2 ..., n synoptic diagram;
Fig. 5: for the present invention swings the result that the peak value of signal 1 extracted and carried out the single index match to shown in Figure 3 declining;
Fig. 6: a typical reflectance spectrum of testing the FBG of the fiber sensing element that is used as for the present invention;
The 1-pulsed laser light source; The 2-optical fiber splitter; 2
1～n-fiber coupler; 3
1～n-adjustable optical attenuator; 4
1～n-1-fibre delay line; 5
1～n-fiber optic loop; 6-optical fiber combiner; The 7-high-speed photodetector; Conversion of 8-high-speed a/d and signal processing module; The 9-fiber coupler; The 10-single-mode fiber; The 11-fiber coupler; The 12-fiber sensing element.
Embodiment
Now in conjunction with the accompanying drawings the present invention is further described:
Wherein said pulsed laser light source 1 is used for producing pulse laser, the time interval between two laser pulses should greater than pulse laser ring-down time in all fiber optic loop and 5 times, line width can cover fiber optic loop 5
1, 5
2, 5
3, 5
4The operation wavelength of interior used fiber sensing element 12, pulse width should be less than each pulse laser respectively in fiber optic loop 5
1, 5
2, 5
3, 5
4In the detour maximal value of all used time.
Described optical fiber splitter 2 is one 1 * 4 wavelength division multiplexers, and its function is the pulse laser that a pulse laser is divided into four different wave lengths, and the intensity of these pulse lasers can be slightly different.
Described adjustable optical attenuator 3
1, 3
2, 3
3, 3
4Function be on the basis that 2 pairs of each pulse laser intensity of optical fiber splitter are roughly regulated, to finely tune again, make the intensity that is coupled into the pulse laser in each fiber optic loop equal substantially so that and the detectivity of follow-up high-speed photodetector 7 be complementary.
Described fibre delay line 4
1, 4
2, 4
3Be made of single-mode fiber, its function is identical, but the length difference all is that paired pulses laser plays delayed-action, but the time that postpones there are differences, the time delay of each fibre delay line paired pulses laser be before it interior pulse laser ring-down time of each fiber optic loop and 5 times.Again because the length L of optical fiber
0By formula L
0=tc/n
EffDecision, wherein t is that pulse laser is L in length
0Optical fiber in travel-time, so first fibre delay line 4
1Length L
1=5 τ
1C/n
Eff, τ wherein
1Be fiber optic loop 5
1The ring-down time of interior pulse laser.Fibre delay line 4
2Length L
2=5 (τ
1+ τ
2) c/n
Eff, τ wherein
2Be fiber optic loop 5
2The ring-down time of interior pulse laser.In like manner can obtain fibre delay line 4
3Length L
3=5 (τ
1+ τ
2+ τ
2) c/n
Eff, τ wherein
3Be fiber optic loop 5
3The ring-down time of interior pulse laser.
The length of described single-mode fiber 10 should make each pulse laser in corresponding fiber optic loop 5
1, 5
2, 5
3, 5
4In detour time in a week all greater than the pulse width of pulse laser.
Described fiber sensing element 12 is FBG, LPFG, F-P optical fiber cavity, optical fiber micro-bending device or single-mode fiber.
Described optical fiber combiner 6 is one 4 * 1 wavelength division multiplexer, and its function is with from each fiber optic loop 5
1, 5
2, 5
3, 5
4Declining of output swung signal and is combined into one the tunnel, and transfers to high-speed photodetector 7, respectively declined by 7 pairs of high-speed photodetectors and swings signal and carry out opto-electronic conversion.
Conversion of described high-speed a/d and signal processing module 8 are that the peak value that swings signal to respectively declining extracts and peak value is carried out the single index match, draw the ring-down time of each pulse laser in fiber optic loop accordingly, and do further data processing.
The groundwork process that the present invention is based on distributed fiberoptic sensor first embodiment of optical fiber cavity attenuation and vibration technique is: at first send a pulse laser by pulsed laser light source 1, this pulse laser is divided into the pulse laser of four bundle different wave lengths to the optical fiber splitter 2 through Optical Fiber Transmission, and wherein first pulse laser is through adjustable optical attenuator 3
11% port by fiber coupler 9 is coupled into fiber optic loop 5
1, second and third, four pulse lasers then pass through corresponding adjustable optical attenuator 3 respectively successively
2, 3
3, 3
4And fibre delay line 4
1, 4
2, 4
31% port by fiber coupler 9 is coupled into corresponding fiber optic loop 5 again
2, 5
3, 5
4, wherein because fibre delay line 4
1, 4
2, 4
3Delayed-action, make the pulse laser postponed after the ring-down time of 5 times of pulse lasers in a last fiber optic loop, to enter corresponding fiber optic loop again.Wherein by fiber coupler 9 coupled into optical fibres rings 5
1Interior pulse laser can be in fiber optic loop 5
1In constantly detour because fiber optic loop 5
1In have various losses, these losses comprise: the coupling loss of fiber coupler 9,11 and insert the loss of tail optical fiber of loss, single-mode fiber 10 and fiber coupler 9,11 and the insertion loss and the insertion loss of four welding points of welding mutually therebetween of fiber sensing element 12.So fiber optic loop 5
1The intensity of interior pulse laser will constantly decay, from 1% the port output of fiber coupler 11 be the laser pulse sequence that peak value is the single index decay, being called declines swings signal 1, Fig. 3 has provided the fiber optic loop 5 of experiment measuring
1Signal is swung in declining of output.5 times to first bundle of pulsed laser in fiber optic loop 5
1After the interior ring-down time, delayed line 4
1Second bundle of pulsed laser that generation time postpones is by 1% port coupled into optical fibres ring 5 of fiber coupler 9
2In, from 1% the port output of fiber coupler 11 also be the laser pulse sequence that peak value is the single index decay, being called declines swings signal 2, based on identical reason, third and fourth bundle of pulsed laser is through corresponding lag line 4
2, 4
3After respectively by fiber optic loop 5
3, 5
4In 1% port of fiber coupler 9 be coupled into fiber optic loop 5
3, 5
4, from fiber optic loop 5
3, 5
4Output declines and swings signal 3,4 respectively, please refer to synoptic diagram 4, and pairing the declining of each fiber optic loop swung signal because fibre delay line 4
1, 4
2, 4
3The effect certain hour that staggers each other, and all be coupled into optical fiber combiner 6.Respectively decline and swing signal and close bundle back through optical fiber combiner 6 and survey, and change light signal into electric signal, change and 8 pairs of signal processing modules respectively decline and swing signal and do further data processing through high-speed a/d then by high-speed photodetector 7 by high-speed photodetector 7.
As shown in Figure 5, decline at each that detects in the present embodiment and swing signal, extract its peak value, adopt single index attenuation function y=Aexp (t/ τ)+y
0Peak value is carried out match obtain the ring-down time τ that this declines and swings signal
0For each fiber optic loop, when fiber sensing element 12 does not perceive time spent of doing of external physical quantity, the ring-down time of pulse laser in fiber optic loop is
T wherein
R=n
EffL/c is that pulse laser detours the used time in a week n in fiber optic loop
EffBe the effective refractive index of optical fiber, L is the length of fiber optic loop, and c is the light velocity in the vacuum, 2 α
cBe the coupling loss and insertion loss, α of two fiber couplers 9 and 11
tLoss, 4 α for the tail optical fiber of single-mode fiber 10 and fiber coupler 9 and 11
fBe the insertion loss of four welding points, α
sInsertion loss for fiber sensing element 12.When fiber sensing element 12 perceives time spent of doing of external physical quantity, the insertion loss meeting of fiber sensing element 12 changes, and the total losses in the fiber optic loop are changed, and the ring-down time of pulse laser this moment in fiber optic loop becomes
Δ α wherein
sPerceive the variable quantity that inserts loss after the effect of external physical quantity for fiber sensing element 12.The variable quantity that can be got fiber sensing element 12 insertion losses by above two formulas is
Because fiber sensing element 12 inserts the variable quantity of loss and the action of external physical quantity is one to one, thereby by Δ α
sCan obtain the action of external physical quantity, reach the purpose of sensing.Based on identical reason, but all effects of its position external physical quantity of perception of the fiber sensing element 12 in each fiber optic loop.
The distributed fiberoptic sensor that the present invention is based on the optical fiber cavity attenuation and vibration technique is at each fiber optic loop 5
1, 5
2, 5
3, 5
4Interior fiber sensing element 12 just can be from each fiber optic loop 5 by one-shot measurement
1, 5
2, 5
3, 5
4The action that demodulates the external physical quantity of 12 perception of fiber sensing element in this fiber optic loop in the signal is swung in declining of output, and owing to separate between each fiber optic loop, has therefore realized the function of distributing optical fiber sensing.
Second embodiment shown in Figure 2 and first embodiment shown in Figure 1 are compared and can find, be to carry out beam split in first embodiment, and be in second embodiment by four 1 * 2 fiber couplers 2 by a wavelength division multiplexer paired pulses Wavelength of Laser
1, 2
2, 2
3, 2
4The intensity of paired pulses laser is carried out beam split one by one; Be to close bundle to swinging signal in first embodiment, and be to close bundle to swinging signal in second embodiment from declining of each fiber optic loop output by one 1 * 4 optical-fiber bundling devices from declining of each fiber optic loop output by a wavelength division multiplexer.Wherein fiber coupler 2
1One end directly is coupled with LASER Light Source 1 and is connected, and an end is via adjustable optical attenuator 3
1With fiber optic loop 5
1In 1% the welding of port phase, the other end and fiber coupler 2 of fiber coupler 9
2Directly phase welding, all the other fiber couplers 2
2, 2
3, 2
4Respectively successively by corresponding adjustable optical attenuator 3
2, 3
3, 3
4With fibre delay line 4
1, 4
2, 4
3With fiber optic loop 5 separately
2, 5
3, 5
4In 1% port of fiber coupler 9 be connected and fiber coupler 2
2, 2
3, 2
4Between welding in turn, fiber coupler 2
4An end and index-matching fluid 2
5Link to each other.
The groundwork process that the present invention is based on distributed fiberoptic sensor second embodiment of optical fiber cavity attenuation and vibration technique is: the pulse laser of LASER Light Source 1 outgoing is through first fiber coupler 2
1Be divided into two bundles, wherein a bundle of pulsed laser is through adjustable optical attenuator 3
1By fiber optic loop 5
1In 1% port of fiber coupler 9 be coupled into fiber optic loop 5
1In, enter fiber optic loop 5
1Pulse laser in fiber optic loop 5
1In constantly detour because fiber optic loop 5
1In have various losses, fiber optic loop 5
1The intensity of interior pulse laser will constantly decay, from fiber optic loop 5
1In fiber coupler 11 the output of 1% port be the laser pulse sequence that peak value is the single index decay, being called declines swings signal 1, another bundle of pulsed laser is through second fiber coupler 2
2Be further divided into two bundles, wherein a bundle of pulsed laser is through adjustable optical attenuator 3
2Again through fibre delay line 4
1Postpone the back by fiber optic loop 5
2In 1% port coupled into optical fibres ring 5 of fiber coupler 9
2In, and through repeatedly detour and attenuation loss after, from fiber optic loop 5
2In fiber coupler 11 the output of 1% port also be the laser pulse sequence that peak value is the single index decay, being called declines swings signal 2, another bundle of pulsed laser is through the 3rd fiber coupler 2
3Be further divided into two bundles.Based on identical reason, respectively successively through fiber coupler 2
3, 2
4With adjustable optical attenuator 3
3, 3
4And fibre delay line 4
2, 4
3Pulse laser is coupled into corresponding fiber optic loop 5
3, 5
4In, from fiber optic loop 5
3, 5
4In fiber coupler 11 the output of 1% port swing signal 3,4 for declining accordingly.Because fibre delay line 4
1, 4
2, 4
3Effect, from fiber optic loop 5
1, 5
2, 5
3, 5
4 Signal 1,2,3,4 certain hour that staggers each other, fibre delay line 4 are swung in declining of output
1, 4
2, 4
3Length depend on that principle is similar to the principle described in first embodiment.
From fiber optic loop 5
1, 5
2, 5
3, 5
4Declining of output swung signal 1,2,3,4 and all closed bundle through optical-fiber bundling device 6, survey by high-speed photodetector 7 again, and change light signal into electric signal by high-speed photodetector 7, respectively decline through high-speed a/d conversion and 8 pairs of signal processing modules then and swing signal and do further data processing.Similar to the disposal route in first embodiment, by measuring twice ring-down time of external physical quantity effect front and back pulse laser in each fiber optic loop, from twice ring-down time, demodulate the action of the external physical quantity of 12 perception of fiber sensing element in this fiber optic loop.
Identical in the present embodiment in addition with used fiber sensing element 12 in first embodiment, also comprise: FBG, LPFG, F-P optical fiber cavity, optical fiber micro-bending device, single-mode fiber.
The distributed fiberoptic sensor that the present invention is based on the optical fiber cavity attenuation and vibration technique is not limited to above-mentioned embodiment, can be further improved, as: the fiber optic loop number in the distributed fiberoptic sensor of the present invention is not limited to four, according to actual needs and cost consideration, the tunable integers order.Fiber sensing element 12 is not limited to FBG, LPFG, F-P optical fiber cavity, optical fiber micro-bending device, single-mode fiber, as long as can cause the total losses in the fiber optic loop certain variation takes place, and can select suitable embodiment and fiber sensing element 12 according to actual needs.
The distributed fiberoptic sensor that the present invention is based on the optical fiber cavity attenuation and vibration technique in sum designs by a plurality of relatively independent fiber optic loop, not only can realize distribution measuring to same physical quantity, also can realize simultaneously measurement to different physical quantities, the measuring accuracy height, speed is fast, and is applied widely, be easy to expand sensing head, and simple to operate, can realize practicability and through engineering approaches, have great actual application value.
Claims (8)
1. the distributed fiberoptic sensor based on the optical fiber cavity attenuation and vibration technique is characterized in that: comprise pulsed laser light source (1), optical fiber splitter (2), some adjustable optical attenuators (3
1～n), some fibre delay lines (4
1～n-1), some fiber optic loop (5
1～n), optical fiber combiner (6), high-speed photodetector (7), high speed analog-digital conversion A/D conversion and signal processing module (8); LASER Light Source (1) links to each other with optical fiber splitter (2), and optical fiber splitter (2) connects some adjustable optical attenuators (3
1～n); First fiber optic loop (5
1) direct and adjustable optical attenuator (3
1) connect other fiber optic loop (5
2～n) all pass through corresponding fibre delay line (4
1～n-1) back and corresponding adjustable optical attenuator (3
2～n) connect; Some fiber optic loop (5
1～n) output terminal connect optical fiber combiner (6), optical fiber combiner (6) interconnects successively with high-speed photodetector (7), high-speed a/d conversion and signal processing module again; Described fiber optic loop (5
1～n) be that the fiber coupler (9) at two ends up and down and the single-mode fiber (10) and the fiber sensing element (12) of (11) and the left and right sides are linked in sequence, wherein the port of the low splitting ratio of fiber coupler (9) is as input end, and the port of the low splitting ratio of fiber coupler (11) is as output terminal.
2. the distributed fiberoptic sensor based on the optical fiber cavity attenuation and vibration technique according to claim 1 is characterized in that: described optical fiber splitter (2) and optical fiber combiner (6) are 1 * n wavelength division multiplexer.
3. the distributed fiberoptic sensor based on the optical fiber cavity attenuation and vibration technique according to claim 1 is characterized in that: described optical fiber splitter (2) is and some adjustable optical attenuators (3
1～n) several 1 * 2 fiber couplers (2 of equating of quantity
1～n) and index-matching fluid (2
N+1) be in series; The optical fiber combiner (6) that adapts with it is n * 1 optical-fiber bundling device.
4. the distributed fiberoptic sensor based on the optical fiber cavity attenuation and vibration technique according to claim 1 is characterized in that: described fibre delay line (4
1～n-1) length L
i=5 (τ
1+ τ
2+ ... + τ
i) c/n
Eff, wherein: i is 0～n-1, τ
iBe fiber optic loop (5
i) in the ring-down time of pulse laser, c is the light velocity, n
EffEffective refractive index for optical fiber.
5. the distributed fiberoptic sensor based on the optical fiber cavity attenuation and vibration technique according to claim 2 is characterized in that:
Described wavelength division multiplexer is: grating type wavelength division multiplexer, dielectric film filtering type wavelength division multiplexer or integrated type optical waveguide wavelength division multiplexer.
6. the distributed fiberoptic sensor based on the optical fiber cavity attenuation and vibration technique according to claim 1 is characterized in that:
Described fiber sensing element (12) is: Fiber Bragg Grating FBG, long period fiber grating, Fabry-Perot optical fiber cavity, optical fiber micro-bending device or single-mode fiber.
7. the distributed fiberoptic sensor based on the optical fiber cavity attenuation and vibration technique according to claim 1 is characterized in that:
Described fiber coupler (9) and (11) are 1 * 2 fiber coupler, and its splitting ratio was greater than 90%: 10%.
8. the distributed fiberoptic sensor based on the optical fiber cavity attenuation and vibration technique according to claim 1 is characterized in that:
The length span of described single-mode fiber (10) exists
With
Between, t wherein
pPulse width for pulsed laser.
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Cited By (17)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102116738A (en) * | 2010-11-30 | 2011-07-06 | 华中科技大学 | Methane gas sensing device based on fiber-loop ring-down cavity |
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| CN102116738B (en) * | 2010-11-30 | 2012-07-04 | 华中科技大学 | Methane gas sensing device based on fiber-loop ring-down cavity |
| CN102116738A (en) * | 2010-11-30 | 2011-07-06 | 华中科技大学 | Methane gas sensing device based on fiber-loop ring-down cavity |
| CN102494703A (en) * | 2011-11-29 | 2012-06-13 | 武汉理工大学 | Fiber ring-down loop time division multiplexing sensing system |
| CN102607608A (en) * | 2012-03-08 | 2012-07-25 | 天津奇谱光电技术有限公司 | Extensible electro-optical sensing system |
| CN102853920A (en) * | 2012-09-29 | 2013-01-02 | 华中科技大学 | High-sensitivity Mach-Zahnder interference system |
| CN102853920B (en) * | 2012-09-29 | 2014-11-26 | 华中科技大学 | High-sensitivity Mach-Zahnder interference system |
| CN103389120A (en) * | 2013-07-29 | 2013-11-13 | 黑龙江大学 | Optical fiber ringdown cavity sensor array device based on wavelength division multiplexing |
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| CN106123933A (en) * | 2016-07-18 | 2016-11-16 | 太原理工大学 | A kind of chaos fiber optic loop declines and swings sensing device and method |
| CN107843273A (en) * | 2017-10-27 | 2018-03-27 | 周燕红 | A kind of fiber optic loop sensor-based system and implementation method |
| CN107941253A (en) * | 2017-10-27 | 2018-04-20 | 周燕红 | A kind of fiber optic loop sensor-based system and implementation method |
| CN107941250A (en) * | 2017-11-21 | 2018-04-20 | 太原理工大学 | A kind of high-resolution chaos fiber optic loop with loss balancing structure, which declines, swings sensing device and method |
| CN107941250B (en) * | 2017-11-21 | 2019-09-17 | 太原理工大学 | A kind of high-resolution chaos fiber optic loop with loss balancing structure, which declines, swings sensing device and method |
| CN108225540A (en) * | 2017-12-29 | 2018-06-29 | 北京航天控制仪器研究所 | A kind of heterodyne interference type fiber-optic hydrophone system of Larger Dynamic range |
| CN108225540B (en) * | 2017-12-29 | 2020-05-12 | 北京航天控制仪器研究所 | Heterodyne interference type optical fiber hydrophone system with large dynamic range |
| CN108827913A (en) * | 2018-07-12 | 2018-11-16 | 河南师范大学 | A kind of multiple spot humidity sensor network based on fiber optic loop cavity-type BPM |
| CN109150311A (en) * | 2018-07-12 | 2019-01-04 | 河南师范大学 | A kind of multi-parameter sensing network based on fiber optic loop cavity attenuation and vibration technique |
| CN109141487A (en) * | 2018-07-25 | 2019-01-04 | 国网河北省电力有限公司电力科学研究院 | A kind of distributed fiberoptic sensor |
| CN109520533A (en) * | 2019-01-23 | 2019-03-26 | 国网江西省电力有限公司信息通信分公司 | Fiber grating demodulation device and method based on fiber optic loop microwave photon filter |
| CN110873589A (en) * | 2019-12-06 | 2020-03-10 | 河南师范大学 | Fiber ring cavity ring-down temperature and humidity measurement method based on TDM technology |
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