CN100535636C - Multi-point optical fiber mash gas sensing system based on optical fiber caching machine - Google Patents
Multi-point optical fiber mash gas sensing system based on optical fiber caching machine Download PDFInfo
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- CN100535636C CN100535636C CNB2007101760331A CN200710176033A CN100535636C CN 100535636 C CN100535636 C CN 100535636C CN B2007101760331 A CNB2007101760331 A CN B2007101760331A CN 200710176033 A CN200710176033 A CN 200710176033A CN 100535636 C CN100535636 C CN 100535636C
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Abstract
The invention relates to a multipoint gas sensing system based on an optical fiber buffer, which comprises an address encoder, a double-wavelength light source, a multipoint optical fiber sensing network and a demodulator. The address encoder generates an address code and a read-write control signal of different monitoring points; each detecting unit of the multipoint optical fiber sensing network adopts a buffer structure introduced with a gas absorbing chamber in an optical fiber loop; a double-loop coupling all-optical buffer and a polarization type all-optical buffer can be adopted; under the control of a write signal, the optical signal of the address code is written into the optical fiber loop of the detecting unit and circularly absorbed by the gas many times; the absorbed optical signal is read out and sent to the demodulator for photoelectric conversion, comparison with the reference light, address decoding and data processing in order to gain the gas concentration in different points and realize the multipoint gas monitoring. The system gains the good effects through improving the structure of the absorbing chamber, adding an optical amplifier, a polarization control and a device with the wavelength of 1665nm, and is used in the monitoring of the gas which has the wavelength of 1665 nm and is near provided with an absorption peak.
Description
Technical field
The present invention relates to a kind of multiple spot methane gas sensor-based system, belong to optical fiber sensing system to measure methane gas concentration technical field based on optical fiber buffer memory.
Background technology
Energy scarcity has become the key factor of the present national sustained economic development of restriction China.In primary energy (coal, nuclear energy, oil, rock gas, wind-force, morning and evening tides, sun power), coal is the topmost primary energy of China, has critical role.But the safety case in current colliery is but very troubling.In various mine disasters, gas explosion ranks first place, so the gas monitor technology is the important technology of mine safety always.Through long term studies and development, developed the gas detection equipment of multiple series: as utilize the height change of flame to detect gas calibrating lamp; Gas detector based on interference of light principle; , the gas detector tube that change color (depth or displacement) is determined gas concentration takes place when utilizing detection agent and tested gas to carry out chemical reaction; Utilize the difference of tested gas and air thermal conductivity to realize the heat-conducted gas detector that detects; And the air-sensitive formula gas detector that conductivity changes with concentration when utilizing some gas of gas sensitive surface adsorption etc., but obtain to use because there are a lot of shortcomings in they.
Widespread use at present be the methane detector of electrochemical heat Catalysis Principles, utilize catalytic materials, make low-concentration methane sustained combustion at a lower temperature (oxidation), the methane of variable concentrations is the liberated heat difference when catalytic combustion, thereby therefore the generation temperature variation can measure methane concentration.The advantage of this detector is that output signal is big, good linearity, and signal Processing and demonstration are all more convenient, the designs simplification of circuit and instrument; Be subjected to environmental influence very little during measurement, can save various absorbing agents; Other inflammable gas (butane, pentane etc.) beyond the methane also can be reacted to some extent; Realize automatic continuous monitoring easily.Its shortcoming is anti-(sulfuretted hydrogen, the organosilicon steam) poor-performing of poisoning; Need frequent the correction (week); Measurement range when concentration is higher, not only can occur activating phenomenon generally below 5%, and 10% when above, " ambiguity " (identical reading appears in variable concentrations) also occur.
Domestic had several gas safety monitoring systems, such as the KJ1 of Changzhou robotization research institute, and the KJ2 system, the JK4 system of Great Wall scientific ﹠ technical corporation, and A1 system, KJ2000 systems etc. have brought into play vital role aspect Safety of Coal Mine Production.Yet these systems utilize the advanced computer technology and the communication technology that monitoring system is transformed, and work hard with gathering in transmission of Information, do not have substantial improvement for foremost firedamp sensor.For many years, the consistent firedamp sensor of continuing to use based on electrochemical principle of gas monitoring system, it must adopt remote power-feeding, itself just has potential safety hazard, also has intoxicating phenomenon, and the life-span is short.And its reaction velocity is slow, when occurring can not in time reflecting when gas is outstanding.People are seeking substitute and new sensing principle always for many years.Before 10 years, people have just proposed to utilize the optical fiber fabrication firedamp sensor greatly.But, make slow progress over 10 years, there is not an optical fiber gas sensor to reach the practicability level so far in the colliery underground work.
The ultimate principle of optical fiber gas sensing is based on the Beer law that gas absorbs for special spectral line in the spectrum, i.e. I=I
0Exp (α CL), wherein I
0With I be light through the light intensity before and after the gas, α is an absorption coefficient, C is a gas concentration, L is an absorption length.By following formula as can be known, higher detection sensitivity if desired must increase absorption coefficient or absorption length.If utilize optical fiber, absorbing wavelength is fallen within the transparent wavelength range of optical fiber.
Gas has 4 for the absorbing wavelength of light: 3.43 μ m, and 6.522 μ m, 3.312 μ m and 7.658 μ m, they all can not see through in silica fibre, can only measure their harmonic wave for this reason.Past is all used the wavelength of 1.31 μ m for the research of optical fiber gas sensor, and that occur on this wavelength is ν
2+ 3 ν
3Combination harmonic, absorption coefficient is low-down.When air chamber length reaches 0.5m, even reaching blast, the concentration of air chamber went up critical 25% o'clock, only be 0.03dB to the absorption loss of 1.3312 mum wavelengths.This loss magnitude has been in flashing decides below the scope, and it is very difficult requiring to measure very accurate.
In order to obtain higher detection sensitivity, must be than long absorption length, the air chamber length of people's employing at present is about 50cm.This means and light will be penetrated that through converging in the optical fiber behind the absorption chamber of 50cm, that yes is very difficult for this again from optical fiber.Though it is feasible on principle, infeasible technically.And the absorption length of 50cm is for a sensing head, and volume is too huge, and the influence that is subjected to environment is very big.In a mine that has been full of dust and steam, can not obtain practical application.And, the concentration of sensor air chamber also should change thereupon when the gas density of environment changes, but excessive air chamber will cause the interior concentration of air chamber and the gas concentration of environment to differ greatly, and perhaps lags behind in time, has reduced the sensitivity and the response speed of sensor.Therefore, though optical fiber gas sensor has proposed for many years, many research institutions have reported that they in breadboard result of study, do not have practicability so far, are difficult to use in the small space of abominable coal-face.
The approach that improves detection sensitivity and response speed has two: (1) dwindles the volume of absorption chamber; (2) absorption of raising unit length.For reduced volume, but will guarantee enough absorption lengths, unique method is to improve to absorb number of times.In other words, can utilize same light pulse repeatedly to see through the method for air chamber, the increase absorption length of equivalence.
Purpose of the present invention is exactly a kind of new construction that proposes at the deficiencies in the prior art, promptly utilizes light pulse repeatedly circulation absorption in the optical fiber buffer memory that contains gas absorption air chamber, and the length of dwindling air chamber greatly increases equivalent absorption length; And utilize coding modulation technique, and each buffer is carried out " writing " and " reading " control, realize carrying out multiplexing to a plurality of check points with a light source and demodulating system.
In order to improve absorptivity, the present invention with absorbing wavelength from ν
2+ 3 ν
3Combination harmonic transfer to ν
32 subharmonic (1.665 μ m), its absorption coefficient increases an order of magnitude, can make air chamber length shorten to 5cm from 50cm.Thereby improve the dirigibility that detects greatly, be convenient to practicability.
In order further to improve accuracy of detection, the present invention adopts the dual wavelength mode, and one is absorbing wavelength, and another is a reference wavelength.The two is through same light path, except absorption loss different and, other optical path loss is all identical, and is right by differential ratio, can obtain very high detection sensitivity.
Summary of the invention
The objective of the invention is to realize by the following technical solutions a kind of multiple spot optical fiber gas sensing system based on optical fiber buffer memory, it is by an address scrambler, a double-wavelength light source, a multiple spot optical fiber sensing network, and a detuner forms, and is used for high precision, high sensitivity, monitors the methane gas concentration of multiple spot under the coal mine in real time.
Address scrambler produces the serial address sign indicating number be used for different monitoring points, and double-wavelength light source is modulated, and produces simultaneously to be used for different monitoring points " is write " and the control signal of " reading ".
The light that double-wavelength light source sends is sent into the multiple spot optical fiber sensing network after modulating through address scrambler.
The multiple spot optical fiber sensing network comprises a plurality of detecting units, and each unit adopts the structure of optical-fiber type complete optical buffer register, and has increased a gas absorption chamber in the optical fiber loop of optical buffer.Optical buffer comprises annexes such as the amplifier, Polarization Controller, wave division multiplex coupler of the optical fiber loop that is used for the buffer memory light signal and loop, a nonlinear element that is used for " writing " and " reading ", and a gas absorption chamber.Each detecting unit will be loaded with the light signal of this check point address information under the control of address scrambler, in the optical fiber loop of " writing " this unit, and repeatedly circulation; Absorption chamber is all passed through in each circulation one time, thereby is repeatedly absorbed by gas.Then, under the control of address scrambler, will " be read " by the light signal that gas repeatedly absorbs, and send into detuner.
After detuner carries out light-to-current inversion to the light signal of receiving that is loaded with different addresses and gas absorption information, light signal with reference wavelength compares again, carry out address decoder and data processing, obtain the different gas concentration parameters that absorb air chamber, thereby realize real-time monitoring the multiple spot gas density.Different sign indicating number types are easy to they are distinguished when they arrive same detuner corresponding to different monitoring points.
Technical scheme of the present invention is equally applicable to have the sensing and the monitoring of other gases of optical absorption peak near the 1665nm wavelength.
The invention has the beneficial effects as follows:
(1) based on the multiple spot optical fiber gas gas sensing system of optical fiber buffer memory, fully in conjunction with the new and high technology of the modern optical communications field and the new and high technology of sensory field, comprise the light coding techniques, the full optical buffer technology, optical fiber transmission technique, modulation-demodulation technique, multiplexing technique, be used for coal mine gas distribution of gas formula and detect, the methane gas concentration of a plurality of positions is carried out high sensitivity, high precision, monitoring in real time, for ensureing that mine safety provides important evidence.
(2) technique effect based on the multiple spot optical fiber gas sensing system of optical fiber buffer memory can also be improved by following means.
The first, the The Nomenclature Composition and Structure of Complexes of improvement gas absorption chamber improves the absorption chamber performance, reduces the optic path loss, can improve the absorption efficiency of gas to light, reduces noise, thereby improves the performance of sensor-based system.
The second, the structure of improvement optic fiber ring-shaped cavity is included in and installs image intensifer in the fiber optic loop additional, with the compensation optical path loss.Because the part fibre circuit at scene under coal mine, the abominable situation complexity of environment may cause labile factors such as added losses and self-excitation noise, and is bigger to optical fiber transmission property and ring cavity performance impact.Therefore, improve the structure of optical fiber loop and the performance that control mode can improve sensor-based system.
The 3rd, improve or choose more the sign indicating number type and modulation, multiplex mode optimized, can improve the control signal and the time synchronized performance of photoswitch in the full optical buffer, the dirigibility and the accuracy of raising distributing optical fiber sensing technology, thereby the performance of raising sensor-based system.
The 4th, when choosing double-wavelength light source, its two operation wavelengths should be distinguished absorbing wavelength and reference wavelength, and it is approaching to try one's best again, and guaranteeing playing reference role conscientiously, and their wavelength and luminous power all should be stablized.Therefore, choose the double-wavelength light source of the power stability of high-quality, can improve the performance of sensor.
The 5th, take the quick polarization stabilization technique, the interference effect when can improve a plurality of sensing heads (absorption chamber) associated working, thereby the performance of raising sensor-based system.
The 6th, the function of sensor system signals processing section is improved, and also helps improving the technique effect of sensor.
The 7th, the function of sensing system other parts is improved, select relative photo devices such as the dual wavelength continuous wave laser supporting, coupling mechanism, circulator, wave filter, isolator for use and improve performance, all help improving the technique effect of sensing system with methane gas second harmonic absorption peak corresponding wavelength (1665nm).
Description of drawings
Fig. 1 is the multiple spot optical fiber gas sensing system structural representation based on optical fiber buffer memory;
Fig. 2 is the structural representation based on the multiple spot optical fiber gas sensing system of double-ring coupled full optical buffer;
Fig. 3 is the structural representation based on the multiple spot optical fiber gas sensing system of polarization-type full optical buffer.
Embodiment
The present invention will be further described below in conjunction with case study on implementation and accompanying drawing.
Embodiment 1: the multiple spot optical fiber gas sensing system that adopts double-ring coupled full optical buffer;
As shown in Figure 1, based on the multiple spot optical fiber gas sensing system of double-ring coupled full optical buffer by an address scrambler 1,2, one multiple spot optical fiber sensing networks of forming by a plurality of double-ring coupled full optical buffers 3 of a double-wavelength light source, and a detuner 4 is formed.Multiple spot optical fiber sensing network 3 as shown in Figure 2, it is made up of a plurality of double-ring coupled full optical buffers, each double-ring coupled full optical buffer, comprise a circulator 5,3 * 3 coupling mechanisms 6 that are arranged in parallel, about two optical fiber loops 7 and 8, absorption chamber 9 and a nonlinear element 10.
After the light signal that is loaded with different addresses and gas absorption information that detuner 4 is received carries out light-to-current inversion earlier, carry out address decoder and data processing then, obtain the gas concentration parameter of different absorption chambers, thereby realize real-time monitoring the multiple spot gas density.
Nonlinear element 10 the effect here is to produce nonlinear phase shift, therefore can this function can be realized at the device of 1665nm wavelength generation nonlinear phase shift, specifically ordinary optic fibre, highly nonlinear optical fiber, photonic crystal fiber, semiconductor optical amplifier and electroabsorption modulator etc. can be used.
Embodiment 2: the multiple spot optical fiber gas sensing system that adopts the polarization-type full optical buffer;
As shown in Figure 1, based on the multiple spot optical fiber gas sensing system of double-ring coupled full optical buffer by an address scrambler 1,2, one multiple spot optical fiber sensing networks of forming by a plurality of polarization-type full optical buffers 3 of a double-wavelength light source, and a detuner 4 is formed.Multiple spot optical fiber sensing network 3 as shown in Figure 3, a polarization-type full optical buffer is used in each monitoring point, and settles a gas absorption chamber 6 in the optical fiber loop of buffer.Therefore each polarization-type full optical buffer all comprises a nonlinear element 5, absorption chamber 6, one section optical fiber loop 7.Here the optical fiber loop 7 that refers to comprises one section optical fiber and the annex that improves loop performance, such as Polarization Controller, amplifier etc.
Nonlinear element 5 the effect here is to produce the nonlinear polarization rotation, therefore can this function can be realized at the device that the 1665nm wavelength produces non-linear rotation, specifically ordinary optic fibre, highly nonlinear optical fiber, photonic crystal fiber, semiconductor optical amplifier and electroabsorption modulator etc. can be used.
Claims (7)
1. multiple spot optical fiber gas sensing system based on optical-fiber type complete optical buffer register, it is characterized in that: this system mainly is by an address scrambler, a double-wavelength light source, a multiple spot optical fiber sensing network, and a detuner is formed; Wherein:
Address scrambler produces the serial address sign indicating number be used for different monitoring points, and double-wavelength light source is modulated, and produces simultaneously to be used for different monitoring points " is write " and the control signal of " reading ";
The light that double-wavelength light source sends is sent into the multiple spot optical fiber sensing network through after the modulation of address scrambler;
The multiple spot optical fiber sensing network comprises a plurality of detecting units, each unit adopts the structure of optical-fiber type complete optical buffer register, and a gas absorption chamber is arranged in the optical fiber loop of buffer, each detecting unit is under the control of address scrambler, the light signal of this check point address information will be loaded with, " write " in the optical fiber loop of this unit, and repeatedly circulation; Absorption chamber is all passed through in each circulation one time, thereby is repeatedly absorbed by gas; Then, under the control of address scrambler, will " be read " by the light signal that gas repeatedly absorbs, and send into detuner;
Detuner carries out light-to-current inversion, address decoder and data processing after receiving the light signal that is loaded with different addresses and gas absorption information, obtains the gas concentration parameter of different absorption chambers, thereby realizes the real-time monitoring to the multiple spot gas density.
2. a kind of multiple spot optical fiber gas sensing system based on optical-fiber type complete optical buffer register according to claim 1 is characterized in that: adopt 1665nm dual wavelength mode, a wavelength is an absorbing wavelength, and a wavelength is a reference wavelength; The two is through same light path, and except the absorption loss difference, other optical path loss is all identical, and is right by differential ratio, can obtain very high detection sensitivity.
3. a kind of multiple spot optical fiber gas sensing system according to claim 1 based on optical-fiber type complete optical buffer register, it is characterized in that: a double-ring coupled full optical buffer is used in each monitoring point of multiple spot optical fiber sensing network, and the control light that utilizes 1550nm is realized the nonlinear phase shift for the flashlight of 1665nm wavelength, nonlinear element is ordinary optic fibre, highly nonlinear optical fiber or photonic crystal fiber, thereby realizes " read-write " operation.
4. the multiple spot optical fiber gas sensing system based on optical-fiber type complete optical buffer register according to claim 1, it is characterized in that: a polarization-type full optical buffer is used in each monitoring point of multiple spot optical fiber sensing network, and utilizes 1550nm control light to realize rotating for the nonlinear polarization of 1665nm wavelength signals light; Nonlinear element is ordinary optic fibre, highly nonlinear optical fiber or photonic crystal fiber, thereby realizes " read-write " operation.
5. a kind of multiple spot optical fiber gas sensing system according to claim 1 based on optical-fiber type complete optical buffer register, it is characterized in that: the light signal through all gas absorption chamber arrives same detuner, compare with the light signal of reference wavelength, handle through separating the mediation follow-up signal, obtain the absorption loss of the absorption chamber of different monitoring points to light, thereby obtain the methane gas concentration of each site, monitoring point, realize multiple spot methane gas sensing.
6. a kind of multiple spot optical fiber gas sensing system based on optical-fiber type complete optical buffer register according to claim 1 is characterized in that: select corresponding wavelength 1665nm supporting dual wavelength continuous wave laser, coupling mechanism, circulator, wave filter, isolator for use.
7. a kind of multiple spot optical fiber gas sensing system based on optical-fiber type complete optical buffer register according to claim 1, it is characterized in that: this system is used for sensing and the monitoring for the gas that optical absorption peak is arranged near the 1665nm wavelength.
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| CN101793821A (en) * | 2010-03-23 | 2010-08-04 | 北京交通大学 | Sensing system used for monitoring multipoint gas concentration |
| CN102411985B (en) * | 2011-09-13 | 2014-08-20 | 北京交通大学 | Storing device and method of optical fibre double-ring capable of erasing optical information |
| US9030663B2 (en) * | 2011-10-31 | 2015-05-12 | Exelis Inc. | Remote absorption spectroscopy by coded transmission |
| CN109152140A (en) | 2018-09-18 | 2019-01-04 | 台州市椒江萤星电子电器有限公司 | A kind of decoration LED light string structure and its assemble method |
| CN109406450B (en) * | 2018-10-18 | 2021-05-28 | 山东大学 | Multiple absorption type trace gas detection system |
| CN112432664B (en) * | 2020-11-11 | 2022-04-08 | 山东大学 | All-fiber laser detection system for tunnel safety monitoring and working method |
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