CN108226094B - Gas concentration monitoring system, method and device - Google Patents
Gas concentration monitoring system, method and device Download PDFInfo
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- CN108226094B CN108226094B CN201810066012.2A CN201810066012A CN108226094B CN 108226094 B CN108226094 B CN 108226094B CN 201810066012 A CN201810066012 A CN 201810066012A CN 108226094 B CN108226094 B CN 108226094B
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Abstract
The embodiment of the invention provides a gas concentration monitoring system, a method and a device, and relates to the field of optical fiber sensing. The system comprises a laser generating device, a microcontroller, a photoelectric detection device and a gas optical fiber sensing device. The microcontroller is electrically connected with the photoelectric detection device. The gas optical fiber sensing device is used for detecting the gas to be detected. The laser generating device is used for outputting signal light. The signal light is transmitted into the gas optical fiber sensing device, one part of the signal light is absorbed by the gas to be detected in the gas optical fiber sensing device, and the other part of the signal light is output from the gas optical fiber sensing device and transmitted to the photoelectric detection device. The photoelectric detection device is used for converting the received signal light into a first electric signal and sending the first electric signal to the microcontroller. The microcontroller is used for obtaining the concentration of the gas to be detected based on the first electric signal, and detecting the gas to be detected through the gas optical fiber sensing device, so that the high-sensitivity quantitative monitoring of the gas to be detected is realized, and the gas to be detected can stably run for a long time and is safe.
Description
Technical Field
The invention relates to the technical field of optical fiber sensing, in particular to a gas concentration monitoring system, a method and a device.
Background
The traditional gas on-site monitoring technical means comprise catalytic combustion, electrochemistry, infrared absorption spectrum and the like. The sensor devices related to the technical methods are electrified to operate on a monitoring site, and are one of the causes of fire and explosion accidents, and belong to non-intrinsically safe technical means. The current scheme for monitoring the gas has low sensitivity, low safety and the like.
Disclosure of Invention
The present invention is directed to a system, method and apparatus for monitoring gas concentration to improve the above-mentioned problems. In order to achieve the above purpose, the technical scheme adopted by the invention is as follows:
in a first aspect, an embodiment of the present invention provides a gas concentration monitoring system, including a laser generating device, a microcontroller, a photoelectric detection device, and a gas optical fiber sensing device. The microcontroller is electrically connected with the photoelectric detection device. The gas optical fiber sensing device is used for detecting gas to be detected. The laser generating device is used for outputting signal light. The signal light is transmitted into the gas optical fiber sensing device, one part of the signal light is absorbed by the gas to be detected in the gas optical fiber sensing device, and the other part of the signal light is output from the gas optical fiber sensing device and transmitted to the photoelectric detection device. The photoelectric detection device is used for converting the received signal light into a first electric signal and sending the first electric signal to the microcontroller. The microcontroller is used for obtaining the concentration of the gas to be detected based on the first electric signal.
Further, the gas optical fiber sensing device comprises at least two optical fiber sensing modules and at least one delayer. The at least two optical fiber sensing modules comprise a first optical fiber sensing module and a second optical fiber sensing module. The at least one delayer comprises a first delayer. The first optical fiber sensing module is connected with the second optical fiber sensing module through the first delayer. The first optical fiber sensing module is used for detecting the gas to be detected at a first monitoring point. The second optical fiber sensing module is used for detecting the gas to be detected at a second monitoring point. The signal light is transmitted into the first optical fiber sensing module, one part of the signal light is absorbed by the gas to be detected in the first optical fiber sensing module, the first sub-signal light in the first signal light in the other part of the signal light is absorbed by the gas to be detected in the first optical fiber sensing module, the second sub-signal light in the first signal light is output from the first optical fiber sensing module and transmitted to the photoelectric detection device, and the second signal light in the other part of the signal light is transmitted to the second optical fiber sensing module through the first delay device. And one part of the second signal light is absorbed by the gas to be detected in the second optical fiber sensing module, the other part of the third sub-signal light in the second signal light is sequentially absorbed by the gas to be detected in the second optical fiber sensing module and the gas to be detected in the first optical fiber sensing module, and the other part of the fourth sub-signal light in the second signal light is output from the first optical fiber sensing module and transmitted to the photoelectric detection device.
Further, the first optical fiber sensing module includes a first photonic crystal fiber and a first fiber grating. The second optical fiber sensing module comprises a second photonic crystal fiber and a second fiber grating. The first photonic crystal fiber is connected with the second fiber grating through the first fiber grating, the first delay device and the second photonic crystal fiber in sequence. The signal light is transmitted into the first photonic crystal fiber, a part of the signal light is absorbed by the gas to be detected in the first photonic crystal fiber, a part of the first sub-signal light in the first signal light is transmitted to the first fiber grating, the first sub-signal light is reflected back into the first photonic crystal fiber by the first fiber grating and absorbed by the gas to be detected in the first photonic crystal fiber, a second sub-signal light in the first signal light is output from the first photonic crystal fiber and transmitted to the photoelectric detection device, and a part of the second signal light in the signal light is transmitted into the second photonic crystal fiber through the first delay device. And one part of the second signal light is absorbed by the gas to be detected in the second photonic crystal fiber, the other part of the third sub-signal light in the second signal light is transmitted to the second fiber grating, is reflected back into the second photonic crystal fiber and the first photonic crystal fiber by the second fiber grating, is sequentially absorbed by the gas to be detected in the second photonic crystal fiber and the gas to be detected in the first photonic crystal fiber, and the other part of the fourth sub-signal light in the second signal light is output from the first photonic crystal fiber and is transmitted to the photoelectric detection device.
Further, the system further comprises a circulator. The first end of the circulator is connected with the laser generating device, the second end of the circulator is connected with the gas optical fiber sensing device, and the third end of the circulator is connected with the photoelectric detection device. The signal light is transmitted into the gas optical fiber sensing device through the circulator, one part of the signal light is absorbed by the gas to be detected in the gas optical fiber sensing device, and the other part of the signal light is output from the gas optical fiber sensing device and then transmitted to the photoelectric detection device through the circulator.
Further, the laser generating device is also used for outputting reference light. The absolute value of the difference between the light intensity of the signal light and the reference light output by the laser generating device is smaller than a preset value. The photoelectric detection device is also used for receiving the reference light output by the laser generation device, converting the reference light into a second electric signal and sending the second electric signal to the microcontroller. The microcontroller is used for obtaining the concentration of the gas to be detected based on the first electric signal and the second electric signal.
Further, the laser generating device includes a laser and a beam splitter. The output end of the laser is electrically connected with the input end of the beam splitter, and the laser beam output by the laser is transmitted to the beam splitter and split into the signal light and the reference light through the beam splitter.
Further, the laser generating device further comprises an optical switch. The first end of the optical switch is electrically connected with the output end of the laser, the second end of the optical switch is coupled with the input end of the beam splitter, and the third end of the optical switch is electrically connected with the microcontroller. The optical switch obtains a pulse control signal from the microcontroller through the third end and is periodically in an open state or a closed state based on the pulse control signal so as to enable the laser beam output by the laser to be transmitted to the beam splitter.
Further, the system also comprises a display module. The display module is electrically connected with the microcontroller. The display module is used for displaying the concentration of the gas to be detected.
In a second aspect, an embodiment of the present invention provides a method for monitoring a gas concentration, which is applied to the system described above, where the method includes: obtaining energy values of at least one echo signal according to the obtained first electric signals, wherein the energy value of each echo signal corresponds to the absorption amount of the gas to be detected at least one monitoring point in the gas optical fiber sensing device to the signal light; and obtaining the concentration of the gas to be detected of at least one monitoring point in the gas optical fiber sensing device based on the energy value of the at least one echo signal and a preset recurrence rule.
In a third aspect, an embodiment of the present invention provides a gas concentration monitoring device, which is a microcontroller running in the above system, and includes an acquisition unit and a processing unit. The acquisition unit is used for acquiring the energy value of at least one echo signal according to the acquired first electric signal, wherein the energy value of each echo signal corresponds to the absorption quantity of the gas to be detected at least one monitoring point in the gas optical fiber sensing device to the signal light. And the processing unit is used for obtaining the concentration of the gas to be detected of at least one monitoring point in the gas optical fiber sensing device based on the energy value of the at least one echo signal and a preset recurrence rule.
The embodiment of the invention provides a system, a method and a device for monitoring gas concentration, comprising a laser generating device, a microcontroller, a photoelectric detection device and a gas optical fiber sensing device. The microcontroller is electrically connected with the photoelectric detection device. The gas optical fiber sensing device is used for detecting gas to be detected. The laser generating device is used for outputting signal light. The signal light is transmitted into the gas optical fiber sensing device, one part of the signal light is absorbed by the gas to be detected in the gas optical fiber sensing device, and the other part of the signal light is output from the gas optical fiber sensing device and transmitted to the photoelectric detection device. The photoelectric detection device is used for converting the received signal light into a first electric signal and sending the first electric signal to the microcontroller. The microcontroller is used for processing the first electric signal to obtain the concentration of the gas to be detected, so that the gas to be detected is detected through the gas optical fiber sensing device, and high-sensitivity quantitative monitoring of the gas to be detected is realized.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are needed in the embodiments will be briefly described below, it being understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and other related drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a block diagram of a gas concentration monitoring system according to a first embodiment of the present invention;
FIG. 2 is a block diagram of a gas concentration monitoring system according to a first embodiment of the present invention;
FIG. 3 is a schematic diagram of a gas fiber sensor device in a gas concentration monitoring system according to a first embodiment of the present invention;
FIG. 4 is a flow chart of a method for monitoring gas concentration according to a second embodiment of the present invention;
FIG. 5 is a schematic diagram of each echo signal in a gas concentration monitoring method according to a second embodiment of the present invention;
fig. 6 is a block diagram of a gas concentration monitoring apparatus according to a third embodiment of the present invention.
In the figure: 10-system; 11-a laser generating device; a 111-laser; 112-beam splitter; 113-an optical switch; 114-a laser driving circuit; 115-an optical parametric oscillator; 116-a fiber coupler; 12-a microcontroller; 13-a photoelectric detection device; 131-a first photodetector; 132-a second photodetector; 14-a gas fiber optic sensing device; 14 a-detecting optical fiber; 141-a first optical fiber sensing module; 141 a-a first delay; 141 b-a first photonic crystal fiber; 141 c-a first fiber grating; 142-a second fiber optic sensing module; 142 a-a second photonic crystal fiber; 142 b-a second fiber grating; 15-a circulator; 16-a first conductive optical fiber; 17-a second conductive optical fiber; 18-a display module; 19-data acquisition circuitry.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments of the present invention. The components of the embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations.
Thus, the following detailed description of the embodiments of the invention, as presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
It should be noted that: like reference numerals and letters denote like items in the following figures, and thus once an item is defined in one figure, no further definition or explanation thereof is necessary in the following figures.
In the description of the present invention, it should be noted that, the azimuth or positional relationship indicated by the terms "inner", "outer", etc. are based on the azimuth or positional relationship shown in the drawings, or the azimuth or positional relationship in which the inventive product is conventionally put in use, are merely for convenience of describing the present invention and simplifying the description, and are not indicative or implying that the apparatus or element to be referred to must have a specific azimuth, be configured and operated in a specific azimuth, and therefore, should not be construed as limiting the present invention. Furthermore, the terms "first," "second," "third," and the like are used merely to distinguish between descriptions and should not be construed as indicating or implying relative importance.
In the description of the present invention, it should also be noted that, unless explicitly specified and limited otherwise, the terms "disposed," "electrically connected," and "electrically connected" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; can be mechanically and electrically connected or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The specific meaning of the above terms in the present invention will be understood in specific cases by those of ordinary skill in the art.
Furthermore, the terms "output," "passing," "transmitting," and the like are to be understood as describing an optical, electrical change or optical, electrical process. For example, "output" merely means that an optical or electrical signal is optically or electrically changed after passing through the apparatus, instrument or device, such that the optical or electrical signal is processed to obtain a signal required for implementing the technical solution or solving the technical problem.
In the drawings of the specific embodiments of the present invention, in order to better and more clearly describe the working principles of each device, instrument and apparatus in the gas concentration monitoring system and represent the passing logic of optical signals and electrical signals in the system, only the relative positional relationship among each device, instrument and apparatus is obviously distinguished, and the limitations on the optical path, the circuit direction and the size, the dimension and the shape of the device instrument cannot be formed.
The optical fiber is a high-performance sensing device which is widely used at present and has huge application potential due to the high sensitivity response capability of the optical fiber to external environment change and the characteristic of realizing distributed multipoint simultaneous detection. Currently, application examples of sensing external environment parameters by adopting optical fibers are mainly focused on the fields of distributed temperature monitoring, pressure monitoring and the like. However, the present inventors have searched for the current gas monitoring field, and in most cases, the optical fiber is only used as an optical signal transmission waveguide, and the sensing and detection of the gas occur in a special optical structure formed by a reflecting mirror, and the optical fiber itself does not participate in the substantial gas detection. Therefore, the advantages of high sensitivity of the optical fiber and distributed multipoint simultaneous monitoring are not fully utilized in gas monitoring. There is currently no monitoring device for high sensitivity detection of gases.
In view of the above, the embodiments of the present invention provide a system, a method, and a device for monitoring gas concentration, which participate in gas detection by using an optical fiber, so that concentration monitoring of a gas to be detected with high sensitivity can be effectively realized.
First embodiment
Referring to fig. 1, the present embodiment provides a gas concentration monitoring system 10, which may include a laser generating device 11, a microcontroller 12, a photoelectric detection device 13, and a gas fiber sensing device 14. The microcontroller 12 is electrically connected to the photodetector device 13. The gas fiber sensing device 14 is used for detecting the gas to be detected. The laser generating device 11 is used for outputting signal light. The signal light is transmitted into the gas optical fiber sensing device 14, one part of the signal light is absorbed by the gas to be detected in the gas optical fiber sensing device 14, and the other part of the signal light is output from the gas optical fiber sensing device 14 and transmitted to the photoelectric detection device 13. The photodetector device 13 is configured to convert the received signal light into a first electrical signal and send the first electrical signal to the microcontroller 12. The microcontroller 12 is configured to obtain the concentration of the gas to be measured based on the first electrical signal.
Further, the laser generating device 11 is also used for outputting reference light. Referring to fig. 2, the laser generating device 11 may include a laser 111 and a beam splitter 112. The output end of the laser 111 is electrically connected with the input end of the beam splitter 112, and the laser beam output by the laser 111 is transmitted to the beam splitter 112, and can be split into the signal light and the reference light through the beam splitter 112. The absolute value of the difference between the light intensity of the signal light and the reference light output by the laser generating device 11 is smaller than a preset value. Wherein the preset value is a small value, close to 0. In this embodiment, the light intensities of the signal light and the reference light are equal. Correspondingly, the photoelectric detection device 13 is further configured to receive the reference light output by the laser generating device 11, convert the reference light into a second electrical signal, and send the second electrical signal to the microcontroller 12. The microcontroller 12 is configured to obtain the concentration of the gas to be measured based on the first electrical signal and the second electrical signal.
It should be noted that, as an embodiment, the light intensity of the reference light may be preset and stored in the microcontroller 12, and the laser generating device 11 is not required to output the reference light at this time. For example, when the light intensity of the signal light output from the beam splitter 112 is known to be 1mW in advance, the light intensity of the reference light may be stored in advance in the microcontroller 12 as 1mW. Of course, in order to improve the stability of the gas concentration monitoring system 10, the laser generator 11 needs to generate reference light in addition to the signal light.
Referring to fig. 2, in order to implement pulse modulation of the laser beam output by the laser 111, the laser generating device 11 may further include an optical switch 113. A first end of the optical switch 113 is electrically connected to the output of the laser 111, a second end of the optical switch 113 is coupled to the input of the beam splitter 112, and a third end of the optical switch 113 is electrically connected to the microcontroller 12. The optical switch 113 obtains a pulse control signal from the microcontroller 12 through the third terminal, and is periodically in an on state or an off state based on the pulse control signal, so that the laser beam output by the laser 111 is transmitted to the beam splitter 112. Specifically, when a high level in the pulse control signal of the microcontroller 12 comes, the control optical switch 113 is turned on to allow the laser beam to be transmitted to the beam splitter 112, and the signal light and the reference light output can be split into beams by the beam splitter 112; when a low level in the pulse control signal of the microcontroller 12 comes, the optical switch 113 is controlled to be turned off so as not to allow the laser beam to pass. Therefore, the laser beam has high loss suppression, and pulse modulation of the laser beam is realized.
Referring to fig. 2, further, in order to improve the practicability of the gas concentration monitoring system 10, the laser generating device 11 may further include a laser driving circuit 114, an optical parametric oscillator 115, and a fiber coupler 116. The input end of the laser 111 is electrically connected to the microcontroller 12 through the laser driving circuit 114, and the output end of the laser 111 is electrically connected to the first end of the optical switch 113 through the optical parametric oscillator 115 and the optical fiber coupler 116 in sequence.
The microcontroller 12 sends a stepped periodic digital signal to the laser drive circuit 114 with a period of time T. The laser driving circuit 114 converts the received stepwise periodic digital signal into an analog sawtooth scanning current signal having a period of time T, and continuously transmits the sawtooth scanning current signal to the input terminal of the laser 111. For example, the input terminal of the laser 111 may be a control current input pin of the laser 111, and the laser driving circuit 114 converts the received stepped periodic digital signal into an analog sawtooth scanning current signal with the period T as a period, and continuously injects the sawtooth scanning current signal into the control current input pin of the laser 111. Under the control of the sawtooth wave scanning current signal, the laser 111 periodically and continuously outputs a scanning laser beam with the wavelength from short to long, and transmits the scanning laser beam into the optical parametric oscillator 115, so that the optical parametric oscillator 115 is continuously pumped, and the wavelength tuning range of the scanning laser beam is further modulated. Under the action of the optical parametric oscillator 115, the wavelength scanning center of the scanning laser beam is tuned to the absorption wavelength corresponding to the gas to be measured, and the scanning range covers the characteristic absorption peak of the gas to be measured near the absorption wavelength corresponding to the gas to be measured, and the tuned scanning laser beam is transmitted to the optical switch 113.
For example, the gas to be measured may be, but is not limited to, carbon monoxide. Correspondingly, the absorption wavelength of the gas to be measured is 2.3 μm.
In this embodiment, the laser 111 may be a tunable semiconductor laser, such as a tunable semiconductor DFB (Distributed Feedback Laser) laser. The tunable semiconductor DFB (Distributed Feedback Laser) laser is used as a pumping light source, and the optical parametric oscillator 115 (OPO) is continuously pumped, so that near infrared and mid infrared multiband tunable laser beams can be realized, and the tunable optical parametric oscillator has wide applicability to gases with different characteristic absorption peaks.
Referring to fig. 3, the gas fiber sensing device 14 may include at least two fiber sensing modules and at least one delay. The gas fiber sensing device 14 may also include a detection fiber 14a. The at least two fiber sensing modules and the at least one delay are disposed within the detection fiber 14a. At least two optical fiber sensing modules are sequentially arranged and distributed in the detection optical fiber 14a, and every two adjacent optical fiber sensing modules are connected through a delay device and are arranged into a gas optical fiber sensing array. Each optical fiber sensor module is used for detecting the gas to be detected of one monitoring point. The number of the optical fiber sensing modules can be set according to actual needs, and correspondingly, the number of the delayers is 1 less than the number of the optical fiber sensing modules. For example, in the gas concentration monitoring system 10, it is necessary to monitor the concentration of the gas to be measured at N monitoring points, and at least two optical fiber sensing modules include at least N optical fiber sensing modules, and correspondingly, at least one delay device includes at least N-1 delay devices.
Referring to fig. 3, the at least two optical fiber sensing modules may include a first optical fiber sensing module 141 and a second optical fiber sensing module 142. The at least one delayer may include a first delayer 141a. The first optical fiber sensing module 141 is connected to the second optical fiber sensing module 142 through the first delay 141a. The first optical fiber sensing module 141, the second optical fiber sensing module 142 and the first delay 141a are all disposed in the detecting optical fiber 14 a.
The first optical fiber sensing module 141 is configured to detect the gas to be detected at a first monitoring point. The second optical fiber sensing module 142 is configured to detect the gas to be detected at a second monitoring point.
The signal light is transmitted into the first optical fiber sensing module 141, a part of the signal light is absorbed by the gas to be measured in the first optical fiber sensing module 141, a first sub-signal light in a first signal light in another part of the signal light is absorbed by the gas to be measured in the first optical fiber sensing module 141, a second sub-signal light in the first signal light is output from the first optical fiber sensing module 141 and transmitted to the photoelectric detection device 13, and a second signal light in another part of the signal light is transmitted to the second optical fiber sensing module 142 through the first delay 141a.
A part of the second signal light is absorbed by the gas to be detected in the second optical fiber sensing module 142, another part of the third sub-signal light in the second signal light is sequentially absorbed by the gas to be detected in the second optical fiber sensing module 142 and the gas to be detected in the first optical fiber sensing module 141, and another part of the fourth sub-signal light in the second signal light is output from the first optical fiber sensing module 141 and transmitted to the photoelectric detection device 13.
Further, each fiber sensing module may include a photonic crystal fiber and a fiber grating coupled to the photonic crystal fiber. The adoption of the fiber bragg grating-photonic crystal fiber structure replaces the traditional absorption air chamber, so that the whole system 10 is higher in integration, more stable in performance and lower in price.
As a specific embodiment, the fiber grating may be a chirped fiber grating, and in the detection fiber 14a, fiber perforation and grating inscription are implemented by a femtosecond laser processing technology, so as to respectively implement the fabrication of the photonic crystal fiber and the chirped fiber grating.
The first optical fiber sensing module 141 may include a first photonic crystal fiber 141b and a first fiber grating 141c. The second optical fiber sensing module 142 may include a second photonic crystal fiber 142a and a second fiber grating 142b. The first photonic crystal fiber 141b is connected to the second fiber grating 142b through the first fiber grating 141c, the first delay 141a, and the second photonic crystal fiber 142a in sequence.
The signal light is transmitted into the first photonic crystal fiber 141b, a part of the signal light is absorbed by the gas to be detected in the first photonic crystal fiber 141b, a first sub-signal light in the first signal light in another part of the signal light is transmitted to the first fiber grating 141c, reflected back into the first photonic crystal fiber 141b by the first fiber grating 141c, absorbed by the gas to be detected in the first photonic crystal fiber 141b, a second sub-signal light in the first signal light is output from the first photonic crystal fiber 141b and transmitted to the photoelectric detection device 13, and a second signal light in another part of the signal light is transmitted into the second photonic crystal fiber 142a through the first delay device 141 a.
A part of the second signal light is absorbed by the gas to be detected in the second photonic crystal fiber 142a, another part of the third sub-signal light in the second signal light is transmitted to the second fiber grating 142b, and is reflected by the second fiber grating 142b back into the second photonic crystal fiber 142a and into the first photonic crystal fiber 141b, and is sequentially absorbed by the gas to be detected in the second photonic crystal fiber 142a and the gas to be detected in the first photonic crystal fiber 141b, and another part of the fourth sub-signal light in the second signal light is output from the first photonic crystal fiber 141b and is transmitted to the photoelectric detection device 13.
Further, referring to fig. 2, the system 10 may also include a circulator 15. The first end of the circulator 15 is connected with the laser generating device 11, the second end of the circulator 15 is connected with the gas optical fiber sensing device 14, and the third end of the circulator 15 is connected with the photoelectric detection device 13. The signal light is transmitted to the gas optical fiber sensing device 14 through the circulator 15, one part of the signal light is absorbed by the gas to be detected in the gas optical fiber sensing device 14, and the other part of the signal light is output from the gas optical fiber sensing device 14 and then transmitted to the photoelectric detection device 13 through the circulator 15. Further, a first end of the circulator 15 is connected to an output end of the beam splitter 112, and a second end of the circulator 15 is connected to a detection fiber 14a of the gas fiber sensing device 14.
Referring to fig. 2 and 3 in combination, in the gas concentration monitoring system 10, the concentration of the gas to be monitored at N monitoring points is required, and at least two optical fiber sensing modules at least include N optical fiber sensing modules, which are a first optical fiber sensing module 141, a second optical fiber sensing module 142, a N-1 optical fiber sensing module … …, and a N optical fiber sensing module. Correspondingly, the at least one delayer at least comprises N-1 delayers, namely a first delayer 141a and a second delayer … …, namely an N-1 delayer. H represents a hole, F1 represents an N-1 optical fiber sensing module, F2 represents an N-1 time delay device, and F3 represents an N optical fiber sensing module. The tuned scanning laser beam is divided into signal light and reference light by a beam splitter 112, the light intensity of the signal light and the reference light are equal and respectively account for 50%, and the light intensity of the signal light and the reference light are respectively I 0 . The system 10 may also include a first conductive optical fiber 16 and a second conductive optical fiber 17. The light intensity is I 0 Is transmitted to the photodetector 13 via the first conductive optical fiber 16. The light intensity is I 0 Is transmitted into the first photonic crystal fiber 141b, the signal light includes a part of the signal light and another part of the signal light, and a part of the signal light is transmitted into the first photonic crystal fiber 141bThe gas to be measured in the gas absorber absorbs the other part of the signal light which comprises a first signal light and a second signal light, and the light intensity of the other part of the signal light is I 1 ' a first sub-signal light in a first signal light of another part of the signal light is transmitted to the first fiber grating 141c, and the light intensity of the first signal light is I 1 ′r 1 The second sub-signal light in the first signal light is output from the first photonic crystal fiber 141b, passes through the circulator 15 and is transmitted to the photoelectric detection device 13, and the light intensity of the second sub-signal light is I 1 The second sub-signal light is defined as a first echo signal;
the light intensity of the second signal light is I 1 ′t 1 Another part of the second signal light is transmitted to the second photonic crystal fiber 142a through the first delay 141a, one part of the second signal light is absorbed by the gas to be detected in the second photonic crystal fiber 142a, another part of the third sub-signal light in the second signal light is transmitted to the second fiber grating 142b, reflected by the second fiber grating 142b back to the second photonic crystal fiber 142a and the first photonic crystal fiber 141b, and is sequentially absorbed by the gas to be detected in the second photonic crystal fiber 142a and the gas to be detected in the first photonic crystal fiber 141b, the other part of the fourth sub-signal light in the second signal light is output from the first photonic crystal fiber 141b, guided to the second conducting fiber 17 through the circulator 15, and transmitted to the photoelectric detection device 13, and the light intensity of the fourth sub-signal light is I 2 The fourth sub-signal light is defined as a second echo signal, … …, and so on, the signal light energy is attenuated, and the light intensity of the other part of the second signal light is I 2 'the corresponding attenuation has a luminous intensity of I' 2 r 2 Is a part of light with the light intensity of I' 2 t 2 To the N-1 optical fiber sensing module, the light intensity is I' n-1 、I′ n-1 r n-1 、I′ n-1 t n-1 To the nth optical fiberThe light intensity of the sensing module is I' n 、I′ n r n Is the N-th echo signal I' n (n=1, 2, … N), the respective echo signals, i.e. the first echo signal, the second echo signal, … …, the nth echo signal I ', are due to the delay means provided' n (n=1, 2, … N) are transmitted to the photodetector device 13 at different times.
The gas optical fiber sensing device 14 takes optical fibers as carriers, forms a linear array to be distributed on the whole optical fibers and is distributed in a laying path of the optical fibers along with the optical fibers, so that a gas multi-point distributed detection mode is truly realized. By adopting an optical time domain analysis technology, a beam of laser pulse can realize simultaneous detection of a plurality of monitoring points, and the utilization efficiency of a light source is greatly improved.
It can be understood that the most important difference between the optical fiber sensing module, such as the nth optical fiber sensing module, and the first optical fiber sensing module 141 and the second optical fiber sensing module 142 is that the placed monitoring points are different, and the optical fiber sensing module has the same structure as the first optical fiber sensing module 141 and the second optical fiber sensing module 142, so that the related principles are consistent, and are not repeated herein. The most important difference between at least one delayer, such as the N-1 delayer, and the first delayer 141a is that the placed monitoring points are different, and the at least one delayer has the same structure as the first delayer 141a, and the related principles are also consistent, and are not repeated here.
The photo detection means 13 may comprise at least one photo detector. The photodetector may be, but is not limited to, an infrared photodetector. The at least one photodetector is configured to receive the reference light and each echo signal, convert the received echo signal into a first electrical signal, and send the first electrical signal to the microcontroller 12, and convert the received reference light into a second electrical signal, and send the second electrical signal to the microcontroller 12.
The at least one photodetector may include a first photodetector 131 and a second photodetector 132. In the gas concentration monitoring system 10, the concentration of the gas to be measured at N monitoring points needs to be monitored, and the first electrical signal includes a first sub-signal, a second sub-signal, … …, and an nth sub-signal. The second photodetector 132 is configured to receive the reference light and convert the received reference light into a second electrical signal. The first photodetector 131 is configured to receive each echo signal at different times, and correspondingly convert each received echo signal into a first sub-signal, a second sub-signal, … …, and an nth sub-signal.
Further, the system 10 may also include a display module 18. The display module 18 is electrically connected to the microcontroller 12. The display module 18 is used for displaying the concentration of the gas to be measured. The microcontroller 12 processes the first sub-signal, the second sub-signal … …, the nth sub-signal and the second electrical signal to obtain the concentration of the gas to be measured at each monitoring point, and then sends the concentration to the display module 18 for display. For example, display module 18 may display the concentration of carbon monoxide at each monitoring point.
Further, the system 10 may also include a data acquisition circuit 19. The data acquisition circuit 19 is electrically connected with the microcontroller 12 and the photoelectric detection device 13 respectively. Under the control of the microcontroller 12, the data acquisition circuit 19 converts the signal light and the reference light received by the photodetection device 13 into a first electrical signal and a second electrical signal, and sends the first electrical signal and the second electrical signal to the microcontroller 12.
In addition, the system 10 may also include an alarm module electrically coupled to the microcontroller 12. The microcontroller 12 is further configured to send an alarm instruction to the alarm module when the obtained concentration of the gas to be detected is greater than a preset threshold value; and the alarm module alarms after receiving the alarm instruction. The preset threshold value can be set according to the concentration threshold value of the gas to be detected. For example, the alarm module may be a voice alarm or an audible and visual alarm.
The working principle of the gas concentration monitoring system 10 provided by the embodiment of the invention is as follows:
the concentration of the gas to be detected at the N monitoring points is required to be monitored, the laser beam output by the laser 111 is split into signal light and reference light by the beam splitter 112, and the light intensity is I 0 Is transmitted through the first conductive optical fiber 16 to the second photodetector 132. The second photodetector 132 converts the received reference light into a second electrical signal via the data acquisition circuit 19 and transmits the second electrical signal to the microcontroller 12.
The light intensity is I 0 Is transmitted to the firstIn the photonic crystal fiber 141b, the signal light includes a part of the signal light and another part of the signal light, wherein a part of the signal light is absorbed by the gas to be measured in the first photonic crystal fiber 141b, another part of the signal light includes a first signal light and a second signal light, and a light intensity of another part of the signal light is I 1 ' a first sub-signal light in a first signal light of another part of the signal light is transmitted to the first fiber grating 141c, and the light intensity of the first signal light is I 1 ′r 1 The second sub-signal light in the first signal light is output from the first photonic crystal fiber 141b, passes through the circulator 15 and is transmitted to the photoelectric detection device 13, and the light intensity of the second sub-signal light is I 1 The second sub-signal light is defined as a first echo signal;
the light intensity of the second signal light is I 1 ′t 1 Another part of the second signal light is transmitted to the second photonic crystal fiber 142a through the first delay 141a, one part of the second signal light is absorbed by the gas to be detected in the second photonic crystal fiber 142a, another part of the third sub-signal light in the second signal light is transmitted to the second fiber grating 142b, reflected by the second fiber grating 142b back to the second photonic crystal fiber 142a and the first photonic crystal fiber 141b, and is sequentially absorbed by the gas to be detected in the second photonic crystal fiber 142a and the gas to be detected in the first photonic crystal fiber 141b, the other part of the fourth sub-signal light in the second signal light is output from the first photonic crystal fiber 141b, guided to the second conducting fiber 17 through the circulator 15, and transmitted to the photoelectric detection device 13, and the light intensity of the fourth sub-signal light is I 2 The fourth sub-signal light is defined as a second echo signal; by analogy, due to the set delays, the respective echo signals, i.e. the first echo signal, the second echo signal … …, and the nth echo signal are transmitted to the first photodetector 131 at different times.
The first photodetector 131 receives each echo signal at different times, and converts each received echo signal into a first sub-signal, a second sub-signal, … …, and an nth sub-signal through the data acquisition circuit 19, and sends the first sub-signal, the second sub-signal, … …, and the nth sub-signal to the microcontroller 12.
The microcontroller 12 processes the first sub-signal, the second sub-signal … … nth sub-signal and the second electrical signal to obtain an energy value of at least one echo signal, wherein the energy value of each echo signal corresponds to the absorption of signal light by the gas to be detected at least one monitoring point in the gas fiber sensing device 14; and obtaining the concentration of the gas to be detected at least at one monitoring point in the gas optical fiber sensing device 14 based on the energy value of the at least one echo signal and a preset recurrence rule. Microcontroller 12 also sends the concentration of the gas under test at the at least one monitoring point to display module 18 for display. The microcontroller 12 also sends an alarm instruction to the alarm module when the obtained concentration of the gas to be detected is greater than a preset threshold value; the alarm module receives the alarm instruction and then gives an alarm, so that high-sensitivity quantitative analysis and distributed multipoint simultaneous monitoring of the gas to be detected of each monitoring point are realized, and the gas monitoring system has the important characteristics of long-time stable operation and intrinsic safety.
In the gas concentration monitoring system 10 provided by the embodiment of the invention, the gas to be detected is detected by the gas optical fiber sensing device 14, and the laser generating device 11 outputs signal light. The signal light is transmitted into the gas optical fiber sensing device 14, one part of the signal light is absorbed by the gas to be detected in the gas optical fiber sensing device 14, and the other part of the signal light is output from the gas optical fiber sensing device 14 and transmitted to the photoelectric detection device 13. The photodetector device 13 converts the received signal light into a first electrical signal and transmits the first electrical signal to the microcontroller 12. The microcontroller 12 obtains the concentration of the gas to be measured based on the first electrical signal. Therefore, the high-sensitivity quantitative analysis and the distributed multi-point simultaneous monitoring of the gas to be detected of each monitoring point are realized, and the device has the important characteristics of long-time stable operation and intrinsic safety.
Second embodiment
Referring to fig. 4, an embodiment of the present invention provides a gas concentration monitoring method applied to the system 10 in the first embodiment. The method comprises the following steps: step S200 and step S210.
Step S200: and obtaining the energy value of at least one echo signal according to the acquired first electric signal, wherein the energy value of each echo signal corresponds to the absorption amount of the gas to be detected at least one monitoring point in the gas optical fiber sensing device to the signal light.
In the gas concentration monitoring system 10, the concentration of the gas to be measured at N monitoring points needs to be monitored, and the first electrical signal includes a first sub-signal, a second sub-signal … … and an nth sub-signal. The first photodetector 131 receives each echo signal at different times, and converts each received echo signal into a first sub-signal and a second sub-signal … … nth sub-signal through the data acquisition circuit 19, and sends the first sub-signal and the second sub-signal to the microcontroller 12. The second photodetector 132 receives the reference light and converts the received reference light into a second electrical signal.
The microcontroller 12 processes the first sub-signal, the second sub-signal … … nth sub-signal and the second electrical signal to obtain energy values of at least one echo signal, wherein the energy value of each echo signal corresponds to an absorption amount of signal light by the gas to be detected at least one monitoring point in the gas fiber sensor 14.
The intensity of the second electric signal generated by directly irradiating the acquired reference light to the second photodetector 132 is defined as I 0 。
The ratio of the intensity of the second electrical signal generated by directly irradiating the second photodetector 132 with the acquired reference light to the intensity of the first sub-signal generated by irradiating the first photodetector 131 with the first echo signal of the at least one echo signal is defined as the energy value of the first echo signal, I 1 . It is understood that the energy value of the first echo signal may represent an absorption of signal light by the gas under test at a first monitoring point of the at least one monitoring point. A second electricity generated by directly irradiating the acquired reference light to the second photodetector 132The ratio of the signal intensity to the intensity of the second sub-signal generated by the second echo signal of the at least one echo signal irradiated to the first photodetector 131 is defined as the energy value of the second echo signal, I 2 . The energy value of the second echo signal may characterize a common absorption of signal light by the gas under test of the first and second monitoring points of the at least one monitoring point. … … by analogy, the ratio of the intensity of the second electrical signal generated by directly irradiating the second photodetector 132 with the acquired reference light to the intensity of the nth sub-signal generated by irradiating the first photodetector 131 with the nth echo signal of the at least one echo signal is defined as the energy value of the nth echo signal, I n . The energy value of the nth echo signal may represent a common absorption of signal light by the gas under test of the first monitoring point, the second monitoring point … …, and the nth monitoring point of the at least one monitoring point. The energy value of the at least one echo signal comprises I n (n=1, 2, … N). Taking the gas to be measured as carbon monoxide as an example, the characteristics of each obtained echo signal are shown in fig. 5. As the number of the monitoring points increases, the gas to be detected of each monitoring point absorbs the signal light, and the first echo signal and the second echo signal … … Nth echo signal show the characteristic of attenuation in sequence.
Step S210: and obtaining the concentration of the gas to be detected of at least one monitoring point in the gas optical fiber sensing device based on the energy value of the at least one echo signal and a preset recurrence rule.
According to lambert-beer law, the preset recurrence rule is formula (1):
in the formula (1), I n (n=1, 2, … N) is the energy value of the nth echo signal, r n (n＝1,2,…N)、K n (n＝1,2,…N)、β n (n＝1,2,…N)、t n (n=1, 2, … N) are all preset constants, c n (n=1, 2, … … N) is the concentration of the gas to be measured at the nth monitoring point.
Equation (1) is equivalent to equation (2). The formula (2) reflects the relation between the concentration value of the gas to be detected at each monitoring point and the energy value of each echo signal, and each preset constant can be calculated and obtained by the concentration value of the gas to be detected at each monitoring point and the formula (1) in reverse. And (3) obtaining the concentration of the gas to be detected of at least one monitoring point in the gas optical fiber sensing device based on the formula (2).
For example, n=2, the gas to be measured is carbon monoxide, the concentration of carbon monoxide at 2 monitoring points is measured, and the intensity I of the obtained second electrical signal is calculated 0 Energy value I of first echo signal 1 Is brought intoObtaining the concentration value c of carbon monoxide at a first monitoring point 1 Bringing the energy value of the acquired second echo signal into I 2 And the concentration value c of carbon monoxide at the first monitoring point 1 ，/>Obtaining the concentration value c of carbon monoxide at the second monitoring point 2 。
When the concentration of the gas to be detected is calculated, the gas absorption characteristic peak in the scanning spectrum is extracted through a spectrum analysis algorithm, and the spectrum background caused by the attenuation factor is subtracted, so that the absorption spectrum only carrying the concentration information of the gas to be detected is extracted, and the accurate calculation of the gas concentration is completed. It should be noted that the pulse laser beam reflected by the nth fiber bragg grating will reflect back and forth between the nth-1 fiber bragg grating and the nth fiber bragg grating, and weak energy is transmitted through the nth-1 fiber bragg grating, the nth-2 fiber bragg grating, and the … … nth-1 fiber bragg grating to reach the photosensitive surface of the first photodetector, and cause a response. However, compared with the primary reflection signal, the signal is very weak and can be ignored, and the signal presents the characteristic of time domain continuous distribution and is easy to deduct through algorithms such as spectrum background fitting and the like.
It will be clearly understood by those skilled in the art that, for convenience and brevity of description, the specific working process of the gas concentration monitoring method described above may refer to the corresponding process in the foregoing system embodiment, which is not repeated herein.
The gas concentration monitoring method provided by the embodiment of the invention is applied to the system, realizes high-sensitivity quantitative analysis and distributed multipoint simultaneous monitoring on the gas to be detected of each monitoring point, and has the important characteristics of long-time stable operation and intrinsic safety.
Third embodiment
Referring to fig. 6, an embodiment of the present invention provides a gas concentration monitoring apparatus 300, which is a microcontroller operating in the system, and includes an acquisition unit 310 and a processing unit 320.
And an obtaining unit 310, configured to obtain an energy value of at least one echo signal according to the obtained first electrical signal, where the energy value of each echo signal corresponds to an absorption amount of the signal light by the gas to be detected at one monitoring point in the gas optical fiber sensing device.
And the processing unit 320 is configured to obtain the concentration of the gas to be detected at the at least one monitoring point in the gas optical fiber sensing device based on the energy value of the at least one echo signal and a preset recurrence rule.
The above units may be implemented in software code, in which case they may be stored in a memory included in the microcontroller 12. The above units may equally be implemented by hardware, e.g. an integrated circuit chip.
The gas concentration monitoring device 300 according to the embodiment of the present invention has the same implementation principle and technical effects as those of the foregoing method embodiment, and for brevity, reference may be made to the corresponding content in the foregoing method embodiment where the device embodiment is not mentioned.
The above description is only of the preferred embodiments of the present invention and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (8)
1. The gas concentration monitoring system is characterized by comprising a laser generating device, a microcontroller, a photoelectric detection device and a gas optical fiber sensing device, wherein the microcontroller is electrically connected with the photoelectric detection device, and the gas optical fiber sensing device is used for detecting gas to be detected;
the laser generating device is used for outputting signal light;
The signal light is transmitted into the gas optical fiber sensing device, one part of the signal light is absorbed by the gas to be detected in the gas optical fiber sensing device, and the other part of the signal light is output from the gas optical fiber sensing device and transmitted to the photoelectric detection device;
the photoelectric detection device is used for converting the received signal light into a first electric signal and sending the first electric signal to the microcontroller;
the microcontroller is used for obtaining the concentration of the gas to be detected based on the first electric signal;
the gas optical fiber sensing device comprises at least two optical fiber sensing modules and at least one delayer, wherein the at least two optical fiber sensing modules comprise a first optical fiber sensing module and a second optical fiber sensing module, the at least one delayer comprises a first delayer, and the first optical fiber sensing module is connected with the second optical fiber sensing module through the first delayer;
the first optical fiber sensing module is used for detecting the gas to be detected at a first monitoring point;
the second optical fiber sensing module is used for detecting the gas to be detected at a second monitoring point;
the signal light is transmitted into the first optical fiber sensing module, one part of the signal light is absorbed by the gas to be detected in the first optical fiber sensing module, the first sub-signal light in the first signal light in the other part of the signal light is absorbed by the gas to be detected in the first optical fiber sensing module, the second sub-signal light in the first signal light is output from the first optical fiber sensing module and transmitted to the photoelectric detection device, and the second signal light in the other part of the signal light is transmitted to the second optical fiber sensing module through the first delay device;
A part of the second signal light is absorbed by the gas to be detected in the second optical fiber sensing module, the other part of the third sub-signal light in the second signal light is sequentially absorbed by the gas to be detected in the second optical fiber sensing module and the gas to be detected in the first optical fiber sensing module, and the other part of the fourth sub-signal light in the second signal light is output from the first optical fiber sensing module and transmitted to the photoelectric detection device;
the first optical fiber sensing module comprises a first photonic crystal fiber and a first optical fiber grating, the second optical fiber sensing module comprises a second photonic crystal fiber and a second optical fiber grating, and the first photonic crystal fiber is connected with the second optical fiber grating through the first optical fiber grating, the first delay device and the second photonic crystal fiber in sequence;
the signal light is transmitted into the first photonic crystal fiber, one part of the signal light is absorbed by the gas to be detected in the first photonic crystal fiber, the other part of the first sub-signal light in the first signal light is transmitted into the first fiber grating, the first sub-signal light is reflected back into the first photonic crystal fiber by the first fiber grating and absorbed by the gas to be detected in the first photonic crystal fiber, the second sub-signal light in the first signal light is output from the first photonic crystal fiber and transmitted to the photoelectric detection device, and the other part of the second signal light in the signal light is transmitted into the second photonic crystal fiber through the first delay device;
And one part of the second signal light is absorbed by the gas to be detected in the second photonic crystal fiber, the other part of the third sub-signal light in the second signal light is transmitted to the second fiber grating, is reflected back into the second photonic crystal fiber and the first photonic crystal fiber by the second fiber grating, is sequentially absorbed by the gas to be detected in the second photonic crystal fiber and the gas to be detected in the first photonic crystal fiber, and the other part of the fourth sub-signal light in the second signal light is output from the first photonic crystal fiber and is transmitted to the photoelectric detection device.
2. The system of claim 1, further comprising a circulator, a first end of the circulator being connected to the laser generating device, a second end of the circulator being connected to the gas fiber optic sensing device, a third end of the circulator being connected to the photodetector device;
the signal light is transmitted into the gas optical fiber sensing device through the circulator, one part of the signal light is absorbed by the gas to be detected in the gas optical fiber sensing device, and the other part of the signal light is output from the gas optical fiber sensing device and then transmitted to the photoelectric detection device through the circulator.
3. The system according to claim 1, wherein the laser generating device is further configured to output a reference light, and an absolute value of a difference between the light intensity of the signal light output by the laser generating device and the reference light is smaller than a preset value;
the photoelectric detection device is also used for receiving the reference light output by the laser generation device, converting the reference light into a second electric signal and sending the second electric signal to the microcontroller;
the microcontroller is used for obtaining the concentration of the gas to be detected based on the first electric signal and the second electric signal.
4. A system according to claim 3, wherein the laser generating device comprises a laser and a beam splitter, an output end of the laser is electrically connected to an input end of the beam splitter, and a laser beam output by the laser is transmitted to the beam splitter, and split into the signal light and the reference light output by the beam splitter.
5. The system of claim 4, wherein the laser generating device further comprises an optical switch having a first end electrically connected to the output of the laser, a second end coupled to the input of the beam splitter, a third end electrically connected to the microcontroller, the optical switch obtaining a pulse control signal from the microcontroller through the third end and periodically being in an on state or an off state based on the pulse control signal to transmit the laser beam output by the laser to the beam splitter.
6. The system of claim 1, further comprising a display module electrically connected to the microcontroller, the display module configured to display the concentration of the gas under test.
7. A method of monitoring gas concentration as claimed in any one of claims 1 to 6, the method comprising:
obtaining energy values of at least one echo signal according to the obtained first electric signals, wherein the energy value of each echo signal corresponds to the absorption amount of the gas to be detected at least one monitoring point in the gas optical fiber sensing device to the signal light;
and obtaining the concentration of the gas to be detected of at least one monitoring point in the gas optical fiber sensing device based on the energy value of the at least one echo signal and a preset recurrence rule.
8. A gas concentration monitoring device, characterized by a microcontroller operating in the system according to any one of claims 1-6, the gas concentration monitoring device comprising:
the acquisition unit is used for acquiring the energy value of at least one echo signal according to the acquired first electric signal, wherein the energy value of each echo signal corresponds to the absorption quantity of the gas to be detected at least one monitoring point in the gas optical fiber sensing device to the signal light;
And the processing unit is used for obtaining the concentration of the gas to be detected of at least one monitoring point in the gas optical fiber sensing device based on the energy value of the at least one echo signal and a preset recurrence rule.
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