CN217466666U - Multipoint gas detection device based on photothermal effect and wavelength division multiplexing interferometer - Google Patents
Multipoint gas detection device based on photothermal effect and wavelength division multiplexing interferometer Download PDFInfo
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Abstract
A multipoint gas detection device based on a photothermal effect and a wavelength division multiplexing interferometer comprises a wavelength scanning laser, a circulator, a coupler, an optical fiber delay ring, a plurality of detection units, an optical fiber splitter, a filter, a chopper, a space collimating device, an erbium-doped optical fiber amplifier, a pumping laser, a photoelectric detector, a data acquisition card and a computer system; the circulator is connected with one input end of the coupler, two output ends of the coupler are respectively connected with the optical fiber delay ring and the detection unit, and the detection units are arranged in parallel and connected with the optical fiber branching unit; the circulator is also respectively connected with the wavelength scanning laser and the photoelectric detector; the optical fiber branching device is connected with the filter, the filter is connected with the output end of the space collimating device, and the middle of the space collimating device is provided with the chopper; the input end of the spatial collimating device is connected with the output end of the erbium-doped fiber amplifier, and the input end of the erbium-doped fiber amplifier is connected with the pump laser; the photoelectric detector is connected with a data acquisition card, and the data acquisition card is connected with a computer system.
Description
Technical Field
The utility model relates to a gaseous detection technology field on a large scale especially relates to a gaseous detection device of multiple spot based on light and heat effect and wavelength division multiplexing interferometer.
Background
The multipoint (quasi-distributed) or distributed gas detection method can accurately measure the gas concentration at different positions in a large range. The method has important significance in long-distance pipeline gas transmission [1,2], large-area underground mine gas monitoring [3] and urban road gas pollution detection [ 4-6 ]. At present, multipoint gas detection is mainly based on an optical fiber multiplexing technology [7], including Space Division Multiplexing (SDM) [3,8,9], Time Division Multiplexing (TDM) [ 10-12 ], Frequency Division Multiplexing (FDM) [13,14] and Wavelength Division Multiplexing (WDM) [ 15-17 ].
For SDM [3,8,9], multiple gas sensors may share a laser, but multiple photodetectors are required to detect multiple signals. TDM [10 ~ 12] generally uses wavelength scanning pulsed laser source, and the different time delays of pulsed light can distinguish a plurality of gas sensors, but spatial resolution is usually difficult to improve. FDM [13,14] is primarily based on Frequency Modulated Continuous Wave (FMCW), typically using an intensity modulated swept laser for positioning the chamber at different locations in space, but the system and signal processing is relatively complex. WDM [ 15-17 ] usually uses multiple FBGs matching the gas absorption peak to distinguish multiple gas sensors by different wavelengths, so the signal crosstalk between multiple sensors is generally small. However, the number of detections is limited by the number of gas absorption peaks, and the absorption coefficient of each gas absorption peak is different, resulting in a significant difference in the signal-to-noise ratio of each gas cell. Furthermore, the wavelength of FBGs often drifts due to environmental influences, which may lead to measurement errors.
In addition, stronger phosgene interactions have been demonstrated based on hollow photonic band gap fiber (HC-PBF) gas cells [ 18-20 ]. Distributed gas detection systems based on hollow-core fiber and photo-thermal (PT) interferometry have also been reported [21], with spatial resolution of about 30 m. The system uses a double pulse heterodyne Optical Time Domain Reflectometer (OTDR) to detect gas induced phase changes. However, the detection distance, spatial resolution and response speed are limited by the fabrication of hollow-core fibers (e.g., fs-laser is required to fabricate multiple micro-channels along the HC-PBF and to precisely control the hole pitch), which increases the engineering cost and affects the stability in practical applications.
Reference to the literature
[1]D.Inaudi and B.Glisic,"Long-range pipeline monitoring by distributed fiber optic sensing,"Journal of pressure vessel technology 132(2010).
[2]S.Datta and S.Sarkar,"A review on different pipeline fault detection methods,"Journal of Loss Prevention in the Process Industries 41,97-106(2016).
[3]Z.Wang,T.Chang,X.Zeng,H.Wang,L.Cheng,C.Wu,J.Chen,Z.Luo,and H.-L.Cui,"Fiber optic multipoint remote methane sensing system based on pseudo differential detection,"Optics and Lasers in Engineering 114,50-59(2019).
[4]B.Culshaw and A.Kersey,"Fiber-optic sensing:A historical perspective,"Journal of lightwave technology 26,1064-1078(2008).
[5]C.Pijolat,C.Pupier,M.Sauvan,G.Tournier,and R.Lalauze,"Gas detection for automotive pollution control,"Sensors and Actuators B:Chemical 59,195-202(1999).
[6]M.A.Moeckli,M.Fierz,and M.W.Sigrist,"Emission factors for ethene and ammonia from a tunnel study with a photoacoustic trace gas detection system,"Environmental science&technology 30,2864-2867(1996).
[7]C.K.Kirkendall and A.Dandridge,"Overview of high performance fibre-optic sensing,"Journal of Physics D:Applied Physics 37,R197(2004).
[8]G.Stewart,C.Tandy,D.Moodie,M.Morante,and F.Dong,"Design of a fibre optic multi-point sensor for gas detection,"Sensors and Actuators B:Chemical 51,227-232(1998).
[9]S.B.Schoonbaert,D.R.Tyner,and M.R.Johnson,"Remote ambient methane monitoring using fiber-optically coupled optical sensors,"Applied Physics B 119,133-142(2015).
[10]W.Jin,"Performance analysis of a time-division-multiplexed fiber-optic gas-sensor array by wavelength modulation of a distributed-feedback laser,"Applied optics 38,5290-5297(1999).
[11]C.Floridia,J.B.Rosolem,J.P.V.Fracarolli,F.R.Bassan,R.S.Penze,L.M.Pereira,and M.A.C.da Motta Resende,"Evaluation of Environmental Influences on a Multi-Point Optical Fiber Methane Leak Monitoring System,"Remote Sensing 11,1249(2019).
[12]C.Sun,Y.Chen,G.Zhang,F.Wang,G.Liu,and J.Ding,"Multipoint remote methane measurement system based on spectrum absorption and reflective TDM,"IEEE Photonics Technology Letters 28,2487-2490(2016).
[13]H.Ho,W.Jin,H.Yu,K.Chan,C.Chan,and M.Demokan,"Experimental demonstration of a fiber-optic gas sensor network addressed by FMCW,"IEEE photonics technology letters 12,1546-1548(2000).
[14]F.Ye,L.Qian,and B.Qi,"Multipoint chemical gas sensing using frequency-shifted interferometry,"Journal of Lightwave Technology 27,5356-5364(2009).
[15]Y.Zhang,M.Zhang,and W.Jin,"Multi-point,fiber-optic gas detection with intra-cavity spectroscopy,"Optics Communications 220,361-364(2003).
[16]M.Lu,K.Nonaka,H.Kobayashi,J.Yang,and L.Yuan,"Quasi-distributed region selectable gas sensing for long distance pipeline maintenance,"Measurement Science and Technology 24,095104(2013).
[17]H.Zhang,Y.Lu,L.Duan,Z.Zhao,W.Shi,and J.Yao,"Intracavity absorption multiplexed sensor network based on dense wavelength division multiplexing filter,"Optics Express 22,24545-24550(2014).
[18]A.Cubillas,M.Silva-Lopez,J.Lazaro,O.Conde,M.Petrovich,and J.Lopez-Higuera,"Methane detection at 1670-nm band using a hollow-core photonic bandgap fiber and a multiline algorithm,"Optics Express 15,17570-17576(2007).
[19]W.Jin,Y.Cao,F.Yang,and H.L.J.N.c.Ho,"Ultra-sensitive all-fibre photothermal spectroscopy with large dynamic range,"6,6767(2015).
[20]J.Li,H.Yan,H.Dang,and F.Meng,"Structure design and application of hollow core microstructured optical fiber gas sensor:A review,"Optics&Laser Technology 135,106658(2021).
[21]Y.Lin,F.Liu,X.He,W.Jin,M.Zhang,F.Yang,H.L.Ho,Y.Tan,and L.Gu,"Distributed gas sensing with optical fibre photothermal interferometry,"Optics express 25,31568-31585(2017).
Disclosure of Invention
An object of the utility model is to solve the above-mentioned problem among the prior art, provide a gaseous detection device of multiple spot based on photothermal effect and wavelength division multiplexing interferometer, the device separates different wavelengths through a plurality of wavelength division multiplexer and fiber grating, and the same linear Sagnac interferometer can be multiplexed to different wavelengths to derive gas concentration with the intensity of the photothermal phase place that detects. Because the wavelength is selected and is irrelevant to the gas absorption peak, the number of the measuring points can be flexibly adjusted according to the bandwidth of the light source and the bandwidth of the wavelength division multiplexer. And a data acquisition card is used for carrying out Fourier transform on the signals and carrying out superposition averaging in a frequency domain, and finally, the obtained gas minimum detection limit is obviously improved. By integrating gas concentration data under various wavelengths, the gas concentration conditions under different positions to be measured can be accurately evaluated.
In order to achieve the above purpose, the utility model adopts the following technical scheme:
a multipoint gas detection device based on a photothermal effect and a wavelength division multiplexing interferometer comprises a wavelength scanning laser, a circulator, a coupler, an optical fiber delay ring, a plurality of detection units, an optical fiber splitter, a filter, a chopper, a space collimating device, an erbium-doped optical fiber amplifier, a pumping laser, a photoelectric detector, a data acquisition card and a computer system;
the circulator is a three-port optical fiber circulator, the circulator is connected with one input end of the coupler, two output ends of the coupler are respectively connected with the optical fiber delay ring and the detection unit, and the detection units are arranged in parallel and connected with the optical fiber branching unit; the circulator is also respectively connected with the wavelength scanning laser and the photoelectric detector;
the optical fiber branching device is connected with a filter, the filter is connected with the output end of the space collimating device, and a chopper is arranged in the middle of the space collimating device; the input end of the spatial collimating device is connected with the output end of the erbium-doped fiber amplifier, and the input end of the erbium-doped fiber amplifier is connected with the pump laser;
the photoelectric detector is connected with a data acquisition card, the data acquisition card is connected with a computer system, and the data acquisition card is used for acquiring the demodulated voltage signal data and transmitting the data to the computer system for signal processing and gas concentration calculation.
The detection unit comprises a sequential wavelength division multiplexer, an absorption gas chamber, a gas sensor and a fiber bragg grating; the incident end of the wavelength division multiplexer is connected with the output end of the coupler or the reflection end of the wavelength division multiplexer of the previous detection unit, the transmission end of the wavelength division multiplexer is connected with an absorption gas chamber, the absorption gas chamber is connected with a gas sensor, and the gas sensor is connected with the fiber bragg grating; the fiber grating is connected with the fiber splitter.
The gas sensor comprises a first collimator and a second collimator, the first collimator is arranged at the front end of the absorption gas chamber, and the second collimator is arranged at the rear end of the absorption gas chamber; and laser emitted by the first collimator passes through the absorption gas chamber, enters the second collimator and is transmitted to the fiber grating.
The wavelength scanning laser is a laser with tunable wavelength in a C wave band.
The splitting ratio of the coupler is 50: 50.
The pump laser is a semiconductor laser and aims at a gas absorption peak through tuning wavelength.
The spatial collimating device comprises a first collimator and a second collimator, and laser emitted by the first collimator enters the second collimator through the chopper and is transmitted to the filter.
Compared with the prior art, the utility model discloses technical scheme obtains beneficial effect is:
the utility model discloses a wavelength division multiplexing interferometer has realized the gaseous detection of multiple spot. Different with traditional wavelength division multiplexing method, the utility model discloses can not be subject to the gas absorption peak and influence the measurement point number, also can not be subject to the absorption coefficient of gas absorption peak, and influence the SNR of multiple spot signal. In a conventional Mach-Zehnder Interferometer (MZI), the working point is moved due to the change of the length difference of two arms caused by the disturbance of the external environment, which causes the phase fading phenomenon of the Interferometer, and in a linear Sagnac Interferometer, two beams of interference light are transmitted in the same single-mode optical fiber, so the optical path difference is theoretically zero, the phase fading caused by the change of the optical path difference of the two arms can be overcome, and the environment interference is reduced. The first-order photothermal signals are collected through a low-cost collection card, and are subjected to superposition averaging in a frequency domain for signal processing, so that the signal-to-noise ratio and the minimum detection limit can be effectively improved, and the method is more suitable and effective in multi-point application occasions.
Drawings
Fig. 1 is a schematic view of the overall structure of the present invention.
Detailed Description
In order to make the technical problem, technical solution and beneficial effects to be solved by the present invention clearer and more obvious, the following description is made in detail with reference to the accompanying drawings and embodiments.
Referring to fig. 1, the present embodiment provides a multipoint gas detection apparatus based on photothermal effect and wavelength division multiplexing interferometer, including a wavelength scanning laser 1, a circulator 2, a photodetector 3, a data acquisition card 4, a computer system 5, a coupler 6, a fiber delay loop 7, a first wavelength division multiplexer 8, a second wavelength division multiplexer 9, a third wavelength division multiplexer 10, a first gas sensor 11, a second gas sensor 12, a third gas sensor 13, a first absorption gas chamber 14, a second absorption gas chamber 15, a third absorption gas chamber 16, a first third fiber grating 17, a second fiber grating 18, a third fiber grating 19, a fiber splitter 20, a filter 21, a spatial collimating device 22, a chopper 23, an erbium-doped fiber amplifier 24, and a pump laser 25.
The wavelength scanning laser 1 is connected with a circulator 2, the circulator 2 is connected with one input end of a coupler 6, two output ends of the coupler 6 are respectively connected with an optical fiber delay ring 7 and an incident end of a first wavelength division multiplexer 8, a reflecting end of the first wavelength division multiplexer 8 is connected with an incident end of a second wavelength division multiplexer 9, a reflecting end of the second wavelength division multiplexer 9 is connected with an incident end of a third wavelength division multiplexer 10, transmission ends of the first, second and third wavelength division multiplexers 8-10 are respectively connected with first, second and third gas sensors 11-13, the first, second and third gas sensors 11-13 are respectively connected with absorption gas chambers 14-16, the first, second and third gas sensors 11-13 are respectively connected with first, second and third optical fiber gratings 17-19, the first, second and third optical gratings 17-19 are respectively connected with an optical fiber splitter 20, the optical fiber splitter 20 is connected with a filter 21, the filter 21 is connected with the output end of a spatial collimating device 22, and the spatial collimating device 22 is used for collimating the optical path in space; a chopper 23 is fixedly arranged in the middle of the space collimator 22, the input end of the space collimator 22 is connected with the output end of an erbium-doped optical fiber amplifier 24, the erbium-doped optical fiber amplifier 24 is used for amplifying optical power, and the input end of the erbium-doped optical fiber amplifier 24 is connected with a pump laser 25;
the circulator 2 is connected with the photoelectric detector 3, the photoelectric detector 3 is connected with the data acquisition card 4, and the data acquisition card 4 is used for acquiring the demodulated voltage signal data and then transmitting the data to the computer system 5 through a usb data line for signal processing and gas concentration calculation.
The wavelength scanning laser 1 is a laser with tunable wavelength in a C-band (1525-1565 nm). The laser has stable and tunable wavelength and narrow line width, and ensures that the light source is fast and intuitive in operation and control. In the experiment, the wavelengths of 1543.07nm, 1558.90nm and 1555.70nm are respectively fixed to realize the detection of three absorption gas chambers.
The splitting ratio of the coupler is 50:50, namely the coupler comprises two light paths, and the laser ratio of the two light paths is 50% and 50%; the first optical path is transmitted to the optical fiber delay ring and returns to the coupler through the optical fiber, and the second optical path is transmitted to the first wavelength division multiplexer through the optical fiber.
The circulator 2 is a three-port fiber circulator, and emits laser light from a port 202 when the laser light enters from a port 201 of the circulator 2, and emits laser light from a port 203 when the laser light enters from the port 202 of the circulator 2. The working wavelength of the optical fiber circulator 2 is in a C wave band, the isolation is at least larger than 40dB, and the maximum insertion loss is not more than 1.1 dB.
The central wavelengths of the first, second and third wavelength division multiplexers 8-10 are 1542.92nm, 1555.74nm and 1559.02nm respectively, the bandwidth is 0.8nm, the channel isolation interval is 100GHz, and the isolation is more than 30 dB.
The first, second and third gas sensors 11 to 13 include a first collimator 1101, a second collimator 1102, a third collimator 1201, a fourth collimator 1202, a fifth collimator 1301 and a sixth collimator 1302, the first collimator 1101 is disposed at the front end of the first absorption gas chamber 11, and the emitted laser light enters the second collimator 1102 after passing through the first absorption gas chamber 11 and is transmitted to the first fiber grating 17. The third collimator 1201, the fourth collimator 1201, the fifth collimator 1301, and the sixth collimator 1302 are respectively disposed at the front and rear ends of the second absorption gas chamber 12 and the third absorption gas chamber 13 and are transmitted to the second fiber grating 18 and the third fiber grating 19.
The central wavelengths of the first, second and third fiber gratings 17-19 are 1543.00nm, 1555.69nm and 1558.93nm respectively, the bandwidth is 0.2nm, and the reflectivity is more than 90%.
The pump laser 25 is a semiconductor laser, and the central wavelength of the filter is 1530.33nm by tuning the wavelength to align with the absorption peak (1530.38nm) of gas (acetylene), and the 3dB bandwidth is about 0.8 nm.
The spatial collimating device structure 22 comprises a first collimator 2201, a second collimator 2202 and a U-shaped metal plate, wherein the first collimator 2201 is adhered to the U-shaped metal plate by glue, and the second collimator 2202 is adhered to the U-shaped metal plate by glue. The laser light coming out of the first collimator 2201 enters the second collimator 2202 through the chopper 23 and is transmitted to the filter 21. The chopper 20 realizes the intensity modulation of the gas absorption of the pump laser by adjusting the chopping frequency.
After the data acquisition card 4 is connected to the computer system 5, software programming is adopted to perform signal processing, Fourier transformation is performed on the photo-thermal signals in the time domain in real time, and the signals in the frequency domain are accumulated and averaged in real time, so that the aims of optimizing the signal-to-noise ratio and improving the minimum detection limit are fulfilled.
The embodiment of the utility model provides a detection step as follows:
the method comprises the steps of starting a pump laser 25, aligning to an absorption peak 1530.38nm of gas (acetylene) to be detected, starting an erbium-doped optical fiber amplifier 24, amplifying pump laser power, starting a chopper 23, setting chopper modulation frequency to realize intensity modulation of the pump laser 25, enabling the pump laser 25 to enter a first absorption air chamber, a second absorption air chamber and a third absorption air chamber 14-16 after passing through an optical fiber splitter 20, and enabling gas in the first absorption air chamber, the second absorption air chamber and the third absorption air chamber 14-16 to be subjected to periodic intensity modulation of the laser, and then releasing heat locally periodically to cause periodic change of local effective refractive index. The wavelength scanning laser 1 is started, the fixed wavelength is 1543.07nm, and the laser enters the input port of the circulator 2 and enters the linear Sagnac interferometer through the output port of the circulator 2. The optical paths of the two interference lights under the first wavelength are as follows:
the first beam light path passes through the coupler 6 → the first wavelength division multiplexer 8 → the first collimator 1101 of the first gas sensor → the first absorption gas cell 14 → the second collimator 1102 of the first gas sensor → the first fiber grating 17 → the second collimator 1102 of the first gas sensor → the first absorption gas cell 14 → the first collimator 1101 of the first gas sensor → the first wavelength division multiplexer 8 → the coupler 6 → the fiber delay ring 7 → the circulator 2;
the second light path passes through the coupler 6 → the optical fiber delay ring 7 → the first wavelength division multiplexer 8 → the first collimator 1101 of the first gas sensor → the first absorption gas cell 14 → the second collimator 1102 of the first gas sensor → the first fiber grating 17 → the second collimator 1102 of the first gas sensor → the first absorption gas cell 14 → the first collimator 1101 of the first gas sensor → the first wavelength division multiplexer 8 → the coupler 6 → the circulator 2.
Since the gas in the first absorption gas chamber 14 is modulated by the pump laser, the phase change is caused by the local refractive index change, and when two interference lights pass through the absorption gas chamber, the two interference lights carry the phase information of the gas concentration information. Finally, two beams of interference light enter the photoelectric detector 3 through the circulator 2, the photoelectric detector 3 converts an interference light intensity signal into a voltage signal, and then the voltage signal is collected by the data acquisition card 4 and then transmitted to the computer system 5 for signal processing and gas concentration calculation.
Changing and fixing the wavelength of the scanning laser to be a second wavelength, wherein laser enters a second wavelength division multiplexer 9 from the reflection end of the first wavelength division multiplexer 8, enters a first collimator 1201 of the second gas sensor 12, enters a first collimator 1202 of the second gas sensor 12 through a second absorption gas chamber 15, is reflected after passing through a second fiber grating 18, and the gas concentration information of the second absorption gas chamber 15 can be obtained at the position of the photoelectric detector 3; changing and fixing the wavelength of the scanning laser to be a third wavelength, the laser enters the third wavelength division multiplexer 10 from the second wavelength division multiplexer 9, enters the first collimator 1301 of the third gas sensor 13, enters the second collimator 1302 of the third gas sensor 13 through the third absorption gas chamber 16, and is reflected after passing through the third fiber bragg grating 19, and the gas concentration information of the third absorption gas chamber 16 can be obtained at the position of the photoelectric detector 3.
By integrating gas concentration data under various wavelengths, the gas concentration conditions under different positions to be measured can be accurately evaluated. In order to realize the extraction of weak signals, after the data acquisition card 4 is connected to the computer system 5 through usb, signal processing is carried out by adopting labview software programming, Fourier transformation is carried out on photothermal signals in a time domain in real time, and signals in the frequency domain are accumulated and averaged in real time, so that the signal-to-noise ratio and the minimum detection limit are effectively improved.
Claims (7)
1. The utility model provides a gaseous detection device of multiple spot based on photothermal effect and wavelength division multiplexing interferometer which characterized in that: the device comprises a wavelength scanning laser, a circulator, a coupler, an optical fiber delay ring, a plurality of detection units, an optical fiber splitter, a filter, a chopper, a space collimating device, an erbium-doped optical fiber amplifier, a pump laser, a photoelectric detector, a data acquisition card and a computer system;
the circulator is a three-port optical fiber circulator, the circulator is connected with one input end of the coupler, two output ends of the coupler are respectively connected with the optical fiber delay ring and the detection unit, and the detection units are arranged in parallel and connected with the optical fiber branching unit; the circulator is also respectively connected with the wavelength scanning laser and the photoelectric detector;
the optical fiber branching device is connected with a filter, the filter is connected with the output end of the space collimating device, and a chopper is arranged in the middle of the space collimating device; the input end of the spatial collimating device is connected with the output end of the erbium-doped fiber amplifier, and the input end of the erbium-doped fiber amplifier is connected with the pump laser;
the photoelectric detector is connected with a data acquisition card, the data acquisition card is connected with a computer system, and the data acquisition card is used for acquiring the demodulated voltage signal data and transmitting the data to the computer system for signal processing and gas concentration calculation.
2. The multi-point gas detection device based on photothermal effect and wavelength division multiplexing interferometer of claim 1, wherein: the detection unit comprises a sequential wavelength division multiplexer, an absorption gas chamber, a gas sensor and a fiber bragg grating; the incident end of the wavelength division multiplexer is connected with the output end of the coupler or the reflection end of the wavelength division multiplexer of the previous detection unit, the transmission end of the wavelength division multiplexer is connected with an absorption gas chamber, the absorption gas chamber is connected with a gas sensor, and the gas sensor is connected with the fiber bragg grating; the fiber grating is connected with the fiber splitter.
3. The multi-point gas detection device based on photothermal effect and wavelength division multiplexing interferometer of claim 2, wherein: the gas sensor comprises a first collimator and a second collimator, the first collimator is arranged at the front end of the absorption gas chamber, and the second collimator is arranged at the rear end of the absorption gas chamber; and laser emitted by the first collimator passes through the absorption gas chamber, enters the second collimator and is transmitted to the fiber grating.
4. The multi-point gas detection device based on photothermal effect and wavelength division multiplexing interferometer according to claim 1, wherein: the wavelength scanning laser is a laser with tunable wavelength in a C wave band.
5. The multi-point gas detection device based on photothermal effect and wavelength division multiplexing interferometer according to claim 1, wherein: the splitting ratio of the coupler is 50: 50.
6. The multi-point gas detection device based on photothermal effect and wavelength division multiplexing interferometer according to claim 1, wherein: the pump laser is a semiconductor laser and aims at a gas absorption peak through tuning wavelength.
7. The multi-point gas detection device based on photothermal effect and wavelength division multiplexing interferometer according to claim 1, wherein: the spatial collimating device comprises a first collimator and a second collimator, and laser emitted by the first collimator enters the second collimator through the chopper and is transmitted to the filter.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN117074366A (en) * | 2023-10-12 | 2023-11-17 | 朗思传感科技(深圳)有限公司 | Gas sensing device based on micro-nano optical fiber and concentration detection method |
| WO2024145702A1 (en) * | 2023-01-04 | 2024-07-11 | Petróleo Brasileiro S.A. - Petrobrás | System and method for passive optical monitoring of the concentration of multiple gases and/or multiple parameters at multiple points |
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2022
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2024145702A1 (en) * | 2023-01-04 | 2024-07-11 | Petróleo Brasileiro S.A. - Petrobrás | System and method for passive optical monitoring of the concentration of multiple gases and/or multiple parameters at multiple points |
| CN117074366A (en) * | 2023-10-12 | 2023-11-17 | 朗思传感科技(深圳)有限公司 | Gas sensing device based on micro-nano optical fiber and concentration detection method |
| CN117074366B (en) * | 2023-10-12 | 2023-12-22 | 朗思传感科技(深圳)有限公司 | Gas sensing device based on micro-nano optical fiber and concentration detection method |
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