Gas detection light path structure and gas detection sensor

Abstract

The utility model discloses a gas detection optical path structure and gas detection sensor wherein the gas detection optical path structure comprises: a reference optical path with a first optical waveguide and a detection optical path with a second optical waveguide, on the optical transmission path, the first optical waveguide comprises a directional coupling part and a reference part in order, and the detection optical path comprises a second optical waveguide. The second optical waveguide sequentially comprises an optical coupling part, a transmission part and a detection part; the reference part and the detection part are slot waveguides; the optical coupling part is used for coupling a laser beam, the input end of the transmission part is connected with the optical coupling part and is used for receiving the laser beam, the directional coupling part is coupled with the transmission part and is used for coupling a reference beam, and the output end of the transmission part is connected with the detection part and is used for outputting a detection beam; the reference part is located in a reference gas environment and is used for outputting a reference test light beam; the detection part is located in the detection gas environment and used for outputting the detection test light beam, and the accuracy of the detection result is improved.

Description

Technical Field

[0001] The utility model relates to the technical field of sensors, in particular to a gas detection optical path structure and a gas detection sensor. Background Technique

[0002] With the development of China's power industry, especially remarkable achievements have been made in UHV and smart grid. Therefore, many substations of high-voltage and UHV levels have been built. In substations, pure SF6 gas is often filled in gas-insulated metal-enclosed switchgear (GIS) to improve arc extinguishing and insulation capabilities. However, due to internal defects of GIS equipment and other problems, SF6 will react with impurities such as O2 and H2O in the gas to generate various gas decomposition products. The long-term accumulation of these gas decomposition products will reduce the purity of SF6 gas. In addition, since some of the decomposition product gases are corrosive, the long-term existence will pose a threat to the safety of high-voltage equipment. Therefore, it is necessary to monitor the operation of GIS equipment to timely understand the status of GIS equipment.

[0003] In related technologies, gas sensors are generally used to monitor the status of GIS equipment by detecting various gas decomposition products generated by the reaction of SF6 with impurities such as O2 and H2O in the gas. Gas sensors generally include off-line detection devices, tunable diode absorption spectroscopy sensors, and cavity ring-down spectroscopy technology sensors. However, the problems are that off-line detection devices cannot detect in real time, and the baseline may be inconsistent each time; sensors prepared based on absorption spectrum detection have high costs; sensors prepared based on cavity ring-down spectroscopy have complex system structures, require multiple mirrors to cooperate, and the mirrors are easily contaminated, resulting in inaccurate detection. Summary of the Utility Model

[0004] The utility model provides a gas detection optical path structure and a gas detection sensor to realize on-line detection of GIS equipment, reduce the cost of gas sensors, and improve the accuracy of detection results.

[0005] To achieve the above object, the first aspect embodiment of the utility model provides a gas detection optical path structure, including: a reference optical path and a detection optical path. The reference optical path includes a first optical waveguide, and the detection optical path includes a second optical waveguide; on the optical transmission path, the first optical waveguide sequentially includes a directional coupling part and a reference part, and the second optical waveguide sequentially includes an optical coupling input part, a transmission part, and a detection part; both the reference part and the detection part are slot waveguides.

[0006] Among them, the optical coupler input part is used to couple in a laser beam. The input end of the transmission part is connected to the optical coupler input part and is used to receive the laser beam. The directional coupler is coupled with the transmission part, and the directional coupler is used to couple in a reference beam. The output end of the transmission part is connected to the detection part and is used to output a detection beam. The reference part is located in a reference gas environment and is used to output a reference test beam based on the interaction between the reference beam and the reference gas. The detection part is located in a detection gas environment and is used to output a detection test beam based on the interaction between the detection beam and the detection gas.

[0007] Optionally, the gas detection optical path structure further includes a mode spot converter. The input end of the mode spot converter is connected to the output end of the transmission part, and the output end of the mode spot converter is connected to the input end of the detection part.

[0008] Optionally, along the direction of light transmission, the diameter of the input end of the optical coupler input part is smaller than that of the output end.

[0009] Optionally, the relationship between the diameter D and the length L of the optical coupler input part satisfies: D = k×L 2 +b, where k and b are constants.

[0010] Optionally, the transmission part is a straight waveguide, and the diameter of the straight waveguide is the same as that of the output end of the optical coupler input part.

[0011] Optionally, the gap range of the slot waveguide is 0.1um to 0.5um.

[0012] Optionally, the shape of the detection part is one of a spiral shape, a wavy shape, or a taiji diagram shape.

[0013] Optionally, when the detection part is in a wavy shape, the detection part includes a linear waveguide arranged in parallel with at least one of the transmission parts and an arc waveguide part for connecting between the linear waveguides.

[0014] Optionally, the distance between adjacent linear waveguides is smaller than the diameter of the arc waveguide part.

[0015] To achieve the above object, a second aspect embodiment of the present invention proposes a gas detection sensor, including at least one group of the gas detection optical path structures according to any embodiment of the present invention, and further including: a processor, at least one group of lasers, a first photodetector, and a second photodetector;

[0016] The output end of the laser is connected to the optical coupler input part in the corresponding gas detection optical path structure and is used to output a laser beam;

[0017] The first photodetector is connected to the output end of the reference part in the corresponding gas detection optical path structure, and is used to convert the reference test beam into a reference electrical signal;

[0018] The second photodetector is connected to the output end of the detection part in the corresponding gas detection optical path structure, and is used to convert the detection test beam into a detection electrical signal;

[0019] The processor includes a first input end, a second input end and a result output end. The first input end is connected to the first photodetector in each group, the second input end is connected to the second photodetector in each group, and the result output end is used to output the detection result.

[0020] According to the gas detection optical path structure and the gas detection sensor proposed by the embodiments of the present invention, the gas detection optical path structure includes: a reference optical path and a detection optical path. The reference optical path includes a first optical waveguide, and the detection optical path includes a second optical waveguide; on the optical transmission path, the first optical waveguide sequentially includes a directional coupling part and a reference part, and the second optical waveguide sequentially includes an optical coupling input part, a transmission part and a detection part; both the reference part and the detection part are slot waveguides; the optical coupling input part is used to couple in a laser beam, the input end of the transmission part is connected to the optical coupling input part and is used to receive the laser beam, the directional coupling part is coupled with the transmission part, and the directional coupling part is used to couple in a reference beam. The output end of the transmission part is connected to the detection part and is used to output a detection beam; the reference part is located in a reference gas environment and is used to output a reference test beam based on the interaction between the reference beam and the reference gas; the detection part is located in a detection gas environment and outputs a detection test beam based on the interaction between the detection beam and the detection gas. Thus, the gas detection sensor can obtain the concentration of the detection gas based on the light intensity of the reference test beam, the light intensity of the detection test beam and the concentration of the reference gas. And, through the setting of the reference optical path, the problem of inaccurate results caused by the aging of the detection optical path can be avoided. The setting of the slot waveguide increases the contact area between the waveguide and the gas, which is beneficial to improving the accuracy of the detection result.

[0021] It should be understood that the content described in this part is not intended to identify the key or important features of the embodiments of the present invention, nor is it used to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. Description of the Drawings

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0023] Figure 1 It is a schematic diagram of the gas detection optical path structure proposed by an embodiment of the present utility model;

[0024] Figure 2 It is a partial schematic diagram of the gas detection optical path structure proposed by an embodiment of the present utility model;

[0025] Figure 3 It is a schematic diagram of the relationship between the slit width, the cladding confinement factor, and the optical loss in an embodiment of the present utility model;

[0026] Figure 4 It is a schematic diagram of the relationship between the waveguide width, the cladding confinement factor, and the optical loss in an embodiment of the present utility model;

[0027] Figure 5 It is a cross-sectional schematic diagram of the slit waveguide in an embodiment of the present utility model;

[0028] Figure 6 It is the optical energy distribution diagram of the slit waveguide in an embodiment of the present utility model;

[0029] Figure 7 It is a block schematic diagram of the gas detection sensor proposed by an embodiment of the present utility model. Detailed implementation manners

[0030] In order to enable those skilled in the art to better understand the solution of the present utility model, the technical solutions in the embodiments of the present utility model will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present utility model. Obviously, the described embodiments are only a part of the embodiments of the present utility model, rather than all the embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present utility model.

[0031] It should be noted that the terms "first", "second", etc. in the specification and claims of the present utility model and the above-mentioned drawings are used to distinguish similar objects, and do not necessarily need to describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances so that the embodiments of the present utility model described herein can be implemented in an order different from those illustrated or described herein.

[0032] With the development of China's power industry, especially the remarkable achievements in UHV and smart grid, many substations at high voltage and UHV levels have been built. In substations, pure SF6 gas is often filled in Gas Insulated Switchgear (GIS) to improve arc extinguishing and insulation capabilities. However, due to internal defects of GIS equipment and other problems, SF6 will react with impurities such as O2 and H2O in the gas to produce various gas decomposition products. The long-term accumulation of these gas decomposition products will reduce the purity of SF6 gas. In addition, since some of the decomposition product gases are corrosive, their long-term existence will pose a threat to the safety of high-voltage equipment.

[0033] Due to the excellent electrical properties of sulfur hexafluoride (SF6) gas, pure SF6 (>99.8%) gas is usually filled in electrical equipment as a super-high-voltage gas insulation dielectric material, such as in Gas Circuit Breakers (GCBs), Gas Insulated Switchgear (GIS), Gas Insulated Transformers (GIT), Gas Insulated Lines (GIL), etc. However, once an insulation fault occurs in the power equipment, the high-temperature arc, electric spark and corona generated by the discharge will cause the SF6 gas to decompose, generating various low-fluoride sulfides such as SF2, SF3, SF4 and S2F 10 and other low-fluoride sulfides. These sulfides will react with trace amounts of water vapor and oxygen in the SF6 gas to form gas derivatives such as HF, SOF4, SOF2, SO2F2, SO2, CO, H2S, CF4, etc., which will have a strong corrosive effect on the metal and insulating materials inside the electrical equipment, thereby accelerating the degradation of the insulation performance and ultimately leading to sudden failures of the equipment. In addition, the long-term accumulation of gas derivatives will reduce the purity of SF6 gas and affect the insulation performance of electrical equipment.

[0034] In related technologies, in order to monitor the operating status of GIS, some off-line SF6 gas decomposition product sensors are used in high-voltage electric fields. However, off-line detection equipment has poor real-time performance and requires human participation, which cannot meet the real-time on-line monitoring needs of power plants. Currently, off-line SF6 gas decomposition product analyzers mainly adopt the principle of electrochemical sensors and have been able to detect the concentrations of gas components such as SO2 and CO in SF6 gas. However, the baseline of this sensor is inconsistent every time it is turned on, requiring a long time of gas path purging. In addition, the performance of the sensor needs to be calibrated every few months, and the gas inspection results of the same instrument for the same gas cylinder are different at different times, which brings troubles to the safety monitoring of GIS equipment.

[0035] However, the problem is that the baseline of this sensor is inconsistent every time it is turned on, requiring a long time of gas path purging. In addition, the performance of the sensor needs to be calibrated every few months, and the gas inspection results of the same instrument for the same gas cylinder are different at different times, which brings troubles to the safety monitoring of GIS equipment.

[0036] In addition, in recent years, tunable diode laser absorption spectroscopy (TDLAS) technology has the advantages of good stability, no need to consume carrier gas, high sensitivity, and the ability to measure multi-component gases, and has been widely used in the fields of trace gas detection, environmental monitoring, etc. In recent years, it has gradually been introduced into the detection of dissolved gases in transformer insulating oil. Using a tunable diode laser as the light source, this laser can adjust the output wavelength within a certain range to make it consistent with the characteristic absorption wavelength of the target gas. The laser passes through the gas sample to be measured. The gas molecules in the sample absorb the laser at a specific wavelength. After the laser passes through the sample, the light intensity will decrease, and the detector measures the laser intensity after passing through the sample. According to Lambert-Beer's law, by measuring the absorption degree of the laser at a specific wavelength, the concentration of the gas can be calculated.

[0037] However, the problems it has are that high-precision tunable diode lasers and high-sensitivity detectors are expensive, and the overall system cost is high. Regular calibration and maintenance are required to ensure measurement accuracy. It is sensitive to environmental conditions. Changes in temperature, pressure, and humidity may affect the measurement results, and compensation for environmental parameters is required. For some gases, there may be no suitable laser wavelength for detection, or the absorption characteristics are not obvious, which limits its application range. Due to the characteristics of sulfur hexafluoride (SF6) such as a relative molecular mass of 146.05, a relative density 5.1 times that of air, and the existence of continuous and dense spectral absorption lines in the infrared region (>3μm) for high-concentration SF6 molecules, many gas sensors using nitrogen (N2) or air as the carrier gas are not applicable to the case of using SF6 as the carrier gas, and it is necessary to specifically design SF6-derived gas sensors suitable for high-voltage power systems.

[0038] Furthermore, cavity ring-down spectroscopy (CRDS) is a high-sensitivity spectroscopic technique used to measure the components and concentrations in gases and liquids. In a CRDS system, a high-reflectivity optical cavity is used, which is usually composed of two high-reflectivity mirrors. The laser reflects multiple times between these two mirrors to form an optical cavity. A short-pulse laser is injected into the optical cavity. When the laser pulse reflects back and forth in the optical cavity, due to the presence of absorbing substances in the optical cavity, the light intensity will decay with time. After each reflection, a small amount of light leaks out of the optical cavity, and the detector measures the intensity of this leaked light and records its decay curve over time. By analyzing the decay time of the light intensity (i.e., the ring-down time), the concentration of the absorbing substances in the optical cavity can be obtained. The shorter the ring-down time, the stronger the absorption, that is, the higher the gas concentration.

[0039] However, the problems are that the cost of mirrors with high reflectivity and precise devices such as lasers and detectors is relatively high, making the price of the CRDS system high. The system structure is relatively complex and requires precise optical alignment and stable control. It is sensitive to changes in environmental conditions and requires control and compensation of parameters such as temperature, pressure, and humidity to ensure the accuracy of measurement. The mirrors with high reflectivity are easily contaminated, affecting the measurement accuracy, so regular maintenance and cleaning are required.

[0040] Therefore, the present utility model proposes a gas detection optical path structure and a gas detection sensor to achieve on-line detection of GIS equipment, reduce the cost of gas sensors, and improve the accuracy of detection results.

[0041] Figure 1 It is a schematic diagram of the gas detection optical path structure proposed by an embodiment of the present utility model. As Figure 1 shown, the gas detection optical path structure 01 includes: a reference optical path 02 and a detection optical path 03. The reference optical path 02 includes a first optical waveguide 100, and the detection optical path 03 includes a second optical waveguide 200. On the light transmission path, the first optical waveguide 100 sequentially includes a directional coupling portion 101 and a reference portion 102, and the second optical waveguide 200 sequentially includes an optical coupling input portion 201, a transmission portion 202, and a detection portion 203. Both the reference portion 102 and the detection portion 203 are slot waveguides;

[0042] Among them, the optical coupling input portion 201 is used to couple in a laser beam. The input end of the transmission portion 202 is connected to the optical coupling input portion 201 and is used to receive the laser beam. The directional coupling portion 101 is coupled with the transmission portion 202. The directional coupling portion 101 is used to couple in a reference beam. The output end of the transmission portion 202 is connected to the detection portion 203 and is used to output a detection beam. The reference portion 102 is located in a reference gas environment and is used to output a reference test beam based on the interaction between the reference beam and the reference gas. The detection portion 203 is located in a detection gas environment and outputs a detection test beam based on the interaction between the detection beam and the detection gas.

[0043] It should be noted that the gas detection optical path structure 01 can be arranged on a substrate 04, and the substrate 04 can be a silicon substrate. The input end of the optical coupling input portion 201 is used to connect to a laser and receive the laser beam emitted by the laser, and output it to the transmission portion 202. After the transmission of the transmission portion 202, an evanescent field is formed between the transmission portion 202 and the directional coupling portion 101. Furthermore, coupling is formed between the directional coupling portion 101 and the transmission portion 202. A part of the light beam in the transmission portion 202 coupled by the directional coupling portion 101 forms a reference beam and is transmitted to the reference portion 102, and the remaining part of the light beam in the transmission portion 202 forms a detection beam and is transmitted to the detection portion 203. In one embodiment, the coupling splitting ratio between the directional coupling portion 101 and the transmission portion 202 is less than 1:2.

[0044] The reference section 102 can be placed in a box of reference gas. The reference beam in the reference section 102 interacts with the reference gas, and the reference section 102 outputs a reference test beam. The detection section 203 is exposed to the detection gas environment. The detection beam in the detection section 203 interacts with the detection gas, and the detection section 203 outputs a detection test beam. Among them, the concentration of the reference gas is known. When the light intensities of the detection test beam and the reference test beam are known, the concentration of the detection gas can be obtained.

[0045] It can be understood that both the reference section 102 and the detection section 203 are slot waveguides. The slots can be filled with the corresponding gas. The setting of the slot waveguides can confine most of the optical field between two parallel strip waveguides. When the width of the slot is within a certain range, the cladding confinement factor can be maximized. Among them, the cladding confinement factor is defined as the proportion of the mode power staying in the air cladding, as a measure of the light-matter interaction through the evanescent field. Continuing to refer Figure 1 , Figure 1 The filled part in it is the slot filled with gas. The optical coupler input section 201, the transmission section 202, and the directional coupling section 101 all include cladding waveguides, and the reference section 102 and the detection section 203 are both two parallel waveguides. In this way, the interaction degree between the optical field in the sensing waveguide region of the first optical waveguide 100 and the second optical waveguide 200 and the gas can be improved. At the same time, the reference section 102 and the detection section 203 are simultaneous in time, such as aging simultaneously. Furthermore, compared with the concentration of the detection gas obtained according to the pre-calibrated relationship, the present invention can obtain the reference light intensity of the reference section 102 with the same aging degree as the detection section 203 in real time, so that the accuracy of the detection result is higher.

[0046] Optionally, referring to Figure 2 as shown, the gas detection optical path structure 01 further includes a mode spot converter 300. The input end of the mode spot converter 300 is connected to the output end of the transmission section 202, and the output end of the mode spot converter 300 is connected to the input end of the detection section 203.

[0047] Among them, by setting the mode spot converter 300, the detection beam output by the transmission section 202 can be coupled into the slot waveguide (detection section 203) as efficiently as possible. In the light transmission direction, the length of the mode spot converter 300 is not less than 10um.

[0048] Optionally, referring to Figure 1 and Figure 2 as shown, along the light transmission direction, the diameter of the input end of the optical coupler input section 201 is smaller than the diameter of the output end.

[0049] Among them, in order to efficiently couple an external laser signal to the second optical waveguide 200, a waveguide region with a nonlinearly tapered waveguide width, i.e., the optical coupling input portion 201, can couple a laser signal with a larger mode field diameter into the chip and achieve adiabatic transmission (where adiabatic transmission has no direct relation with heat and temperature. In optics, adiabatic transmission is a process of energy or information transfer through a non-equilibrium state process inside the system without exchanging energy with the outside world). Thus, the coupling efficiency can be improved and the loss can be reduced.

[0050] Optionally, the relationship between the diameter D and the length L of the optical coupling input portion 201 satisfies: D = k × L 2 + b, where k and b are constants. According to the above relationship, the edge of the optical coupling input portion 201 is in a parabolic shape. Compared with a straight edge, making the edge of the optical coupling input portion in a parabolic shape is beneficial to increasing the coupling efficiency of the input laser.

[0051] Among them, the length L of the optical coupling input portion 201 is usually not less than 100 um, and k and b can be obtained by simulation and calculation according to the actual situation.

[0052] Optionally, the transmission portion 202 is a straight waveguide, and the diameter of the straight waveguide is the same as the diameter of the output end of the optical coupling input portion 201.

[0053] Among them, the transmission portion 202 is a straight waveguide structure with a constant width, which is beneficial to coupling with the directional coupling portion 101. The proportion of the light beam coupled into the directional coupling portion 101 is less than 50% of the laser beam, and the proportion of the light beam output by the transmission portion 202 is more than 50% of the laser beam.

[0054] Optionally, the gap range of the slot waveguide is 0.1 um to 0.5 um.

[0055] Among them, there is a corresponding relationship between the gap width of the slot waveguide, the waveguide width, and the cladding confinement factor. Figure 3 It is a schematic diagram of the relationship between the gap width, the cladding confinement factor, and the optical loss in the embodiment of the present utility model. Figure 4 It is a schematic diagram of the relationship between the waveguide width, the cladding confinement factor, and the optical loss in the embodiment of the present utility model. Figure 5 It is a cross-sectional schematic diagram of the slot waveguide in the embodiment of the present utility model. Refer to Figure 3 、 Figure 4 and Figure 5 As shown, the cladding confinement factor is the proportion of the mode power staying in the air cladding. Since the cladding confinement factor can reflect the ability of the interaction between light and gas, the larger the cladding confinement factor, the better. As can be seen from Figure 3 , when the gap width S1 is 0.2 um, the optical loss is the lowest and the cladding confinement factor is the largest. As can be seen from Figure 4It can be seen that when the gap width S1 is 0.2 um and the waveguide width S2 is 0.52 um, the cladding confinement factor is maximally 48%, and the optical loss is almost zero. Therefore, in the embodiments of the present utility model, it is preferably that the gap width S1 is 0.2 um and the waveguide width S2 is 0.52 um to ensure the maximum interaction between the detection part 203 and the detected gas. It should be noted that the current mature commercial silicon photonics CMOS process limits the waveguide gap processing ability to 0.2 um. If a higher process is adopted, the gap between waveguides can be further reduced.

[0056] Figure 6 is the optical energy distribution diagram of the slot waveguide of the embodiments of the present utility model. As Figure 6 shown, the stronger the optical energy, the redder the color, and the weaker the optical energy, the bluer the color. As can be seen from Figure 6 , during the transmission of light in the slot waveguide, the optical energy is concentrated in the gap between the two waveguides, and the light and the gas can interact fully.

[0057] Optionally, the shape of the detection part 203 is one of a spiral shape, a wavy shape, or a taiji diagram shape. Among them, setting the detection part 203 as one of the above shapes can increase the contact area between the detection part 203 and the detected gas, thereby improving the accuracy of the detection result.

[0058] Optionally, as Figure 1 shown, when the detection part 203 is in a wavy shape, the detection part 203 includes a linear waveguide 2031 arranged in parallel with at least one transmission part 202 and an arc waveguide part 2032 for connecting between the linear waveguides.

[0059] Among them, by winding between the linear waveguide 2031 and the arc waveguide part 2032 to form a wavy S shape, the detection area of the detection part 203 is increased. Furthermore, the interaction area between the detection part 203 and the detected gas is increased. As shown in Figure 1 , the setting between the two arc waveguide parts 2032 can avoid the light between adjacent arc waveguide parts 2032 from interfering with each other. And it enables the bending of the second optical waveguide 200, reducing the volume of the detection part 203 while increasing the interaction area.

[0060] Optionally, the distance between adjacent linear waveguides 2031 is less than the diameter of the arc waveguide part 2032. In one embodiment, when the total length of the second optical waveguide 200 is 10 cm, the radius of the arc waveguide part 2032 is greater than 30 um. This can avoid the arc waveguide part 2032 from breaking and leaking light. The distances between adjacent linear waveguides 2031 can be the same, which is beneficial for process fabrication.

[0061] Figure 7It is a block diagram of the gas detection sensor proposed by the embodiments of the present utility model. As Figure 7 shown, the gas detection sensor includes at least one group of gas detection optical path structures 01 of any embodiment of the present utility model, and further includes: a processor 05, at least one group of lasers 06, a first photodetector 07, and a second photodetector 08;

[0062] The output end of the laser 06 is connected to the optical coupling input part 201 in the corresponding gas detection optical path structure 01 for outputting a laser beam;

[0063] The first photodetector 07 is connected to the output end of the reference part 102 in the corresponding gas detection optical path structure 01 for converting the reference test beam into a reference electrical signal;

[0064] The second photodetector 08 is connected to the output end of the detection part 203 in the corresponding gas detection optical path structure 01 for converting the detection test beam into a detection electrical signal;

[0065] The processor 05 includes a first input end 051, a second input end 052, and a result output end 053. The first input end 051 is connected to the first photodetector 07 in each group, the second input end 052 is connected to the second photodetector 08 in each group, and the result output end 053 is used for outputting the detection result.

[0066] It should be noted that multiple groups of gas detection optical path structures 01, as well as the corresponding lasers 06, first photodetectors 07, and second photodetectors 08, can be provided in the gas detection sensor to adapt to different gas detections. Exemplarily, taking two groups as an example, one group can be used to detect CO gas, and one group can detect SO2 gas. Since the wavelength ranges of the spectral absorption spectra corresponding to the two gases are different, furthermore, different lasers 06 are required to output lasers with different wavelengths, and the corresponding reference parts 102 are encapsulated in boxes filled with different reference gases, and the purity of the reference gas is 100%.

[0067] It can be understood that taking CO gas as an example to introduce the working principle of the gas detection sensor of the present utility model, the laser 06 outputs laser with a central wavelength of 2334 nm, which is coupled with the gas detection optical path structure 01 through an optical fiber. After passing through the gas detection optical path structure 01, a detection test beam and a reference test beam are output. The first photodetector 07 is coupled with the gas detection optical path structure 01 through an optical fiber to convert the optical signal of the reference test beam into a reference electrical signal. The second photodetector 08 is coupled with the gas detection optical path structure 01 through an optical fiber to convert the optical signal of the detection test beam into a detection electrical signal. The processor 05 is electrically connected to the first photodetector 07 and the second photodetector 08. Based on Lambert-Beer's law, the reference electrical signal, the detection electrical signal, and the concentration of the reference gas CO, the concentration of CO in the detected gas in the environment can be obtained.

[0068] By setting multiple groups of gas detection optical path structures 01, as well as the lasers 06, the first photodetectors 07, and the second photodetectors 08 corresponding to the gas detection optical path structure 01, the concentrations of multiple gases can be measured simultaneously. In practical applications, the number of groups can be set according to requirements and costs.

[0069] Thus, the gas detection sensor proposed in the embodiment of the present utility model uses the optical interaction between the gas to be detected and the sensing waveguide for real-time online monitoring, and the surface does not need to be cleaned repeatedly. And a reference optical path is set as a real-time reference, without the need for repeated calibration and compensation. Moreover, the gas detection optical path structure, as a sensing system, is designed and manufactured in a silicon substrate chip, with a small volume, easy to install, easy to integrate into other systems, low manufacturing cost, and low use and maintenance costs.

[0070] In another embodiment, the role of the reference beam can also be to detect the initial light intensity of the light source, to avoid large errors in the results caused by changes in light intensity due to different environments.

[0071] In summary, according to the gas detection optical path structure and gas detection sensor proposed by the embodiments of the present invention, the gas detection optical path structure includes: a reference optical path and a detection optical path. The reference optical path includes a first optical waveguide, and the detection optical path includes a second optical waveguide. On the optical transmission path, the first optical waveguide sequentially includes a directional coupling portion and a reference portion, and the second optical waveguide sequentially includes an optical coupling input portion, a transmission portion, and a detection portion. Both the reference portion and the detection portion are slot waveguides. The optical coupling input portion is used to couple in a laser beam. The input end of the transmission portion is connected to the optical coupling input portion and is used to receive the laser beam. The directional coupling portion is coupled to the transmission portion. The directional coupling portion is used to couple in a reference beam. The output end of the transmission portion is connected to the detection portion and is used to output a detection beam. The reference portion is located in a reference gas environment and is used to output a reference test beam based on the interaction between the reference beam and the reference gas. The detection portion is located in a detection gas environment and is used to output a detection test beam based on the interaction between the detection beam and the detection gas. Thus, the gas detection sensor can obtain the concentration of the detection gas based on the light intensity of the reference test beam, the light intensity of the detection test beam, and the concentration of the reference gas. Moreover, by setting the reference optical path, the problem of inaccurate results caused by the aging of the detection optical path can be avoided. The setting of the slot waveguide increases the contact area between the waveguide and the gas, which is beneficial to improving the accuracy of the detection result.

[0072] The above specific embodiments do not constitute a limitation to the protection scope of the present invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A gas detection optical path structure, characterized in that: include: A reference optical path and a detection optical path, wherein the reference optical path comprises a first optical waveguide, and the detection optical path comprises a second optical waveguide; on the optical transmission path, the first optical waveguide comprises a directional coupling portion and a reference portion in sequence, and the second optical waveguide comprises an optical coupling portion, a transmission portion, and a detection portion in sequence; both the reference portion and the detection portion are slot waveguides; The optical coupling part is used to couple in a laser beam, the input end of the transmission part is connected to the optical coupling part for receiving the laser beam, the directional coupling part is coupled to the transmission part, the directional coupling part is used to couple in a reference beam, and the output end of the transmission part is connected to the detection part for outputting a detection beam; The reference part is located in a reference gas environment, and is used to output a reference test beam based on the interaction between the reference beam and the reference gas; the detection part is located in a detection gas environment, and is used to output a detection test beam based on the interaction between the detection beam and the detection gas.

2. The gas detection optical path structure according to claim 1, characterized in that: It also includes a pattern spot converter, wherein the input end of the pattern spot converter is connected to the output end of the transmission part, and the output end of the pattern spot converter is connected to the input end of the detection part.

3. The gas detection optical path structure according to claim 1, characterized in that: Along the direction of light transmission, the diameter of the input end of the light coupling portion is smaller than the diameter of the output end.

4. The gas detection optical path structure according to claim 3, characterized in that: The relationship between the diameter D and the length L of the light coupling portion satisfies: D = k × L 2 +b, where k and b are constants.

5. The gas detection optical path structure according to claim 1, characterized in that: The transmission part is a straight waveguide, and the diameter of the straight waveguide is the same as the diameter of the output end of the light coupling part.

6. The gas detection optical path structure according to claim 1, characterized in that: The slot waveguide has a slot range of 0.1 um to 0.5 um.

7. The gas detection optical path structure according to claim 1 or 6, characterized in that: The shape of the detection part is one of a spiral shape, a wave shape or a Tai Chi diagram shape.

8. The gas detection optical path structure according to claim 7, characterized in that: When the detection portion is in a wave shape, the detection portion includes a linear waveguide arranged in parallel with at least one of the transmission portions and an arc waveguide portion for connecting the linear waveguides.

9. The gas detection optical path structure according to claim 8, characterized in that: The distance between adjacent linear waveguides is smaller than the diameter of the arc-shaped waveguide portion.

10. A gas detection sensor, characterized in that: The method comprises at least one group of gas detection optical path structures according to any one of claims 1 to 9, and further comprises: a processor, at least one group of lasers, a first photodetector and a second photodetector; The output end of the laser is connected to the optical coupling portion corresponding to the gas detection optical path structure, and is used to output a laser beam; The first photodetector is connected to an output end corresponding to the reference portion in the gas detection optical path structure, and is used to convert a reference test light beam into a reference electrical signal; The second photoelectric detector is connected to the output end of the detection part in the gas detection optical path structure, and is used to convert the detection test light beam into a detection electrical signal; The processor includes a first input terminal, a second input terminal and a result output terminal, the first input terminal is connected to the first photodetector in each group, the second input terminal is connected to the second photodetector in each group, and the result output terminal is used to output the detection result.

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