A gas ethanol optical fiber sensor based on tube-in-tube structure

Abstract

The present invention belongs to the field of optical fiber sensors, and relates to a gas ethanol optical fiber sensor based on a tube-in-tube structure. The tube-in-tube structure is composed of a Teflon inner tube and a PVC outer tube. A D-type multimode optical fiber is built into the Teflon inner tube, and the tube is filled with ethanol absorbent to surround the D-type multimode optical fiber. The PVC outer tube is provided with a gas inlet and outlet. The preparation method of the device mainly includes: forming a tube-in-tube structure by physical nesting; preparing a D-type optical fiber by a side grinding method, and placing it in the Teflon inner tube; preparing an ethanol absorbent by using a glycerol aqueous solution, and injecting it into the Teflon inner tube, so as to obtain a gas ethanol optical fiber sensor. The present invention utilizes the high gas permeability of the Teflon tube to realize the contact between ethanol gas and ethanol absorbent, and the refractive index change of the ethanol absorbent causes the transmission spectrum of the D-type multimode optical fiber to change. The transmission spectrum can be monitored to realize the detection of ethanol gas. The present invention has the advantages of high sensitivity, real-time, simple operation and wide measurement range.

Description

Technical Field

[0001] The invention relates to a gas ethanol sensor, in particular to a gas ethanol sensor based on a tube-in-tube structure and refractive index optical fiber sensing. Background Art

[0002] Ethanol is a commonly used fuel and disinfectant in life, and it is also widely used in traditional Chinese medicine. At present, most Chinese herbal medicines are extracted mainly using high-concentration ethanol. As an organic solvent, ethanol can extract more useful elements from Chinese herbal medicines, and its solubility in useful elements of Chinese herbal medicines is better than that of water. After soaking Chinese herbal medicines in ethanol, most of them use heating and evaporation to separate ethanol and drugs. The currently widely used standard method to judge whether ethanol has been completely separated is "no alcohol taste", that is, to use the sense of smell to feel whether ethanol is still present. This method has low accuracy. There are also electrochemical sensing methods, but this method is only applicable when the ethanol concentration is high enough, and the detection speed is slow. It is necessary to design a miniaturized and high-precision gas ethanol fast detector. Summary of the invention

[0003] In view of the above technical defects, the present invention provides a gas ethanol optical fiber sensor based on a tube-in-tube structure. The tube-in-tube structure is used to achieve indirect contact between gas and liquid. The D-type multimode optical fiber is used to detect the change in the refractive index of ethanol absorbers, and finally a gas ethanol detection system with high sensitivity, real-time, simple operation and wide measurement range is obtained.

[0004] The first purpose of the present invention is to disclose a gas ethanol optical fiber sensor based on a tube-in-tube structure, comprising a PVC outer tube, a Teflon inner tube, a D-type multimode optical fiber, an ethanol absorbent, a gas injection port and a gas exhaust port; the PVC outer tube and the Teflon inner tube form a tube-in-tube structure, the Teflon inner tube is filled with the ethanol absorbent, the D-type multimode optical fiber passes through the Teflon inner tube and retains the input and output ends, the D-type multimode optical fiber in the Teflon inner tube is surrounded by the ethanol absorbent, the two ends of the Teflon inner tube are sealed with AB glue, and the two ends of the PVC outer tube are sealed by a heating and melting collapse method; the gas ethanol to be detected is introduced between the PVC outer tube and the Teflon inner tube through the gas injection port, penetrates into the tube from the tube wall of the Teflon inner tube and is absorbed by the ethanol absorbent, the ethanol absorbent absorbs the gas ethanol and the refractive index changes, causing the transmission spectrum intensity of the D-type multimode optical fiber to change, and after reaching an equilibrium state, the concentration detection of the gas ethanol can be realized by monitoring the spectrum intensity, and after the detection is completed, the gas ethanol is discharged from the system through the gas exhaust port.

[0005] The PVC pipe of the present invention is airtight, has an inner diameter of 10 mm, an outer diameter of 16 mm and a length of 40 mm.

[0006] The Teflon inner tube of the present invention has good gas permeability, an inner diameter of 203 μm, an outer diameter of 254 μm, a length of 40 mm, and a refractive index of 1.29.

[0007] The D-type multimode optical fiber of the present invention has a cladding diameter of 125 μm, a core diameter of 105 μm, and a length of 80 mm. The D-type sensing region is made by a side polishing method, the preferred value of the core retention thickness is 72 μm, and the sensing region length is 20 mm. The light transmitted in the D-type multimode optical fiber partially leaks into the surrounding ethanol absorbent in the sensing region, and the transmission spectrum intensity is very sensitive to the refractive index change of the ethanol absorbent.

[0008] The ethanol absorbent of the present invention is obtained by mixing glycerol and degassed distilled water. Glycerol is an absorbent of ethanol and changes its refractive index after absorbing gaseous ethanol. Degassed distilled water can dilute the concentration of glycerol, with a volume fraction of 70%.

[0009] Preferably, the gas injection port is used to allow the ethanol gas to be tested to enter the sensor, and has a diameter of 5 mm.

[0010] Preferably, the gas exhaust port is used for the residual gas ethanol exhaust sensor and has a diameter of 5 mm.

[0011] The second purpose of the present invention is to disclose a preparation method of a gas ethanol optical fiber sensor based on a tube-in-tube structure, and the steps are as follows: the tube-in-tube structure is made of a PVC outer tube and a Teflon inner tube by using a physical nesting method; the D-type multimode optical fiber is prepared by a side grinding method, and the prepared D-type multimode optical fiber is passed through the Teflon inner tube and the input and output ends are retained; the ethanol absorbent is prepared by mixing glycerol and degassed distilled water, and then the ethanol absorbent is injected into the Teflon inner tube by using a syringe to surround the D-type multimode optical fiber in the Teflon inner tube, the two ends of the Teflon inner tube are sealed with AB glue, and the two ends of the PVC outer tube are sealed by a heating and melting collapse method, and finally a gas ethanol optical fiber sensor based on the tube-in-tube structure is obtained.

[0012] The D-type multimode optical fiber of the present invention is made by optical fiber side polishing method. First, a coating layer with a length of 40 mm is stripped, and then the stripped area is polished. The polishing parameters are polishing length of 20 mm, pressing depth of 43 μm, and the polishing sandpaper model loaded on the grinding wheel is 5000 mesh.

[0013] The beneficial effects of the present invention are as follows: the gas ethanol optical fiber sensor has a simple construction process, glycerol has a high absorption rate for ethanol, and can realize ethanol recovery and detection at low concentrations, and after glycerol absorbs gas ethanol and reaches a state of equilibrium, its refractive index changes significantly, overcoming the shortcomings of the limited detection range and low sensitivity of the traditional gas ethanol detector. In the field of traditional Chinese medicine, the use of the gas ethanol optical fiber sensor can realize the absorption and detection of low-concentration gas ethanol after soaking Chinese herbal medicine in ethanol. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 Schematic diagram of the tube-in-tube structure of the gas ethanol fiber optic sensor.

[0015] Figure 2 It is a schematic diagram of a specific embodiment. DETAILED DESCRIPTION

[0016] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0017] like Figure 1 , which is a schematic diagram of the tube-in-tube structure of the gas ethanol fiber optic sensor, where (1) is the PVC outer tube, (2) is the Teflon inner tube, (3) is the D-type multimode optical fiber, (4) is the ethanol absorber, (5) is the gas injection port, and (6) is the gas exhaust port.

[0018] like Figure 1 The present invention provides a method for preparing a gas ethanol optical fiber sensor based on a tube-in-tube structure, comprising: using a physical nesting method to make a PVC outer tube (1) with a length of 40 mm and a Teflon inner tube (2) with a length of 40 mm to form a tube-in-tube structure; after stripping a 40 mm multimode optical fiber coating layer of a D-type multimode optical fiber (3) using a wire stripper, placing the stripped area in a waiting area of ​​an optical fiber side polishing system, setting the polishing length of the polishing parameters to 20 mm, the pressing depth to 43 μm, and the polishing sandpaper model loaded on the grinding wheel to 5000 mesh, and then selecting to start polishing. The D-type multimode optical fiber is prepared by grinding, and the prepared D-type multimode optical fiber is passed through a Teflon inner tube (2) and the input and output ends are retained; the ethanol absorbent (4) is prepared by mixing glycerol and degassed distilled water in a volume fraction ratio of 3:7, and then the ethanol absorbent (4) is injected into the Teflon inner tube (2) using a syringe so that it surrounds the D-type multimode optical fiber (3), and the two ends of the Teflon inner tube (2) are sealed with AB glue, and the two ends of the PVC outer tube (1) are sealed by heating and melting collapse with an alcohol lamp, and finally a gas ethanol optical fiber sensor based on a tube-in-tube structure is obtained.

[0019] like Figure 2It is a specific embodiment of a gas ethanol optical fiber sensor based on a tube-in-tube structure, wherein (1) is a PVC outer tube for confining gas, (2) is a Teflon inner tube for confining liquid, and together with the PVC outer tube (1) forms a tube-in-tube structure to achieve indirect contact between gas and liquid, (3) is a D-type multimode optical fiber for optical transmission and refractive index sensing, (4) is an ethanol absorber for absorbing gas ethanol and serving as an optical indicator to convert the detected gas concentration into a refractive index change of the ethanol absorber so that it can be better detected by the optical system, (5) is a gas injection port for injecting gas ethanol into the inner tube, and its material is PVC tube, (6) is a gas exhaust port for exhausting gas ethanol, and its material is PVC tube, (7) is a gas control valve for controlling the gas injection system, (8) is an air pressure monitor for monitoring the air pressure in the PVC tube, and (9) is a gas control valve for controlling the gas exhaust system.

[0020] When implementing this example, it is necessary to pass low-concentration gas ethanol through the gas injection port (5) between the PVC outer tube (1) and the Teflon inner tube (2), close the gas control valves (7) and (9), so that the low-concentration gas is sealed in the system, and the gas pressure is monitored by the gas pressure monitor (8); since the ethanol absorber (4) is injected into the Teflon inner tube (2), after the low-concentration gas ethanol is passed, the ethanol absorber (4) will absorb the low-concentration gas ethanol, and the ethanol absorber will change its refractive index; use a broadband light source to emit signal light to the D-type multimode optical fiber (3), when the signal light passes through the D-type sensing area of ​​the D-type multimode optical fiber (3), due to the change in the refractive index of the ethanol absorber (4), the transmission spectrum intensity at the sensing area of ​​the D-type multimode optical fiber (3) will change, changing the characteristics of the signal light, and after the system reaches a balanced state, the concentration of the gas ethanol can be detected by monitoring the spectrum intensity using a spectrometer. After the system is used, the gas valve (9) is opened to allow the residual gas ethanol to be discharged from the sensor from the gas outlet (6).

[0021] Those skilled in the art clearly know that according to the method of the present invention, low-concentration gas ethanol can be detected with high precision and in real time, and can be combined and optimized in design when there is no conflict in technical features.

Claims

1. A gas ethanol optical fiber sensor based on a tube-in-tube structure, characterized in that: An airtight PVC outer tube (1) and a Teflon inner tube (2) with good gas permeability are nested to form a tube-in-tube structure. A D-type multimode optical fiber (3) passes through the Teflon inner tube (2) and retains the input and output ends. An ethanol absorbent (4) fills the Teflon inner tube (2) and surrounds the D-type multimode optical fiber (3). Both ends of the Teflon inner tube (2) are sealed with AB glue, and both ends of the PVC outer tube (1) are sealed by a heating and melting collapse method. The inner diameter of the PVC outer tube (1) is 10 mm, the outer diameter is 16 mm, and the length is 40 mm. The inner diameter of the Teflon inner tube (2) is 203 μm, the outer diameter is 254 μm, the length is 40 mm, and the refractive index is 1.

29. The cladding diameter of the D-type multimode optical fiber (3) is 125 μm, and the core is 10 μm. The diameter is 105 μm, the length is 80 mm, and the sensing area length is 20 mm; the ethanol absorbent (4) is a mixture with glycerol as an absorbent, and the volume fraction of glycerol is 30%; the gas ethanol to be measured is introduced into the space between the PVC outer tube (1) and the Teflon inner tube (2) through the gas injection port (5) on the PVC outer tube (1), penetrates into the tube from the tube wall of the Teflon inner tube (2) and is absorbed by the ethanol absorbent (4); after the ethanol absorbent (4) absorbs the gas ethanol, the refractive index changes, causing the transmission spectrum intensity of the D-type multimode optical fiber (3) to change; after reaching a balanced state, the concentration of the gas ethanol can be detected by monitoring the spectrum intensity; after the detection is completed, the gas ethanol is discharged through the gas discharge port (6) on the PVC outer tube (1).

2. A gas ethanol optical fiber sensor based on a tube-in-tube structure according to claim 1, characterized in that: The D-type sensing area of ​​the D-type multimode optical fiber (3) is manufactured by a side polishing method, and the retained fiber core thickness is 72 μm.

3. The gas ethanol optical fiber sensor based on a tube-in-tube structure according to claim 1, characterized in that: The ethanol absorbent (4) is obtained by mixing glycerol and degassed distilled water, wherein the degassed distilled water is used to dilute the glycerol, and the volume fraction is 70%.

4. The gas ethanol optical fiber sensor based on a tube-in-tube structure according to claim 1, characterized in that: The gas injection port (5) on the PVC outer tube (1) is used for introducing the gas ethanol to be tested and has a diameter of 5 mm.

5. The gas ethanol optical fiber sensor based on a tube-in-tube structure according to claim 1, characterized in that: The gas outlet (6) on the PVC outer tube (1) is used to discharge residual gas ethanol and has a diameter of 5 mm.

6. According to claim 1, a gas ethanol optical fiber sensor based on a tube-in-tube structure, the manufacturing process of which is as follows: first, a gas injection port (5) and a gas exhaust port (6) are processed on the side of a PVC outer tube (1) by a laser ablation method; secondly, the PVC outer tube (1) and the Teflon inner tube (2) are physically nested to form a tube-in-tube; then, a D-type multimode optical fiber (3) is placed in the Teflon inner tube (2); then, an ethanol absorbent (4) is injected into the Teflon inner tube (2) using a syringe to surround the D-type multimode optical fiber (3); finally, AB glue is used to seal the Teflon inner tube (2), and both ends of the PVC outer tube (1) are sealed by heating and melting the tube with an alcohol lamp.

7. The gas ethanol optical fiber sensor based on a tube-in-tube structure according to claim 1, characterized in that: The D-type multimode optical fiber (3) is manufactured by using an optical fiber side polishing method, wherein a coating layer having a length of 40 mm is firstly stripped off, and then the stripped area is polished, wherein the polishing parameters are a polishing length of 20 mm, a pressing depth of 43 μm, and a polishing sandpaper model loaded on the grinding wheel having a mesh size of 5000.

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