CN114659701B - Highly sensitive air pressure sensor for rapid desorption of gas and preparation method thereof - Google Patents

Abstract

The invention discloses a high-sensitivity air pressure sensor for rapid gas desorption, which is characterized in that it includes a first single-mode optical fiber, a first multi-mode optical fiber, a special-shaped optical fiber with a concave open cavity, a second multi-mode optical fiber and a The second single-mode optical fiber; wherein, the special-shaped optical fiber is an optical fiber with a concave open cavity, and the concave open cavity is filled with a gas-sensitive material, and there are porous materials in the gas-sensitive material; the light is incident from the first single-mode optical fiber and passes through the third A multi-mode optical fiber enters the gas-sensitive material and the special-shaped optical fiber to form two optical paths of the MZI. The invention can realize the refractive index response of the optical path of the MZ gas-sensitive material to the gas pressure and simultaneously realize the rapid desorption of the gas-sensitive material to the gas, improve the measurement sensitivity and gas desorption efficiency of the sensor, and realize high-sensitivity measurement of rapid desorption.

Description

Highly sensitive air pressure sensor for rapid desorption of gas and preparation method thereof

Technical field

The invention belongs to the technical field of optical fiber sensing and communication, and specifically relates to a high-sensitivity air pressure sensor that quickly desorbs gas and a preparation method thereof.

Background technique

Fiber optic air pressure sensors are very important equipment in the fields of industrial and environmental monitoring. Over the past few decades, MZ interferometers (MZI, Mach-Zehnder interferometer) based on optical paths of various materials have shown good potential in pressure sensing applications. Common fiber optic pressure sensors include grating type, MZ type, etc. As for the grating type, the grating is usually used as the sensitive unit, which converts changes in external gas pressure into expansion of the grating area position, that is, changes in grating pitch, thus bringing about Spectral shift. Since changes in air pressure cause the optical fiber (main material to be SiO2) to deform very little, the sensitivity of this sensor is usually not high, such as 240pm/MPa, 137pm/MPa and 0.1pm/MPa. Measuring changes in gas pressure with an MZ sensor is nothing more than converting changes in external air pressure into changes in the refractive index of the MZ air path.

There are two main types of MZ-based air pressure sensors. One is the MZ open-cavity air pressure sensor based on pure quartz structure. Its air path is connected to the outside world. When the air pressure changes, it will cause the air refractive index to change, which will cause spectral drift. It is used to measure Changes in air pressure. There is also an MZ air pressure sensor based on film materials. When the external air pressure changes, the refractive index of the material's optical path will change. That is, the spectral drift caused by the change of the material's refractive index as the air pressure changes, to achieve the measurement of air pressure.

However, most of the existing air pressure sensors are based on a single parameter of the refractive index of gas-sensitive materials or gases, which are sensitive to air pressure, but it is difficult for gas-sensitive materials to desorb gases.

Contents of the invention

The present invention aims to solve the problem that existing air pressure sensors are sensitive to air pressure based on a single parameter of the refractive index of gas-sensitive materials or gases and that the gas-sensitive materials are difficult to desorb gases, and provide a high-sensitivity air pressure sensor that quickly desorbs gas and a preparation method thereof. , the optical path of the optical fiber MZ gas-sensitive material is sensitive to air pressure and has a short gas desorption time. It is small in size and has high sensitivity. Its preparation method is simple, easy and low-cost.

The technical solution adopted by the present invention is:

Provides a high-sensitivity air pressure sensor that quickly desorbs gas, including a first single-mode optical fiber, a first multi-mode optical fiber, a special-shaped optical fiber, a second multi-mode optical fiber and a second single-mode optical fiber connected in sequence;

Among them, the special-shaped optical fiber is an optical fiber with a concave open cavity, and the concave open cavity is filled with a gas-sensitive material, and the gas-sensitive material contains a porous material; light is incident from the first single-mode optical fiber and enters the gas-sensitive material through the first multi-mode optical fiber. and special-shaped optical fibers to form the two optical paths of MZI.

Following the above technical solution, the cross-section of the special-shaped optical fiber is groove-shaped.

Following the above technical solution, the cross-section of the special-shaped optical fiber is crescent-shaped.

Following the above technical solution, the gas-sensitive material is a mixture of PDMS and porous materials, with a thickness of 60 to 80 microns.

Following the above technical solution, the gas-sensitive material is a mixture of PDMS and MOF, COF or zeolite.

Following the above technical solution, the gas-sensitive material is completely filled in the concave open cavity, and the gas-sensitive material is connected to the outside world.

Following the above technical solution, the depth of the concave open cavity is 60 to 80 microns, and the bottom thickness of the special-shaped optical fiber is 65 to 85 microns.

Following the above technical solution, among the gas-sensitive materials, the mass ratio of PDMS to porous materials is 85:11~18:1.

The invention also provides a method for manufacturing a high-sensitivity air pressure sensor that quickly desorbs gas, including the following steps:

(1) Use a cutting knife to cut out the flat end faces of the special-shaped optical fiber with a concave open cavity and the multi-mode optical fiber after removing the coating layer. Splice the two ends of the special-shaped optical fiber with the multi-mode optical fiber respectively, and then re-splice the multi-mode optical fiber at both ends. Spliced with single-mode optical fiber to form a fiber interferometer structure;

(2) Fix the prepared optical fiber interferometer structure on the glass piece with UV glue, with the concave open cavity of the special-shaped optical fiber facing upward;

(3) Fill the gas-sensitive material solution into the concave open cavity of the special-shaped optical fiber and heat to solidify.

The present invention also provides a test system for optical fiber sensors. The test system includes a broadband light source, a pressure sensor, and a fiber spectrometer connected in sequence. The pressure sensor is placed in a pressure chamber, and the pressure sensor is the fast desorption gas of the above technical solution. Highly sensitive air pressure sensor.

The beneficial effects produced by the present invention are: the present invention injects the gas-sensitive material into the open cavity of the special-shaped optical fiber as a light path medium, and fuses the special-shaped optical fiber with the multi-mode optical fiber. The light forms two paths of MZ in the special-shaped optical fiber and the gas-sensitive material. Optical path; when the external air pressure increases, the refractive index of the gas-sensitive material increases. Since porous materials are added to the gas-sensitive material, when the air pressure decreases, its refractive index can quickly desorb gas to the initial state, accelerating the gas-sensing process. The material desorbs gas, so the present invention can realize the refractive index response of the optical path of the MZ gas-sensitive material to the gas pressure and simultaneously realize the rapid desorption of the gas-sensitive material to the gas, improve the measurement sensitivity of the sensor and the gas desorption efficiency, and achieve rapid desorption. Attached high sensitivity measurement.

Description of the drawings

The present invention will be further described below in conjunction with the accompanying drawings and examples. In the accompanying drawings:

Figure 1 is a schematic structural diagram of a high-sensitivity air pressure sensor that quickly desorbs gas according to an embodiment of the present invention;

Figure 2 is a schematic diagram of the testing system of the optical fiber sensor according to the embodiment of the present invention;

Figure 3 is a schematic cross-sectional view of several special-shaped optical fibers with different open cavities.

In the picture: 1. Single-mode optical fiber, 2. Multi-mode optical fiber, 3. Special-shaped optical fiber, 4. Gas-sensitive material, 5. Crescent-shaped optical fiber, 6. High-sensitivity air pressure sensor, 7. Light source, 8. Pressure chamber, 9. spectrometer.

Detailed ways

In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention and are not intended to limit the present invention.

The invention provides a high-sensitivity air pressure sensor that quickly desorbs gas, which can realize that the MZ gas-sensitive material is sensitive to air pressure and can quickly desorb gas, thereby greatly improving the sensitivity of the air pressure sensor and the desorption gas efficiency.

The high-sensitivity air pressure sensor that quickly desorbs gas in the embodiment of the present invention includes a single-mode optical fiber 1, a multi-mode optical fiber 2, a special-shaped optical fiber 3, and a gas-sensitive material 4. Both ends of the special-shaped optical fiber 3 are connected to the multi-mode optical fiber 2 through fusion splicing. One end of the two single-mode optical fibers 1 are connected to the multi-mode optical fiber 2 through fusion splicing. The special-shaped optical fiber 3 has a concave open cavity. Fill the gas-sensitive material 4 (the gas-sensitive material 4 contains porous material) to form an optical fiber interferometer structure, which can be fixed on the glass sheet. The gas-sensitive material 4 communicates with the external environment, and light passes through the gas-sensitive material 4 and The special-shaped optical fiber 3 forms the two optical paths of the MZ.

The sensor of the present invention contains porous materials in the gas-sensitive material, that is, performs porosity modification to increase its porosity to improve the problem of difficult gas desorption of traditional gas-sensitive materials. At the same time, the refractive index of the gas-sensitive material itself changes with the air pressure. As an optical path, it can not only improve the sensitivity of the sensor but also shorten the desorption time of the gas-sensitive material to the gas. The gas-sensitive material is filled in the concave open cavity of the special-shaped optical fiber. Together with the special-shaped optical fiber, it constitutes the two optical paths of the MZ. The open cavity is connected to the outside world. When the external air pressure changes, the gas enters the photosensitive material from the special-shaped open cavity, causing its refractive index to change. Therefore, the present invention breaks through the existing problems of low pressure sensitivity of pure quartz structure and difficulty in gas desorption when combined with photosensitive materials. It constructs a mixed porous material as an optical path, which can effectively improve the pressure sensitivity while shortening the desorption of gases by gas-sensitive materials. Attached time.

In a preferred embodiment of the present invention, the single-mode optical fiber 1 has a core diameter of 8.2 microns and an outer diameter of 125 microns.

The gas-sensitive material 4 is a porous material, and the rate of change of its refractive index with the change of air pressure is about -2.1×10 ^-2 RIU per MPa. The gas-sensitive material matrix can be PDMS (polydimethylsiloxane), which is used as a cross-linking agent, and porous materials are added to it and solidified to form a hybrid material. The porous materials used to increase porosity include metal-organic frameworks (MOF), covalent-organic frameworks (COF), zeolites and other materials. The porous materials are added to the PDMS solution and used Mix evenly with a magnetic stirrer and then inject it into the open cavity of the special-shaped optical fiber with a thickness of 60-80 microns.

The material of the porous material is zeolite, MOF or COF material, where the mass ratio of PDMS: porous material is 85:11 to 18:1.

The cross-section of the special-shaped optical fiber can be designed into a crescent shape or other shapes (as shown in Figure 3). In a preferred embodiment of the present invention, the diameter of the crescent-shaped optical fiber is 125 microns, and the diameter of the open cavity is 60-80 microns. The thickness of the bottom of the special-shaped optical fiber (and crescent-shaped bottom) is 65 to 85 microns.

The multimode optical fiber 2 has a core diameter of 105 microns, an outer diameter of 125 microns, and a length of 1 mm.

In one embodiment of the present invention, a method for preparing a highly sensitive air pressure sensor that quickly desorbs gas includes the following steps:

(1) Use a cutting knife to cut out the flat end faces of the special-shaped optical fiber with a concave open cavity and the multi-mode optical fiber after removing the coating layer. Splice the two ends of the special-shaped optical fiber with the multi-mode optical fiber respectively, and then fuse the multi-mode optical fiber with the single-mode optical fiber. Mode fiber (such as tapered single-mode fiber) is welded to form a fiber interferometer structure;

(2) Fix the prepared optical fiber interferometer structure on the glass piece with UV glue, with the open cavity opening of the special-shaped optical fiber facing upward;

(3) Fill the open cavity of the special-shaped optical fiber with the uniformly mixed gas-sensitive material solution, and heat and solidify; the light passes through the cured gas-sensitive material and the special-shaped optical fiber to form two optical paths respectively.

Among them, the gas-sensitive material solution is obtained by weighing PDMS and porous materials respectively with a balance according to a certain mass ratio, then adding the porous material to the PDMS solution, and mixing it evenly with a magnetic stirrer.

Taking the crescent-shaped optical fiber 5 as an example, another embodiment of the present invention provides a method for preparing a high-sensitivity air pressure sensor that quickly desorbs gas, including the following steps:

S1. Use a cutting knife to cut the flat end faces of the crescent-shaped optical fiber and the multi-mode optical fiber with the coating layer removed. Splice the two ends of the crescent-shaped optical fiber with the multi-mode optical fiber respectively, and then fuse the multi-mode optical fiber with the tapered single-mode optical fiber. welding;

S2. Fix the prepared optical fiber interferometer structure on the glass piece with UV glue, with the open cavity of the crescent-shaped optical fiber facing upward;

S3. Weigh the PDMS and porous materials with a balance according to a certain mass ratio, then add the porous material into the PDMS solution and mix it evenly with a magnetic stirrer;

S4. Fill the evenly mixed gas-sensitive material solution into the open cavity of the crescent-shaped optical fiber, and heat and solidify it.

S5. After the light is cured, the gas-sensitive material and the crescent-shaped optical fiber form two optical paths respectively.

It can be seen that the preparation method of the present invention is simple and easy to implement. Two different optical fibers are welded together by cutting and welding, and then the gas-sensitive material is filled in the open cavity of the crescent-shaped optical fiber. This not only protects the gas-sensitive material, but also protects the gas-sensitive material to a great extent. The sensitivity is improved and the desorption time of gas by gas-sensitive materials is shortened.

Figure 2 is a schematic diagram of the test system of the optical fiber sensor of the present invention. The test system includes a broadband light source 7, a pressure chamber 8, a fiber spectrometer 9 and the high-sensitivity air pressure sensor 6 of the above embodiment. The high-sensitivity air pressure sensor 6 mainly includes a single-mode optical fiber 1 , the multimode optical fiber 2 connected to the single-mode optical fiber 1, the special-shaped optical fiber 3 connected to the multi-mode optical fiber, the open cavity of the special-shaped optical fiber 3 is filled with gas-sensitive material 4 and is connected to the outside world. When the external air pressure changes, The gas enters the inside of the photosensitive material 4 from the open cavity of the special-shaped optical fiber 3, causing its refractive index to change and causing spectral drift. One end of the single-mode optical fiber 1 is connected to a broadband light source 7 and the other end is connected to a fiber spectrometer 9 . A high-sensitivity air pressure sensor 6 that quickly desorbs gas is placed in the air pressure chamber 8 .

As shown in Figure 2, during the air pressure sensing experiment, a high-sensitivity air pressure sensor 6 that quickly desorbs gas is sealed in the air pressure chamber 8. The gas in the air pressure chamber is formed by the special-shaped optical fiber 3 (taking the crescent-shaped optical fiber 5 as an example). The open cavity enters the gas-sensitive material 4. When the light emitted by the broadband light source enters the high-sensitivity air pressure sensor 6 based on fast desorption gas, part of the light will be transmitted in the gas-sensitive material 4, and the other part of the light will be transmitted in the crescent-shaped optical fiber 5. , two beams of transmitted light meet and interfere.

The total reflected light intensity of the two reflected lights is:

Where φ _MZI is the phase difference between the two output lights. When φ _MZI is an odd multiple of π, I _MZI takes the minimum value, which is reflected in the interference spectrum as a trough, which can be expressed as:

where Δn _eff is the effective refractive index difference of the light mode transmitted in the crescent optical fiber 5 and the gas-sensitive material 4, and l is the length of the crescent optical fiber 5

From formula (2) we can get:

where q is a positive integer. Since Δn _eff and l change with the air pressure and have a functional relationship, the air pressure sensitivity expression can be obtained according to equation (3):

It is manifested in the drift of the spectral peak in the fiber spectrometer. By measuring the drift of the output center wavelength, the sensing measurement of air pressure can be achieved.

It should be understood that those skilled in the art can make improvements or changes based on the above description, and all these improvements and changes should fall within the protection scope of the appended claims of the present invention.

Claims (10)

1. A high-sensitivity air pressure sensor that quickly desorbs gas, characterized in that it includes a first single-mode optical fiber, a first multi-mode optical fiber, a special-shaped optical fiber, a second multi-mode optical fiber and a second single-mode optical fiber connected in sequence; Among them, the special-shaped optical fiber is an optical fiber with a concave open cavity, and the concave open cavity is filled with a gas-sensitive material, and the gas-sensitive material contains a porous material; light is incident from the first single-mode optical fiber and enters the gas-sensitive material through the first multi-mode optical fiber. and special-shaped optical fibers to form the two optical paths of MZI. 2. The high-sensitivity air pressure sensor for rapid gas desorption according to claim 1, characterized in that the cross-section of the special-shaped optical fiber is groove-shaped. 3. The high-sensitivity air pressure sensor for rapid gas desorption according to claim 1, characterized in that the cross-section of the special-shaped optical fiber is crescent-shaped. 4. The high-sensitivity air pressure sensor for rapid gas desorption according to claim 1, characterized in that the gas-sensitive material is a mixture of PDMS and porous materials, with a thickness of 60 to 80 microns. 5. The high-sensitivity air pressure sensor for rapid gas desorption according to claim 1, wherein the gas-sensitive material is a mixture of PDMS and MOF, COF or zeolite. 6. The high-sensitivity air pressure sensor for rapid gas desorption according to claim 1, characterized in that the gas-sensitive material is completely filled in the concave open cavity, and the gas-sensitive material is connected to the outside world. 7. The high-sensitivity air pressure sensor for rapid gas desorption according to claim 1, characterized in that the depth of the concave open cavity is 60-80 microns, and the bottom thickness of the special-shaped optical fiber is 65-85 microns. 8. The high-sensitivity air pressure sensor for rapid gas desorption according to claim 4, wherein the mass ratio of PDMS to porous material in the gas-sensitive material is 85:11 to 18:1. 9. A method for manufacturing a high-sensitivity air pressure sensor that quickly desorbs gas, which is characterized by including the following steps: (1) Use a cutting knife to cut out the flat end faces of the special-shaped optical fiber with a concave open cavity and the multi-mode optical fiber with the coating layer removed, and fuse the two ends of the special-shaped optical fiber with the multi-mode optical fiber respectively, and then the multi-mode optical fiber at both ends are re-spliced. Spliced with single-mode optical fiber to form a fiber interferometer structure; (2) Fix the prepared optical fiber interferometer structure on the glass piece with UV glue, with the concave open cavity of the special-shaped optical fiber facing upward; (3) Fill the gas-sensitive material solution containing porous materials into the concave open cavity and heat to solidify. 10. A test system for optical fiber sensors, characterized in that the test system includes a broadband light source, an air pressure sensor, and an optical fiber spectrometer connected in sequence, the air pressure sensor is placed in an air pressure chamber, and the air pressure sensor is as claimed in claims 1-8 The high-sensitivity air pressure sensor for rapid desorption of gas according to any one of the above.