An optical fiber, an infrared optical fiber sensor, a preparation method and an application thereof

Abstract

The present invention discloses an optical fiber, an infrared optical fiber sensor, a preparation method and an application thereof, belonging to the technical field of spectral analysis and detection. The optical fiber of the present invention includes an end portion and an intermediate portion. The intermediate portion includes a flat tapered portion and a flat waist portion. The end portion is connected to the flat waist portion through the flat tapered portion, and at least one side between the flat tapered portion and the flat waist portion is in an inclined angle structure. The optical fiber in the present invention and the preparation method of the infrared optical fiber sensor including the optical fiber are simple and have strong practicability. Moreover, the infrared optical fiber sensor has high sensitivity and can not only perform qualitative analysis on substances but also perform quantitative analysis on low-concentration substances. Therefore, it has broad application prospects in the field of high-sensitivity biological and chemical sensing.

Description

Technical Field

[0001] The present invention belongs to the technical field of spectral analysis and detection, and particularly relates to an optical fiber, an infrared optical fiber sensor, a preparation method and an application thereof. Background Art

[0002] The analysis of chemical substances plays an extremely important role in various monitoring fields such as atmospheric science, petrochemical industry, clinical diagnosis, food inspection, etc. The mid-infrared (IR) region covers the fundamental vibration region of compounds, and the vibration mode of each molecule is unique, so it is also called the "fingerprint region". By analyzing the characteristic absorption generated by molecules in the infrared spectrum, infrared spectroscopy can be used for qualitative and quantitative analysis of organic substances quickly, economically and nondestructively. However, in complex analysis, due to the low precision of infrared spectrum quantitative analysis, usually greater than 1%, it is difficult to be applied. And high-sensitivity detection techniques, such as attenuated total reflection (ATR) technique, have high costs, which makes the introduction of this technique in fields such as routine clinical practice an obstacle.

[0003] Infrared optical fiber sensing detection is a brand-new infrared spectrum sampling detection technique. Because the working wavelength covers the fundamental vibration region of compounds, it will be applicable to the detection of various substances, especially organic liquids. Compared with the attenuated total reflection (ATR) sampling technique, infrared optical fiber sensing detection has lower costs, higher flexibility and higher sensitivity. Based on the principle of total internal reflection of light and the principle of evanescent wave, this technique has been applied in fields such as early disease diagnosis and various molecular recognition. The generation of evanescent wave is due to the continuity of electromagnetic waves. When light propagates in an optical fiber, it will briefly leak out of the reflection plane to form an evanescent wave and then return to the optical fiber. In this process, the sample selectively absorbs light with specific wavelengths in the incident light frequency region, that is, characteristic absorption, and generates a spectrum similar to the absorption, so as to obtain the structural information of chemical components in the sample. In order to improve the sensitivity and enhance the interaction between the substance and the evanescent wave, the penetration depth dp of the evanescent wave should be increased. The equation of dp can be expressed as:

[0004]

[0005] Where λ i and θ i are respectively the wavelength and the incident angle of the incident light, and n 1 and n 2 are respectively the refractive indices of the optical fiber and the surrounding medium (i.e., the substance to be measured).

[0006] Although mid-infrared optical fiber evanescent wave sensors have been applied in many fields, there are still problems such as being easily broken during use, poor practicability and low sensitivity. Summary of the Invention

[0007] The object of the present invention is to provide an optical fiber, an infrared optical fiber sensor, a preparation method and an application thereof. The optical fiber in the infrared optical fiber sensor of the present invention has a flat structure, so the penetration depth of the evanescent wave of the optical fiber and the number of times of light emission in the optical fiber are increased, and the sensitivity of the sensor is greatly improved.

[0008] In a first aspect, the present invention provides an optical fiber, which includes an end portion and an intermediate portion. The intermediate portion includes a flat tapered portion and a flat waist portion. The end portion is connected to the flat waist portion through the flat tapered portion, and at least one side between the flat tapered portion and the flat waist portion is in an inclined angle structure.

[0009] In some embodiments, the taper angle between the flat tapered portion and the flat waist portion is 2.5° to 11.5°, for example, it can be 2.5°, 4.5°, 5.6°, 6.5°, 8.5°, 11.5° or other values within this range.

[0010] In the present invention, there is no limitation on the length of the intermediate portion, the thickness and width of the flat waist portion, and the diameter of the end portion, and they can be adjusted according to actual usage conditions. When the optical fiber is used in a sensor, the above parameters of the optical fiber can be adjusted according to the size of the sensor. For example, the length of the intermediate portion is 8 to 27 mm, for example, it can be 8 mm, 11 mm, 14 mm, 17 mm, 20 mm, 23 mm, 23.8 mm, 27 mm or other values within this range; the thickness of the flat waist portion is 100 to 300 μm, for example, it can be 100 μm, 110 μm, 140 μm, 170 μm, 200 μm, 215 μm, 234 μm, 235 μm, 250 μm, 270 μm, 300 μm or other values within this range; the width is 0.1 to 2 mm; for example, it can be 0.1 mm, 0.5 mm, 0.7 mm, 0.9 mm, 1.1 mm, 1.5 mm, 2.0 mm or other values within this range; the diameter of the end portion is 150 to 1000 μm, for example, it can be 150 μm, 250 μm, 350 μm, 450 μm, 550 μm, 650 μm, 750 μm, 850 μm, 1000 μm or other values within this range.

[0011] In some embodiments, the optical fiber is an infrared glass optical fiber, and the infrared glass optical fiber is selected from at least one of Ge-As-Se-Te chalcogenide glass, As-Se chalcogenide glass or Ge-As-Se chalcogenide glass.

[0012] In the optical fiber provided by the present invention, the optical fiber can transmit 850 - 4000 cm -1 mid-infrared light, for example, it can be 850 cm -1 mid-infrared light, 1000 cm -1 mid-infrared light, 1500 cm -1 mid-infrared light, 2000 cm-1 Mid-infrared light, 2500 cm -1 Mid-infrared light, 3000 cm -1 Mid-infrared light, 3500 cm -1 Mid-infrared light, 4000 cm -1 Mid-infrared light or mid-infrared light with other values within this range.

[0013] In a second aspect, the present invention provides an infrared fiber optic sensor, which includes the optical fiber described in any one of the above.

[0014] In some embodiments, the infrared fiber optic sensor further includes a liquid cell and a curing agent. The liquid cell is provided with a through groove and a flow channel. The flow channels are respectively arranged at both ends of the liquid cell and are connected through the groove. The optical fiber is arranged in the groove and the flow channel, and the curing agent is filled in the flow channel for fixing the end of the optical fiber to the liquid cell.

[0015] In some embodiments, the curing agent is selected from UV curable glue or epoxy resin; the material for preparing the liquid cell is selected from at least one of polylactic acid (PLA), acrylonitrile-butadiene-styrene copolymer (ABS), or photosensitive resin.

[0016] It should be noted that the material for preparing the liquid cell in the present invention includes but is not limited to polylactic acid (PLA), acrylonitrile-butadiene-styrene copolymer (ABS), or photosensitive resin, and it can also be other conventional materials in the prior art.

[0017] In some embodiments, a handle is further provided on the liquid cell. By setting the handle, it is convenient to pick up and place the liquid cell, and the liquid cell will not be damaged.

[0018] In a third aspect, the present invention provides a method for preparing the above-described infrared fiber optic sensor, which includes the following steps:

[0019] 1) Process the above infrared glass optical fiber into an optical fiber preform, and use a drawing process (for example, it can be placed in a drawing tower) to draw the optical fiber preform into an optical fiber with a diameter of 150 - 1000 μm (for example, it can be 150 μm, 200 μm, 300 μm, 400 μm, 500 μm, 600 μm, 700 μm, 800 μm, 900 μm, 1000 μm or other values within this range);

[0020] 2) Provide a hot pressing mold with the same structure as the middle part of the above optical fiber, place the optical fiber obtained in step 1) (for example, the length can be 4 - 10 cm, further, it can be 4 cm, 5 cm, 6 cm, 7 cm, 8 cm, 9 cm, 10 cm or other values within this range) in the hot pressing mold, place an aluminum block on the hot pressing mold, and then place it in a muffle furnace for heat treatment to obtain the above optical fiber;

[0021] 3) Place the optical fiber obtained in step 2) on an optical fiber taper machine for local scanning heating to obtain an optical fiber with a smooth surface; Optionally, use the optical fiber taper machine to stretch the optical fiber obtained in step 2) in the same direction to obtain an elongated optical fiber;

[0022] 4) Use 3D software to model the above liquid cell, and then prepare the liquid cell by 3D printing technology;

[0023] 5) Place the optical fiber obtained in step 3) into the liquid cell obtained in step 4), and fix and encapsulate it with a curing agent;

[0024] 6) Use a polishing machine to polish the end face of the encapsulated optical fiber to obtain an infrared optical fiber sensor.

[0025] In the preparation method provided by the present invention, in step 2), the hot pressing die can be made according to the size structure of the middle part of the optical fiber. By controlling the temperature, time, and weight of the aluminum block during the heat treatment, the thickness and width of the flat waist of the optical fiber can be controlled. In step 3), the smoother the smooth optical fiber, the more significantly the loss during the sensing process can be reduced.

[0026] In the fourth aspect, the present invention provides a detection system, which includes any one of the above infrared optical fiber sensors, as well as an infrared light source, a ZnSe lens, an MCT liquid nitrogen cooling detector, and a Fourier transform infrared spectrometer.

[0027] In the detection system provided by the present invention, the infrared optical fiber sensor, the infrared light source, the ZnSe lens, the MCT liquid nitrogen cooling detector, and the Fourier transform infrared spectrometer can be combined and set in a conventional detection manner. For example, the infrared light source, the ZnSe lens, the infrared optical fiber sensor, the MCT liquid nitrogen cooling detector, and the Fourier transform infrared spectrometer are connected in sequence. And, optionally, a ZnSe lens can also be provided between the infrared optical fiber sensor and the MCT liquid nitrogen cooling detector, which can further play a role in focusing light and improve the detection accuracy.

[0028] In the fifth aspect, the present invention provides a method for detecting using the above detection system, which includes the following steps:

[0029] S1. Optical path adjustment: Turn on the Fourier transform infrared spectrometer, adjust the infrared light source to the external optical path mode of the Fourier transform infrared spectrometer, place the infrared optical fiber sensor in the optical path, and adjust the positions of the external optical path MCT liquid nitrogen cooling detector and the infrared optical fiber sensor through a three-dimensional displacement stage to achieve the best signal, so that the focused infrared light is fully coupled into the end face of the optical fiber;

[0030] S2. Background scanning: Scan the infrared absorption spectrum of the infrared optical fiber sensor as the background signal for detection;

[0031] If the liquid to be measured is a known solution, then proceed to step S3:

[0032] S3. Sensitivity and minimum detection limit calibration: Prepare several groups of standard concentration liquids to be measured, use a Fourier transform infrared spectrometer to collect the infrared absorption spectra of the standard concentration liquids to be measured one by one, and establish a linear relationship. The slope is the fiber optic sensitivity, and the lowest detectable concentration is the minimum detection limit;

[0033] Alternatively, if the liquid to be measured is an unknown solution, then proceed to steps S4, S5, and S6:

[0034] S4. Qualitative analysis of unknown substances: Drop the unknown solution into the liquid cell of the infrared fiber optic sensor, collect its infrared absorption spectrum, and compare it with the standard infrared spectrum. After analysis, obtain the composition information of the unknown substance;

[0035] S5. According to the composition information of the unknown substance obtained in step S4, use the method in step S3 to calibrate its sensitivity and minimum detection limit;

[0036] S6. Quantitative analysis of unknown substances: Drop the unknown solution into the liquid cell of the infrared fiber optic sensor, collect its infrared absorption spectrum, and calculate the concentration of the liquid according to the relationship between the concentration - characteristic absorption peak height of the standard liquid established in step S5.

[0037] In the detection method provided by the present invention, the detection method is based on infrared spectroscopy, and the substances that can be detected include those that can cause transitions between vibrational energy levels and rotational energy levels in molecules and absorb infrared light of specific wavelengths in the range of 850 - 4000 cm -1 range.

[0038] In some embodiments, in step S3, the linear relationship is obtained by selecting characteristic absorption peaks with relatively large absorption intensities according to the standard infrared spectrum of the liquid to be measured, then using the Lambert - Beer law to calculate and establish the relationship between the concentration of the standard liquid and the height of its characteristic absorption peak, and finally through fitting.

[0039] In some embodiments, the detection sensitivity of ethanol using the detection system of the present invention is 0.0011 - 0.0275 (a.u. / %), the detection sensitivity of sodium benzoate is 0.0101 - 0.122 (a.u. / %), and the detection sensitivity of potassium sorbate is 0.1153 - 0.2462 (a.u. / %).

[0040] Compared with the prior art, the present invention has the following advantages:

[0041] 1) Compared with the evanescent wave sensor based on the ATR element, the evanescent wave sensor based on the infrared fiber in the present invention has higher sensitivity and lower cost;

[0042] 2) Compared with the evanescent wave sensor based on quartz fiber, the evanescent wave sensor based on infrared fiber of the present invention has a wider working range and can provide more molecular structure information;

[0043] 3) Compared with the infrared fiber evanescent wave sensor based on tapered fiber, the evanescent wave sensor based on infrared fiber of the present invention has a larger sensing area and is easy to prepare a functional coating on the flat fiber surface;

[0044] 4) The preparation method of the infrared fiber sensor of the present invention is simple and has strong practicability; moreover, the infrared fiber sensor of the present invention further improves the sensitivity, can not only perform qualitative analysis on substances, but also perform quantitative analysis on low-concentration substances, and has broad application prospects in the field of high-sensitivity biological and chemical sensing. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 It is a schematic diagram of the sensing principle of the infrared fiber sensor in the present invention;

[0046] Figure 2 It is a schematic diagram of the structure of the infrared fiber sensor in the present invention;

[0047] Figure 3 It is a schematic diagram of the structure of the fiber hot pressing device in the present invention, wherein (A) is a schematic diagram of the structure of the single-sided hot pressing device, and (B) is a schematic diagram of the structure of the double-sided hot pressing device;

[0048] Figure 4 It is a cross-sectional view of the fiber in the present invention, wherein (A) is a cross-sectional view of the single-sided hot pressed fiber, and (B) is a cross-sectional view of the double-sided hot pressed fiber;

[0049] Figure 5 It is an infrared absorption spectrum diagram of ethanol aqueous solutions with five volume concentrations established in Example 1 of the present invention;

[0050] Figure 6 It is a graph showing the relationship between the absorption peak heights at 975 cm -1 and 1150 cm -1 of the infrared fiber sensor (the fiber is Ge-As-Ga-Se chalcogenide glass) established in Example 1 of the present invention and the volume concentration of the ethanol aqueous solution;

[0051] Figure 7 It is a comparison diagram of the infrared spectrum of an unknown solution detected by the infrared fiber sensor (the fiber is Ge-As-Se-Te chalcogenide glass) established in Example 7 of the present invention and the standard infrared spectrum of potassium sorbate;

[0052] Figure 8This is the relationship between the absorption peak height and the molar concentration of the infrared fiber optic sensor (the optical fiber is Ge-As-Se-Te chalcogenide glass) established in Example 7 of the present invention in the aqueous solution of potassium sorbate at 1391.6 cm- 1 and the concentration calibration diagram of the solution with unknown concentration;

[0053] The reference signs in the figure have the following meanings:

[0054] 1: optical fiber; 10: end; 11: middle part; 110: flat cone part; 111: flat waist part; 112: cone angle; 2: liquid cell; 20: groove; 21: flow channel; 22: handle; 3: curing agent; 4: upper mold; 5: aluminum block; 6: glass plate; 7: lower mold. Detailed implementation manners

[0055] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0056] For the experimental methods without specific conditions noted in the embodiments, they are usually carried out according to the conventional conditions and the conditions described in the manuals, or according to the conditions recommended by the manufacturers. For the general equipment, materials, reagents, etc., if not otherwise specified, they can be obtained from commercial channels.

[0057] Unless otherwise clearly defined and limited, the terms "installation", "connection", "connection", "fixation" should be understood in a broad sense. For example, it can be a fixed connection or a detachable connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the internal communication of two components or the interaction relationship between two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0058] Please refer to Figure 1 , which is the sensing principle diagram of the infrared fiber optic sensor in the present invention. The infrared light source after being condensed by the ZnSe lens is coupled into the infrared fiber optic sensor, and an evanescent wave is generated on the fiber surface. The sample to be measured is dropped into the liquid cell to fully contact the fiber and absorb the evanescent wave on the fiber surface, obtaining an infrared spectrogram similar to the transmission absorption, so as to obtain the structural information of the chemical composition of the sample. According to the obtained infrared spectrum, the sample can be directly qualitatively identified and analyzed, or the quantitative concentration of the sample can be detected according to the Lambert-Beer absorption law.

[0059] Continue to refer to Figures 2 - 4 , Figure 2An infrared fiber optic sensor provided by the present invention. The infrared fiber optic sensor includes an optical fiber 1, a liquid cell 2, and a curing agent 3. The liquid cell 2 is provided with a through groove 20 and a flow channel 21. The flow channels 21 are respectively arranged at both ends of the liquid cell 2 and are connected through the groove 20. At the same time, a handle 22 is also provided. The optical fiber is arranged in the groove 20 and the flow channel 21, and the curing agent 3 is filled in the flow channel 21 for fixing the end 10 of the optical fiber to the liquid cell 2.

[0060] Figure 3 A fiber optic hot pressing device provided by the present invention. The hot pressing device includes an optical fiber 1 to be hot pressed, an upper mold 4, an aluminum block 5, and a glass plate 6. During use, the optical fiber 1 is placed on the glass plate 6, and then the upper mold 4 is placed at the corresponding position of the optical fiber 1, and the aluminum block 5 is placed on the upper mold 4. By controlling the weight of the aluminum block 5 and the temperature and time of the hot pressing process, the single-sided hot pressed optical fiber as shown in Figure 4 Figure A can be obtained. For double-sided hot pressing, only a lower mold 7 needs to be placed between the optical fiber 1 and the glass plate 6 to obtain the double-sided hot pressed optical fiber as shown in Figure 4 Figure B.

[0061] Figure 4 A cross-sectional view of an optical fiber provided by the present invention. Among them, the taper angle 112 is an acute angle formed between the flat taper part 110 and the flat waist part 111. Figure 4 Figure A is a schematic diagram of the taper angle 112 formed by single-sided hot pressing, Figure 4 Figure B is a schematic diagram of the taper angle 112 formed by double-sided hot pressing.

[0062] Example 1

[0063] An infrared fiber optic sensor, as shown in Figure 2 Figure, includes an optical fiber 1, a liquid cell 2, and a curing agent 3. The liquid cell 2 is provided with a through groove 20 and a flow channel 21. The flow channels 21 are respectively arranged at both ends of the liquid cell 2 and are connected through the groove 20. At the same time, a handle 22 is also provided. The optical fiber is arranged in the groove 20 and the flow channel 21, and the curing agent 3 is filled in the flow channel 21 for fixing the end 10 of the optical fiber to the liquid cell 2.

[0064] The preparation method of the infrared fiber optic sensor includes the following steps:

[0065] 1) Process a Ge-As-Ga-Se chalcogenide glass into an optical fiber preform, and use a fiber drawing tower to draw the optical fiber preform into an optical fiber with a diameter of 500 μm;

[0066] 2) Take an 8-cm long optical fiber and place it in a single-sided hot pressing mold ( Figure 3In A), the taper angle of this mold is 5.6°, and the waist length is 18 mm. The mold is placed in a muffle furnace, and 3 aluminum blocks of 25 g are placed on the hot-pressing mold. It is kept warm at 285 °C for 15 min, taken out after cooling, and the fiber optic with a taper angle of 5.6° for the flat cone part 110, a thickness of 215 μm for the flat waist 111, a waist length of 18 mm, and a total length of 23.8 mm for the middle part is obtained;

[0067] 3) After the pressing is completed, the fiber optic is locally scanned and heated on a fiber optic taper machine to obtain a fiber optic with a smooth surface;

[0068] 4) Model according to the geometric dimensions of the fiber optic prepared in step 3) using solidworks software, and use polylactic acid (PLA) as the printing material to print out the liquid cell 2;

[0069] 5) Put the fiber optic prepared in step 3) into the liquid cell 2 prepared in step 4), fix and encapsulate it with the UV curable adhesive curing agent 3, and cut off the excess part of the fiber optic so that the end face of the fiber optic is flush with the end face of the liquid cell 2;

[0070] 6) Use a polishing machine to polish the end face of the encapsulated fiber optic to a mirror finish to obtain an infrared fiber optic sensor.

[0071] Use a detection system including the above infrared fiber optic sensor, infrared light source, ZnSe lens, MCT liquid nitrogen cooling detector, and Fourier transform infrared spectrometer for detection. The specific detection method includes the following steps:

[0072] S1. Optical path adjustment: Turn on the Fourier transform infrared spectrometer, adjust the infrared light source to the external optical path mode of the Fourier transform infrared spectrometer, place the Ge-As-Ga-Se chalcogenide glass fiber optic sensor in the optical path, and adjust the positions of the external optical path MCT liquid nitrogen cooling detector and the Ge-As-Ga-Se chalcogenide glass infrared fiber optic sensor through a three-dimensional displacement stage to make the focused infrared light fully coupled into the end face of the fiber optic to achieve the best signal;

[0073] S2. Background scanning: Set the spectrometer resolution to 8 cm -1 , set the number of scans to 32 times, and scan the infrared absorption spectrum of the Ge-As-Ga-Se chalcogenide glass fiber optic sensor as the background signal;

[0074] S3. Sensitivity calibration: Use an ethanol aqueous solution as the test solution, measure the relationship between the absorption peak height of the infrared fiber optic at the characteristic absorption wavelength of the ethanol aqueous solution and the concentration of the ethanol aqueous solution, and establish a concentration-absorption peak height curve. The specific operation steps are as follows: Drop ethanol aqueous solutions with five volume concentrations (10%, 30%, 50%, 70%, 90%) into the liquid cell 2 of the sensor respectively to make the infrared fiber optic fully contact with the ethanol aqueous solution, and obtain asFigure 5 The infrared spectrogram shown. Measure the relationship between the absorption peak height of the infrared optical fiber at 1045.1 cm in the ethanol aqueous solution -1 and the volume concentration of the ethanol aqueous solution, and establish the concentration-absorption peak surface height curve as Figure 6 shown. The slope thereof is the detection sensitivity of the infrared optical fiber sensor based on the Ge-As-Ga-Se chalcogenide glass optical fiber to ethanol in the ethanol aqueous solution, and the sensitivity is 0.00275 (a.u. / %).

[0075] Example 2

[0076] An infrared optical fiber sensor, as Figure 2 shown, includes an optical fiber 1, a liquid cell 2 and a curing agent 3. The liquid cell 2 is provided with a through groove 20 and a flow channel 21. The flow channels 21 are respectively arranged at both ends of the liquid cell 2 and are communicated through the groove 20. At the same time, a handle 22 is also provided. The optical fiber is arranged in the groove 20 and the flow channel 21, and the curing agent 3 is filled in the flow channel 21 for fixing the end portion 10 of the optical fiber to the liquid cell 2.

[0077] The preparation method of the infrared optical fiber sensor includes the following steps:

[0078] 1) Process the Ge-As-Ga-Se chalcogenide glass into an optical fiber preform, and use a fiber drawing tower to draw the optical fiber preform into an optical fiber with a diameter of 500 μm;

[0079] 2) Take an 8-cm-long optical fiber and place it in a single-sided hot pressing mold ( Figure 3 A). The cone angle of this mold is 11.5°, and the waist length is 21 mm. Place the mold in a muffle furnace, place 3 aluminum blocks of 25 g on the hot pressing mold, keep it warm at 285 °C for 15 min, take it out after cooling, and obtain an optical fiber with a cone angle of 11.5° for the flat cone part 110, a thickness of 215 μm for the flat waist 111, a waist length of 21 mm, and a total length of 23.8 mm for the middle part;

[0080] 3) After the pressing is completed, the optical fiber is locally scanned and heated on an optical fiber taper machine to obtain an optical fiber with a smooth surface;

[0081] 4) Model according to the geometric dimensions of the optical fiber prepared in step 3) using solidworks software, and print out the liquid cell 2 with polylactic acid (PLA) as the printing material;

[0082] 5) Put the optical fiber prepared in step 3) into the liquid cell 2 prepared in step 4), fix and encapsulate it with the UV curing glue curing agent 3, and cut off the excess part of the optical fiber so that the end face of the optical fiber is flush with the end face of the liquid cell 2;

[0083] 6) Use a polishing machine to polish the end face of the encapsulated optical fiber until a mirror effect is achieved, obtaining an infrared optical fiber sensor.

[0084] Use a detection system including the above infrared optical fiber sensor, infrared light source, ZnSe lens, MCT liquid nitrogen-cooled detector, and Fourier transform infrared spectrometer for detection. The specific detection method includes the following steps:

[0085] S1. Optical path adjustment: Turn on the Fourier transform infrared spectrometer, adjust the infrared light source to the external optical path mode of the Fourier transform infrared spectrometer, place the Ge-As-Ga-Se chalcogenide glass optical fiber sensor in the optical path, and adjust the positions of the external optical path MCT liquid nitrogen-cooled detector and the Ge-As-Ga-Se chalcogenide glass infrared optical fiber sensor through a three-dimensional displacement stage so that the focused infrared light is fully coupled into the end face of the optical fiber to achieve the best signal;

[0086] S2. Background scanning: Set the spectrometer resolution to 8 cm -1 , set the number of scans to 32 times, and scan the infrared absorption spectrum of the Ge-As-Ga-Se chalcogenide glass optical fiber sensor as the background signal;

[0087] S3. Sensitivity calibration: Use an ethanol aqueous solution as the test solution, measure the relationship between the absorption peak height of the infrared optical fiber at the characteristic absorption wavelength of the ethanol aqueous solution and the concentration of the ethanol aqueous solution, and establish a concentration-absorption peak height curve. The specific operation steps are as follows: Drop five ethanol aqueous solutions with volume concentrations (10%, 30%, 50%, 70%, 90%) into the liquid cell 2 of the sensor respectively, so that the infrared optical fiber is in full contact with the ethanol aqueous solution, obtaining an infrared spectrum. Measure the relationship between the absorption peak height of the infrared optical fiber at 1045.1 cm -1 of the ethanol aqueous solution and the volume concentration of the ethanol aqueous solution, and establish a concentration-absorption peak area height curve. The slope thereof is the detection sensitivity of the infrared optical fiber sensor based on Ge-As-Ga-Se chalcogenide glass optical fiber to ethanol in the ethanol aqueous solution, and its sensitivity is 0.0011 (a.u. / %).

[0088] Example 3

[0089] An infrared optical fiber sensor, as Figure 2 shown, includes an optical fiber 1, a liquid cell 2, and a curing agent 3. The liquid cell 2 is provided with a through groove 20 and a flow channel 21. The flow channels 21 are respectively arranged at both ends of the liquid cell 2 and are connected through the groove 20. At the same time, a handle 22 is also provided. The optical fiber is arranged in the groove 20 and the flow channel 21, and the curing agent 3 is filled in the flow channel 21 for fixing the end 10 of the optical fiber to the liquid cell 2.

[0090] The preparation method of the infrared optical fiber sensor includes the following steps:

[0091] 1) Process the Ge-As-Se-Te chalcogenide glass into an optical fiber preform, and use a fiber drawing tower to draw the optical fiber preform into an optical fiber with a diameter of 500 μm;

[0092] 2) Take a 5-cm length of optical fiber and place it in a single-sided hot pressing mold ( Figure 3 A). The cone angle of this mold is 6.5°, and the waist length is 3.4 mm. Place the mold in a muffle furnace, place 3 aluminum blocks of 25 g on the hot pressing mold, keep it warm at 265 °C for 10 min, take it out after cooling, and obtain an optical fiber with a cone angle of 6.5° for the flat cone part 110, a thickness of 234 μm for the flat waist 111, a waist length of 3.4 mm, and a total length of 8 mm for the middle part;

[0093] 3) After the pressing is completed, the optical fiber is locally scanned and heated on an optical fiber tapering machine to obtain an optical fiber with a smooth surface;

[0094] 4) Model according to the geometric dimensions of the optical fiber prepared in step 3) using solidworks software, and use polylactic acid (PLA) as the printing material to print out the liquid cell 2;

[0095] 5) Place the optical fiber prepared in step 3) into the liquid cell 2 prepared in step 4), fix and encapsulate it with the UV curable adhesive curing agent 3, and cut off the excess part of the optical fiber so that the end face of the optical fiber is flush with the end face of the liquid cell 2;

[0096] 6) Use a polishing machine to polish the end face of the encapsulated optical fiber to a mirror finish to obtain an infrared optical fiber sensor.

[0097] Use a detection system including the above infrared optical fiber sensor, infrared light source, ZnSe lens, MCT liquid nitrogen cooling detector, and Fourier transform infrared spectrometer for detection. The specific detection method includes the following steps:

[0098] S1. Optical path adjustment: Turn on the Fourier transform infrared spectrometer, adjust the infrared light source to the external optical path mode of the Fourier transform infrared spectrometer, place the Ge-As-Ga-Se chalcogenide glass optical fiber sensor in the optical path, and adjust the positions of the external optical path MCT liquid nitrogen cooling detector and the Ge-As-Ga-Se chalcogenide glass infrared optical fiber sensor through a three-dimensional displacement stage so that the focused infrared light is fully coupled into the end face of the optical fiber to achieve the best signal;

[0099] S2. Background scanning: Set the spectrometer resolution to 8 cm -1 , set the number of scans to 32 times, and scan the infrared absorption spectrum of the Ge-As-Se-Te chalcogenide glass optical fiber sensor as the background signal;

[0100] S3. Sensitivity calibration: Using an aqueous solution of sodium benzoate as the test solution, measure the relationship between the absorption peak height of the infrared optical fiber at the absorption wavelength of the aqueous sodium benzoate solution and the concentration of the aqueous sodium benzoate solution, and establish a concentration-absorption peak height curve. The specific operation steps are as follows: Drop aqueous sodium benzoate solutions with five molar concentrations (0.2 mol / L, 0.4 mol / L, 0.6 mol / L, 0.8 mol / L, 1 mol / L) into the liquid cell 2 of the sensor respectively, so that the infrared optical fiber is in full contact with the aqueous sodium benzoate solution to obtain an infrared spectrum. Measure the relationship between the absorption peak height of the infrared optical fiber at 1388.8 cm -1 of the aqueous sodium benzoate solution and the molar concentration of the aqueous sodium benzoate solution, and establish a concentration-absorption peak surface height curve. The slope thereof is the detection sensitivity of the infrared optical fiber sensor based on Ge-As-Se-Te chalcogenide glass fiber to sodium benzoate in the aqueous sodium benzoate solution, and its sensitivity is 0.0101 (a.u. / %).

[0101] Example 4

[0102] An infrared optical fiber sensor, as Figure 2 shown, includes an optical fiber 1, a liquid cell 2 and a curing agent 3. The liquid cell 2 is provided with a through groove 20 and a flow channel 21. The flow channels 21 are respectively arranged at both ends of the liquid cell 2 and communicated through the groove 20. At the same time, a handle 22 is also provided. The optical fiber is arranged in the groove 20 and the flow channel 21, and the curing agent 3 is filled in the flow channel 21 for fixing the end 10 of the optical fiber to the liquid cell 2.

[0103] The preparation method of the infrared optical fiber sensor includes the following steps:

[0104] 1) Process a Ge-As-Se-Te chalcogenide glass into an optical fiber preform, and use a fiber drawing tower to draw the optical fiber preform into an optical fiber with a diameter of 500 μm;

[0105] 2) Take a 5-cm-long optical fiber and place it in a single-sided hot pressing mold ( Figure 3 A). The taper angle of this mold is 6.5°, and the waist length is 1.7 mm. Place the mold in a muffle furnace, place 3 aluminum blocks of 25 g on the hot pressing mold, keep it warm at 265 °C for 20 min, take it out after cooling, and obtain an optical fiber with a taper angle of 6.5° at the flat cone part 110, a thickness of 140 μm at the flat waist 111, a waist length of 1.7 mm, and a total length of 8 mm at the middle part;

[0106] 3) After the pressing is completed, the optical fiber is locally scanned and heated on an optical fiber tapering machine to obtain an optical fiber with a smooth surface;

[0107] 4) Model according to the geometric dimensions of the optical fiber prepared in step 3) using solidworks software, and print out the liquid cell 2 with polylactic acid (PLA) as the printing material;

[0108] 5) Place the optical fiber prepared in step 3) into the liquid cell 2 prepared in step 4), and fix and encapsulate it with the UV curable adhesive curing agent 3. Cut off the excess part of the optical fiber so that the end face of the optical fiber is flush with the end face of the liquid cell 2;

[0109] 6) Use a polishing machine to polish the end face of the encapsulated optical fiber until a mirror effect is achieved, obtaining an infrared optical fiber sensor.

[0110] Use a detection system including the above infrared optical fiber sensor, infrared light source, ZnSe lens, MCT liquid nitrogen cooled detector, and Fourier transform infrared spectrometer for detection. The specific detection method includes the following steps:

[0111] S1. Optical path adjustment: Turn on the Fourier transform infrared spectrometer, adjust the infrared light source to the external optical path mode of the Fourier transform infrared spectrometer, place the Ge-As-Se-Te chalcogenide glass optical fiber sensor in the optical path, and adjust the positions of the external optical path MCT liquid nitrogen cooled detector and the Ge-As-Se-Te chalcogenide glass infrared optical fiber sensor through a three-dimensional displacement stage so that the focused infrared light is fully coupled into the end face of the optical fiber to achieve the best signal;

[0112] S2. Background scanning: Set the spectrometer resolution to 8 cm -1 , set the number of scans to 32 times, and scan the infrared absorption spectrum of the Ge-As-Se-Te chalcogenide glass optical fiber sensor as the background signal;

[0113] S3. Sensitivity calibration: Use an aqueous solution of sodium benzoate as the test solution, measure the relationship between the absorption peak height of the infrared optical fiber at the absorption wavelength of the aqueous solution of sodium benzoate and the concentration of the aqueous solution of sodium benzoate, and establish a concentration-absorption peak height curve. The specific operation steps are as follows: Drop aqueous solutions of sodium benzoate with five molar concentrations (0.2 mol / L, 0.4 mol / L, 0.6 mol / L, 0.8 mol / L, 1 mol / L) into the liquid cell 2 of the sensor respectively, make the infrared optical fiber fully contact with the aqueous solution of sodium benzoate, and obtain an infrared spectrogram. Measure the relationship between the absorption peak height of the infrared optical fiber at 1388.8 cm -1 of the aqueous solution of sodium benzoate and the molar concentration of the aqueous solution of sodium benzoate, and establish a concentration-absorption peak area height curve. The slope thereof is the detection sensitivity of the infrared optical fiber sensor based on Ge-As-Se-Te chalcogenide glass optical fiber to sodium benzoate in the aqueous solution of sodium benzoate, and its sensitivity is 0.0265 (a.u. / %).

[0114] Example 5

[0115] An infrared optical fiber sensor, as Figure 2As shown in the figure, it includes an optical fiber 1, a liquid cell 2 and a curing agent 3. The liquid cell 2 is provided with a through groove 20 and a flow channel 21. The flow channels 21 are arranged at both ends of the liquid cell 2 and are connected through the groove 20. At the same time, a handle 22 is also provided. The optical fiber is arranged in the groove 20 and the flow channel 21, and the curing agent 3 is filled in the flow channel 21 to fix the end 10 of the optical fiber to the liquid cell 2.

[0116] The preparation method of the infrared optical fiber sensor includes the following steps:

[0117] 1) Process the Ge-As-Se-Te chalcogenide glass into an optical fiber preform, and use a fiber drawing tower to draw the optical fiber preform into an optical fiber with a diameter of 500 μm;

[0118] 2) Take an 8-cm-long optical fiber and place it in a single-sided hot pressing mold ( Figure 3 A). The taper angle of this mold is 6.5°, and the waist length is 19.2 mm. Place the mold in a muffle furnace, place 3 aluminum blocks of 25 g on the hot pressing mold, keep it warm at 265 °C for 10 min, take it out after cooling, and obtain an optical fiber with a taper angle of 6.5° for the flat cone part 110, a thickness of 235 μm for the flat waist 111, a waist length of 19.2 mm, and a total length of 23.8 mm for the middle part;

[0119] 3) After the pressing is completed, the optical fiber is locally scanned and heated on an optical fiber taper machine to obtain an optical fiber with a smooth surface;

[0120] 4) Model according to the geometric dimensions of the optical fiber prepared in step 3) using solidworks software, and print out the liquid cell 2 with polylactic acid (PLA) as the printing material;

[0121] 5) Put the optical fiber prepared in step 3) into the liquid cell 2 prepared in step 4), fix and encapsulate it with the UV curable glue curing agent 3, and cut off the excess part of the optical fiber so that the end face of the optical fiber is flush with the end face of the liquid cell 2;

[0122] 6) Use a polishing machine to polish the end face of the encapsulated optical fiber until it has a mirror effect to obtain an infrared optical fiber sensor.

[0123] Use a detection system including the above infrared optical fiber sensor, infrared light source, ZnSe lens, MCT liquid nitrogen cooling detector and Fourier transform infrared spectrometer for detection. The specific detection method includes the following steps:

[0124] S1. Optical path adjustment: Turn on the Fourier transform infrared spectrometer, adjust the infrared light source to the external optical path mode of the Fourier transform infrared spectrometer, place the Ge-As-Se-Te chalcogenide glass fiber sensor in the optical path, and adjust the positions of the external optical path MCT liquid nitrogen-cooled detector and the Ge-As-Se-Te chalcogenide glass infrared fiber sensor through a three-dimensional displacement stage so that the focused infrared light is fully coupled into the end face of the optical fiber to achieve the best signal;

[0125] S2. Background scanning: Set the spectrometer resolution to 8 cm -1 , set the number of scans to 32 times, and scan the infrared absorption spectrum of the Ge-As-Se-Te chalcogenide glass fiber sensor as the background signal;

[0126] S3. Sensitivity calibration: Use an aqueous solution of sodium benzoate as the test solution, measure the relationship between the absorption peak height of the infrared optical fiber at the absorption wavelength of the aqueous solution of sodium benzoate and the concentration of the aqueous solution of sodium benzoate, and establish a concentration-absorption peak height curve. The specific operation steps are as follows: Drop aqueous solutions of sodium benzoate with five molar concentrations (0.2 mol / L, 0.4 mol / L, 0.6 mol / L, 0.8 mol / L, 1 mol / L) into the liquid cell 2 of the sensor respectively, so that the infrared optical fiber is in full contact with the aqueous solution of sodium benzoate to obtain an infrared spectrogram. Measure the relationship between the absorption peak height of the infrared optical fiber at 1388.8 cm -1 of the aqueous solution of sodium benzoate and the molar concentration of the aqueous solution of sodium benzoate, and establish a concentration-absorption peak surface height curve. The slope thereof is the detection sensitivity of the infrared optical fiber sensor based on Ge-As-Se-Te chalcogenide glass fiber to sodium benzoate in the aqueous solution of sodium benzoate, and its sensitivity is 0.0209 (a.u. / %).

[0127] Example 6

[0128] An infrared optical fiber sensor, as Figure 2 shown, includes an optical fiber 1, a liquid cell 2 and a curing agent 3. The liquid cell 2 is provided with a through groove 20 and a flow channel 21. The flow channels 21 are respectively arranged at both ends of the liquid cell 2 and communicated through the groove 20. At the same time, a handle 22 is also provided. The optical fiber is arranged in the groove 20 and the flow channel 21, and the curing agent 3 is filled in the flow channel 21 for fixing the end 10 of the optical fiber to the liquid cell 2.

[0129] The preparation method of the infrared optical fiber sensor includes the following steps:

[0130] 1) Process the Ge-As-Se-Te chalcogenide glass into an optical fiber preform, and use a fiber drawing tower to draw the optical fiber preform into an optical fiber with a diameter of 500 μm;

[0131] 2) Take a 5 cm long optical fiber and place it in a single-sided hot pressing mold ( Figure 3In A), the taper angle of this mold is 6.5°, and the waist length is 3.4 mm. Place the mold in a muffle furnace, place 3 aluminum blocks of 25 g on the hot-pressed mold, keep it warm at 265 °C for 10 min, take it out after cooling, and obtain an optical fiber with a taper angle of 6.5° for the flat taper part 110, a thickness of 234 μm for the flat waist 111, a waist length of 3.4 mm, and a total length of 8 mm for the middle part;

[0132] 3) After pressing is completed, the optical fiber is subjected to local scanning heating and co-directional stretching on an optical fiber taper machine, stretched from the original 8 mm to 27 mm, and an optical fiber with a taper angle of 2.5° for the flat taper part 110, a waist thickness of 110 μm, a waist length of 11.6 mm, and a total length of 27 mm for the middle part is obtained;

[0133] 4) Model according to the geometric dimensions of the optical fiber prepared in step 3) using solidworks software, and use polylactic acid (PLA) as the printing material to print out the liquid pool 2;

[0134] 5) Place the optical fiber prepared in step 3) into the liquid pool 2 prepared in step 4), fix and encapsulate it with the UV curing glue curing agent 3, and cut off the excess part of the optical fiber so that the end face of the optical fiber is flush with the end face of the liquid pool 2;

[0135] 6) Use a polishing machine to polish the end face of the encapsulated optical fiber until it has a mirror effect to obtain an infrared optical fiber sensor.

[0136] Use a detection system including the above infrared optical fiber sensor, infrared light source, ZnSe lens, MCT liquid nitrogen cooling detector, and Fourier transform infrared spectrometer for detection. The specific detection method includes the following steps:

[0137] S1. Optical path adjustment: Turn on the Fourier transform infrared spectrometer, adjust the infrared light source to the external optical path mode of the Fourier transform infrared spectrometer, place the Ge-As-Se-Te chalcogenide glass fiber sensor in the optical path, and adjust the positions of the external optical path MCT liquid nitrogen cooling detector and the Ge-As-Se-Te chalcogenide glass infrared optical fiber sensor through a three-dimensional displacement stage so that the focused infrared light is fully coupled into the end face of the optical fiber to achieve the best signal;

[0138] S2. Background scanning: Set the spectrometer resolution to 8 cm -1 , set the number of scans to 32 times, and scan the infrared absorption spectrum of the Ge-As-Se-Te chalcogenide glass fiber sensor as the background signal;

[0139] S3. Sensitivity Calibration: Using an aqueous solution of sodium benzoate as the solution to be measured, measure the relationship between the absorption peak height of the infrared optical fiber at the absorption wavelength of the aqueous sodium benzoate solution and the concentration of the aqueous sodium benzoate solution, and establish a concentration-absorption peak height curve. The specific operation steps are as follows: Drop aqueous solutions of sodium benzoate with five molar concentrations (0.2 mol / L, 0.4 mol / L, 0.6 mol / L, 0.8 mol / L, 1 mol / L) into the liquid cell of the sensor respectively, so that the infrared optical fiber is in full contact with the aqueous sodium benzoate solution to obtain an infrared spectrum. Measure the relationship between the absorption peak height of the infrared optical fiber at 1388.8 cm -1 of the aqueous sodium benzoate solution and the molar concentration of the aqueous sodium benzoate solution, and establish a concentration-absorption peak surface height curve. The slope thereof is the detection sensitivity of the infrared optical fiber sensor based on Ge-As-Se-Te chalcogenide glass fiber to sodium benzoate in the aqueous sodium benzoate solution, and its sensitivity is 0.122 (a.u. / %).

[0140] Example 7

[0141] An infrared optical fiber sensor, as Figure 2 shown, includes an optical fiber 1, a liquid cell 2 and a curing agent 3. The liquid cell 2 is provided with a through groove 20 and a flow channel 21. The flow channels 21 are respectively arranged at both ends of the liquid cell 2 and are connected through the groove 20. At the same time, a handle 22 is also provided. The optical fiber is arranged in the groove 20 and the flow channel 21, and the curing agent 3 is filled in the flow channel 21 for fixing the end 10 of the optical fiber to the liquid cell 2.

[0142] The preparation method of the infrared optical fiber sensor includes the following steps:

[0143] 1) Process a Ge-As-Se-Te chalcogenide glass into an optical fiber preform, and use a fiber drawing tower to draw the optical fiber preform into an optical fiber with a diameter of 500 μm;

[0144] 2) Take a 5-cm-long optical fiber and place it in a single-sided hot pressing mold ( Figure 3 A). The taper angle of this mold is 6.5°, and the waist length is 3.4 mm. Place the mold in a muffle furnace, place 3 aluminum blocks of 25 g on the hot pressing mold, keep it warm at 265 °C for 10 min, take it out after cooling, and obtain an optical fiber with a taper angle of 6.5° for the flat taper part 110, a thickness of 234 μm for the flat waist part 111, a waist length of 3.4 mm, and a total length of 8 mm for the middle part;

[0145] 3) After the pressing is completed, the optical fiber is subjected to local scanning heating and co-directional stretching on an optical fiber taper machine, and is stretched from the original 8 mm to 27 mm, and an optical fiber with a taper angle of 2.5° for the flat taper part 110, a waist thickness of 110 μm, a waist length of 11.6 mm, and a total length of 27 mm for the middle part is obtained;

[0146] 4) Model according to the geometric dimensions of the optical fiber prepared in step 3) using SolidWorks software, and use acrylonitrile-butadiene-styrene copolymer (ABS) as the printing material to print out the liquid cell 2;

[0147] 5) Place the optical fiber prepared in step 3) into the liquid cell 2 prepared in step 4), fix and encapsulate it with the UV curable adhesive curing agent 3, and cut off the excess part of the optical fiber so that the end face of the optical fiber is flush with the end face of the liquid cell 2;

[0148] 6) Polish the end face of the encapsulated optical fiber using a polishing machine until a mirror effect is achieved to obtain an infrared optical fiber sensor.

[0149] Use a detection system including the above infrared optical fiber sensor, infrared light source, ZnSe lens, MCT liquid nitrogen-cooled detector, and Fourier transform infrared spectrometer for detection. The specific detection method includes the following steps:

[0150] S1. Optical path adjustment: Turn on the Fourier transform infrared spectrometer, adjust the infrared light source to the external optical path mode of the Fourier transform infrared spectrometer, place the Ge-As-Se-Te chalcogenide glass optical fiber sensor in the optical path, and adjust the positions of the external optical path MCT liquid nitrogen-cooled detector and the Ge-As-Se-Te chalcogenide glass infrared optical fiber sensor through a three-dimensional displacement stage so that the focused infrared light is fully coupled into the end face of the optical fiber to achieve the best signal;

[0151] S2. Background scanning: Set the spectrometer resolution to 8 cm -1 , set the number of scans to 32 times, and scan the infrared absorption spectrum of the Ge-As-Se-Te chalcogenide glass optical fiber sensor as the background signal;

[0152] S4. Qualitative analysis of unknown substances: Drop 1 drop of the unknown solution 1 into the liquid cell 2, scan its infrared absorption spectrum, and compare and analyze it with the standard infrared spectrum atlas to know that the unknown solution 1 is a potassium sorbate solution, as Figure 7 shown;

[0153] S5. Sensitivity calibration: Use an aqueous potassium sorbate solution as the test solution, measure the relationship between the absorption peak height of the infrared optical fiber at the absorption wavelength of the aqueous potassium sorbate solution and the concentration of the aqueous potassium sorbate solution, and establish a concentration-absorption peak height curve. The specific operation steps are as follows: Drop aqueous potassium sorbate solutions with five molar concentrations (0.2 mol / L, 0.4 mol / L, 0.6 mol / L, 0.8 mol / L, 1 mol / L) into the liquid cell 2 of the sensor respectively, so that the infrared optical fiber is in full contact with the aqueous potassium sorbate solution to obtain an infrared spectrum. Measure the flat infrared optical fiber at 1391.6 cm of the aqueous potassium sorbate solution -1The relationship between the absorption peak height at a certain position and the molar concentration of the potassium sorbate aqueous solution is used to establish a concentration-absorption peak surface height curve. The slope thereof is the detection sensitivity of the infrared fiber optic sensor based on Ge-As-Se-Te chalcogenide glass fiber to potassium sorbate in the potassium sorbate aqueous solution, and the sensitivity is 0.1153 (a.u. / %).

[0154] S6. Quantitative analysis of unknown substances: The potassium sorbate solution with unknown concentration in step S4 is dropped into the liquid cell 2, and its infrared absorption spectrum is tested. Calculate the liquid concentration according to the relationship between the standard liquid concentration and its characteristic absorption peak height established in step S5. As Figure 8 shown, the measured unknown concentration is 0.1153 mol / L.

[0155] Example 8

[0156] An infrared fiber optic sensor, as Figure 2 shown, includes an optical fiber 1, a liquid cell 2, and a curing agent 3. The liquid cell 2 is provided with a through groove 20 and a flow channel 21. The flow channels 21 are respectively arranged at both ends of the liquid cell 2 and communicated through the groove 20. At the same time, a handle 22 is also provided. The optical fiber is arranged in the groove 20 and the flow channel 21, and the curing agent 3 is filled in the flow channel 21 for fixing the end portion 10 of the optical fiber to the liquid cell 2.

[0157] The preparation method of the infrared fiber optic sensor includes the following steps:

[0158] 1) Process the Ge-As-Se-Te chalcogenide glass into an optical fiber preform, and use a fiber drawing tower to draw the optical fiber preform into an optical fiber with a diameter of 500 μm;

[0159] 2) Take a 5 cm long optical fiber and place it in a double-sided hot pressing mold ( Figure 3 B). The taper angle of this mold is 6.5°, and the waist length is 3.4 mm. Place the mold in a muffle furnace, place 3 aluminum blocks of 25 g on the hot pressing mold, keep it warm at 265 °C for 10 min, take it out after cooling, and obtain an optical fiber with a taper angle of 6.5° for the flat taper portion 110, a thickness of 234 μm for the flat waist portion 111, a waist length of 3.4 mm, and a total length of 8 mm for the middle portion;

[0160] 3) After the pressing is completed, the optical fiber is subjected to local scanning heating and co-directional stretching on an optical fiber taper machine, and is stretched from the original 8 mm to 27 mm, obtaining an optical fiber with a taper angle of 2.5° for the flat taper portion 110, a waist thickness of 110 μm, a waist length of 11.6 mm, and a total length of 27 mm for the middle portion;

[0161] 4) Model according to the geometric dimensions of the optical fiber prepared in step 3) using solidworks software, and use acrylonitrile-butadiene-styrene copolymer (ABS) as the printing material to print out the liquid cell 2;

[0162] 5) Place the optical fiber prepared in step 3) into the liquid cell 2 prepared in step 4), and fix and encapsulate it with the UV curable adhesive curing agent 3. Cut off the excess part of the optical fiber so that the end face of the optical fiber is flush with the end face of the liquid cell 2;

[0163] 6) Use a polishing machine to polish the end face of the encapsulated optical fiber until a mirror effect is achieved, obtaining an infrared optical fiber sensor.

[0164] Use a detection system including the above infrared optical fiber sensor, infrared light source, ZnSe lens, MCT liquid nitrogen cooled detector, and Fourier transform infrared spectrometer for detection. The specific detection method includes the following steps:

[0165] S1. Optical path adjustment: Turn on the Fourier transform infrared spectrometer, adjust the infrared light source to the external optical path mode of the Fourier transform infrared spectrometer, place the Ge-As-Se-Te chalcogenide glass optical fiber sensor in the optical path, and adjust the positions of the external optical path MCT liquid nitrogen cooled detector and the Ge-As-Se-Te chalcogenide glass infrared optical fiber sensor through a three-dimensional displacement stage so that the focused infrared light is fully coupled into the end face of the optical fiber to achieve the best signal;

[0166] S2. Background scanning: Set the spectrometer resolution to 8 cm -1 , set the number of scans to 32 times, and scan the infrared absorption spectrum of the Ge-As-Se-Te chalcogenide glass optical fiber sensor as the background signal;

[0167] S3. Sensitivity calibration: Use an aqueous solution of potassium sorbate as the test solution, measure the relationship between the absorption peak height of the infrared optical fiber at the absorption wavelength of the aqueous solution of potassium sorbate and the concentration of the aqueous solution of potassium sorbate, and establish a concentration-absorption peak height curve. The specific operation steps are as follows: Drop aqueous solutions of potassium sorbate with five molar concentrations (0.2 mol / L, 0.4 mol / L, 0.6 mol / L, 0.8 mol / L, 1 mol / L) into the liquid cell 2 of the sensor respectively, make the infrared optical fiber fully contact with the aqueous solution of potassium sorbate, and obtain an infrared spectrum. Measure the relationship between the absorption peak height of the infrared optical fiber at 1391.6 cm -1 of the aqueous solution of potassium sorbate and the molar concentration of the aqueous solution of potassium sorbate, and establish a concentration-absorption peak area height curve. The slope thereof is the detection sensitivity of the infrared optical fiber sensor based on Ge-As-Se-Te chalcogenide glass optical fiber to potassium sorbate in the aqueous solution of potassium sorbate, and its sensitivity is 0.2462 (a.u. / %).

[0168] Comparative example

[0169] In the infrared optical fiber sensor in this comparative example, the optical fiber is not flattened and is directly drawn into an optical fiber with a diameter of 500 μm.

[0170] The detection method in Example 1 was used for testing. The results showed that the detection sensitivity of the infrared fiber optic sensor in this comparative example to ethanol in an ethanol aqueous solution was 0.000568 (a.u. / %).

[0171] In summary, the infrared fiber optic sensor of the present invention has higher sensitivity compared to the infrared fiber optic sensor in the comparative example. It can not only perform qualitative analysis on substances but also quantitative analysis on low-concentration substances. Therefore, it has broad application prospects in the field of high-sensitivity biological and chemical sensing.

[0172] It should be noted that the above embodiments all belong to the same inventive concept. The descriptions of the embodiments have their own focuses. For the parts not described in detail in individual embodiments, reference can be made to the descriptions in other embodiments.

[0173] The above embodiments only represent the implementation modes of the present invention. The descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be pointed out that for those of ordinary skill in the art, without departing from the inventive concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the appended claims.

Claims

1. An infrared optical fiber sensor, characterized in that: Includes fiber optics; The optical fiber includes an end portion and a middle portion, the middle portion includes a flat cone portion and a flat waist portion, the end portion is connected to the flat waist portion through the flat cone portion, and the flat cone portion and the flat waist portion have an inclined structure on both sides; The cone angle between the flat cone portion and the flat waist portion is 2.5° to 6.5°; The optical fiber is an infrared glass optical fiber, and the infrared glass optical fiber is selected from at least one of Ge-As-Se-Te chalcogenide glass, As-Se chalcogenide glass or Ge-As-Se chalcogenide glass; The infrared fiber optic sensor also includes a liquid pool and a curing agent. The liquid pool is provided with a through groove and a flow channel. The flow channel is provided at both ends of the liquid pool and is connected through the groove. The optical fiber is provided in the groove and the flow channel. The curing agent is filled in the flow channel to fix the end of the optical fiber to the liquid pool.

2. The infrared optical fiber sensor according to claim 1, characterized in that: The curing agent is selected from UV curing glue or epoxy resin; The liquid pool is prepared by a material selected from at least one of polylactic acid, acrylonitrile-butadiene-styrene copolymer or photosensitive resin.

3. The method for preparing the infrared optical fiber sensor according to any one of claims 1 to 2, characterized in that: The steps include: 1) Processing the infrared glass optical fiber into an optical fiber preform, and drawing the optical fiber preform into an optical fiber with a diameter of 150-1000 μm by a wire drawing process; 2) providing a hot pressing mold having the optical fiber middle structure, placing the optical fiber obtained in step 1) in the hot pressing mold, placing an aluminum block on the hot pressing mold, and then placing the mold in a muffle furnace for heating to obtain the optical fiber; 3) placing the optical fiber obtained in step 2) on an optical fiber taper drawing machine for local scanning heating to obtain an optical fiber with a smooth surface; optionally, using the optical fiber taper drawing machine to unidirectionally stretch the optical fiber obtained in step 2) to obtain a slender optical fiber; 4) Modeling the liquid pool using three-dimensional software, and then preparing the liquid pool using 3D printing technology; 5) placing the optical fiber obtained in step 3) in the liquid pool obtained in step 4) and fixing and encapsulating it with a curing agent; 6) Using a polishing machine to polish the end face of the packaged optical fiber to obtain the infrared optical fiber sensor.

4. A detection system, characterized in that: The infrared optical fiber sensor comprises any one of claims 1 to 2, as well as an infrared light source, a ZnSe lens, an MCT liquid nitrogen refrigeration detector and a Fourier infrared spectrometer; The infrared light source, the ZnSe lens, the infrared optical fiber sensor, the MCT liquid nitrogen refrigeration detector and the Fourier infrared spectrometer are connected in sequence.

5. A method for detection using the detection system according to claim 4, characterized in that: The steps include: S1. Adjustment of optical path: Turn on the Fourier infrared spectrometer, adjust the infrared light source to the external optical path mode of the Fourier infrared spectrometer, place the infrared fiber sensor in the optical path, and adjust the positions of the external optical path MCT liquid nitrogen cooling detector and the infrared fiber sensor through the three-dimensional translation stage to achieve the best signal, so that the focused infrared light is fully coupled into the end face of the optical fiber; S2, background scanning: scanning the infrared absorption spectrum of the infrared fiber optic sensor as the background signal for detection; If the liquid to be tested is a known solution, proceed to step S3: S3, sensitivity and minimum detection limit calibration: prepare several groups of test liquids with standard concentrations, use Fourier infrared spectrometer to collect infrared absorption spectra of the test liquids with standard concentrations one by one, and establish a linear relationship, the slope of which is the fiber sensitivity, and the lowest detectable concentration is the minimum detection limit; Alternatively, if the liquid to be tested is an unknown solution, steps S4, S5 and S6 are performed: S4. Qualitative analysis of unknown substances: drop the unknown solution into the liquid pool of the infrared fiber sensor, collect its infrared absorption spectrum, and compare it with the standard infrared spectrum. After analysis, the composition information of the unknown substance is obtained; S5. According to the composition information of the unknown substance obtained in step S4, the sensitivity and minimum detection limit are calibrated using the method in step S3; S6. Quantitative analysis of unknown substances: drop the unknown solution into the liquid pool of the infrared optical fiber sensor, collect its infrared absorption spectrum, and calculate the concentration of the liquid according to the relationship between the concentration of the standard liquid and the characteristic absorption peak height established in step S5.

6. The method according to claim 5, characterized in that In step S3, the linear relationship is obtained by selecting a characteristic absorption peak with a relatively large absorption intensity according to the standard infrared spectrum of the liquid to be tested, and then calculating and establishing the relationship between the standard liquid concentration and its characteristic absorption peak height using the Beer-Lambert law, and finally obtaining the linear relationship through fitting.

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