WO2023103373A1

WO2023103373A1 - Fabry-perot interference optical fiber pressure sensor for eliminating temperature interference, and manufacturing method therefor

Info

Publication number: WO2023103373A1
Application number: PCT/CN2022/104645
Authority: WO
Inventors: 王文华; 吴伟娜; 李乐凡; 李思东; 师文庆; 熊正烨; 谢玉萍; 罗元政; 黄江; 何启浪
Original assignee: 广东海洋大学
Priority date: 2021-12-08
Filing date: 2022-07-08
Publication date: 2023-06-15
Also published as: LU503041B1; CN113916438A; CN113916438B

Abstract

A Fabry-Perot interference optical fiber pressure sensor for eliminating temperature interference. The sensor comprises an incident optical fiber, an optical fiber collimating sleeve (4) and a reflective quartz optical fiber (3), wherein the incident optical fiber and the reflective quartz optical fiber (3) are located in the optical fiber collimating sleeve (4); the incident optical fiber and the reflective quartz optical fiber (3) do not come in contact with each other, and form a first Fabry-Perot interference cavity; the incident optical fiber comprises an incident quartz optical fiber (1) and an N,O-carboxymethyl chitosan optical fiber (2); and the N,O-carboxymethyl chitosan optical fiber (2) comprises a fourth end face (13) and a fifth end face (14), and the fourth end face (13) and the fifth end face (14) form a second Fabry-Perot interference cavity. Two completely independent Fabry-Perot interference cavities are formed, the first Fabry-Perot interference cavity is used for detecting a pressure change, and the second Fabry-Perot interference cavity is used for detecting a temperature change, such that the influence of ambient temperature is eliminated during the measurement of the optical fiber pressure sensor. The manufacturing process is simple, environmentally friendly and convenient; and the sensor is safe and reliable, and has good stability. Further provided is a method for manufacturing a Fabry-Perot interference optical fiber pressure sensor for eliminating temperature interference.

Description

Faber interferometric optical fiber pressure sensor for eliminating temperature interference and its manufacturing method

technical field

The application belongs to the field of intersecting technical fields of optical fiber technology, F-P interference and optical fiber preparation of polymer materials, and in particular relates to a F-P interference optical fiber pressure sensor for eliminating temperature interference and a manufacturing method thereof.

Background technique

Optical fiber sensors have broad application prospects in civil engineering, petrochemical, aerospace and other fields. They have electrical insulation, anti-electromagnetic interference, high sensitivity, corrosion resistance, and passive sensor terminals, so they are intrinsically safe. They can be remote without signal conversion and amplifiers. Distance transmission, as well as small size, light weight and other advantages. Optical fiber sensors are divided into two types: functional type and light transmission type, including phase modulation, light intensity modulation and wavelength modulation sensors. Phase-modulated fiber optic sensors usually use light interference to convert phase changes into light intensity changes to detect external parameters, such as pressure, strain, and temperature. Due to the interference of light, the phase modulation fiber optic sensor has high sensitivity. Currently commonly used interference techniques include Fabry-Perot interference (Fabry-Perot interference for short), Michelson interference, Mach-Zehnder interference, etc. Among them, the Fabry-Perot interference fiber sensor is simple in structure, high Higher merit has been widely concerned and researched by people.

There are extrinsic type and intrinsic type of Fabry interferometric optical fiber sensor, which were proposed in 1988 and 1991 respectively, and both have been deeply studied. The extrinsic sensor is formed by the end face of the incident optical fiber and the end face of the reflective optical fiber or the inner surface of the pressure sensitive diaphragm to form a Fab cavity. The temperature sensitivity is lower than that of the intrinsic sensor, but the sensor is still affected by the temperature when it is used to measure the pressure- The interference of pressure cross-sensitivity leads to large measurement errors. Temperature-pressure cross-sensitivity is the key problem of Fabry interferometric fiber optic pressure sensors. Therefore, people have been studying various methods or new structures of sensors to reduce temperature-pressure cross-sensitivity. The effect of sensitivity on pressure measurements. At present, one of the main solutions is to measure temperature and pressure at the same time, and then eliminate the interference part of the measured pressure by temperature through the accurately measured temperature, so that the sensor will not produce unnecessary pressure measurement due to the change of ambient temperature when measuring the pressure. Error, and finally eliminate the influence of temperature-pressure cross-sensitivity of Fabry interferometric fiber optic pressure sensor.

The present invention aims at the problem that the Fabry interferometric optical fiber pressure sensor will be affected by the temperature-pressure cross-sensitivity when measuring the pressure, and designs a sensor structure with two small sections of semi-cylindrical optical fibers of different materials, and utilizes the light in the selected wavelength range The signal generation absorbs or reflects the film layer structure, thus ingeniously forming two completely independent Falper interference cavities, which are used to measure temperature and pressure respectively, so as to realize the optical fiber pressure sensor when measuring The influence of ambient temperature is eliminated, the production process is simple, environmentally friendly and convenient, and the sensor is safe, reliable and stable.

Contents of the invention

This application proposes a Fabry interferometric optical fiber pressure sensor that eliminates temperature interference and a manufacturing method thereof, and reduces the influence of temperature-pressure cross-sensitivity on pressure measurement through a novel structure of the sensor.

In order to achieve the above object, the application provides the following scheme:

Fabry interference optical fiber pressure sensor to eliminate temperature interference, including incident optical fiber, optical fiber collimation sleeve and reflective silica optical fiber;

The incident optical fiber and the reflective silica optical fiber are located in the optical fiber collimation sleeve;

There is no contact between the incident optical fiber and the reflective silica optical fiber, and a first Fappaure interference cavity is formed, and the first Fappaure interference cavity is used to detect pressure changes;

The incident optical fiber comprises incident silica optical fiber and N,O-carboxymethyl chitosan optical fiber;

The N,O-carboxymethyl chitosan optical fiber includes a fourth end face and a fifth end face, the fourth end face and the fifth end face constitute a second Fappaure interference cavity, and the second Fappaure interference cavity is used for for detecting temperature changes.

Optionally, the incident silica fiber includes a first end face, a second section and a third end face;

The first end face is the end face of the mosaic connection between the N,O-carboxymethyl chitosan optical fiber and the incident silica optical fiber;

The second section is the section where the N,O-carboxymethyl chitosan optical fiber is mosaically connected to the incident silica optical fiber;

The third end face is an end face adjacent to the incident silica fiber and the reflection fiber.

Optionally, the first end surface is coated with a first coating film, the second section is coated with a second coating film, and the third end surface is coated with a third coating film;

The first coating is used for partial reflection of the long half-wavelength optical signal and total absorption of the short half-wavelength optical signal;

The second coating is used to produce total reflection on the optical signal;

The third coating is used for partial reflection of the short half-wavelength optical signal, and full absorption of the long half-wavelength optical signal.

Optionally, the N,O-carboxymethyl chitosan optical fiber is inlaid connected with the incident silica optical fiber, and connected with the optical fiber collimation sleeve, and the N,O-carboxymethyl chitosan optical fiber The fourth end face of the incident silica fiber is flush with the third end face of the incident silica fiber.

Optionally, in the N,O-carboxymethyl chitosan optical fiber;

The fourth end face is coated with a fourth coating;

The fifth end face is the end face of the N,O-carboxymethyl chitosan optical fiber connected to the first end face;

The fourth end face is the end face of the N,O-carboxymethyl chitosan optical fiber which is flush with the third end face, and the fourth coating is used for total reflection of optical signals.

On the other hand, the present invention also provides a method for manufacturing a Fabry interferometric optical fiber pressure sensor that eliminates temperature interference, including:

Selecting an optical fiber alignment sleeve, cleaning and drying the optical fiber alignment sleeve;

Preparation of incident optical fiber, including preparation of incident silica optical fiber and preparation of N,O-carboxymethyl chitosan optical fiber;

Prepare reflective silica fiber;

Insert the incident fiber and the reflective silica fiber into the fiber collimation sleeve and connect them to the fiber collimation sleeve, wherein a preset cavity length is left between the incident fiber and the reflective silica fiber , forming the first Fapling interference cavity, and forming the Fapling interference optical fiber pressure sensor.

Optionally, preparing the incident optical fiber includes;

The N,O-carboxymethyl chitosan optical fiber is embedded in one end of the incident silica fiber, and the N,O-carboxymethyl chitosan optical fiber is flush with the end face of the incident silica optical fiber, forming the the incident fiber.

Optionally, preparing the incident optical fiber also includes;

Keep the predetermined shape of the silica fiber along the axial direction, remove the excess part, and obtain a semi-cylindrical vacant area;

The vacant area of the semi-cylindrical body includes a first end surface and a second section, the first end surface is coated to obtain a first coating, and the second section is coated to obtain a second coating to form a coated silica optical fiber;

Configure N,O-carboxymethyl chitosan solution;

Inserting the coated silica optical fiber into the processed capillary, causing the vacant area of the semi-cylindrical body to leak out, filling the vacant area of the semi-cylindrical body with the N,O-carboxymethyl chitosan solution to obtain a filled Full silica fiber;

Pulling the filled silica optical fiber into the capillary, leaving it to dry;

Cutting the silica optical fiber after standing and drying to obtain a flat end face, the end face including a third end face and a fourth end face;

Coating the fourth end face to obtain a fourth coating film to form the N,O-carboxymethyl chitosan optical fiber, the N,O-carboxymethyl chitosan optical fiber also includes a fifth end face, the The fourth end face and the fifth end face form a second Fapé interference cavity;

Coating the third end face to obtain a third end face coating film to form the incident silica optical fiber.

The beneficial effect of this application is:

N,O-carboxymethyl chitosan is selected as the material of half of the cylindrical optical fiber. The whole process does not require chemical corrosion and other processes, and does not require other toxic chemical reagents. It is green and environmentally friendly, and has good temperature stability and casting properties, etc. performance. By rationally designing two Fap-Pert cavities to interfere with half of the light source wavelength signals respectively, the Fap-Per interference optical fiber pressure sensor can accurately detect the ambient temperature when detecting the ambient pressure, so that the detected temperature information can be used to eliminate the detection environment. The influence of temperature on pressure can finally eliminate the influence of temperature-pressure cross-sensitivity of the Faber interference sensor.

The present invention aims at the problem that the F-P interference optical fiber pressure sensor is affected by temperature-pressure cross-sensitivity, designs a sensor structure with two small sections of semi-cylindrical optical fibers of different materials, and utilizes the ability to absorb or reflect optical signals in a selected wavelength range The film layer structure cleverly forms two completely independent Fabry interference cavities, which are used to measure temperature and pressure respectively, so that the optical fiber pressure sensor can eliminate the influence of ambient temperature when measuring. The process is simple, environmentally friendly and convenient, and the sensor is safe, reliable and stable.

Description of drawings

In order to illustrate the technical solution of the present application more clearly, the accompanying drawings used in the embodiments are briefly introduced below. Obviously, the accompanying drawings in the following description are only some embodiments of the present application. Technical personnel can also obtain other drawings based on these drawings without paying creative labor.

Fig. 1 is the schematic structural diagram of the Fabry interferometric optical fiber pressure sensor that eliminates temperature interference in the first embodiment of the present application;

FIG. 2 is a schematic diagram of the position of each end face in Embodiment 1 of the present application, that is, the structure of the coating film;

FIG. 3 is a schematic diagram of the wavelength range of the light source in Embodiment 1 of the present application;

FIG. 4 is a schematic diagram of the internal optical paths of the first Fabry interference cavity and the second Fabry interference cavity in Embodiment 1 of the present application;

Fig. 5 is the schematic cross-sectional view of the quartz optical fiber processed by femtosecond laser in Embodiment 2 of the present application;

6 is a schematic diagram of a flat end face of the incident optical fiber in Embodiment 2 of the present application after being cut;

7 is a schematic diagram of the end face of the incident optical fiber in Embodiment 2 of the present application after being cut;

FIG. 8 is a schematic diagram of the entire sensing system in Embodiment 3 of the present application.

Explanation of reference signs:

1 is incident silica fiber, 2 is N,O-carboxymethyl chitosan fiber, 3 is reflective silica fiber, 4 is fiber collimation sleeve, 5 is the first coating, 6 is the second coating, 7 is the third Coating, 8 is the fourth coating, 9 is the laser welding spot, 10 is the first end face, 11 is the second section, 12 is the third end face, 13 is the fourth end face, 14 is the fifth end face, 15 is the optical fiber, 16 is Optical fiber coupler, 17 is a sensor, 18 is a wave division multiplexer, 19 is a first detection and signal modulator, 20 is a second detection and signal modulator.

Detailed ways

The following will clearly and completely describe the technical solutions in the embodiments of the application with reference to the drawings in the embodiments of the application. Apparently, the described embodiments are only some of the embodiments of the application, not all of them. Based on the embodiments in this application, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the scope of protection of this application.

In order to make the above objects, features and advantages of the present application more obvious and comprehensible, the present application will be further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

Embodiment one

As shown in Fig. 1, it is the structural representation of the Fapau interference optical fiber pressure sensor that eliminates temperature interference in the embodiment one of the present application, mainly includes:

Incident fiber, fiber collimation sleeve 4 and reflection silica fiber 3; incident fiber and reflection silica fiber 3 are located in fiber collimation sleeve 4; there is no contact between incident fiber and reflection silica fiber 3, and constitute the first FAP interference Cavities, the first Fappaure interference cavity is used to detect pressure changes; the incident fiber includes incident silica fiber 1 and N,O-carboxymethyl chitosan fiber 2; N,O-carboxymethyl chitosan fiber 2 includes the fourth The end face 13 and the fifth end face 14 , the fourth end face 13 and the fifth end face 14 form a second FAPO interference cavity, and the second FAPO interference cavity is used for detecting temperature changes.

In this embodiment, the optical fiber collimation sleeve 4 can be made of quartz glass, borosilicate glass and other materials for fixing the optical fiber, and the incident optical fiber includes the incident silica optical fiber 1 and N,O-carboxymethyl chitosan optical fiber 2, One end of the incident silica fiber 1 inserted into the fiber collimation sleeve 4 is processed into a semi-cylindrical shape, and the semi-cylindrical part removed by processing is replaced by N, O-carboxymethyl chitosan, a material transparent to optical signals, that is, the optical fiber is processed into a semi-cylindrical shape. The other half of the end of the cylindrical shape is N, O-carboxymethyl chitosan material "optical fiber", and the thermal expansion coefficient of the prepared N, O-carboxymethyl chitosan material is 1-4 orders of magnitude multiples of the silica optical fiber. Adjacent and non-contact between the incident optical fiber and the reflective quartz optical fiber 3 constitutes the first Falper interference cavity, the first Falper interference cavity is a Far-Per interference air cavity, which is used to detect pressure changes, but it will be affected when detecting pressure changes. Temperature interference, that is, the problem of temperature-pressure cross-sensitivity effects; the two end faces of the N,O-carboxymethyl chitosan optical fiber, namely the fifth end face and the fourth end face, constitute the second Falper interference cavity, and the second Falper The interference cavity is a Farpert interference cavity, which is used to detect temperature changes.

Incident silica optical fiber 1 includes a first end face 10, a second section 11 and a third end face 12; the first end face 10 is coated with a first coating 5, the second section 11 is coated with a second coating 6, and the third end face 12 is coated with There is a third coating 7; the first end face 10 is the end face of N,O-carboxymethyl chitosan optical fiber 2 inlaid with the incident silica optical fiber 1, and the first coating 5 is used to generate partial reflection and short The half-wavelength optical signal is fully absorbed; the second section 11 is the section where the N,O-carboxymethyl chitosan optical fiber 2 is mosaically connected to the incident silica optical fiber 1, and the second coating 6 is used to generate total reflection on the optical signal; the third end surface 12 is the end face adjacent to the incident silica fiber 1 and the reflective silica fiber 3, the third coating 7 is used for partial reflection of the short half-wavelength optical signal, and full absorption of the long half-wavelength optical signal. The schematic diagram of the location of each end face is shown in Figure 2.

The N,O-carboxymethyl chitosan optical fiber is inlaid connected with the incident silica optical fiber 1, and connected with the fiber collimation sleeve 3, the fourth end face 13 of the N,O-carboxymethyl chitosan optical fiber 2 is connected with the incident silica optical fiber The third end surface 12 of 1 is flush with each other.

In the N,O-carboxymethyl chitosan optical fiber 2, the fourth end face 13 is coated with the fourth coating 8; the fifth end face 14 is the N,O-carboxymethyl chitosan optical fiber connected to the first end face 10 2; the fourth end face 13 is the end face of the N,O-carboxymethyl chitosan optical fiber 2 flush with the third end face 12, and the fourth coating 8 is used to produce total reflection on the optical signal.

In this embodiment, when the optical signal is transmitted to the semi-cylindrical part along the incident silica fiber 1, the characteristics of the optical signal transmission at this time are: all the wavelength signals of the light source will be transmitted through the semi-cylindrical silica fiber, and then the half-wavelength signal (λ ₀ -λ ₂ wavelengths, the wavelength range of the light source is λ ₁ -λ ₂ , λ ₀ is the central wavelength, as shown in Figure 3) is absorbed by the third coating 7 of the incident silica fiber 1, and the short half-wavelength signal (λ ₁ -λ ₀ light wavelength, the wavelength range of the light source is λ ₁ -λ ₂ , λ ₀ is the central wavelength, as shown in Figure 3) between the incident optical fiber and the adjacent end faces of the reflective silica optical fiber 3, a Fa-Per interference air cavity is formed, namely The first Fappaut interference cavity, the first Fappaut interference cavity is used to respond to pressure changes and temperature changes, changes in external pressure and temperature changes lead to changes in the interference spectrum; λ ₀ -λ ₂ wavelengths of optical signals except along the incident quartz fiber In addition to the transmission of the semi-cylindrical silica fiber in 1, part of the power is reflected by the interface (the first coating 5 coated on the first end face 10) of the N,O-carboxymethyl chitosan fiber 2 and the incident silica fiber 1, while the rest Part of it enters the semi-cylindrical N,O-carboxymethyl chitosan optical fiber 2 and is transmitted to its end face and then returned by the total reflection of the end face. The two end faces of the semi-cylindrical N,O-carboxymethyl chitosan optical fiber form The interference cavity, that is, the fourth end face 13 and the fifth end face 14 constitute the second Fappel interference cavity, which is used to respond to temperature changes. The second Fabry interference cavity has nothing to do with the ambient pressure and is only affected by temperature. The optical fiber collimation sleeve 4 is an environmental pressure isolation device for the second Fabry interference cavity, therefore, affected by the second Fabry interference cavity, the change of the external temperature causes the interference spectrum of the λ ₀ -λ ₂ wavelength to change; There are only λ ₀ -λ ₂ wavelength optical signals in the first Falper interference cavity, and there are only λ ₁ -λ ₀ wavelength optical signals in the second Far-Per interference cavity; the schematic diagrams of the internal optical paths of the first F-P interference cavity and the second F-P interference cavity are as follows Figure 4 shows.

N,O-carboxymethyl chitosan is selected as the material of half of the cylindrical optical fiber. The whole process does not require chemical corrosion and other processes, and does not require other toxic chemical reagents. It is green and environmentally friendly, and has good temperature stability and casting properties, etc. Performance, by rationally designing two Fap interferometric cavities to interfere with half of the light source wavelength signals, the Fap interferometric optical fiber pressure sensor can accurately detect the ambient temperature when detecting the ambient pressure, so that the detected temperature information can be used Eliminate the influence of temperature when detecting ambient pressure, and finally eliminate the influence of temperature-pressure cross-sensitivity of the Farper interferometric sensor.

Embodiment two

Embodiment 2 of the present application proposes a fabrication method of a Fabry interferometric optical fiber pressure sensor that eliminates temperature interference, including:

Select the optical fiber collimation sleeve 4, clean and dry the optical fiber collimation sleeve 4; prepare the incident optical fiber, including the preparation of the incident silica optical fiber 1 and the preparation of the N,O-carboxymethyl chitosan optical fiber 2; prepare the reflective silica optical fiber 3; Insert the incident fiber and reflective silica fiber 3 into the fiber collimation sleeve 4 and connect with the fiber collimation sleeve 4 .

In this embodiment, preparing the optical fiber alignment sleeve 4 includes selecting an optical fiber alignment sleeve with an outer diameter of 0.3-1 mm and a length of 5-15 mm, placing it in an alcohol solution for ultrasonic cleaning for 2-5 minutes, and repeating the cleaning for 2-3 minutes. and then dry on high heat.

The preparation of incident optical fiber includes: embedding N,O-carboxymethyl chitosan optical fiber 2 in one end of incident silica optical fiber 1, and N,O-carboxymethyl chitosan optical fiber 2 is flush with the end face of incident silica optical fiber 1, forming incident fiber.

The preparation of the incident optical fiber also includes: retaining the predetermined shape of the silica optical fiber along the axial direction, removing the excess part, and obtaining a semi-cylindrical vacant area; the semi-cylindrical vacant area includes the first end face 10 and the second section 11, and coating the first end face 10 The first coating film 5 is obtained, the second section 11 is coated to obtain the second coating film 6, and a coated silica optical fiber is formed.

Prepare N,O-carboxymethyl chitosan solution; insert the coated quartz optical fiber into the treated capillary to make the semi-cylindrical vacant area leak out, and fill the semi-cylindrical with N,O-carboxymethyl chitosan solution In the vacant area, get the filled silica fiber;

Pulling the filled silica optical fiber into the capillary, standing and drying; cutting the silica fiber after standing and drying to obtain a flat end face, the end face includes a third end face 12 and a fourth end face 13; The four end faces 13 are coated to obtain a fourth coating 8 to form an N, O-carboxymethyl chitosan optical fiber 2. The N, O-carboxymethyl chitosan optical fiber 2 also includes a fifth end face 14, and the fourth end face 13 and The fifth end face 14 forms a second Fappaut interference cavity; the third end face 12 is coated to obtain a third coating 7 to form an incident silica optical fiber 1 .

In this embodiment, preparing the incident optical fiber includes;

First, select a section of 5-15mm from the ordinary silica fiber to peel off the coating layer and clean it, then keep the predetermined shape of the silica fiber along the axis direction, remove the excess part, and obtain a semi-cylindrical vacant area; specifically, use femtosecond laser along It is processed into a semi-cylindrical shape along the axial direction, and the cross-sectional diagram left after processing is shown in Figure 5. The length of the semi-cylindrical is 0.05-0.4mm, and then cleaned and wiped clean with absolute alcohol.

The paraffin is heated and melted, and then the two end faces (the cross section marked in Fig. 5) left by the semi-cylindrical optical fiber prepared above are coated with a thin layer of paraffin for protection, and then the meridian plane area of the semi-cylindrical is plated with a gold film, namely The second cross-sectional area is coated so that the plane can produce total reflection on the optical signal; then the paraffin wax on the two ends of the semi-cylindrical optical fiber is heated and cleaned, and a thin layer of paraffin protective gold film is applied to the gold-coated surface. Then one of the end faces is coated with a film so that it can produce a reflectivity of about 40% for the λ ₀ -λ ₂ light wavelength signal incident on the surface of the film (the wavelength range of the light source is λ ₁ -λ ₂ , λ ₀ is the central wavelength) The remaining optical power after reflection is transmitted, and the λ ₁ -λ ₀ light wavelength signals incident on the surface of the film are all absorbed. After the coating is completed, the paraffin wax is washed off by heating, and the coated semi-cylindrical silica fiber is obtained.

Select N,O-carboxymethyl chitosan with a molecular weight of 100,000-300,000, a degree of carboxylation of 80-90%, and a degree of deacetylation of 85-95%, and dissolve it in sterile deionized water to form a N,O-carboxymethyl chitosan solution with a concentration of 0.8-1.8%, add TiO ₂ according to the mass ratio of carboxymethyl chitosan and nano-TiO ₂ at 1-6:1 during the configuration and stirring process, and ultrasonically oscillate the solution After 5-8 minutes, the nano-TiO ₂ is evenly distributed in the solution, and the N,O-carboxymethyl chitosan is completely dissolved and formed into the desired viscous shape. At the same time, add a defoamer to make the prepared solution free of bubbles.

Select a capillary with an inner diameter of 125-126 microns, clean it in alcohol with ultrasonic waves and dry it, then insert the above-mentioned semi-cylindrical optical fiber coated with the film into the capillary and expose the coating area of the semi-cylindrical part, and then in the semi-cylindrical The coated area of the optical fiber is coated with viscous N,O-carboxymethyl chitosan, so that the entire area of the cut semi-cylindrical silica fiber is filled, and then the optical fiber is pulled to make the semi-cylindrical part enter the capillary, and the semi-cylindrical part enters the capillary. After the whole shaped part enters the capillary, put it into a drying oven and let it stand at room temperature for 3-8 hours, so that the semi-cylindrical N,O-carboxymethyl chitosan is formed and begins to harden, and then gently remove the capillary.

Soak the semi-cylindrical N,O-carboxymethyl chitosan with 1-5% calcium chloride aqueous solution for 10-50 seconds to make it cross-linked and solidified, put it in an infrared drying oven, set the temperature at 40-50°C for the semi-cylindrical Form N,O-carboxymethyl chitosan lasts 2-5 hours for drying.

Select the above-mentioned dried optical fiber, and cut it with an optical fiber cutter at the end of the semi-cylindrical silica fiber that is not coated, so that it has a flat end face. As shown in Figure 6, the semi-cylindrical optical fiber is cut The end face after cutting is shown in Figure 7.

A layer of thin paraffin is applied to the semicircular end face part (the third end face 12) of the above-mentioned cut flat end face of the quartz optical fiber, and then a gold-plated film is formed on the semicircular end face part (the fourth end face 13) of N, O-carboxymethyl chitosan. The fourth coating 8 enables it to perform total reflection on the transmitted optical signal. The N,O-carboxymethyl chitosan after coating constitutes the N,O-carboxymethyl chitosan optical fiber 2, and the N,O- The fourth end face 13 and the fifth end face 14 in the carboxymethyl chitosan optical fiber 2 form the second Faber interference cavity; then remove the paraffin of the semi-cylindrical silica optical fiber end face part (the third end face 12), then in the semi-cylindrical The surface of the gold film on the end face of N,O-carboxymethyl chitosan is coated with a thin layer of paraffin, and then the end face of the quartz semi-cylindrical optical fiber is coated to form the third coating 7, so that it can transmit the semi-cylindrical silica optical fiber. The optical signal (the optical signal in the wavelength range of λ ₁ -λ ₀ ) is partially reflected, and the remaining 75% of the light is transmitted and then transmitted to the end face of the reflective fiber, while the other half of the light source wavelength signal λ0-λ2 is completely absorbed. After the coating is completed Remove paraffin and set aside. The coated silica optical fiber constitutes the incident silica optical fiber 1 . After all the coatings are completed, the coating schematic diagram of the incident optical fiber structure section is shown in Figure 2.

In this embodiment, preparing the reflective silica optical fiber 3 includes cutting and wiping the silica optical fiber to obtain a reflective silica optical fiber.

Insert the reflective silica fiber 3 and the incident optical fiber into the prepared fiber collimation sleeve 4, set the cavity length of the sensor Fab cavity so that there is no contact between the incident optical fiber and the reflective silica optical fiber 3, and form the first cavity Then, the reflective silica fiber and the incident fiber are fixed on the inner wall of the fiber collimation sleeve by laser thermal fusion to form a F-Per interference fiber sensor. The optical paths of the first Fabry interference cavity and the second Fapling interference cavity in the Fabry interferometric optical fiber sensor are shown in FIG. 3 .

Embodiment three

As shown in FIG. 8 , it is a schematic diagram of the entire sensing system in Embodiment 3 of the present application. Optical signals in the wavelength range of λ ₀ -λ ₂ interfere with the Fab cavity formed by the semi-cylindrical N,O-carboxymethyl chitosan optical fiber, while optical signals of λ ₁ -λ ₀ wavelength enter the silica fiber through the semi-cylindrical The F-P air cavity formed by the third end face and the reflective fiber end face interferes, and the interference signal generated by the two F-P cavity returns along the incident optical fiber, and is demultiplexed by the wavelength division multiplexer 18 after passing through the optical fiber coupler 16. The obtained two interference signals in the λ ₀ -λ ₂ wavelength range and the λ ₁ -λ ₀ wavelength range are respectively processed by the first detection and signal demodulator 19 and the second detection and signal demodulator 20 to obtain corresponding environmental information , the interference spectrum information of λ ₀ -λ ₂ wavelength is temperature signal, and the interference spectrum information of λ ₁ -λ ₀ wavelength is temperature and pressure signal.

The present invention aims at the problem that the Fab interference optical fiber pressure sensor is affected by the temperature-pressure cross sensitivity, designs a sensor structure with two small sections of semi-cylindrical optical fibers of different materials, and utilizes the absorption or reflection of the optical signal in the selected wavelength range The film layer structure, thus ingeniously forming two completely independent Fappaure cavities, the second Fappaure interference cavity is used to measure temperature, and the first Fappaure interference cavity is used to measure temperature and pressure, so as to realize the optical fiber pressure sensor to eliminate Influenced by ambient temperature, the production process is simple, environmentally friendly and convenient, and the sensor is safe, reliable and stable.

The above-mentioned embodiments are only a description of the preferred mode of the application, and are not intended to limit the scope of the application. Variations and improvements should fall within the scope of protection determined by the claims of the present application.

Claims

The F-P interference optical fiber pressure sensor for eliminating temperature interference is characterized in that it includes an incident optical fiber, an optical fiber collimation sleeve and a reflective silica optical fiber;

The incident optical fiber and the reflective silica optical fiber are located in the optical fiber collimation sleeve;

There is no contact between the incident optical fiber and the reflective silica optical fiber, and a first Fappaure interference cavity is formed, and the first Fappaure interference cavity is used to detect pressure changes;

The incident optical fiber comprises incident silica optical fiber and N,O-carboxymethyl chitosan optical fiber;

The N,O-carboxymethyl chitosan optical fiber includes a fourth end face and a fifth end face, the fourth end face and the fifth end face constitute a second Fappaure interference cavity, and the second Fappaure interference cavity is used for for detecting temperature changes.
The Fabry interference optical fiber pressure sensor that eliminates temperature interference according to claim 1, is characterized in that;

The incident silica fiber includes a first end face, a second section and a third end face;

The first end face is the end face of the mosaic connection between the N,O-carboxymethyl chitosan optical fiber and the incident silica optical fiber;

The second section is the section where the N,O-carboxymethyl chitosan optical fiber is mosaically connected to the incident silica optical fiber;

The third end face is an end face adjacent to the incident silica fiber and the reflection fiber.
The Fabry interferometric optical fiber pressure sensor that eliminates temperature interference according to claim 2, is characterized in that;

The first end surface is coated with a first coating film, the second section is coated with a second coating film, and the third end surface is coated with a third coating film;

The first coating is used for partial reflection of the long half-wavelength optical signal and total absorption of the short half-wavelength optical signal;

The second coating is used to produce total reflection on the optical signal;

The third coating is used for partial reflection of the short half-wavelength optical signal, and full absorption of the long half-wavelength optical signal.
The Faber interferometric fiber optic pressure sensor for eliminating temperature interference according to claim 3, characterized in that,

The N,O-carboxymethyl chitosan optical fiber is inlaid and connected with the incident silica optical fiber, and connected with the optical fiber collimation sleeve, the first N,O-carboxymethyl chitosan optical fiber The four end faces are flush with the third end face of the incident silica fiber.
The method for eliminating temperature interference according to claim 4, characterized in that, in the N, O-carboxymethyl chitosan optical fiber;

The fourth end face is coated with a fourth coating;

The fifth end face is the end face of the N,O-carboxymethyl chitosan optical fiber connected to the first end face;

The fourth end face is the end face of the N,O-carboxymethyl chitosan optical fiber which is flush with the third end face, and the fourth coating is used for total reflection of optical signals.
A method for manufacturing a Fabry interferometric optical fiber pressure sensor that eliminates temperature interference, characterized in that it includes;

Selecting an optical fiber alignment sleeve, cleaning and drying the optical fiber alignment sleeve;

Preparation of incident optical fiber, including preparation of incident silica optical fiber and preparation of N,O-carboxymethyl chitosan optical fiber;

Prepare reflective silica fiber;

Insert the incident fiber and the reflective silica fiber into the fiber collimation sleeve and connect them to the fiber collimation sleeve; wherein, there is a preset cavity length between the incident fiber and the reflective silica fiber , forming the first Fapling interference cavity, and forming the Fapling interference optical fiber pressure sensor.
The manufacturing method of the Faber interference optical fiber pressure sensor for eliminating temperature interference according to claim 6, wherein preparing the incident optical fiber comprises;

The N, O-carboxymethyl chitosan optical fiber is embedded in one end of the incident silica fiber, and the N, O-carboxymethyl chitosan optical fiber is flush with the end face of the incident silica optical fiber, forming the the incident fiber.
The manufacturing method of the Faber interference optical fiber pressure sensor for eliminating temperature interference according to claim 7, wherein preparing the incident optical fiber also includes;

Keep the predetermined shape of the silica fiber along the axial direction, remove the excess part, and obtain a semi-cylindrical vacant area;

The vacant area of the semi-cylindrical body includes a first end surface and a second section, the first end surface is coated to obtain a first coating, and the second section is coated to obtain a second coating to form a coated silica optical fiber;

Configure N,O-carboxymethyl chitosan solution;

Inserting the coated silica optical fiber into the processed capillary, causing the vacant area of the semi-cylindrical body to leak out, filling the vacant area of the semi-cylindrical body with the N,O-carboxymethyl chitosan solution to obtain a filled Full silica fiber;

Pulling the filled silica optical fiber into the capillary, leaving it to dry;

Cutting the silica optical fiber after standing and drying to obtain a flat end face, the end face includes a third end face and a fourth end face;

Coating the fourth end face to obtain a fourth coating film to form the N,O-carboxymethyl chitosan optical fiber, the N,O-carboxymethyl chitosan optical fiber also includes a fifth end face, the The fourth end face and the fifth end face form a second Fapé interference cavity;

Coating the third end face to obtain a third end face coating film to form the incident silica optical fiber.