Optical fiber temperature and pressure sensor based on spherical lens and preparation method thereof

Abstract

The invention discloses an optical fiber temperature and pressure sensor based on a spherical lens and a preparation method thereof, and the sensor comprises a filler neck which is internally provided with a pressure medium channel; the sensitive diaphragm separates the pressure medium channel from the internal structure of the sensor, and can sense the pressure change of the pressure medium and convert the pressure change into self deformation; the optical fiber insertion core is used for fixing an optical fiber, so that the front end face of the optical fiber is close to and right faces the sensitive element sensitive diaphragm to form an optical FP cavity so as to realize pressure measurement; the spherical lens is used for converging light beams, improving the coupling efficiency of light entering the optical fiber end face and improving the optical signal intensity; the flat plate lens forms a reference FP cavity and is used for measuring temperature; the diaphragm base is used for mounting and fixing the sensitive diaphragm, the flat plate lens, the spherical lens and the optical fiber insertion core and ensuring that the sensitive diaphragm, the flat plate lens, the spherical lens and the optical fiber insertion core are coaxial and the relative positions are not changed; according to the scheme, the optical fiber has the characteristics of small size, high temperature resistance, high insulating property, high electromagnetic interference resistance and the like, and can be used for a long time in a high-temperature environment to measure the temperature and the pressure at the same time.

Description

Technical Field

[0001] The present invention relates to the technical field of temperature and pressure sensors, and in particular to a ball lens-based optical fiber temperature and pressure sensor and a preparation method thereof. Background Art

[0002] A fiber optic sensor is a device that uses the physical quantity to be measured to modulate a characteristic parameter of a light wave signal, extracts the signal containing the modulation information and demodulates it, thereby realizing the detection of external physical quantities. In recent years, fiber optic sensing technology has achieved rapid development with the development of micro-nano processing technology and in-depth research on fiber optic materials. Fiber optic sensors have been widely used in aerospace, shipbuilding, petrochemical, electric power, health monitoring and other fields.

[0003] In the above fields, the demand for obtaining pressure parameters under high temperature environment is becoming increasingly urgent, such as the pressure in chemical reactors and smelting towers, the downhole pressure of oil drilling and the pressure in the cylinder of internal combustion engines, and the pressure in the combustion chamber of gas turbines. Such environments often have the characteristics of high temperature, high pressure, high vibration intensity, strict electrical insulation requirements, and complex electromagnetic environment. Conventional pressure sensors need to be protected during use, such as wrapping insulation materials on the outside of the sensor, using drainage pipes to drain and cool the medium to be measured, etc. These protection measures not only solve the problem of environmental conditions, but also introduce a series of problems such as increased overall weight of the sensor, hysteresis of test pressure signals, and increased difficulty in electromagnetic compatibility design. Fiber optic sensors have a series of unique advantages such as high sensitivity, simple structure, small size, light weight, corrosion resistance, and high temperature resistance. In particular, fiber optic sensors use optical signals as the carrier of information transmission, have extremely strong electrical insulation and anti-electromagnetic interference capabilities, and are an effective breakthrough in solving the problem of pressure measurement in high temperature environments. Summary of the invention

[0004] In view of the above-mentioned deficiencies in the prior art, the present invention provides a spherical lens-based optical fiber temperature and pressure sensor and a preparation method thereof, which solves the problem that the existing pressure sensors have poor accuracy and reliability in temperature and pressure measurement under high temperature environments.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is:

[0006] In a first aspect, a ball lens-based optical fiber temperature and pressure sensor is provided, which includes: a take-over nozzle, a pressure medium channel connected to a high-temperature pressure measurement environment is arranged inside the take-over nozzle; a diaphragm base, two ends of which are respectively sealed and connected to the take-over nozzle and the tail pipe, a mounting hole is arranged inside the diaphragm base, and the mounting hole is separated from the pressure medium channel by a sensitive diaphragm arranged at its port; an optical fiber, which is limited and fixed in the mounting hole, the front end of the optical fiber is close to and facing the sensitive diaphragm, a ball lens is arranged in the mounting hole located at the front end of the optical fiber, and the rear end of the optical fiber is led out from the inside of the tail pipe; a flat lens, a gap of which is arranged between the ball lens and the sensitive diaphragm.

[0007] Furthermore, the optical signal transmitted by the optical fiber is focused and collimated by the spherical lens and then irradiated on the flat lens and the sensitive diaphragm in sequence to form multi-beam interference, and the optical signal forms a base FP cavity for measuring temperature on the front and rear surfaces of the flat lens, and forms a sensitive FP cavity for measuring pressure on the rear surface of the flat lens and the surface of the sensitive diaphragm.

[0008] Furthermore, the front end of the optical fiber is fixedly inserted into the ceramic ferrule, the ceramic ferrule is fixedly arranged in the metal ferrule, the metal ferrule is provided with an external thread, and a threaded hole matching the external thread is provided at the end of the mounting hole close to the tail pipe.

[0009] Furthermore, the surface of the spherical lens is coated with an anti-reflection film, and an annular clamping platform is provided in the mounting hole between the optical fiber and the sensitive membrane. The spherical lens is clamped between the annular clamping platform and the front end of the metal insert, and the ends of the annular clamping platform and the metal insert close to each other are provided with chamfered grooves for easy fitting and fixing with the spherical lens.

[0010] Furthermore, the cross section of the sensitive membrane is corrugated, and a metal reflective coating is plated on the side of the sensitive membrane close to the optical fiber.

[0011] Furthermore, a pressure ring is crimped on the edge of the sensitive diaphragm to facilitate welding and sealing between the sensitive diaphragm and the diaphragm base.

[0012] Furthermore, a step hole is provided at the port of the mounting hole close to the nozzle, and the flat lens is fixedly mounted in the step hole, and both side surfaces of the flat lens are perpendicular to the incident direction of the optical fiber.

[0013] In a second aspect, a method for preparing a spherical lens-based optical fiber temperature and pressure sensor is provided, which comprises the following steps:

[0014] S1: A mounting hole is opened on the diaphragm base, a step hole and a threaded hole are opened at both ends of the mounting hole, and an annular clamping platform is arranged on the inner side of the step hole;

[0015] S2: placing a flat lens in the middle of the step hole, placing glass solder between the flat lens and the step hole, and applying high temperature to sinter and solidify the glass solder and limit and fix the flat lens;

[0016] S3: Place the sensitive diaphragm at the port of the step hole, and press the edge of the sensitive diaphragm with a pressure ring, and then seal and weld the pressure ring, the sensitive diaphragm and the diaphragm base together by continuous laser welding to ensure air tightness;

[0017] S4: sequentially placing the ball lens and the metal insert into the mounting hole of the diaphragm base, setting the ball lens limiter between the chamfered groove at the front end of the metal insert and the chamfered groove of the annular clamping table, the rear end of the metal insert is threadedly matched with the threaded hole and fastened, and then continuously laser welding the joint position of the rear end of the metal insert and the diaphragm base;

[0018] S5: insert the optical fiber into the optical fiber through hole of the ceramic ferrule until the front end surface of the optical fiber is flush with the front end surface of the ceramic ferrule, and sinter and solidify it with high temperature resistant ceramic glue, and then use optical fiber grinding equipment to grind the front end surface of the ceramic ferrule until the front end surface of the optical fiber is polished and smooth;

[0019] S6: insert the ceramic ferrule and the optical fiber into the metal ferrule together, and adjust them to a predetermined position using a micro-motion platform, and then sinter and solidify the rear ends of the optical fiber, the ceramic ferrule and the metal ferrule into a whole by sintering with high-temperature resistant ceramic glue;

[0020] S7: Place the nozzle and tail pipe at the corresponding steps at both ends of the diaphragm base, and weld them by continuous laser sealing. The rear end of the optical fiber is led out from the inside of the tail pipe, and the rear end of the optical fiber is protected by a metal armor sheath.

[0021] Furthermore, the diaphragm base is made of a low expansion alloy material, the sensitive diaphragm is made of a high temperature resistant alloy material, and the flat lens is made of a silicon dioxide material.

[0022] The beneficial effects of the present invention are:

[0023] 1. This solution utilizes the high temperature resistance properties of materials such as optical fiber, high temperature alloy, glass and the preparation process, so that the sensor of this solution can be directly installed and used in a high temperature environment, such as the extreme environment inside the engine cylinder, thereby realizing the simultaneous measurement of temperature and pressure signals in a high temperature and high pressure environment, solving the problem that traditional pressure sensors must take insulation measures or divert the pressure to a remote end for measurement when used in a high temperature environment; at the same time, compared with electrical pressure sensors that are prone to failure and inaccurate measurements under extreme temperatures and electromagnetic interference, the sensitive part of the sensor probe of this solution has no electronic components, and the external electromagnetic environment has no effect on the optical signal, so it has a strong ability to resist electromagnetic interference.

[0024] 2. In the substrate FP cavity of this scheme, there is an optical path difference between the light reflected from the front surface of the flat lens and the light reflected from the rear surface of the flat lens to form an interference spectrum, and the optical path difference is only related to the thickness of the flat lens. When the temperature of the external environment changes, the thickness of the flat lens changes, and the optical path difference also changes accordingly, causing the interference spectrum formed by the substrate FP cavity to change. Finally, the temperature of the external environment can be obtained by demodulating the signal of the interference spectrum.

[0025] 3. In this scheme, the optical path difference between the light reflected from the reflective surface of the sensitive diaphragm and the light reflected from the rear surface of the flat lens in the sensitive FP cavity forms an interference spectrum, and the optical path difference is related to the distance from the rear surface of the flat lens to the reflective surface of the sensitive diaphragm; the sensitive diaphragm will deform under the pressure of the high-pressure environment, and the deformation will cause the distance between the reflective surface of the sensitive diaphragm and the rear surface of the flat lens to change, resulting in a change in the interference spectrum formed by the sensitive FP cavity. Finally, the pressure of the external environment can be obtained by demodulating the signal of the interference spectrum.

[0026] 4. This solution can effectively increase the light intensity of the optical signal coupled into the fiber core by adding a spherical lens to converge the light beam, thereby improving the signal-to-noise ratio of the interference spectrum. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a structural cross-sectional view of the optical fiber temperature and pressure sensor based on a ball lens.

[0028] Figure 2 Schematic diagram of the structure of the composite FP cavity.

[0029] Figure 3 This is the spectrum diagram of the composite FP cavity.

[0030] Figure 4 This is the spectrum diagram of the base FP cavity.

[0031] Figure 5 Spectrum diagram of the sensitive FP cavity.

[0032] Figure 6 is the frequency spectrum after Fourier transform.

[0033] Figure 7 Schematic diagram of the propagation of optical signals in the FP cavity.

[0034] Figure 8 Schematic diagram of the propagation of optical signals in the FP cavity after adding a ball lens.

[0035] Among them, 1. take-over nozzle, 2. diaphragm base, 3. tail pipe, 4. pressure medium channel, 5. mounting hole, 6. sensitive diaphragm, 7. pressure ring, 8. optical fiber, 9. ceramic ferrule, 10. metal ferrule, 11. ball lens, 12. ring card table, 13. flat lens, 14. glass solder, 15. base FP cavity, 16. sensitive FP cavity. DETAILED DESCRIPTION

[0036] The specific implementation modes of the present invention are described below so that those skilled in the art can understand the present invention. However, it should be clear that the present invention is not limited to the scope of the specific implementation modes. For those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the attached claims, these changes are obvious, and all inventions and creations utilizing the concept of the present invention are protected.

[0037] like Figure 1 and Figure 2 As shown, the optical fiber temperature and pressure sensor based on the spherical lens of the present scheme includes a take-over nozzle 1, a diaphragm base 2 and a tail pipe 3. A pressure medium channel 4 connected to a high-temperature pressure measurement environment is provided inside the take-over nozzle 1. The pressure medium channel 4 is used to install the sensor and connect the sensor with the high-temperature and high-pressure environment to be measured, and can be designed according to the actual installation situation. The two ends of the diaphragm base 2 are sealed and docked with the take-over nozzle 1 and the tail pipe 3 respectively.

[0038] A mounting hole 5 is provided in the diaphragm base 2, and the mounting hole 5 is separated from the pressure medium channel 4 by a sensitive diaphragm 6 provided at its port. A pressure ring 7 is crimped at the edge of the sensitive diaphragm 6, and the pressure ring 7, the sensitive diaphragm 6 and the diaphragm base 2 are sealed and welded together; the cross section of the sensitive diaphragm 6 is corrugated to ensure that the bottom surface of the sensitive diaphragm 6 always remains flat during the deformation process. The material of the sensitive diaphragm 6 is a high-temperature resistant alloy. Through the design of the shape of the sensitive diaphragm 6 and the selection of the material, the sensitive diaphragm 6 can produce a displacement of about 20μm to 200μm under high temperature and high pressure environment, and has lower creep, smaller hysteresis and nonlinear effects, and can achieve a fatigue life of more than tens of millions of pressure cycles; the side of the sensitive diaphragm 6 close to the optical fiber 8 is plated with a metal reflective coating to improve the reflectivity of the inner surface of the sensitive diaphragm 6 to the optical signal; in specific implementation, the reflective surface of the sensitive diaphragm 6 can be plated with gold, silver, copper, etc. by chemical plating, electroplating, magnetron sputtering and other process means.

[0039] An optical fiber 8 is fixed in position in the mounting hole 5. Specifically, the front end of the optical fiber 8 is fixedly inserted into the ceramic ferrule 9, the ceramic ferrule 9 is fixedly arranged in the metal ferrule 10, the metal ferrule 10 is provided with an external thread, and a threaded hole matching the external thread is provided at the end of the mounting hole 5 close to the tail pipe 3; the front end of the optical fiber 8 is close to and facing the sensitive diaphragm 6, and the rear end of the optical fiber 8 is led out from the inside of the tail pipe 3.

[0040] A ball lens 11 is arranged in the mounting hole 5 located at the front end of the optical fiber 8, and an annular clamping platform 12 is arranged in the mounting hole 5 between the optical fiber 8 and the sensitive membrane 6. The ball lens 11 is clamped between the annular clamping platform 12 and the front end of the metal ferrule 10, and the ends of the annular clamping platform 12 and the metal ferrule 10 that are close to each other are provided with chamfered grooves that are convenient for fitting with the ball lens 11.

[0041] A flat lens 13 is provided in the gap between the ball lens 11 and the sensitive diaphragm 6. Specifically, a step hole is provided at the end of the mounting hole 5 close to the nozzle 1. The flat lens 13 is fixedly installed in the step hole. The two side surfaces of the flat lens 13 are perpendicular to the incident direction of the optical fiber 8. The material of the flat lens 13 is silicon dioxide, and its melting point exceeds 1200°C. The material of the diaphragm base 2 is a low expansion alloy. The diaphragm base 2 is made of a suitable metal material, and the optical fiber 8 and the diaphragm base 2 are sintered together by using glass solder 14, so that the sensitive probe of the optical fiber 8 can withstand a temperature exceeding 400°C as a whole.

[0042] The sensitive diaphragm 6 and the flat lens 13 in this scheme form a composite FP cavity. The light signal transmitted by the optical fiber 8 is focused and collimated by the ball lens 11 and then irradiated on the flat lens 13 and the sensitive diaphragm 6 in turn to form multi-beam interference. The light signal forms a base FP cavity 15 for measuring temperature on the front and rear surfaces of the flat lens 13, and forms a sensitive FP cavity 16 for measuring pressure on the rear surface of the flat lens 13 and the surface of the sensitive diaphragm 6. The specific principle is as follows:

[0043] The substrate FP cavity 15 and the sensitive FP cavity 16 form a composite FP cavity. The interference spectrum of the composite FP cavity is as follows: Figure 3 As shown; the interference pattern is formed by the superposition of the interference spectra of the substrate FP cavity 15 and the sensitive FP cavity 16.

[0044] In the substrate FP cavity 15, the optical path difference between the light reflected from the front surface of the flat lens 13 and the light reflected from the rear surface of the flat lens 13 forms an interference spectrum as shown in FIG. Figure 4 As shown, the optical path difference is only related to the thickness of the flat lens 13. When the temperature of the external environment changes, the thickness of the flat lens 13 changes, and the optical path difference also changes, resulting in a change in the interference spectrum formed by the substrate FP cavity 15. Finally, the temperature of the external environment can be obtained by demodulating the signal of the interference spectrum.

[0045] In the sensitive FP cavity 16, the optical path difference between the light reflected from the reflective surface of the sensitive diaphragm 6 and the light reflected from the rear surface of the flat lens 13 forms an interference spectrum as shown in FIG. Figure 5As shown, the optical path difference is related to the distance from the rear surface of the flat lens 13 to the reflective surface of the sensitive diaphragm 6; the sensitive diaphragm 6 will be deformed under the pressure of the high-pressure environment, and the deformation will cause the distance between the reflective surface of the sensitive diaphragm 6 and the rear surface of the flat lens 13 to change, resulting in a change in the interference spectrum formed by the sensitive FP cavity 16. Finally, the pressure of the external environment can be obtained by demodulating the signal of the interference spectrum.

[0046] Specifically, when the optical fiber temperature and pressure sensor is working, the spectral signal is collected as follows: Figure 3 As shown, the spectrum is transformed by Fourier transform to obtain Figure 6 The time-frequency domain spectrum shown in the figure, where the frequency corresponding to F1 represents the cavity length of the sensitive FP cavity 16, and the frequency corresponding to F2 represents the cavity length of the base FP cavity 15; F1 and F2 are superimposed to form a hybrid cavity, and the changes in the cavity lengths of the sensitive FP cavity 16 and the base FP cavity 15 are demodulated to achieve simultaneous measurement of temperature and pressure.

[0047] When the external pressure of the optical fiber temperature and pressure sensor changes, the sensitive diaphragm 6 is deformed by the external pressure, and the distance between the reflective surface of the sensitive diaphragm 6 and the rear surface of the flat lens 13 changes, that is, the cavity length of the sensitive FP cavity 16 changes, and the cavity length is only related to the change of the external pressure. After the cavity length of the sensitive FP cavity 16 changes, its interference spectrum changes, so that the frequency corresponding to F1 in the frequency spectrum changes, and the external pressure change is obtained by calculating the frequency corresponding to F1; when the external temperature of the optical fiber temperature and pressure sensor changes, the flat lens 13 is deformed under the action of temperature, and the distance between the front and rear surfaces of the flat lens 13 changes, that is, the cavity length of the substrate FP cavity 15 changes, and the cavity length is only related to the change of the external temperature; after the cavity length of the substrate FP cavity 15 changes, its interference spectrum changes, so that the frequency corresponding to F2 in the frequency spectrum changes, and the external temperature change is obtained by calculating the frequency corresponding to F2.

[0048] In particular, in conventional FP cavity interference, the optical signal is directly emitted from the end face of the optical fiber 8, and is coupled back into the optical fiber 8 after being reflected by the surface of the sensitive diaphragm 6; the optical path propagation of the optical signal in the FP cavity is as follows: Figure 7 As shown; after reflection, the ratio of the energy that can be coupled back into the fiber core to the total energy of the optical signal can be determined by the ratio of the reflected light spot area to the fiber core area; therefore, the energy that can be coupled back into the fiber core is relatively low. In this scheme, the light beam is converged by adding a spherical lens 11, and the light path propagation is shown in Figure 8 As shown; the ball lens 11 can effectively increase the light intensity of the optical signal coupled into the fiber core, thereby improving the intensity of the interference spectrum; the surface of the ball lens 11 is coated with an anti-reflection film to reduce the light reflection on the front and rear surfaces of the ball lens 11, thereby avoiding mixing into unnecessary FP cavities.

[0049] This solution also provides a method for preparing an optical fiber 8 temperature and pressure sensor based on a ball lens 11, which comprises the following steps:

[0050] S1: A mounting hole 5 is formed on the diaphragm base 2, a step hole and a threaded hole are formed at both ends of the mounting hole 5, and an annular clamping platform 12 is arranged inside the step hole;

[0051] S2: placing the flat lens 13 in the middle of the step hole, placing glass solder 14 between the flat lens 13 and the step hole, and applying high temperature to sinter and solidify the glass solder 14 and positionally fix the flat lens 13, wherein the glass solder 14 may be glass paste, glass powder or a glass pre-sintered part;

[0052] S3: placing the sensitive diaphragm 6 at the end of the step hole, and pressing the edge of the sensitive diaphragm 6 with the pressure ring 7, and then sealing and welding the pressure ring 7, the sensitive diaphragm 6 and the diaphragm base 2 together by continuous laser welding to ensure air tightness;

[0053] S4: sequentially placing the ball lens 11 and the metal insert 10 into the mounting hole 5 of the diaphragm base 2, and setting the ball lens 11 between the chamfered groove at the front end of the metal insert 10 and the chamfered groove of the annular clamping platform 12, and the rear end of the metal insert 10 is threadedly matched with the threaded hole and fastened, and then the rear end of the metal insert 10 and the joint position of the diaphragm base 2 are continuously laser welded;

[0054] S5: insert the front end of the optical fiber 8 into the optical fiber 8 through hole of the ceramic ferrule 9 until the front end surface of the optical fiber 8 is flush with the front end surface of the ceramic ferrule 9, and sinter and solidify with high temperature resistant ceramic glue, and then use the optical fiber 8 grinding equipment to grind the front end surface of the ceramic ferrule 9 until the front end surface of the optical fiber 8 is polished and smooth;

[0055] S6: insert the ceramic ferrule 9 and the optical fiber 8 into the metal ferrule 10 together, and adjust them to a predetermined position using a micro-motion platform, and then sinter and solidify the rear ends of the optical fiber 8, the ceramic ferrule 9 and the metal ferrule 10 into a whole by sintering with a high-temperature resistant ceramic glue;

[0056] S7: Place the nozzle 1 and the tail pipe 3 at the corresponding steps at both ends of the diaphragm base 2 respectively, and through continuous laser sealing welding, the rear end of the optical fiber 8 is led out from the inside of the tail pipe 3, and the rear end of the optical fiber 8 is protected by a metal armor sheath.

[0057] In summary, this solution utilizes the characteristics of optical fiber 8 such as small size, high temperature resistance, strong insulation performance and anti-electromagnetic interference performance, and solves the problem that traditional pressure sensors must take insulation measures or divert the pressure to a remote end for measurement when used in high temperature environments. At the same time, the sensor of this solution can be used for a long time in a high temperature environment and can measure temperature and pressure at the same time.

Claims

1. An optical fiber temperature and pressure sensor based on a ball lens, characterized in that: include: A take-over nozzle, the interior of which is provided with a pressure medium channel communicating with a high-temperature pressure measuring environment; The diaphragm base has two ends which are respectively sealed and butted with the nozzle and the tail pipe, and a mounting hole is arranged in the diaphragm base, and the mounting hole is separated from the pressure medium channel by a sensitive diaphragm arranged at its end; An optical fiber is fixed in a position in a mounting hole, the front end of the optical fiber is close to and directly facing the sensitive diaphragm, a ball lens is arranged in the mounting hole at the front end of the optical fiber, and the rear end of the optical fiber is led out from the inside of the tail tube; The gap of the flat lens is set between the ball lens and the sensitive membrane.

2. The optical fiber temperature and pressure sensor based on a ball lens according to claim 1, characterized in that: The optical signal transmitted by the optical fiber is focused and collimated by the ball lens and then irradiated on the flat lens and the sensitive membrane in sequence to form multi-beam interference. The optical signal forms a base FP cavity for measuring temperature on the front and rear surfaces of the flat lens, and forms a sensitive FP cavity for measuring pressure on the rear surface of the flat lens and the surface of the sensitive membrane.

3. The optical fiber temperature and pressure sensor based on a ball lens according to claim 1, characterized in that: The front end of the optical fiber is fixedly inserted into the ceramic ferrule, the ceramic ferrule is fixedly arranged in the metal ferrule, the metal ferrule is provided with an external thread, and a threaded hole matching the external thread is provided at the end of the mounting hole close to the tail pipe.

4. The optical fiber temperature and pressure sensor based on a ball lens according to claim 3, characterized in that: The surface of the ball lens is plated with an anti-reflection film, and an annular clamping platform is arranged in the mounting hole between the optical fiber and the sensitive membrane. The ball lens is clamped between the annular clamping platform and the front end of the metal insert, and the ends of the annular clamping platform and the metal insert close to each other are provided with chamfered grooves for easy fitting and fixing with the ball lens.

5. The optical fiber temperature and pressure sensor based on a ball lens according to claim 1, characterized in that: The cross section of the sensitive membrane is corrugated, and a metal reflective coating is plated on the side of the sensitive membrane close to the optical fiber.

6. The optical fiber temperature and pressure sensor based on a ball lens according to claim 1, characterized in that: A pressure ring is crimped at the edge of the sensitive diaphragm to facilitate welding and sealing between the sensitive diaphragm and the diaphragm base.

7. The optical fiber temperature and pressure sensor based on a ball lens according to claim 1, characterized in that: A step hole is arranged at the port of the mounting hole close to the nozzle, and the flat lens is fixedly mounted in the step hole. Both side surfaces of the flat lens are perpendicular to the incident direction of the optical fiber.

8. A method for preparing a ball lens-based optical fiber temperature and pressure sensor according to any one of claims 1 to 7, characterized in that: The following steps are involved: S1: A mounting hole is opened on the diaphragm base, a step hole and a threaded hole are opened at both ends of the mounting hole, and an annular clamping platform is arranged on the inner side of the step hole; S2: placing a flat lens in the middle of the step hole, placing glass solder between the flat lens and the step hole, and applying high temperature to sinter and solidify the glass solder and limit and fix the flat lens; S3: placing the sensitive diaphragm at the port of the step hole, and pressing the edge of the sensitive diaphragm with a pressure ring, and then sealing and welding the pressure ring, the sensitive diaphragm and the diaphragm base together by continuous laser welding; S4: sequentially placing the ball lens and the metal insert into the mounting hole of the diaphragm base, setting the ball lens limiter between the chamfered groove at the front end of the metal insert and the chamfered groove of the annular clamping table, the rear end of the metal insert is threadedly matched with the threaded hole and fastened, and then continuously laser welding the joint position of the rear end of the metal insert and the diaphragm base; S5: insert the optical fiber into the optical fiber through hole of the ceramic ferrule until the front end surface of the optical fiber is flush with the front end surface of the ceramic ferrule, and sinter and solidify it with high temperature resistant ceramic glue, and then use optical fiber grinding equipment to grind the front end surface of the ceramic ferrule until the front end surface of the optical fiber is polished and smooth; S6: insert the ceramic ferrule and the optical fiber into the metal ferrule together, and adjust them to a predetermined position using a micro-motion platform, and then sinter and solidify the rear ends of the optical fiber, the ceramic ferrule and the metal ferrule into a whole by sintering with high-temperature resistant ceramic glue; S7: Place the nozzle and tail pipe at the corresponding steps at both ends of the diaphragm base, and weld them by continuous laser sealing. The rear end of the optical fiber is led out from the inside of the tail pipe, and the rear end of the optical fiber is protected by a metal armor sheath.

9. The method for preparing the ball lens-based optical fiber temperature and pressure sensor according to claim 8, characterized in that: The diaphragm base is made of a low expansion alloy material, the sensitive diaphragm is made of a high temperature resistant alloy material, and the flat lens is made of a silicon dioxide material.

Images