CN110553774A - Miniature full-quartz optical fiber Fizeau cavity high-frequency dynamic pressure sensor and manufacturing method thereof - Google Patents

Abstract

The invention discloses an ultra-miniature all-quartz fiber Fizeau cavity high-frequency dynamic pressure sensor and a manufacturing method thereof. The manufacturing method includes the following steps: (1) welding a single-mode fiber and a quartz glass capillary with an optical fiber fusion splicer; Cut the quartz capillary short under the microscope to form the F-P cavity; ③ Weld the second single-mode fiber prepared at the other end of the quartz capillary to form the F-P cavity; ④ Under the microscope, the second single-mode fiber was Cut the optical fiber as short as possible; ⑤ Use a bare fiber grinder to grind the cut single-mode optical fiber into a quartz diaphragm of the required thickness; ⑥ Etch the quartz diaphragm to remove the reflected light on the outer surface of the quartz diaphragm to form Fizeau cavity pressure sensitive sheet. The sensor produced by the invention has an all-quartz structure, is small in size, is inherently resistant to electromagnetic interference, and is resistant to high temperature.

Description

Micro All-Quartz Fiber Fizeau Cavity High-Response Dynamic Pressure Sensor and Its Fabrication method

technical field

The invention relates to an optical fiber F-P cavity, in particular to the field of high-frequency response dynamic pressure testing based on an all-quartz, ultra-miniature optical fiber Fizeau cavity.

Background technique

For the test of high-frequency response dynamic pressure, piezoelectric sensors and silicon piezoresistive sensors are mainly used at present. Both of them have a common disadvantage: ① can not work normally in the environment of strong electromagnetic interference and high ion radiation; ② can not work in high temperature environment; ③ it is difficult to realize long-distance telemetry. The optical fiber sensor is inherently resistant to electromagnetic interference, the quartz material itself is resistant to high temperature and has a very small temperature expansion coefficient. Taking advantage of the "both sensing and transmission" advantages of optical fiber, it is easy to achieve long-distance telemetry, and the outer diameter of the optical fiber F-P cavity pressure sensor is only 125 microns. It has the ability to achieve extremely high temporal and spatial resolution. Therefore, for the occasions where piezoelectric and piezoresistive sensors cannot be used, such as: strong electromagnetic interference, high temperature, long-distance telemetry and extremely small sensors, the fiber F-P cavity pressure sensor is of great significance.

SUMMARY OF THE INVENTION

The purpose of the invention is to make an ultra-miniature all-quartz fiber Fizeau cavity high-response dynamic pressure sensor, which is suitable for the occasions of strong electromagnetic interference, high temperature, long-distance telemetry and extremely small sensors.

In order to achieve the above object, the present invention provides a method for making an ultra-miniature all-quartz fiber Fizeau cavity high-frequency dynamic pressure sensor, which is characterized in that comprising the following steps:

① Weld the single-mode optical fiber and the quartz glass capillary together with an optical fiber fusion splicer;

②Cut the quartz capillary tube short under the microscope to form the F-P cavity;

③ Weld the second single-mode optical fiber prepared at the other end of the quartz capillary to form an F-P cavity;

④Cut the second single-mode fiber as short as possible under the microscope;

⑤Use a bare fiber grinder to grind the cut single-mode fiber into a quartz diaphragm of the required thickness;

⑥ The quartz diaphragm is etched and textured to remove the reflected light on the outer surface of the quartz diaphragm to form a Fizeau cavity pressure sensitive thin plate.

In connection with the above technical solution, in step ①, the welding parameters are: discharge intensity 45mA, discharge time 250ms, pre-melting time 80ms, and the end face reflectivity after welding reaches 2.89%.

Connect above-mentioned technical scheme, in step 2., the quartz capillary length after the cut is

In connection with the above technical solution, in step ③, the welding parameters are: discharge intensity 45mA, discharge time 250ms, pre-melting time 80ms, and the end face reflectivity after welding reaches 2.89%.

Connect the above technical scheme, in step ⑤, the single-mode optical fiber is ground into a thickness of quartz diaphragm.

In connection with the above technical scheme, in step ⑥, the etching time is 2 min, and the etching rate is 1.5 μm/min. After etching, the reflectivity of the reflected light on the outer surface of the quartz diaphragm is reduced to 0.00012%, and the thickness of the quartz diaphragm is reduced on the original basis. Thin 3μm.

Connect the above technical scheme, in step ⑥, use 40% HF solution to etch and texture the quartz diaphragm

The present invention also provides an ultra-miniature all-quartz fiber Fizeau cavity high-response dynamic pressure sensor fabricated according to the above technical solution.

Following the above technical solution, the outer diameter of the quartz capillary of the formed F-P cavity is 125 μm and the inner diameter is 75 μm.

Description of drawings

Figure 1 is a flow chart of the fabrication of the sensor.

Figure 2 shows the cutting control system used in the sensor manufacturing process.

Figure 3 is a light path diagram of the sensor.

Figure 4 is a schematic diagram of the key parameter test of the Fizeau cavity.

In the picture: 1. Single-mode fiber, 2. Silica capillary, 3. Silica diaphragm, 4. Cleaver, 5. Fiber grinder, 6.40% HF solution, 7. Five-dimensional fiber fine-tuning frame, 8. Fiber clamp, 9. 2D translation stage, 10. Fiber clamp, 11. 5D fiber fine-tuning frame, 12. F-P cavity, 13. Broadband light source, 14. Fiber circulator, 15. Flange, 16. APC connector, 17. PC connector: That is, the reflectivity is 3.16% standard Fresnel reflector, 18. Fiber Spectrometer, 19. Fizeau Cavity;.

Detailed ways

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

The invention mainly adopts a special micro-arc welding process of an optical fiber fusion splicer to weld a conducting optical fiber 1 with an outer diameter of 125 microns, a quartz glass capillary 2 and a quartz diaphragm 3 to form a low-finesse Fizeau cavity interferometer. A high-precision cutting control system built under a stereo microscope using a two-dimensional translation stage and two five-dimensional fiber fine-tuning stands can effectively control the length of the quartz capillary (the length of the F-P cavity) and the thickness of the quartz diaphragm. . The thickness of the pressure-sensitive quartz diaphragm can be precisely controlled at the micron level by grinding with a special bare fiber grinding machine. The reverse transfer function of the Fizeau cavity is measured by the comparison method, and the data fitting is performed with the cascaded double F-P cavity interference output formula to realize the measurement of the key characteristic parameters of the Fizeau cavity (the reflectivity of each end face, the cavity length and the thickness of the diaphragm. Using the etching process to eliminate the interference of the reflected light on the outer surface of the quartz diaphragm can ensure that the reverse detection interference output of the Fizeau cavity is close to the ideal sinusoidal double-beam interference output, which is convenient to use the passive homodyne technology of three-wavelength excitation and arbitrary deterministic phase interval. The F-P cavity transiently changes the phase for high-speed demodulation.

Preferred embodiment: the concrete steps of the ultra-miniature all-quartz fiber Fizeau cavity high-response dynamic pressure sensor manufacturing method of the present invention are:

① Weld the single-mode optical fiber and the quartz glass capillary together with an optical fiber fusion splicer, as shown in Figure 1(a). The welding parameters are: discharge intensity 45mA, discharge time 250ms, pre-melting time 80ms, and the end face reflectivity after welding can reach 2.89%.

②Cut out a quartz capillary with a suitable length (25-50) μm under a microscope, as shown in Figure 1(b);

③ Weld the second single-mode optical fiber prepared at the other end of the quartz capillary, as shown in Figure 1(c). The welding parameters are: discharge intensity 45mA, discharge time 250ms, pre-melting time 80ms, and the end face reflectivity after welding can reach 2.89%.

④Cut the second single-mode fiber as short as possible under the microscope to reduce the grinding time, see Figure 1(d).

⑤Use a bare fiber grinder to grind the short single-mode fiber into a quartz diaphragm with the required thickness (5-23) μm, see Figure 1(e). Among them, the type of abrasive paper is 5 μm.

⑥ Use 40% HF to etch and texture the quartz diaphragm to remove the reflected light on the outer surface of the quartz diaphragm, as shown in Figure 1(f). The etching time is 2min, and the etching rate is about 1.5μm/min. Finally, the reflectivity of the outer surface of the quartz diaphragm is reduced to 0.00012%, and the thickness of the diaphragm is further reduced by 3μm.

The connection mode between the single-mode optical fiber 1, the quartz capillary 2, and the quartz diaphragm 3 in Fig. 1 is micro-arc welding of the optical fiber fusion splicer; cutting control system.

In FIG. 2 , the optical fiber clamp 8 is fixed to the five-dimensional optical fiber fine-tuning frame 7 by bolts, the optical fiber clamp 10 is fixed to the five-dimensional optical fiber fine-tuning frame 11 by bolts, and the cleaver 4 is fixed to the two-dimensional displacement stage 9 by bolts.

The main purpose of the cutting control system shown in Fig. 2 is to cut the quartz glass capillary to form the F-P cavity according to the above step ② and to form the pressure sensitive diaphragm according to the step ④. The cutting control method is:

First, place the guide fiber welded with the silica glass capillary on the fiber cleaver, and fix the two ends of the welded guide fiber and the silica glass capillary to the five-dimensional fiber fine-tuning frame on both sides of the cleaver (see Figure 2); Adjust the two five-dimensional fiber fine-tuning racks to make the guide fiber/quartz glass capillary to be cleaved in a horizontal and collimated state. Push the blade of the optical fiber cleaving knife of the special mechanical fixture directly under the optical fiber, and then use the two five-dimensional fiber fine-tuning frames on both sides to move the optical fiber so that the welding point between the optical fiber and the quartz capillary is near the cutting knife. The length of the quartz capillary in between is the length of the developed Fizeau cavity, which can be calculated by reading the magnification of the stereo microscope and the number of graduations the length occupies in the microscope field of view. Finally, in order to prevent the relative position of the welding point and the cleaving knife from changing due to tension at both ends of the fiber, the cover of the cleaving knife must be closed to fix the fiber to be cleaved, and then the two five-dimensional fiber fine-tuning racks at the two ends are loosened. The fiber is fixed, and the desired F-P cavity length can be obtained after cutting. This method is simple and has good reproducibility.

FIG. 3 shows an optical fiber FP cavity composed of an ultra-miniature flat circular thin plate structure, which is called an optical fiber Fizeau cavity 12 . The reflected light (R ₁ ) of the fiber end face is guided in the circular cavity as the reference beam, and the reflected light (R ₂ ) of the inner surface of the pressure sensitive sheet is used as the sensing beam, which forms an external intrinsic Fizeau cavity pressure sensor. It is based on the vibration of the pressure-sensitive film under the action of the shock wave, and then modulates the interference phase between the sensing beam (R ₁ ) and the reference beam (R ₂ ) to sense the external dynamic pressure. Based on the fact that the pressure-sensitive sheet is made of quartz glass, reflected light (R ₃ ) will be formed on the outer surface of the pressure-sensitive sheet, which provides useful information for real-time measurement of the thickness of the pressure-sensitive sheet when the pressure-sensitive sheet is ground and thinned; Under the condition that the thickness of the pressure-sensitive sheet is basically controlled and determined, the reflected light is reduced or even eliminated as much as possible by hydrofluoric acid etching to form a fully enclosed Fizeau cavity.

The all-quartz fiber Fizeau cavity high-response dynamic pressure sensor fabricated according to the manufacturing method of the ultra-miniature all-quartz fiber Fizeau cavity high-response dynamic pressure sensor of the above-mentioned embodiment is characterized by: all-quartz structure, small size (only 125 microns), and intrinsically anti-electromagnetic Interference and high temperature resistance. The dynamic pressure is sensed by a pressure sensitive silicon cup composed of a quartz capillary and a quartz diaphragm. Its sensitivity is determined by the thickness and effective diameter of the quartz diaphragm, and its bandwidth is determined by the resonant frequency of the sensitive diaphragm. The sensor is made of all-quartz material. The conductive fiber, the quartz capillary cavity and the quartz diaphragm that constitute the FP cavity are fused together by the micro-arc welding process of the fiber fusion splicer, which greatly improves the reliability and sturdiness, and can work in a high temperature environment; The cavity length of the fiber Fizeau cavity is obtained by the control of the fiber cleaver under the microscope, and the cavity length range is in the range of It can be adjusted arbitrarily according to the needs; the quartz sensitive diaphragm is also cut by a fiber cleaver, supplemented by a bare fiber grinder for grinding and thinning and HF corrosion, and its thickness is between The range can be adjusted arbitrarily as needed, the sensor fabrication process is simple, and the outer diameter is only 125μm.

Figure 4 shows the measurement method for the thickness of the pressure sensitive diaphragm and other key characteristic parameters of the sensor in step ⑤:

Through the comparison method, the output transfer function of the developed F-P cavity reverse detection and its key performance parameters can be directly measured by the spectrometer. Fig. 4 is the test method schematic diagram, and the steps are as follows:

①Connect the APC connector of a standard APC/PC conversion jumper to port 1 of the circulator with the flange plate. Based on the optical Fresnel reflection effect of the PC connector of the conversion jumper, scanning with a spectrometer can obtain the relationship curve between the system reverse detection optical power density and the scanning wavelength when the etalon with a reflectivity of 3.16% is connected. It includes the spectral density of the broadband light source, the fluctuation characteristics of each optical performance index of the circulator with the wavelength change, and the loss of each connector. It will serve as a reference for normalizing the reflectivity of the fiber F-P cavity.

②Connect the F-P cavity with the APC connector at one end instead of the APC/PC standard jumper. Similarly, the relationship curve between the reverse probe optical power density and the scanning wavelength of the developed fiber F-P cavity is measured by a spectrometer.

③Using the optical power spectral density measured by the standard jumper as the reference value, point by point along the scanning wavelength, normalize the optical power density test value of the developed F-P cavity according to formula (1), and then the developed F-P cavity can be obtained. Cavity reverse probe output transfer function curve.

④ Adopt cascaded double F-P cavity interference output formula (2) or double beam interference sinusoidal output standard formula (3):

(2) and (3) where: n is the optical refractive index of the quartz diaphragm. By curve fitting the above data, various characteristics of the F-P cavity can be obtained: the optical cavity length L, the three end face reflectances R1, R2 and R3 and the pressure diaphragm thickness d.

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

Claims (9)

1. A manufacturing method of an ultra-micro full-quartz fiber Fizeau cavity high-frequency dynamic pressure sensor is characterized by comprising the following steps:

Welding a single-mode optical fiber and a quartz glass capillary together by using an optical fiber welding machine;

Cutting the quartz capillary under a microscope to form an F-P cavity;

Welding a second prepared single-mode fiber at the other end of the quartz capillary to form an F-P cavity;

Cutting the second single mode fiber as short as possible under a microscope;

Grinding the cut single-mode optical fiber into a quartz diaphragm with the required thickness by using a bare fiber grinder;

Sixthly, etching and texturing the quartz diaphragm, and removing reflected light on the outer surface of the quartz diaphragm to form the Fizeau cavity pressure sensitive sheet.

2. The manufacturing method of the ultra-miniature all-silica fiber Fizeau cavity high-frequency dynamic pressure sensor according to claim 1, wherein in the step (r), welding parameters are as follows: the discharge intensity is 45mA, the discharge time is 250ms, the pre-melting time is 80ms, and the reflectivity of the end face after welding reaches 2.89%.

3. the method for manufacturing an ultra-miniature all-silica fiber Fizeau cavity high-frequency dynamic pressure sensor according to claim 1, wherein in step two, the length of the quartz capillary after being cut short is equal to

4. The manufacturing method of the ultra-miniature all-silica fiber Fizeau cavity high-frequency dynamic pressure sensor according to claim 1, wherein in the third step, the welding parameters are as follows: the discharge intensity is 45mA, the discharge time is 250ms, the pre-melting time is 80ms, and the reflectivity of the end face after welding reaches 2.89%.

5. The method for manufacturing an ultra-miniature all-silica fiber Fizeau cavity high-frequency dynamic pressure sensor according to claim 1, wherein in the fifth step, the single-mode fiber is ground to a thickness ofThe quartz membrane of (1).

6. The method for manufacturing an ultra-micro all-silica fiber Fizeau cavity high-frequency dynamic pressure sensor according to claim 1, wherein in the step (sixthly), the etching time is 2min, the etching rate is 1.5 μm/min, the reflection rate of the reflected light on the outer surface of the quartz diaphragm is reduced to 0.00012% after etching, and the thickness of the quartz diaphragm is reduced by 3 μm again on the original basis.

7. the method for manufacturing an ultra-micro all-silica fiber Fizeau cavity high-frequency dynamic pressure sensor according to claim 1, wherein in step (sixth), a 40% HF solution is used to etch and roughen the silica membrane.

8. An ultra-miniature all-silica fiber Fizeau cavity high frequency dynamic pressure sensor, characterized in that the sensor is manufactured according to the manufacturing method of any one of claims 1-7.

9. The ultra-miniature all-silica fiber Fizeau cavity high-frequency dynamic pressure sensor according to claim 8, wherein the quartz capillary of the F-P cavity is formed to have an outer diameter of 125 μm and an inner diameter of 75 μm.