CN111272306B

CN111272306B - Preparation method of optical fiber microstructure sensing device based on double sealed cavities

Info

Publication number: CN111272306B
Application number: CN202010117444.9A
Authority: CN
Inventors: 刘颖刚; 王钰玺; 杨丹青; 张庭; 傅海威; 贾振安
Original assignee: Xian Shiyou University
Current assignee: Heze New Century Electronic Technology Co ltd
Priority date: 2020-02-25
Filing date: 2020-02-25
Publication date: 2021-11-23
Anticipated expiration: 2040-02-25
Also published as: CN111272306A

Abstract

A method for preparing an optical fiber microstructure sensor device based on a double closed cavity, comprising the following steps: taking a piece of single-mode optical fiber and placing it on a three-dimensional micro-movement platform with CCD display, and processing two square microholes; Place it in HF solution to clean off the material residue on the surface and in the hole during processing; put the cleaned structure under the welding machine, select the manual welding program, and make two micropores with the same shape by high temperature discharge. , a circular closed cavity with a distance of about 500 microns; connect the fabricated sensor to the demodulator to collect data, extract the frequency of each cavity through fast Fourier transform, and then pass the Fourier filter method to The closed cavity and the optical fiber cavity frequency image between the two closed cavities are determined respectively; the invention can distinguish the measurement temperature and the tensile force at the same time, the sensor is small in size, can work in a small environment, and has the characteristics of simple structure and low production cost.

Description

Preparation method of optical fiber microstructure sensing device based on double sealed cavities

Technical Field

The invention relates to the technical field of optical fiber sensors, in particular to a preparation method of an optical fiber microstructure sensor based on a double-sealed cavity.

Background

Since the first optical fiber sensor in the world comes out in 1970, the optical fiber sensing device is applied to detection in a plurality of fields by virtue of the advantages of small volume, high sensitivity, low loss, high cost performance and the like, so that the optical fiber sensing technology makes a great breakthrough in the aspects of principle, application development and the like. The sensor generates multi-parameter sensors of measuring parameters such as temperature, pressure intensity, stress, flow velocity, magnetic field and the like. The microstructure optical fiber sensing technology is accompanied with the optical fiber sensing principle due to the diversity of the structureComplexity has been a focus of research. The microstructure optical fiber sensing technology based on laser processing is a new stage of the development of the optical fiber sensing technology. In 2003, Jiangtao et al studied the precise micromachining of K9 optical glass by using KrF excimer laser with wavelength of 248nm, and conducted experiments on cutting and surface drilling of glass to punch micropores of about 0.8mm, and further studied the interaction mechanism between excimer laser and glass. In 2006, li vereian et al, the university of wuhan-han theory, studied the processing characteristics of a 157nm laser on SiO2 material, etched the end face of a crystal fiber with a 157nm laser, and quantitatively analyzed the etching depth and ablation degree with the micropore profile of the crystal fiber as a reference. When the laser energy flux density is 2J/cm2, the etching rate can reach 210nm pulse, which proves that the 7.9eV photon energy of 157nm laser can be measured by SiO₂The material absorbs strongly and breaks down.

The existing 193nm excimer laser is also based on the principle, the cost is lower than that of femtosecond laser, and the processing precision is higher than that of 157nm laser. Combining these two features, 193nm excimer lasers are also popular with various institutional groups. Therefore, the processing of the optical fiber microstructure sensing device by using the laser is also an inevitable trend in the current development stage.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention aims to provide a method for preparing an optical fiber microstructure sensing device based on a double-sealed cavity, the sensor can simultaneously distinguish the measurement temperature and the tension, has small volume, can work in a micro environment, and has the characteristics of simple structure and low production cost.

In order to achieve the purpose, the invention adopts the technical scheme that:

a method for preparing an optical fiber microstructure sensing device based on a double-sealed cavity comprises the following steps;

the method comprises the following steps: placing a section of single-mode optical fiber on a three-dimensional micromotion platform with a CCD display, adjusting the light stop of a 193nm excimer laser to a square light spot with the size of 40 microns, and opening the laser to process a first square micropore penetrating through a fiber core;

step two: the laser drives a three-dimensional micro-motion platform for placing the optical fiber to process a first hole, then the optical fiber is transversely moved by 500 microns, and a second identical through hole is manufactured according to the method in the step one;

step three: placing the processed double micropores in a 5% HF solution for 1-2 minutes, and cleaning material residues on the surfaces and in the holes during processing;

step four: putting the cleaned structure under a welding machine for welding, and manufacturing two round sealed cavities with the same shape and the distance of about 500 microns for the two micropores in a high-temperature discharge mode;

step five: the manufactured sensor is accessed into a demodulator to acquire data, the frequency of each cavity is extracted through fast Fourier transform, and the frequency images of the optical fiber cavity between the closed cavity and the two closed cavities are respectively determined through a Fourier sub-band filtering method;

step six: connecting one end of a manufactured optical fiber sensor with a demodulator, clamping the other end of the manufactured optical fiber sensor on an electronic dynamometer, recording data from 0N to 2.2N every 0.2N, waiting for two minutes every time of recording, and waiting for the uniform stress of all optical fibers to be recorded again;

step seven: after tension measurement is completed, the sensor is placed into a thermostat, before a temperature measurement experiment, the sensor is placed into the thermostat with the temperature of 300 ℃ for quenching treatment for half an hour to eliminate residual stress in the process of manufacturing the sensor, the temperature is set from room temperature to 500 ℃, data is obtained every 50 ℃, reading is waited for two minutes every time, and data accuracy is guaranteed.

In the step 1, the punch-through can be carried out after 5 to 8 seconds of processing under the condition that the voltage of the laser is 1.2 KV.

And 4, selecting a manual welding program according to the welding conditions of the step 4 by adopting parameters of 80 discharge intensity, 0 advancing distance, 160ms of pre-welding time, 200ms of cleaning discharge time and 220ms of welding discharge time.

The invention has the beneficial effects that:

firstly, the method comprises the following steps: the manufacturing material is only single mode fiber, and the cost of the manufacturing instrument is 193nm excimer laser which is far less than the processing cost of femtosecond laser.

Secondly, the method comprises the following steps: the femtosecond laser processing and the corrosion processing both adopt end face manufacturing defects and then are welded, the invention is easy to be manufactured on the all-fiber, firstly, the manufacturing process is easy to be carried out in other modes, the mechanical toughness of the processed sensor is far greater than that of the end face processing method, and the measurable range is comparable to that of the all-fiber.

Thirdly, the method comprises the following steps: the temperature and tension can be distinguished and measured, and the tension sensitivity is four times higher than that of a common grating. And can also be used as a tension sensor with high sensitivity.

Drawings

FIG. 1 is a schematic diagram of the 193nm excimer laser processing principle of the present invention.

Fig. 2 is a diagram of two square holes machined by a laser.

Fig. 3 is a schematic diagram of two closed cavities formed after the welding machine discharges.

Fig. 4 is a diagram of a sensor tension measuring device.

FIG. 5 is a diagram of the original spectrum at room temperature and pressure.

FIG. 6 is a schematic diagram of the variation of the spectrum of the closed cavity with tension after Fourier band-pass filtering.

FIG. 7 is a graph showing the change of optical fiber cavity spectrum with tension.

Fig. 8 is a linear fitting diagram of the sensitivity of the closed cavity pull force.

FIG. 9 is a graph of a linear fit of the fiber cavity pull sensitivity.

Fig. 10 is a diagram of a sensor temperature measuring device.

FIG. 11 is a graph showing the variation of cavity spectra with temperature.

FIG. 12 is a graph showing the change of fiber spectra with temperature.

FIG. 13 is a graph showing a linear fit of the temperature sensitivity of the fiber cavity.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings.

step two: software carried by the laser can drive a three-dimensional micromotion platform for placing the optical fiber to process a first hole, then transversely move the optical fiber by 500 microns, and manufacture a second same through hole according to the method in the step one;

step three: because the fiber material residues are left on the surface and in the hole of the processed micropore, the processed double micropore is placed in 5 percent HF solution for 1-2 minutes, and the material residues on the surface and in the hole during processing are cleaned; the purpose is to remove machining residues left in the holes and on the surface.

Step four: placing the cleaned structure under a welding machine, selecting a manual welding program by adopting parameters of 80 discharge intensity, 0 advancing distance, 160ms premelting time, 200ms cleaning discharge time and 220ms welding discharge time, and manufacturing two circular sealed cavities with the same shape and the distance of about 500 micrometers for two micropores in a high-temperature discharge mode;

step five: the manufactured sensor is accessed into a demodulator to acquire data, the frequency of each cavity is extracted through fast Fourier transform, and the frequency images of the optical fiber cavity between the closed cavity and the two closed cavities are respectively determined through a Fourier sub-band filtering method; the closed cavity has no response to temperature and has obvious response to tension, and the optical fiber cavity has response to both temperature and tension. Therefore, the temperature and tension can be distinguished and measured by utilizing the characteristic that the temperature of the closed cavity does not respond;

FIG. 1 is a schematic diagram of the operation of a 193nm excimer laser, in which a single mode fiber is stripped of a coating layer and placed on a processing platform, two square holes with the size of 40 micrometers and the distance of 500 micrometers are etched by using ultraviolet laser, and the preliminary test result is shown in FIG. 2.

In the attached drawing 1, 1-8 are all reflectors for increasing the image distance, 9 is a laser light source, 10 is a diaphragm, and 11 is a three-dimensional processing platform.

And (3) putting the structure in the figure 2 into a 5% HF solution for cleaning for 1-2 minutes to remove impurities remained after processing. Then, the microstructure optical fiber sensor shown in fig. 3 was manufactured by high-temperature discharge of a fusion splicer.

The fabricated sensor was clamped to a tension measuring device as shown in fig. 4. The initial spectrum is shown in FIG. 5 as a reflection spectrum of a normal temperature and pressure tension of 0N. The tension measurements were recorded every 0.2N starting from 0N to 2.2N. Spectral lines of the closed cavity (figure 6) and the optical fiber cavity (figure 7) are respectively extracted by Fourier band-pass filtering after all data are acquired. By measuring the line shifts of fig. 6, 7, fig. 8, 9, respectively, follow the fit. From the experimental results, the pull sensitivity of the closed cavity is 4.91nm/N (the fitting degree is 0.997), and the pull sensitivity of the optical fiber cavity is 1.38nm/N (the fitting degree is 0.997). It can be seen that the sensitivity of the closed cavity tension is four times that of the common optical fiber cavity.

After the tension was measured, the sensor was connected to a temperature measuring device as shown in fig. 10. The temperature was from room temperature to 500 ℃ and data was collected every 50 ℃. The sensor is placed in an environment at 300 ℃ and calcined for 30 minutes to eliminate environmental stress before data are recorded formally. The acquired data are also subjected to Fourier band-pass filtering to extract the spectral drift amounts of the closed cavity and the optical fiber cavity as shown in fig. 11 and fig. 12, the temperature of the closed cavity can be observed to be not drifted from 50-500 ℃ by observing the fig. 11, and fig. 13 is a fitting graph of the temperature sensitivity of the optical fiber cavity. It can be seen that the sealed cavity is not sensitive to temperature, and the temperature sensitivity of the fiber cavity is 10.74 pm/deg.C.

The invention provides a multi-parameter measuring sensor which can simultaneously distinguish the measuring temperature and the tension, has small volume, simple structure and low production cost, can work in a tiny environment and has good utilization value in industrial measurement.

Claims

1. A method for preparing an optical fiber microstructure sensing device based on a double airtight cavity, characterized in that, comprising the following steps;

Step 1: Take a piece of single-mode fiber and place it on a three-dimensional micro-movement platform with CCD display, adjust the 193nm excimer laser aperture to a square spot with a size of 40 microns, and turn on the laser to process the first square micro-fiber passing through the fiber core. hole;

Step 2: The laser-driven three-dimensional micro-movement platform for placing the optical fiber will move the optical fiber laterally by 500 microns after processing the first hole, and make the second same perforation according to the method in step 1;

Step 3: Place the processed double micro-holes in a 5% HF solution for 1-2 minutes to remove the material residues on the surface and in the holes during processing;

Step 4: Put the cleaned structure under the welding machine for welding, and make two circular closed cavities with the same shape and a distance of about 500 microns through the high-temperature discharge of the two micro-holes;

Step 5: Connect the fabricated sensor to the demodulator to collect data, extract the frequency of each cavity through fast Fourier transform, and then filter the closed cavity and the optical fiber between the two closed cavities through the Fourier filter method. The cavity frequency images are determined separately;

Step 6: Connect one end of the optical fiber sensor to the demodulator, and clamp the other end to the electronic dynamometer. From 0N to 2.2N, record a data every 0.2N, and wait for two minutes for each recording, and wait for the full fiber The force is uniform and then recorded;

Step 7: After the tensile force measurement is completed, put the sensor into the incubator. Before the temperature measurement experiment, put the sensor into the incubator at 300 °C for quenching for half an hour to eliminate the residual stress in the process of making the sensor. Set The temperature is from room temperature to 500°C, and a data is taken every 50°C, and each reading waits for two minutes to ensure the accuracy of the data;

In the described step 1, the laser voltage is processed for 5-8 seconds under the state of 1.2KV to penetrate;

The welding condition of the described step 4 is to adopt the parameter that the discharge intensity is 80, the advancing distance is 0, the pre-melting time is 160ms, the cleaning discharge time is 200ms, and the welding discharge time is 220ms, and the manual welding procedure is selected.